今天来分析一下 startActivity 的启动过程。
1. Activity
/base/core/java/android/app/Activity.java
@Override
public void startActivity(Intent intent) {
this.startActivity(intent, null);
}
@Override
public void startActivity(Intent intent, @Nullable Bundle options) {
// 如果bunder不为空，则传入options参数
if (options != null) {
startActivityForResult(intent, -1, options);
} else {
startActivityForResult(intent, -1);
}
}
public void startActivityForResult(@RequiresPermission Intent intent, int requestCode,
@Nullable Bundle options) {
if (mParent == null) {
// 调用 Instrumentation的execStartActivity函数启动Activity
// mAppThread: 数据类型为ApplicationThread，通过mMainThread.getApplicationThread()方法获取。
// mToken: 数据类型为IBinder.
Instrumentation.ActivityResult ar =
mInstrumentation.execStartActivity(
this, mMainThread.getApplicationThread(), mToken, this,
intent, requestCode, options);
if (ar != null) {
mMainThread.sendActivityResult(
mToken, mEmbeddedID, requestCode, ar.getResultCode(),
ar.getResultData());
}
// 此时requestCode =-1
if (requestCode >= 0) {
mStartedActivity = true;
}
} else {
// ...
}
}可以看到，最终调用了 Instrumentation.execStartActivity()。
2. Instrumentation
/base/core/java/android/app/Instrumentation.java
// 执行启动Activity函数
public ActivityResult execStartActivity(
Context who, IBinder contextThread, IBinder token, Activity target,
Intent intent, int requestCode, Bundle options) {
// 将IBinder转换成IApplicationThread
IApplicationThread whoThread = (IApplicationThread) contextThread;
Uri referrer = target != null ? target.onProvideReferrer() : null;
if (referrer != null) {
intent.putExtra(Intent.EXTRA_REFERRER, referrer);
}
if (mActivityMonitors != null) {
synchronized (mSync) {
final int N = mActivityMonitors.size();
for (int i=0; i<N; i++) {
final ActivityMonitor am = mActivityMonitors.get(i);
if (am.match(who, null, intent)) {
am.mHits++;
// 当该monitor阻塞activity启动,则直接返回
if (am.isBlocking()) {
return requestCode >= 0 ? am.getResult() : null;
}
break;
}
}
}
}
try {
intent.migrateExtraStreamToClipData();
intent.prepareToLeaveProcess(who);
// 使用ActivityManagerNative的startActivity启动
/**
* 关于 ActivityManagerNative.getDefault()返回的是ActivityManagerProxy对象.
* 此处startActivity()的共有10个参数, 下面说说每个参数传递AMP.startActivity()每一项的对应值:
*
* caller: 当前应用的ApplicationThread对象mAppThread;
* callingPackage: 调用当前ContextImpl.getBasePackageName(),获取当前Activity所在包名;
* intent: 这便是启动Activity时,传递过来的参数;
* resolvedType: 调用intent.resolveTypeIfNeeded而获取;
* resultTo: 来自于当前Activity.mToken
* resultWho: 来自于当前Activity.mEmbeddedID
* requestCode = -1;
* startFlags = 0;
* profilerInfo = null;
* options = null;
*/
int result = ActivityManagerNative.getDefault()
.startActivity(whoThread, who.getBasePackageName(), intent,
intent.resolveTypeIfNeeded(who.getContentResolver()),
token, target != null ? target.mEmbeddedID : null,
requestCode, 0, null, options);
// 检查activity是否启动成功
checkStartActivityResult(result, intent);
} catch (RemoteException e) {
throw new RuntimeException("Failure from system", e);
}
return null;
}最后会调用 ActivityManagerNative.getDefault().startActivity()，这句在前面的文章中出现了很多次了，先获取 app 进程的 ActivtyManagerProxy，然后进入 system server 进程，到 ActivityManagerNative，最终到达 ActivityManagerService。
3. ActivityManagerService
/base/services/core/java/com/android/server/am/ActivityManagerService.java
// ActivityManagerNative会进入到ActivityManagerService的startActivity函数
@Override
public final int startActivity(IApplicationThread caller, String callingPackage,
Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
int startFlags, ProfilerInfo profilerInfo, Bundle bOptions) {
// 启动Activity
return startActivityAsUser(caller, callingPackage, intent, resolvedType, resultTo,
resultWho, requestCode, startFlags, profilerInfo, bOptions,
UserHandle.getCallingUserId());
}
@Override
public final int startActivityAsUser(IApplicationThread caller, String callingPackage,
Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
int startFlags, ProfilerInfo profilerInfo, Bundle bOptions, int userId) {
enforceNotIsolatedCaller("startActivity");
userId = mUserController.handleIncomingUser(Binder.getCallingPid(), Binder.getCallingUid(),
userId, false, ALLOW_FULL_ONLY, "startActivity", null);
return mActivityStarter.startActivityMayWait(caller, -1, callingPackage, intent,
resolvedType, null, null, resultTo, resultWho, requestCode, startFlags,
profilerInfo, null, null, bOptions, false, userId, null, null);
}此时位于 system server 进程，最后会调用 ActivityStarter.startActivityMayWait()。
4. ActivityStarter
/base/services/core/java/com/android/server/am/ActivityStarter.java
// 从ActivityManagerService进入ActivityStarter的startActivityMayWait()函数
// 启动Activity
final int startActivityMayWait(IApplicationThread caller, int callingUid,
String callingPackage, Intent intent, String resolvedType,
IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
IBinder resultTo, String resultWho, int requestCode, int startFlags,
ProfilerInfo profilerInfo, IActivityManager.WaitResult outResult, Configuration config,
Bundle bOptions, boolean ignoreTargetSecurity, int userId,
IActivityContainer iContainer, TaskRecord inTask) {
final Intent ephemeralIntent = new Intent(intent);
intent = new Intent(intent);
// 解析出 ResolveInfo
ResolveInfo rInfo = mSupervisor.resolveIntent(intent, resolvedType, userId);
if (rInfo == null) {
// ...
}
// 通过ActivityStackSupervisor解析Activity
ActivityInfo aInfo = mSupervisor.resolveActivity(intent, rInfo, startFlags, profilerInfo);
ActivityOptions options = ActivityOptions.fromBundle(bOptions);
ActivityStackSupervisor.ActivityContainer container =
(ActivityStackSupervisor.ActivityContainer)iContainer;
synchronized (mService) {
if (container != null && container.mParentActivity != null &&
container.mParentActivity.state != RESUMED) {
return ActivityManager.START_CANCELED;
}
final ActivityStack stack;
if (container == null || container.mStack.isOnHomeDisplay()) {
stack = mSupervisor.mFocusedStack;
} else {
stack = container.mStack;
}
}
final ActivityRecord[] outRecord = new ActivityRecord[1];
// 启动Activity
int res = startActivityLocked(caller, intent, ephemeralIntent, resolvedType,
aInfo, rInfo, voiceSession, voiceInteractor,
resultTo, resultWho, requestCode, callingPid,
callingUid, callingPackage, realCallingPid, realCallingUid, startFlags,
options, ignoreTargetSecurity, componentSpecified, outRecord, container,
inTask);
// ...
return res;
}
}这里面调用了 ActivityStackSupervisor 去解析 Intent 和 Activity。
- 4.1 ActivityStackSupervisor
/base/services/core/java/com/android/server/am/ActivityStackSupervisor.java
ResolveInfo resolveIntent(Intent intent, String resolvedType, int userId) {
return resolveIntent(intent, resolvedType, userId, 0);
}
ResolveInfo resolveIntent(Intent intent, String resolvedType, int userId, int flags) {
try {
return AppGlobals.getPackageManager().resolveIntent(intent, resolvedType,
PackageManager.MATCH_DEFAULT_ONLY | flags
| ActivityManagerService.STOCK_PM_FLAGS, userId);
} catch (RemoteException e) {
}
return null;
}
ActivityInfo resolveActivity(Intent intent, String resolvedType, int startFlags,
ProfilerInfo profilerInfo, int userId) {
final ResolveInfo rInfo = resolveIntent(intent, resolvedType, userId);
return resolveActivity(intent, rInfo, startFlags, profilerInfo);
}
// 收集Intent所指向的Activity信息, 当存在多个可供选择的Activity,则直接向用户弹出
ActivityInfo resolveActivity(Intent intent, ResolveInfo rInfo, int startFlags,
ProfilerInfo profilerInfo) {
final ActivityInfo aInfo = rInfo != null ? rInfo.activityInfo : null;
if (aInfo != null) {
intent.setComponent(new ComponentName(aInfo.applicationInfo.packageName, aInfo.name));
// Don't debug things in the system process
if (!aInfo.processName.equals("system")) {
if ((startFlags & ActivityManager.START_FLAG_DEBUG) != 0) {
mService.setDebugApp(aInfo.processName, true, false);
}
if ((startFlags & ActivityManager.START_FLAG_NATIVE_DEBUGGING) != 0) {
mService.setNativeDebuggingAppLocked(aInfo.applicationInfo, aInfo.processName);
}
if ((startFlags & ActivityManager.START_FLAG_TRACK_ALLOCATION) != 0) {
mService.setTrackAllocationApp(aInfo.applicationInfo, aInfo.processName);
}
if (profilerInfo != null) {
mService.setProfileApp(aInfo.applicationInfo, aInfo.processName, profilerInfo);
}
}
}
return aInfo;
}resolveIntent() 调用的是 AppGlobals，最终调用的是 PackageManagerService；resolveActivity() 方法的核心功能是找到相应的Activity 组件，并保存到 intent 对象。
- 4.2 PackageManagerService
/base/services/core/java/com/android/server/pm/PackageManagerService.java
@Override
public ResolveInfo resolveIntent(Intent intent, String resolvedType,
int flags, int userId) {
try {
if (!sUserManager.exists(userId)) return null;
flags = updateFlagsForResolve(flags, userId, intent);
// 检查权限
enforceCrossUserPermission(Binder.getCallingUid(), userId,
false /*requireFullPermission*/, false /*checkShell*/, "resolve intent");
Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "queryIntentActivities");
final List<ResolveInfo> query = queryIntentActivitiesInternal(intent, resolvedType,
flags, userId);
Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
final ResolveInfo bestChoice =
chooseBestActivity(intent, resolvedType, flags, query, userId);
// ...
return bestChoice;
} finally {
Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
}
}
private @NonNull List<ResolveInfo> queryIntentActivitiesInternal(Intent intent,
String resolvedType, int flags, int userId) {
if (!sUserManager.exists(userId)) return Collections.emptyList();
flags = updateFlagsForResolve(flags, userId, intent);
// 检查权限
enforceCrossUserPermission(Binder.getCallingUid(), userId,
false /* requireFullPermission */, false /* checkShell */,
"query intent activities");
ComponentName comp = intent.getComponent();
if (comp == null) {
if (intent.getSelector() != null) {
intent = intent.getSelector();
comp = intent.getComponent();
}
}
if (comp != null) {
final List<ResolveInfo> list = new ArrayList<ResolveInfo>(1);
final ActivityInfo ai = getActivityInfo(comp, flags, userId);
if (ai != null) {
final ResolveInfo ri = new ResolveInfo();
ri.activityInfo = ai;
list.add(ri);
}
return list;
}
// reader
synchronized (mPackages) {
final String pkgName = intent.getPackage();
if (pkgName == null) {
List<CrossProfileIntentFilter> matchingFilters =
getMatchingCrossProfileIntentFilters(intent, resolvedType, userId);
// Check for results that need to skip the current profile.
ResolveInfo xpResolveInfo = querySkipCurrentProfileIntents(matchingFilters, intent,
resolvedType, flags, userId);
if (xpResolveInfo != null) {
List<ResolveInfo> result = new ArrayList<ResolveInfo>(1);
result.add(xpResolveInfo);
return filterIfNotSystemUser(result, userId);
}
List<ResolveInfo> result = mActivities.queryIntent(
intent, resolvedType, flags, userId);
result = filterIfNotSystemUser(result, userId);
// Check for cross profile results.
boolean hasNonNegativePriorityResult = hasNonNegativePriority(result);
xpResolveInfo = queryCrossProfileIntents(
matchingFilters, intent, resolvedType, flags, userId,
hasNonNegativePriorityResult);
if (xpResolveInfo != null && isUserEnabled(xpResolveInfo.targetUserId)) {
boolean isVisibleToUser = filterIfNotSystemUser(
Collections.singletonList(xpResolveInfo), userId).size() > 0;
if (isVisibleToUser) {
result.add(xpResolveInfo);
Collections.sort(result, mResolvePrioritySorter);
}
}
if (hasWebURI(intent)) {
CrossProfileDomainInfo xpDomainInfo = null;
final UserInfo parent = getProfileParent(userId);
if (parent != null) {
xpDomainInfo = getCrossProfileDomainPreferredLpr(intent, resolvedType,
flags, userId, parent.id);
}
if (xpDomainInfo != null) {
if (xpResolveInfo != null) {
// If we didn't remove it, the cross-profile ResolveInfo would be twice
// in the result.
result.remove(xpResolveInfo);
}
if (result.size() == 0) {
result.add(xpDomainInfo.resolveInfo);
return result;
}
} else if (result.size() <= 1) {
return result;
}
result = filterCandidatesWithDomainPreferredActivitiesLPr(intent, flags, result,
xpDomainInfo, userId);
Collections.sort(result, mResolvePrioritySorter);
}
return result;
}
final PackageParser.Package pkg = mPackages.get(pkgName);
if (pkg != null) {
return filterIfNotSystemUser(
mActivities.queryIntentForPackage(
intent, resolvedType, flags, pkg.activities, userId),
userId);
}
return new ArrayList<ResolveInfo>();
}
}做的工作就是检查权限，从 Manifest 中读取 Activity 的配置，然后再回到 ActivityStarter.startActivityLocked():
/**
* 将该Activity所对应的AMS和WMS的task，分别移至栈顶；
* 从mTaskHistory获取该Activity所属的task;
* 当Activity所属进程没有启动，则需要显示启动窗口，即showStartingIcon=true;
* 创建AppWindowToken，并添加到WMS的mTokenMap；
* 设置启动窗口(StartingWindow);
* 恢复栈顶部的Activity;
*/
final int startActivityLocked(IApplicationThread caller, Intent intent, Intent ephemeralIntent,
String resolvedType, ActivityInfo aInfo, ResolveInfo rInfo,
IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
IBinder resultTo, String resultWho, int requestCode, int callingPid, int callingUid,
String callingPackage, int realCallingPid, int realCallingUid, int startFlags,
ActivityOptions options, boolean ignoreTargetSecurity, boolean componentSpecified,
ActivityRecord[] outActivity, ActivityStackSupervisor.ActivityContainer container,
TaskRecord inTask) {
int err = ActivityManager.START_SUCCESS;
// 获取调用者的进程记录对象
ProcessRecord callerApp = null;
if (caller != null) {
callerApp = mService.getRecordForAppLocked(caller);
if (callerApp != null) {
callingPid = callerApp.pid;
callingUid = callerApp.info.uid;
} else {
Slog.w(TAG, "Unable to find app for caller " + caller
+ " (pid=" + callingPid + ") when starting: "
+ intent.toString());
err = ActivityManager.START_PERMISSION_DENIED;
}
}
final int userId = aInfo != null ? UserHandle.getUserId(aInfo.applicationInfo.uid) : 0;
if (err == ActivityManager.START_SUCCESS) {
Slog.i(TAG, "START u" + userId + " {" + intent.toShortString(true, true, true, false)
+ "} from uid " + callingUid
+ " on display " + (container == null ? (mSupervisor.mFocusedStack == null ?
Display.DEFAULT_DISPLAY : mSupervisor.mFocusedStack.mDisplayId) :
(container.mActivityDisplay == null ? Display.DEFAULT_DISPLAY :
container.mActivityDisplay.mDisplayId)));
}
ActivityRecord sourceRecord = null;
ActivityRecord resultRecord = null;
if (resultTo != null) {
// 获取调用者所在的Activity
sourceRecord = mSupervisor.isInAnyStackLocked(resultTo);
if (DEBUG_RESULTS) Slog.v(TAG_RESULTS,
"Will send result to " + resultTo + " " + sourceRecord);
if (sourceRecord != null) {
if (requestCode >= 0 && !sourceRecord.finishing) {
resultRecord = sourceRecord;
}
}
}
final int launchFlags = intent.getFlags();
if ((launchFlags & Intent.FLAG_ACTIVITY_FORWARD_RESULT) != 0 && sourceRecord != null) {
// activity执行结果的返回由源Activity转换到新Activity, 不需要返回结果则不会进入该分支
// Transfer the result target from the source activity to the new
// one being started, including any failures.
if (requestCode >= 0) {
ActivityOptions.abort(options);
return ActivityManager.START_FORWARD_AND_REQUEST_CONFLICT;
}
resultRecord = sourceRecord.resultTo;
if (resultRecord != null && !resultRecord.isInStackLocked()) {
resultRecord = null;
}
resultWho = sourceRecord.resultWho;
requestCode = sourceRecord.requestCode;
sourceRecord.resultTo = null;
if (resultRecord != null) {
resultRecord.removeResultsLocked(sourceRecord, resultWho, requestCode);
}
if (sourceRecord.launchedFromUid == callingUid) {
callingPackage = sourceRecord.launchedFromPackage;
}
}
if (err == ActivityManager.START_SUCCESS && intent.getComponent() == null) {
// 从Intent中无法找到相应的Component
err = ActivityManager.START_INTENT_NOT_RESOLVED;
}
if (err == ActivityManager.START_SUCCESS && aInfo == null) {
err = ActivityManager.START_CLASS_NOT_FOUND;
}
if (err == ActivityManager.START_SUCCESS && sourceRecord != null
&& sourceRecord.task.voiceSession != null) {
if ((launchFlags & FLAG_ACTIVITY_NEW_TASK) == 0
&& sourceRecord.info.applicationInfo.uid != aInfo.applicationInfo.uid) {
try {
intent.addCategory(Intent.CATEGORY_VOICE);
if (!AppGlobals.getPackageManager().activitySupportsIntent(
intent.getComponent(), intent, resolvedType)) {
err = ActivityManager.START_NOT_VOICE_COMPATIBLE;
}
} catch (RemoteException e) {
Slog.w(TAG, "Failure checking voice capabilities", e);
err = ActivityManager.START_NOT_VOICE_COMPATIBLE;
}
}
}
if (err == ActivityManager.START_SUCCESS && voiceSession != null) {
try {
if (!AppGlobals.getPackageManager().activitySupportsIntent(intent.getComponent(),
intent, resolvedType)) {
Slog.w(TAG,
"Activity being started in new voice task does not support: "
+ intent);
err = ActivityManager.START_NOT_VOICE_COMPATIBLE;
}
} catch (RemoteException e) {
Slog.w(TAG, "Failure checking voice capabilities", e);
err = ActivityManager.START_NOT_VOICE_COMPATIBLE;
}
}
// ActivityStack
final ActivityStack resultStack = resultRecord == null ? null : resultRecord.task.stack;
if (err != START_SUCCESS) {
if (resultRecord != null) {
resultStack.sendActivityResultLocked(
-1, resultRecord, resultWho, requestCode, RESULT_CANCELED, null);
}
ActivityOptions.abort(options);
return err;
}
// 检测Activity权限
boolean abort = !mSupervisor.checkStartAnyActivityPermission(intent, aInfo, resultWho,
requestCode, callingPid, callingUid, callingPackage, ignoreTargetSecurity, callerApp,
resultRecord, resultStack, options);
abort |= !mService.mIntentFirewall.checkStartActivity(intent, callingUid,
callingPid, resolvedType, aInfo.applicationInfo);
if (mService.mController != null) {
try {
Intent watchIntent = intent.cloneFilter();
abort |= !mService.mController.activityStarting(watchIntent,
aInfo.applicationInfo.packageName);
} catch (RemoteException e) {
mService.mController = null;
}
}
mInterceptor.setStates(userId, realCallingPid, realCallingUid, startFlags, callingPackage);
mInterceptor.intercept(intent, rInfo, aInfo, resolvedType, inTask, callingPid, callingUid,
options);
intent = mInterceptor.mIntent;
rInfo = mInterceptor.mRInfo;
aInfo = mInterceptor.mAInfo;
resolvedType = mInterceptor.mResolvedType;
inTask = mInterceptor.mInTask;
callingPid = mInterceptor.mCallingPid;
callingUid = mInterceptor.mCallingUid;
options = mInterceptor.mActivityOptions;
if (abort) {
if (resultRecord != null) {
resultStack.sendActivityResultLocked(-1, resultRecord, resultWho, requestCode,
RESULT_CANCELED, null);
}
ActivityOptions.abort(options);
return START_SUCCESS;
}
// If permissions need a review before any of the app components can run, we
// launch the review activity and pass a pending intent to start the activity
// we are to launching now after the review is completed.
if (Build.PERMISSIONS_REVIEW_REQUIRED && aInfo != null) {
if (mService.getPackageManagerInternalLocked().isPermissionsReviewRequired(
aInfo.packageName, userId)) {
IIntentSender target = mService.getIntentSenderLocked(
ActivityManager.INTENT_SENDER_ACTIVITY, callingPackage,
callingUid, userId, null, null, 0, new Intent[]{intent},
new String[]{resolvedType}, PendingIntent.FLAG_CANCEL_CURRENT
| PendingIntent.FLAG_ONE_SHOT, null);
final int flags = intent.getFlags();
Intent newIntent = new Intent(Intent.ACTION_REVIEW_PERMISSIONS);
newIntent.setFlags(flags
| Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS);
newIntent.putExtra(Intent.EXTRA_PACKAGE_NAME, aInfo.packageName);
newIntent.putExtra(Intent.EXTRA_INTENT, new IntentSender(target));
if (resultRecord != null) {
newIntent.putExtra(Intent.EXTRA_RESULT_NEEDED, true);
}
intent = newIntent;
resolvedType = null;
callingUid = realCallingUid;
callingPid = realCallingPid;
rInfo = mSupervisor.resolveIntent(intent, resolvedType, userId);
aInfo = mSupervisor.resolveActivity(intent, rInfo, startFlags,
null /*profilerInfo*/);
}
}
if (rInfo != null && rInfo.ephemeralResolveInfo != null) {
final IIntentSender failureTarget = mService.getIntentSenderLocked(
ActivityManager.INTENT_SENDER_ACTIVITY, callingPackage,
Binder.getCallingUid(), userId, null, null, 0, new Intent[]{ intent },
new String[]{ resolvedType },
PendingIntent.FLAG_CANCEL_CURRENT | PendingIntent.FLAG_ONE_SHOT
| PendingIntent.FLAG_IMMUTABLE, null);
// Create a pending intent to start the ephemeral application; force it to be
// directed to the ephemeral package.
ephemeralIntent.setPackage(rInfo.ephemeralResolveInfo.getPackageName());
final IIntentSender ephemeralTarget = mService.getIntentSenderLocked(
ActivityManager.INTENT_SENDER_ACTIVITY, callingPackage,
Binder.getCallingUid(), userId, null, null, 0, new Intent[]{ ephemeralIntent },
new String[]{ resolvedType },
PendingIntent.FLAG_CANCEL_CURRENT | PendingIntent.FLAG_ONE_SHOT
| PendingIntent.FLAG_IMMUTABLE, null);
int flags = intent.getFlags();
intent = new Intent();
intent.setFlags(flags
| Intent.FLAG_ACTIVITY_NEW_TASK
| Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS);
intent.putExtra(Intent.EXTRA_PACKAGE_NAME,
rInfo.ephemeralResolveInfo.getPackageName());
intent.putExtra(Intent.EXTRA_EPHEMERAL_FAILURE, new IntentSender(failureTarget));
intent.putExtra(Intent.EXTRA_EPHEMERAL_SUCCESS, new IntentSender(ephemeralTarget));
resolvedType = null;
callingUid = realCallingUid;
callingPid = realCallingPid;
rInfo = rInfo.ephemeralInstaller;
aInfo = mSupervisor.resolveActivity(intent, rInfo, startFlags, null /*profilerInfo*/);
}
ActivityRecord r = new ActivityRecord(mService, callerApp, callingUid, callingPackage,
intent, resolvedType, aInfo, mService.mConfiguration, resultRecord, resultWho,
requestCode, componentSpecified, voiceSession != null, mSupervisor, container,
options, sourceRecord);
if (outActivity != null) {
outActivity[0] = r;
}
if (r.appTimeTracker == null && sourceRecord != null) {
r.appTimeTracker = sourceRecord.appTimeTracker;
}
final ActivityStack stack = mSupervisor.mFocusedStack;
if (voiceSession == null && (stack.mResumedActivity == null
|| stack.mResumedActivity.info.applicationInfo.uid != callingUid)) {
if (!mService.checkAppSwitchAllowedLocked(callingPid, callingUid,
realCallingPid, realCallingUid, "Activity start")) {
PendingActivityLaunch pal = new PendingActivityLaunch(r,
sourceRecord, startFlags, stack, callerApp);
mPendingActivityLaunches.add(pal);
ActivityOptions.abort(options);
return ActivityManager.START_SWITCHES_CANCELED;
}
}
if (mService.mDidAppSwitch) {
mService.mAppSwitchesAllowedTime = 0;
} else {
mService.mDidAppSwitch = true;
}
doPendingActivityLaunchesLocked(false);
try {
mService.mWindowManager.deferSurfaceLayout();
err = startActivityUnchecked(r, sourceRecord, voiceSession, voiceInteractor, startFlags,
true, options, inTask);
} finally {
mService.mWindowManager.continueSurfaceLayout();
}
postStartActivityUncheckedProcessing(r, err, stack.mStackId, mSourceRecord, mTargetStack);
return err;
}最后经过层层调用，到达：ActivityStack.startActivityLocked()。
5. ActivityStack
/base/services/core/java/com/android/server/am/ActivityStack.java
/**
* 启动Activity
*
* WMS.moveTaskToTop：将Window相应task移至顶部；
* WMS.addAppToken：创建AppWindowToken对象atoken，并添加到mTokenMap;
* WMS.prepareAppTransition：设置transition方式以及5s超时消息；
* WMS.setAppStartingWindow：创建startingData启动数据，并发送消息到”android.display”线程来处理ADD_STARTING消息。
*
* @param r
* @param newTask
* @param keepCurTransition
* @param options
*/
final void startActivityLocked(ActivityRecord r, boolean newTask, boolean keepCurTransition,
ActivityOptions options) {
TaskRecord rTask = r.task;
final int taskId = rTask.taskId;
// mLaunchTaskBehind tasks get placed at the back of the task stack.
if (!r.mLaunchTaskBehind && (taskForIdLocked(taskId) == null || newTask)) {
// Last activity in task had been removed or ActivityManagerService is reusing task.
// Insert or replace.
// Might not even be in.
insertTaskAtTop(rTask, r);
// 将Window相应task移至顶部，调用WindowManagerService
mWindowManager.moveTaskToTop(taskId);
}
TaskRecord task = null;
if (!newTask) {
// If starting in an existing task, find where that is...
boolean startIt = true;
for (int taskNdx = mTaskHistory.size() - 1; taskNdx >= 0; --taskNdx) {
task = mTaskHistory.get(taskNdx);
if (task.getTopActivity() == null) {
continue;
}
if (task == r.task) {
if (!startIt) {
task.addActivityToTop(r);
r.putInHistory();
// 创建AppWindowToken对象
addConfigOverride(r, task);
if (VALIDATE_TOKENS) {
validateAppTokensLocked();
}
ActivityOptions.abort(options);
return;
}
break;
} else if (task.numFullscreen > 0) {
startIt = false;
}
}
}
if (task == r.task && mTaskHistory.indexOf(task) != (mTaskHistory.size() - 1)) {
mStackSupervisor.mUserLeaving = false;
if (DEBUG_USER_LEAVING) Slog.v(TAG_USER_LEAVING,
"startActivity() behind front, mUserLeaving=false");
}
task = r.task;
task.addActivityToTop(r);
task.setFrontOfTask();
r.putInHistory();
if (!isHomeStack() || numActivities() > 0) {
boolean showStartingIcon = newTask;
ProcessRecord proc = r.app;
if (proc == null) {
proc = mService.mProcessNames.get(r.processName, r.info.applicationInfo.uid);
}
if (proc == null || proc.thread == null) {
showStartingIcon = true;
}
if (DEBUG_TRANSITION) Slog.v(TAG_TRANSITION,
"Prepare open transition: starting " + r);
// 准备window动画，进入，移除动画等
if ((r.intent.getFlags() & Intent.FLAG_ACTIVITY_NO_ANIMATION) != 0) {
mWindowManager.prepareAppTransition(TRANSIT_NONE, keepCurTransition);
mNoAnimActivities.add(r);
} else {
mWindowManager.prepareAppTransition(newTask
? r.mLaunchTaskBehind
? TRANSIT_TASK_OPEN_BEHIND
: TRANSIT_TASK_OPEN
: TRANSIT_ACTIVITY_OPEN, keepCurTransition);
mNoAnimActivities.remove(r);
}
addConfigOverride(r, task);
boolean doShow = true;
if (newTask) {
if ((r.intent.getFlags() & Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED) != 0) {
resetTaskIfNeededLocked(r, r);
doShow = topRunningNonDelayedActivityLocked(null) == r;
}
} else if (options != null && options.getAnimationType()
== ActivityOptions.ANIM_SCENE_TRANSITION) {
doShow = false;
}
if (r.mLaunchTaskBehind) {
// Don't do a starting window for mLaunchTaskBehind. More importantly make sure we
// tell WindowManager that r is visible even though it is at the back of the stack.
mWindowManager.setAppVisibility(r.appToken, true);
ensureActivitiesVisibleLocked(null, 0, !PRESERVE_WINDOWS);
} else if (SHOW_APP_STARTING_PREVIEW && doShow) {
ActivityRecord prev = r.task.topRunningActivityWithStartingWindowLocked();
if (prev != null) {
if (prev.task != r.task) {
prev = null;
}
else if (prev.nowVisible) {
prev = null;
}
}
r.showStartingWindow(prev, showStartingIcon);
}
} else {
addConfigOverride(r, task);
ActivityOptions.abort(options);
options = null;
}
if (VALIDATE_TOKENS) {
validateAppTokensLocked();
}
}private boolean resumeTopActivityInnerLocked(ActivityRecord prev, ActivityOptions options) {
if (!mService.mBooting && !mService.mBooted) {
return false;
}
ActivityRecord parent = mActivityContainer.mParentActivity;
if ((parent != null && parent.state != ActivityState.RESUMED) ||
!mActivityContainer.isAttachedLocked()) {
return false;
}
mStackSupervisor.cancelInitializingActivities();
final ActivityRecord next = topRunningActivityLocked();
final boolean userLeaving = mStackSupervisor.mUserLeaving;
mStackSupervisor.mUserLeaving = false;
final TaskRecord prevTask = prev != null ? prev.task : null;
if (next == null) {
final String reason = "noMoreActivities";
final int returnTaskType = prevTask == null || !prevTask.isOverHomeStack()
? HOME_ACTIVITY_TYPE : prevTask.getTaskToReturnTo();
if (!mFullscreen && adjustFocusToNextFocusableStackLocked(returnTaskType, reason)) {
return mStackSupervisor.resumeFocusedStackTopActivityLocked(
mStackSupervisor.getFocusedStack(), prev, null);
}
ActivityOptions.abort(options);
if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
return isOnHomeDisplay() &&
mStackSupervisor.resumeHomeStackTask(returnTaskType, prev, reason);
}
next.delayedResume = false;
if (mResumedActivity == next && next.state == ActivityState.RESUMED &&
mStackSupervisor.allResumedActivitiesComplete()) {
mWindowManager.executeAppTransition();
mNoAnimActivities.clear();
ActivityOptions.abort(options);
return false;
}
final TaskRecord nextTask = next.task;
if (prevTask != null && prevTask.stack == this &&
prevTask.isOverHomeStack() && prev.finishing && prev.frontOfTask) {
if (prevTask == nextTask) {
prevTask.setFrontOfTask();
} else if (prevTask != topTask()) {
final int taskNdx = mTaskHistory.indexOf(prevTask) + 1;
mTaskHistory.get(taskNdx).setTaskToReturnTo(HOME_ACTIVITY_TYPE);
} else if (!isOnHomeDisplay()) {
return false;
} else if (!isHomeStack()){
if (DEBUG_STATES) Slog.d(TAG_STATES,
"resumeTopActivityLocked: Launching home next");
final int returnTaskType = prevTask == null || !prevTask.isOverHomeStack() ?
HOME_ACTIVITY_TYPE : prevTask.getTaskToReturnTo();
return isOnHomeDisplay() &&
mStackSupervisor.resumeHomeStackTask(returnTaskType, prev, "prevFinished");
}
}
mStackSupervisor.mStoppingActivities.remove(next);
mStackSupervisor.mGoingToSleepActivities.remove(next);
next.sleeping = false;
mStackSupervisor.mWaitingVisibleActivities.remove(next);
if (DEBUG_SWITCH) Slog.v(TAG_SWITCH, "Resuming " + next);
if (!mStackSupervisor.allPausedActivitiesComplete()) {
if (DEBUG_SWITCH || DEBUG_PAUSE || DEBUG_STATES) Slog.v(TAG_PAUSE,
"resumeTopActivityLocked: Skip resume: some activity pausing.");
if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
return false;
}
mStackSupervisor.setLaunchSource(next.info.applicationInfo.uid);
// We need to start pausing the current activity so the top one can be resumed...
final boolean dontWaitForPause = (next.info.flags & FLAG_RESUME_WHILE_PAUSING) != 0;
boolean pausing = mStackSupervisor.pauseBackStacks(userLeaving, true, dontWaitForPause);
if (mResumedActivity != null) {
if (DEBUG_STATES) Slog.d(TAG_STATES,
"resumeTopActivityLocked: Pausing " + mResumedActivity);
pausing |= startPausingLocked(userLeaving, false, true, dontWaitForPause);
}
if (pausing) {
if (next.app != null && next.app.thread != null) {
mService.updateLruProcessLocked(next.app, true, null);
}
if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
return true;
} else if (mResumedActivity == next && next.state == ActivityState.RESUMED &&
mStackSupervisor.allResumedActivitiesComplete()) {
mWindowManager.executeAppTransition();
mNoAnimActivities.clear();
ActivityOptions.abort(options);
if (DEBUG_STATES) Slog.d(TAG_STATES,
"resumeTopActivityLocked: Top activity resumed (dontWaitForPause) " + next);
if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
return true;
}
if (mService.isSleepingLocked() && mLastNoHistoryActivity != null &&
!mLastNoHistoryActivity.finishing) {
if (DEBUG_STATES) Slog.d(TAG_STATES,
"no-history finish of " + mLastNoHistoryActivity + " on new resume");
requestFinishActivityLocked(mLastNoHistoryActivity.appToken, Activity.RESULT_CANCELED,
null, "resume-no-history", false);
mLastNoHistoryActivity = null;
}
if (prev != null && prev != next) {
if (!mStackSupervisor.mWaitingVisibleActivities.contains(prev)
&& next != null && !next.nowVisible) {
mStackSupervisor.mWaitingVisibleActivities.add(prev);
if (DEBUG_SWITCH) Slog.v(TAG_SWITCH,
"Resuming top, waiting visible to hide: " + prev);
} else {
//...
}
}
try {
AppGlobals.getPackageManager().setPackageStoppedState(
next.packageName, false, next.userId); /* TODO: Verify if correct userid */
} catch (RemoteException e1) {
} catch (IllegalArgumentException e) {
Slog.w(TAG, "Failed trying to unstop package "
+ next.packageName + ": " + e);
}
boolean anim = true;
if (prev != null) {
if (prev.finishing) {
if (DEBUG_TRANSITION) Slog.v(TAG_TRANSITION,
"Prepare close transition: prev=" + prev);
if (mNoAnimActivities.contains(prev)) {
anim = false;
mWindowManager.prepareAppTransition(TRANSIT_NONE, false);
} else {
mWindowManager.prepareAppTransition(prev.task == next.task
? TRANSIT_ACTIVITY_CLOSE
: TRANSIT_TASK_CLOSE, false);
}
mWindowManager.setAppVisibility(prev.appToken, false);
} else {
if (DEBUG_TRANSITION) Slog.v(TAG_TRANSITION,
"Prepare open transition: prev=" + prev);
if (mNoAnimActivities.contains(next)) {
anim = false;
mWindowManager.prepareAppTransition(TRANSIT_NONE, false);
} else {
mWindowManager.prepareAppTransition(prev.task == next.task
? TRANSIT_ACTIVITY_OPEN
: next.mLaunchTaskBehind
? TRANSIT_TASK_OPEN_BEHIND
: TRANSIT_TASK_OPEN, false);
}
}
} else {
if (DEBUG_TRANSITION) Slog.v(TAG_TRANSITION, "Prepare open transition: no previous");
if (mNoAnimActivities.contains(next)) {
anim = false;
mWindowManager.prepareAppTransition(TRANSIT_NONE, false);
} else {
mWindowManager.prepareAppTransition(TRANSIT_ACTIVITY_OPEN, false);
}
}
Bundle resumeAnimOptions = null;
if (anim) {
ActivityOptions opts = next.getOptionsForTargetActivityLocked();
if (opts != null) {
resumeAnimOptions = opts.toBundle();
}
next.applyOptionsLocked();
} else {
next.clearOptionsLocked();
}
ActivityStack lastStack = mStackSupervisor.getLastStack();
if (next.app != null && next.app.thread != null) {
final boolean lastActivityTranslucent = lastStack != null
&& (!lastStack.mFullscreen
|| (lastStack.mLastPausedActivity != null
&& !lastStack.mLastPausedActivity.fullscreen));
// This activity is now becoming visible.
if (!next.visible || next.stopped || lastActivityTranslucent) {
mWindowManager.setAppVisibility(next.appToken, true);
}
// schedule launch ticks to collect information about slow apps.
next.startLaunchTickingLocked();
ActivityRecord lastResumedActivity =
lastStack == null ? null :lastStack.mResumedActivity;
ActivityState lastState = next.state;
mService.updateCpuStats();
if (DEBUG_STATES) Slog.v(TAG_STATES, "Moving to RESUMED: " + next + " (in existing)");
next.state = ActivityState.RESUMED;
mResumedActivity = next;
next.task.touchActiveTime();
mRecentTasks.addLocked(next.task);
mService.updateLruProcessLocked(next.app, true, null);
updateLRUListLocked(next);
mService.updateOomAdjLocked();
// Have the window manager re-evaluate the orientation of
// the screen based on the new activity order.
boolean notUpdated = true;
if (mStackSupervisor.isFocusedStack(this)) {
Configuration config = mWindowManager.updateOrientationFromAppTokens(
mService.mConfiguration,
next.mayFreezeScreenLocked(next.app) ? next.appToken : null);
if (config != null) {
next.frozenBeforeDestroy = true;
}
notUpdated = !mService.updateConfigurationLocked(config, next, false);
}
if (notUpdated) {
if (nextNext != next) {
// Do over!
mStackSupervisor.scheduleResumeTopActivities();
}
if (mStackSupervisor.reportResumedActivityLocked(next)) {
mNoAnimActivities.clear();
if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
return true;
}
if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
return false;
}
try {
// Deliver all pending results.
ArrayList<ResultInfo> a = next.results;
if (a != null) {
final int N = a.size();
if (!next.finishing && N > 0) {
if (DEBUG_RESULTS) Slog.v(TAG_RESULTS,
"Delivering results to " + next + ": " + a);
next.app.thread.scheduleSendResult(next.appToken, a);
}
}
if (next.newIntents != null) {
next.app.thread.scheduleNewIntent(next.newIntents, next.appToken);
}
// Well the app will no longer be stopped.
// Clear app token stopped state in window manager if needed.
mWindowManager.notifyAppStopped(next.appToken, false);
EventLog.writeEvent(EventLogTags.AM_RESUME_ACTIVITY, next.userId,
System.identityHashCode(next), next.task.taskId, next.shortComponentName);
next.sleeping = false;
mService.showUnsupportedZoomDialogIfNeededLocked(next);
mService.showAskCompatModeDialogLocked(next);
next.app.pendingUiClean = true;
next.app.forceProcessStateUpTo(mService.mTopProcessState);
next.clearOptionsLocked();
next.app.thread.scheduleResumeActivity(next.appToken, next.app.repProcState,
mService.isNextTransitionForward(), resumeAnimOptions);
mStackSupervisor.checkReadyForSleepLocked();
if (DEBUG_STATES) Slog.d(TAG_STATES, "resumeTopActivityLocked: Resumed " + next);
} catch (Exception e) {
// Whoops, need to restart this activity!
if (DEBUG_STATES) Slog.v(TAG_STATES, "Resume failed; resetting state to "
+ lastState + ": " + next);
next.state = lastState;
if (lastStack != null) {
lastStack.mResumedActivity = lastResumedActivity;
}
Slog.i(TAG, "Restarting because process died: " + next);
if (!next.hasBeenLaunched) {
next.hasBeenLaunched = true;
} else if (SHOW_APP_STARTING_PREVIEW && lastStack != null &&
mStackSupervisor.isFrontStack(lastStack)) {
next.showStartingWindow(null, true);
}
mStackSupervisor.startSpecificActivityLocked(next, true, false);
if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
return true;
}
// From this point on, if something goes wrong there is no way
// to recover the activity.
try {
completeResumeLocked(next);
} catch (Exception e) {
// If any exception gets thrown, toss away this
// activity and try the next one.
Slog.w(TAG, "Exception thrown during resume of " + next, e);
requestFinishActivityLocked(next.appToken, Activity.RESULT_CANCELED, null,
"resume-exception", true);
if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
return true;
}
} else {
// Whoops, need to restart this activity!
if (!next.hasBeenLaunched) {
next.hasBeenLaunched = true;
} else {
if (SHOW_APP_STARTING_PREVIEW) {
next.showStartingWindow(null, true);
}
if (DEBUG_SWITCH) Slog.v(TAG_SWITCH, "Restarting: " + next);
}
if (DEBUG_STATES) Slog.d(TAG_STATES, "resumeTopActivityLocked: Restarting " + next);
mStackSupervisor.startSpecificActivityLocked(next, true, true);
}
if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
return true;
}最后经过层层调用，终于到达 ActivityManagerService.startProcessLocked()。
6. ActivityManagerService
/base/services/core/java/com/android/server/am/ActivityManagerService.java
在 Framework篇 - 四大组件与进程启动的关系 这篇文章中，详细介绍了 ActivityManagerService.startProcessLocked() 整个过程，创建完新进程后会在新进程中调用 ActivityManagerProxy.attachApplication() ，该方法经过 Binder IPC 后调用到 ActivityManagerService.attachApplicationLocked()。
boolean attachApplicationLocked(ProcessRecord app) throws RemoteException {
final String processName = app.processName;
boolean didSomething = false;
for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {
ArrayList<ActivityStack> stacks = mActivityDisplays.valueAt(displayNdx).mStacks;
for (int stackNdx = stacks.size() - 1; stackNdx >= 0; --stackNdx) {
final ActivityStack stack = stacks.get(stackNdx);
if (!isFrontStack(stack)) {
continue;
}
//获取前台stack中栈顶第一个非finishing的Activity
ActivityRecord hr = stack.topRunningActivityLocked(null);
if (hr != null) {
if (hr.app == null && app.uid == hr.info.applicationInfo.uid
&& processName.equals(hr.processName)) {
try {
//真正的启动Activity
if (realStartActivityLocked(hr, app, true, true)) {
didSomething = true;
}
} catch (RemoteException e) {
throw e;
}
}
}
}
}
if (!didSomething) {
//启动Activity不成功，则确保有可见的Activity
ensureActivitiesVisibleLocked(null, 0);
}
return didSomething;
}final boolean realStartActivityLocked(ActivityRecord r, ProcessRecord app, boolean andResume, boolean checkConfig) throws RemoteException {
if (andResume) {
r.startFreezingScreenLocked(app, 0);
mWindowManager.setAppVisibility(r.appToken, true);
//调度启动ticks用以收集应用启动慢的信息
r.startLaunchTickingLocked();
}
if (checkConfig) {
Configuration config = mWindowManager.updateOrientationFromAppTokens(
mService.mConfiguration,
r.mayFreezeScreenLocked(app) ? r.appToken : null);
//更新Configuration
mService.updateConfigurationLocked(config, r, false, false);
}
r.app = app;
app.waitingToKill = null;
r.launchCount++;
r.lastLaunchTime = SystemClock.uptimeMillis();
int idx = app.activities.indexOf(r);
if (idx < 0) {
app.activities.add(r);
}
mService.updateLruProcessLocked(app, true, null);
mService.updateOomAdjLocked();
final TaskRecord task = r.task;
if (task.mLockTaskAuth == LOCK_TASK_AUTH_LAUNCHABLE ||
task.mLockTaskAuth == LOCK_TASK_AUTH_LAUNCHABLE_PRIV) {
setLockTaskModeLocked(task, LOCK_TASK_MODE_LOCKED, "mLockTaskAuth==LAUNCHABLE", false);
}
final ActivityStack stack = task.stack;
try {
if (app.thread == null) {
throw new RemoteException();
}
List<ResultInfo> results = null;
List<ReferrerIntent> newIntents = null;
if (andResume) {
results = r.results;
newIntents = r.newIntents;
}
if (r.isHomeActivity() && r.isNotResolverActivity()) {
//home进程是该栈的根进程
mService.mHomeProcess = task.mActivities.get(0).app;
}
mService.ensurePackageDexOpt(r.intent.getComponent().getPackageName());
...
if (andResume) {
app.hasShownUi = true;
app.pendingUiClean = true;
}
//将该进程设置为前台进程PROCESS_STATE_TOP
app.forceProcessStateUpTo(mService.mTopProcessState);
app.thread.scheduleLaunchActivity(new Intent(r.intent), r.appToken,
System.identityHashCode(r), r.info, new Configuration(mService.mConfiguration),
new Configuration(stack.mOverrideConfig), r.compat, r.launchedFromPackage,
task.voiceInteractor, app.repProcState, r.icicle, r.persistentState, results,
newIntents, !andResume, mService.isNextTransitionForward(), profilerInfo);
if ((app.info.privateFlags&ApplicationInfo.PRIVATE_FLAG_CANT_SAVE_STATE) != 0) {
... //处理heavy-weight进程
}
} catch (RemoteException e) {
if (r.launchFailed) {
//第二次启动失败，则结束该activity
mService.appDiedLocked(app);
stack.requestFinishActivityLocked(r.appToken, Activity.RESULT_CANCELED, null,
"2nd-crash", false);
return false;
}
//这是第一个启动失败，则重启进程
app.activities.remove(r);
throw e;
}
//将该进程加入到mLRUActivities队列顶部
stack.updateLRUListLocked(r)；
if (andResume) {
//启动过程的一部分
stack.minimalResumeActivityLocked(r);
} else {
r.state = STOPPED;
r.stopped = true;
}
if (isFrontStack(stack)) {
//当系统发生更新时，只会执行一次的用户向导
mService.startSetupActivityLocked();
}
//更新所有与该Activity具有绑定关系的Service连接
mService.mServices.updateServiceConnectionActivitiesLocked(r.app);
return true;
}里面调用了 ApplicationThreadProxy.scheduleLaunchActivity()。
7. ApplicationThreadProxy
/base/core/java/android/app/ApplicationThreadNative.java
public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident,
ActivityInfo info, Configuration curConfig, Configuration overrideConfig,
CompatibilityInfo compatInfo, String referrer, IVoiceInteractor voiceInteractor,
int procState, Bundle state, PersistableBundle persistentState,
List<ResultInfo> pendingResults, List<ReferrerIntent> pendingNewIntents,
boolean notResumed, boolean isForward, ProfilerInfo profilerInfo) throws RemoteException {
Parcel data = Parcel.obtain();
data.writeInterfaceToken(IApplicationThread.descriptor);
intent.writeToParcel(data, 0);
data.writeStrongBinder(token);
data.writeInt(ident);
info.writeToParcel(data, 0);
curConfig.writeToParcel(data, 0);
if (overrideConfig != null) {
data.writeInt(1);
overrideConfig.writeToParcel(data, 0);
} else {
data.writeInt(0);
}
compatInfo.writeToParcel(data, 0);
data.writeString(referrer);
data.writeStrongBinder(voiceInteractor != null ? voiceInteractor.asBinder() : null);
data.writeInt(procState);
data.writeBundle(state);
data.writePersistableBundle(persistentState);
data.writeTypedList(pendingResults);
data.writeTypedList(pendingNewIntents);
data.writeInt(notResumed ? 1 : 0);
data.writeInt(isForward ? 1 : 0);
if (profilerInfo != null) {
data.writeInt(1);
profilerInfo.writeToParcel(data, Parcelable.PARCELABLE_WRITE_RETURN_VALUE);
} else {
data.writeInt(0);
}
mRemote.transact(SCHEDULE_LAUNCH_ACTIVITY_TRANSACTION, data, null,
IBinder.FLAG_ONEWAY);
data.recycle();
}IPC 到 ActivityManagerNative 的 onTransaction():
@Override
public boolean onTransact(int code, Parcel data, Parcel reply, int flags)
throws RemoteException {
//...
case SCHEDULE_LAUNCH_ACTIVITY_TRANSACTION:
{
data.enforceInterface(IApplicationThread.descriptor);
Intent intent = Intent.CREATOR.createFromParcel(data);
IBinder b = data.readStrongBinder();
int ident = data.readInt();
ActivityInfo info = ActivityInfo.CREATOR.createFromParcel(data);
Configuration curConfig = Configuration.CREATOR.createFromParcel(data);
Configuration overrideConfig = null;
if (data.readInt() != 0) {
overrideConfig = Configuration.CREATOR.createFromParcel(data);
}
CompatibilityInfo compatInfo = CompatibilityInfo.CREATOR.createFromParcel(data);
String referrer = data.readString();
IVoiceInteractor voiceInteractor = IVoiceInteractor.Stub.asInterface(
data.readStrongBinder());
int procState = data.readInt();
Bundle state = data.readBundle();
PersistableBundle persistentState = data.readPersistableBundle();
List<ResultInfo> ri = data.createTypedArrayList(ResultInfo.CREATOR);
List<ReferrerIntent> pi = data.createTypedArrayList(ReferrerIntent.CREATOR);
boolean notResumed = data.readInt() != 0;
boolean isForward = data.readInt() != 0;
ProfilerInfo profilerInfo = data.readInt() != 0
? ProfilerInfo.CREATOR.createFromParcel(data) : null;
scheduleLaunchActivity(intent, b, ident, info, curConfig, overrideConfig, compatInfo,
referrer, voiceInteractor, procState, state, persistentState, ri, pi,
notResumed, isForward, profilerInfo);
return true;
}
}
8. ActivityThread (内部有 ApplicationThread 内部类)
/base/core/java/android/app/ActivityThread.java
public final class ActivityThread {
private class ApplicationThread extends ApplicationThreadNative {
@Override
public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident,
ActivityInfo info, Configuration curConfig, Configuration overrideConfig,
CompatibilityInfo compatInfo, String referrer, IVoiceInteractor voiceInteractor,
int procState, Bundle state, PersistableBundle persistentState,
List<ResultInfo> pendingResults, List<ReferrerIntent> pendingNewIntents,
boolean notResumed, boolean isForward, ProfilerInfo profilerInfo) {
updateProcessState(procState, false);
ActivityClientRecord r = new ActivityClientRecord();
r.token = token;
r.ident = ident;
r.intent = intent;
r.referrer = referrer;
r.voiceInteractor = voiceInteractor;
r.activityInfo = info;
r.compatInfo = compatInfo;
r.state = state;
r.persistentState = persistentState;
r.pendingResults = pendingResults;
r.pendingIntents = pendingNewIntents;
r.startsNotResumed = notResumed;
r.isForward = isForward;
r.profilerInfo = profilerInfo;
r.overrideConfig = overrideConfig;
updatePendingConfiguration(curConfig);
sendMessage(H.LAUNCH_ACTIVITY, r);
}
}
}会发送消息到 ActivityThread 的 H 类：
private class H extends Handler {
//...
case LAUNCH_ACTIVITY: {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStart");
final ActivityClientRecord r = (ActivityClientRecord) msg.obj;
r.packageInfo = getPackageInfoNoCheck(
r.activityInfo.applicationInfo, r.compatInfo);
handleLaunchActivity(r, null, "LAUNCH_ACTIVITY");
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
} break;
}然后会调用 ActivityThread.handleLauchActivity()：
private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent, String reason) {
unscheduleGcIdler();
mSomeActivitiesChanged = true;
if (r.profilerInfo != null) {
mProfiler.setProfiler(r.profilerInfo);
mProfiler.startProfiling();
}
handleConfigurationChanged(null, null);
WindowManagerGlobal.initialize();
Activity a = performLaunchActivity(r, customIntent);
if (a != null) {
r.createdConfig = new Configuration(mConfiguration);
reportSizeConfigurations(r);
Bundle oldState = r.state;
handleResumeActivity(r.token, false, r.isForward,
!r.activity.mFinished && !r.startsNotResumed, r.lastProcessedSeq, reason);
if (!r.activity.mFinished && r.startsNotResumed) {
performPauseActivityIfNeeded(r, reason);
if (r.isPreHoneycomb()) {
r.state = oldState;
}
}
} else {
try {
ActivityManagerNative.getDefault()
.finishActivity(r.token, Activity.RESULT_CANCELED, null,
Activity.DONT_FINISH_TASK_WITH_ACTIVITY);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
}
}
然后调用 ActivityThread 的 performLaunchActivity():
/**
* 该方法主要功能：
*
* 创建LoadedApk对象;
* 创建ComponentName对象;
* 获取ClassLoader;
* 创建目标Activity对象;
* 创建Application对象;
* 回调onCreate()，一般地该方法内执行setContentView()操作；
*
* @param r
* @param customIntent
* @return
*/
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
// System.out.println("##### [" + System.currentTimeMillis() + "] ActivityThread.performLaunchActivity(" + r + ")");
ActivityInfo aInfo = r.activityInfo;
if (r.packageInfo == null) {
// 创建LoadedApk对象
r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,
Context.CONTEXT_INCLUDE_CODE);
}
ComponentName component = r.intent.getComponent();
if (component == null) {
component = r.intent.resolveActivity(
mInitialApplication.getPackageManager());
r.intent.setComponent(component);
}
if (r.activityInfo.targetActivity != null) {
// 创建ComponentName对象
component = new ComponentName(r.activityInfo.packageName,
r.activityInfo.targetActivity);
}
Activity activity = null;
try {
// 获取ClassLoader
java.lang.ClassLoader cl = r.packageInfo.getClassLoader();
// 创建目标Activity对象，反射调用
activity = mInstrumentation.newActivity(
cl, component.getClassName(), r.intent);
StrictMode.incrementExpectedActivityCount(activity.getClass());
r.intent.setExtrasClassLoader(cl);
r.intent.prepareToEnterProcess();
if (r.state != null) {
r.state.setClassLoader(cl);
}
} catch (Exception e) {
if (!mInstrumentation.onException(activity, e)) {
throw new RuntimeException(
"Unable to instantiate activity " + component
+ ": " + e.toString(), e);
}
}
try {
// 创建Application对象
Application app = r.packageInfo.makeApplication(false, mInstrumentation);
if (localLOGV) Slog.v(TAG, "Performing launch of " + r);
if (localLOGV) Slog.v(
TAG, r + ": app=" + app
+ ", appName=" + app.getPackageName()
+ ", pkg=" + r.packageInfo.getPackageName()
+ ", comp=" + r.intent.getComponent().toShortString()
+ ", dir=" + r.packageInfo.getAppDir());
if (activity != null) {
Context appContext = createBaseContextForActivity(r, activity);
CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());
Configuration config = new Configuration(mCompatConfiguration);
if (r.overrideConfig != null) {
config.updateFrom(r.overrideConfig);
}
if (DEBUG_CONFIGURATION) Slog.v(TAG, "Launching activity "
+ r.activityInfo.name + " with config " + config);
Window window = null;
if (r.mPendingRemoveWindow != null && r.mPreserveWindow) {
window = r.mPendingRemoveWindow;
r.mPendingRemoveWindow = null;
r.mPendingRemoveWindowManager = null;
}
// 变量赋值操作
activity.attach(appContext, this, getInstrumentation(), r.token,
r.ident, app, r.intent, r.activityInfo, title, r.parent,
r.embeddedID, r.lastNonConfigurationInstances, config,
r.referrer, r.voiceInteractor, window);
if (customIntent != null) {
activity.mIntent = customIntent;
}
r.lastNonConfigurationInstances = null;
activity.mStartedActivity = false;
int theme = r.activityInfo.getThemeResource();
if (theme != 0) {
activity.setTheme(theme);
}
activity.mCalled = false;
// 回掉Activity的onCreate()方法，调用Instrumentation类
if (r.isPersistable()) {
mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
} else {
mInstrumentation.callActivityOnCreate(activity, r.state);
}
if (!activity.mCalled) {
throw new SuperNotCalledException(
"Activity " + r.intent.getComponent().toShortString() +
" did not call through to super.onCreate()");
}
r.activity = activity;
r.stopped = true;
if (!r.activity.mFinished) {
activity.performStart();
r.stopped = false;
}
if (!r.activity.mFinished) {
if (r.isPersistable()) {
if (r.state != null || r.persistentState != null) {
mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state,
r.persistentState);
}
} else if (r.state != null) {
mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);
}
}
if (!r.activity.mFinished) {
activity.mCalled = false;
if (r.isPersistable()) {
mInstrumentation.callActivityOnPostCreate(activity, r.state,
r.persistentState);
} else {
mInstrumentation.callActivityOnPostCreate(activity, r.state);
}
if (!activity.mCalled) {
throw new SuperNotCalledException(
"Activity " + r.intent.getComponent().toShortString() +
" did not call through to super.onPostCreate()");
}
}
}
r.paused = true;
mActivities.put(r.token, r);
} catch (SuperNotCalledException e) {
throw e;
} catch (Exception e) {
if (!mInstrumentation.onException(activity, e)) {
throw new RuntimeException(
"Unable to start activity " + component
+ ": " + e.toString(), e);
}
}
return activity;
}到此，正式进入了 Activity 的 onCreate，onStart，onResume 这些生命周期的过程，具体分析 Framework篇 - 四大组件与进程启动的关系 这篇文章中都有。
9. 总结
- 点击桌面 App 图标，Launcher 进程采用 Binder IPC 向 system_server 进程发起 startActivity 请求；
- system_server 进程接收到请求后，向 zygote 进程发送创建进程的请求；
- Zygote 进程 fork 出新的子进程，即 App 进程；
- App 进程，通过 Binder IPC 向 sytem_server 进程发起 attachApplication 请求；
- system_server 进程在收到请求后，进行一系列准备工作后，再通过 binder IPC 向 App 进程发送 scheduleLaunchActivity 请求；
- App 进程的 Binder 线程 (ApplicationThread) 在收到请求后，通过 handler 向主线程发送 LAUNCH_ACTIVITY 消息；
- 主线程在收到 Message 后，通过发射机制创建目标 Activity，并回调 Activity.onCreate() 等方法；
- 到此，App 便正式启动，开始进入 Activity 生命周期，执行完 onCreate/onStart/onResume 方法，UI 渲染结束后便可以看到App 的主界面。
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