每一个Activity组件都有一个关联的Window对象,用来描述一个应用程序窗口。每一个应用程序窗口内部又包含有一个View对象,用来描述应用程序窗口的视图。应用程序窗口视图是真正用来实现UI内容和布局的,也就是说,每一个Activity组件的UI内容和布局都是通过与其所关联的一个Window对象的内部的一个View对象来实现的。在本文中,我们就详细分析应用程序窗口视图的创建过程。
应用程序窗口内部所包含的视图对象的实际类型为DecorView。DecorView类继承了View类,是作为容器(ViewGroup)来使用的,它的实现如图
每一个Activity对象都有一个关联的ViewRootImpl对象,相当于是MVC模型中的Controller,它有以下职责:
1. 负责为应用程序窗口视图创建Surface。
2. 配合WindowManagerService来管理系统的应用程序窗口。
3. 负责管理、布局和渲染应用程序窗口视图的UI。
从前面Android应用程序启动过程源代码分析一文可以知道,Activity组件在启动的过程中,会调用ActivityThread类的成员函数handleLaunchActivity,用来创建以及首次激活Activity组件,因此,接下来我们就从这个函数开始,具体分析应用程序窗口的视图对象及其所关联的ViewRootImpl对象的创建过程,如图所示
setContentView中创建DecorView对象
一般在Activity的子类的onCreate方法中都会实现setContentView函数,我们来看Activity的这个函数:
public void setContentView(View view) {
getWindow().setContentView(view);
initWindowDecorActionBar();
}
调用了PhoneWindow的setContentView函数,而在这个函数中调用了installDecor函数来创建DecorView对象
@Override
public void setContentView(View view, ViewGroup.LayoutParams params) {
// Note: FEATURE_CONTENT_TRANSITIONS may be set in the process of installing the window
// decor, when theme attributes and the like are crystalized. Do not check the feature
// before this happens.
if (mContentParent == null) {
installDecor();
} else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
mContentParent.removeAllViews();
}
if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
view.setLayoutParams(params);
final Scene newScene = new Scene(mContentParent, view);
transitionTo(newScene);
} else {
mContentParent.addView(view, params);
}
mContentParent.requestApplyInsets();
final Callback cb = getCallback();
if (cb != null && !isDestroyed()) {
cb.onContentChanged();
}
}
在installDecor函数中调用了generateDecor函数来创建DecorView
private void installDecor() {
if (mDecor == null) {
mDecor = generateDecor();
......
protected DecorView generateDecor() {
return new DecorView(getContext(), -1);
}
创建ViewRootImpl对象
下面我们再从ActivityThread的handleResumeActivity函数看,先调用了performResumeActivity函数来查找这个Activity,后面主要调用了WindowManager的addView函数。
final void handleResumeActivity(IBinder token,
boolean clearHide, boolean isForward, boolean reallyResume) {
// If we are getting ready to gc after going to the background, well
// we are back active so skip it.
unscheduleGcIdler();
mSomeActivitiesChanged = true;
// TODO Push resumeArgs into the activity for consideration
ActivityClientRecord r = performResumeActivity(token, clearHide);
if (r != null) {
final Activity a = r.activity;
if (localLOGV) Slog.v(
TAG, "Resume " + r + " started activity: " +
a.mStartedActivity + ", hideForNow: " + r.hideForNow
+ ", finished: " + a.mFinished);
final int forwardBit = isForward ?
WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION : 0;
// If the window hasn't yet been added to the window manager,
// and this guy didn't finish itself or start another activity,
// then go ahead and add the window.
boolean willBeVisible = !a.mStartedActivity;
if (!willBeVisible) {
try {
willBeVisible = ActivityManagerNative.getDefault().willActivityBeVisible(
a.getActivityToken());
} catch (RemoteException e) {
}
}
if (r.window == null && !a.mFinished && willBeVisible) {
r.window = r.activity.getWindow();
View decor = r.window.getDecorView();
decor.setVisibility(View.INVISIBLE);
ViewManager wm = a.getWindowManager();
WindowManager.LayoutParams l = r.window.getAttributes();
a.mDecor = decor;
l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;
l.softInputMode |= forwardBit;
if (a.mVisibleFromClient) {
a.mWindowAdded = true;
wm.addView(decor, l);
}
我们先来看performResumeActivity函数,这个函数主要是根据token来寻找ActivityClientRecord,然后调用了Activity的performResume方法。
public final ActivityClientRecord performResumeActivity(IBinder token,
boolean clearHide) {
ActivityClientRecord r = mActivities.get(token);
if (localLOGV) Slog.v(TAG, "Performing resume of " + r
+ " finished=" + r.activity.mFinished);
if (r != null && !r.activity.mFinished) {
if (clearHide) {
r.hideForNow = false;
r.activity.mStartedActivity = false;
}
try {
r.activity.onStateNotSaved();
r.activity.mFragments.noteStateNotSaved();
if (r.pendingIntents != null) {
deliverNewIntents(r, r.pendingIntents);
r.pendingIntents = null;
}
if (r.pendingResults != null) {
deliverResults(r, r.pendingResults);
r.pendingResults = null;
}
r.activity.performResume();
EventLog.writeEvent(LOG_AM_ON_RESUME_CALLED,
UserHandle.myUserId(), r.activity.getComponentName().getClassName());
r.paused = false;
r.stopped = false;
r.state = null;
r.persistentState = null;
} catch (Exception e) {
if (!mInstrumentation.onException(r.activity, e)) {
throw new RuntimeException(
"Unable to resume activity "
+ r.intent.getComponent().toShortString()
+ ": " + e.toString(), e);
}
}
}
return r;
}
后面有调用了Activity的getWindowManager方法获取WindowManager,之前的博客有分析过,这个WindowManager就是WindowManagerImpl对象。下面也就是调用了WindowManagerImpl的addView函数。
我们来看WindowManagerImpl的addView函数,其实就是调用了WindowManagerGlobal的addView函数
@Override
public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
applyDefaultToken(params);
mGlobal.addView(view, params, mDisplay, mParentWindow);
}
之前也分析过WindowManagerGlobal,它有3个重要的成员变量:
private final ArrayList<View> mViews = new ArrayList<View>();//所有的DecorView对象
private final ArrayList<ViewRootImpl> mRoots = new ArrayList<ViewRootImpl>();//所有的ViewRootImpl对象
private final ArrayList<WindowManager.LayoutParams> mParams =//所有顶层View的layout参数
new ArrayList<WindowManager.LayoutParams>();
我们再来看WindowManagerGlobal的addView函数,这个函数先是查找是否已经在WindowManagerGlobal中已经有这个view,如果有的话就调用其ViewRootImpl的doDie函数中主要是调用WindowManagerGlobal函数去除这个ViewRootImpl对象,在这个主要是创建了ViewRootImpl,并且把DecorView,RootViewRootImpl,layout参数都保存起来了。然后调用了ViewRootImpl的setView函数。
public void addView(View view, ViewGroup.LayoutParams params,
Display display, Window parentWindow) {
......
int index = findViewLocked(view, false);//查找是否有该view,获取其index
if (index >= 0) {
if (mDyingViews.contains(view)) {
// Don't wait for MSG_DIE to make it's way through root's queue.
mRoots.get(index).doDie();//调用ViewRootImpl的doDie函数
} else {
throw new IllegalStateException("View " + view
+ " has already been added to the window manager.");
}
// The previous removeView() had not completed executing. Now it has.
}
......
root = new ViewRootImpl(view.getContext(), display);//新建ViewRootImpl对象
view.setLayoutParams(wparams);
mViews.add(view);//成员变量增加
mRoots.add(root);
mParams.add(wparams);
}
// do this last because it fires off messages to start doing things
try {
root.setView(view, wparams, panelParentView);//调用ViewRootImpl的setView函数
} catch (RuntimeException e) {
// BadTokenException or InvalidDisplayException, clean up.
synchronized (mLock) {
final int index = findViewLocked(view, false);
if (index >= 0) {
removeViewLocked(index, true);
}
}
throw e;
}
}
我们再来看下ViewRootImpl的doDie函数中最后有下面一行代码:
WindowManagerGlobal.getInstance().doRemoveView(this);
而在WindowManagerGlobal中就是去除相关所有的保存。
void doRemoveView(ViewRootImpl root) {
synchronized (mLock) {
final int index = mRoots.indexOf(root);
if (index >= 0) {
mRoots.remove(index);
mParams.remove(index);
final View view = mViews.remove(index);
mDyingViews.remove(view);
}
}
if (HardwareRenderer.sTrimForeground && HardwareRenderer.isAvailable()) {
doTrimForeground();
}
}
ViewRootImpl的setView函数
下面我们再来看看ViewRootImpl的setView函数:
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
synchronized (this) {
if (mView == null) {
mView = view;
mAttachInfo.mDisplayState = mDisplay.getState();
mDisplayManager.registerDisplayListener(mDisplayListener, mHandler);
mViewLayoutDirectionInitial = mView.getRawLayoutDirection();
mFallbackEventHandler.setView(view);
mWindowAttributes.copyFrom(attrs);
if (mWindowAttributes.packageName == null) {
mWindowAttributes.packageName = mBasePackageName;
}
attrs = mWindowAttributes;
// Keep track of the actual window flags supplied by the client.
mClientWindowLayoutFlags = attrs.flags;
setAccessibilityFocus(null, null);
if (view instanceof RootViewSurfaceTaker) {
mSurfaceHolderCallback =
((RootViewSurfaceTaker)view).willYouTakeTheSurface();
if (mSurfaceHolderCallback != null) {
mSurfaceHolder = new TakenSurfaceHolder();
mSurfaceHolder.setFormat(PixelFormat.UNKNOWN);
}
}
// Compute surface insets required to draw at specified Z value.
// TODO: Use real shadow insets for a constant max Z.
if (!attrs.hasManualSurfaceInsets) {
final int surfaceInset = (int) Math.ceil(view.getZ() * 2);
attrs.surfaceInsets.set(surfaceInset, surfaceInset, surfaceInset, surfaceInset);
}
CompatibilityInfo compatibilityInfo = mDisplayAdjustments.getCompatibilityInfo();
mTranslator = compatibilityInfo.getTranslator();
// If the application owns the surface, don't enable hardware acceleration
if (mSurfaceHolder == null) {
enableHardwareAcceleration(attrs);
}
boolean restore = false;
if (mTranslator != null) {
mSurface.setCompatibilityTranslator(mTranslator);
restore = true;
attrs.backup();
mTranslator.translateWindowLayout(attrs);
}
if (DEBUG_LAYOUT) Log.d(TAG, "WindowLayout in setView:" + attrs);
if (!compatibilityInfo.supportsScreen()) {
attrs.privateFlags |= WindowManager.LayoutParams.PRIVATE_FLAG_COMPATIBLE_WINDOW;
mLastInCompatMode = true;
}
mSoftInputMode = attrs.softInputMode;
mWindowAttributesChanged = true;
mWindowAttributesChangesFlag = WindowManager.LayoutParams.EVERYTHING_CHANGED;
mAttachInfo.mRootView = view;
mAttachInfo.mScalingRequired = mTranslator != null;
mAttachInfo.mApplicationScale =
mTranslator == null ? 1.0f : mTranslator.applicationScale;
if (panelParentView != null) {
mAttachInfo.mPanelParentWindowToken
= panelParentView.getApplicationWindowToken();
}
mAdded = true;
int res; /* = WindowManagerImpl.ADD_OKAY; */
// Schedule the first layout -before- adding to the window
// manager, to make sure we do the relayout before receiving
// any other events from the system.
requestLayout();//绘制UI布局
if ((mWindowAttributes.inputFeatures
& WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
mInputChannel = new InputChannel();//创建按键通道
}
try {
mOrigWindowType = mWindowAttributes.type;
mAttachInfo.mRecomputeGlobalAttributes = true;
collectViewAttributes();
res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
getHostVisibility(), mDisplay.getDisplayId(),
mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
mAttachInfo.mOutsets, mInputChannel);
} catch (RemoteException e) {
mAdded = false;
mView = null;
mAttachInfo.mRootView = null;
mInputChannel = null;
mFallbackEventHandler.setView(null);
unscheduleTraversals();
setAccessibilityFocus(null, null);
throw new RuntimeException("Adding window failed", e);
} finally {
if (restore) {
attrs.restore();
}
}
if (mTranslator != null) {
mTranslator.translateRectInScreenToAppWindow(mAttachInfo.mContentInsets);
}
mPendingOverscanInsets.set(0, 0, 0, 0);
mPendingContentInsets.set(mAttachInfo.mContentInsets);
mPendingStableInsets.set(mAttachInfo.mStableInsets);
mPendingVisibleInsets.set(0, 0, 0, 0);
if (DEBUG_LAYOUT) Log.v(TAG, "Added window " + mWindow);
if (res < WindowManagerGlobal.ADD_OKAY) {
mAttachInfo.mRootView = null;
mAdded = false;
mFallbackEventHandler.setView(null);
unscheduleTraversals();
setAccessibilityFocus(null, null);
switch (res) {
case WindowManagerGlobal.ADD_BAD_APP_TOKEN:
case WindowManagerGlobal.ADD_BAD_SUBWINDOW_TOKEN:
throw new WindowManager.BadTokenException(
"Unable to add window -- token " + attrs.token
+ " is not valid; is your activity running?");
case WindowManagerGlobal.ADD_NOT_APP_TOKEN:
throw new WindowManager.BadTokenException(
"Unable to add window -- token " + attrs.token
+ " is not for an application");
case WindowManagerGlobal.ADD_APP_EXITING:
throw new WindowManager.BadTokenException(
"Unable to add window -- app for token " + attrs.token
+ " is exiting");
case WindowManagerGlobal.ADD_DUPLICATE_ADD:
throw new WindowManager.BadTokenException(
"Unable to add window -- window " + mWindow
+ " has already been added");
case WindowManagerGlobal.ADD_STARTING_NOT_NEEDED:
// Silently ignore -- we would have just removed it
// right away, anyway.
return;
case WindowManagerGlobal.ADD_MULTIPLE_SINGLETON:
throw new WindowManager.BadTokenException(
"Unable to add window " + mWindow +
" -- another window of this type already exists");
case WindowManagerGlobal.ADD_PERMISSION_DENIED:
throw new WindowManager.BadTokenException(
"Unable to add window " + mWindow +
" -- permission denied for this window type");
case WindowManagerGlobal.ADD_INVALID_DISPLAY:
throw new WindowManager.InvalidDisplayException(
"Unable to add window " + mWindow +
" -- the specified display can not be found");
case WindowManagerGlobal.ADD_INVALID_TYPE:
throw new WindowManager.InvalidDisplayException(
"Unable to add window " + mWindow
+ " -- the specified window type is not valid");
}
throw new RuntimeException(
"Unable to add window -- unknown error code " + res);
}
if (view instanceof RootViewSurfaceTaker) {
mInputQueueCallback =
((RootViewSurfaceTaker)view).willYouTakeTheInputQueue();
}
if (mInputChannel != null) {
if (mInputQueueCallback != null) {
mInputQueue = new InputQueue();
mInputQueueCallback.onInputQueueCreated(mInputQueue);
}
mInputEventReceiver = new WindowInputEventReceiver(mInputChannel,//创建按键应用层接受对象
Looper.myLooper());
}
view.assignParent(this);
mAddedTouchMode = (res & WindowManagerGlobal.ADD_FLAG_IN_TOUCH_MODE) != 0;
mAppVisible = (res & WindowManagerGlobal.ADD_FLAG_APP_VISIBLE) != 0;
if (mAccessibilityManager.isEnabled()) {
mAccessibilityInteractionConnectionManager.ensureConnection();
}
if (view.getImportantForAccessibility() == View.IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
view.setImportantForAccessibility(View.IMPORTANT_FOR_ACCESSIBILITY_YES);
}
// Set up the input pipeline.
CharSequence counterSuffix = attrs.getTitle();
mSyntheticInputStage = new SyntheticInputStage();//按键的一些流程类
InputStage viewPostImeStage = new ViewPostImeInputStage(mSyntheticInputStage);
InputStage nativePostImeStage = new NativePostImeInputStage(viewPostImeStage,
"aq:native-post-ime:" + counterSuffix);
InputStage earlyPostImeStage = new EarlyPostImeInputStage(nativePostImeStage);
InputStage imeStage = new ImeInputStage(earlyPostImeStage,
"aq:ime:" + counterSuffix);
InputStage viewPreImeStage = new ViewPreImeInputStage(imeStage);
InputStage nativePreImeStage = new NativePreImeInputStage(viewPreImeStage,
"aq:native-pre-ime:" + counterSuffix);
mFirstInputStage = nativePreImeStage;
mFirstPostImeInputStage = earlyPostImeStage;
mPendingInputEventQueueLengthCounterName = "aq:pending:" + counterSuffix;
}
}
}
这个函数主要是调用了requestLayout函数来对应用窗口的UI布局,然后创建了InputChannel。调用ViewRoot类的静态成员变量sWindowSession所描述的一个类型为Session的Binder代理对象的成员函数add来请求WindowManagerService增加一个WindowState对象,以便可以用来描述当前正在处理的一个ViewRootImpl所关联的一个应用程序窗口。
最后创建了WindowInputEventReceiver应用层的按键接受,以及一些按键在应用层的流程的相关类。