一直没有仔细看看setContentView调用流程。最近看到了深入理解Android卷I一书，结合书上的介绍，把自己看的梳理了一遍。虽然会遗忘，但是记录下来，多看看，总是好的~
在Activity的OnCreate中，会调用setContentView来设置布局：
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.xxx);
}
在Activity中，
setContentView的实现：
//setContentView有几个重载的函数，这个是我们最经常使用的
public void setContentView(int layoutResID) {
getWindow().setContentView(layoutResID); //调用PhoneWindow中的setContentView方法
initActionBar();
}public Window getWindow() {
return mWindow; //实际类型是PhoneWindow，PhoneWindow是Window的子类
}private Window mWindow; //Window是一个抽象类：public abstract class Window
在Activity的
attach方法中，有对mWindow其进行初始化，至于attach方法在何时被调用，后面在分析Activity的启动中会详细介绍，
final void attach(Context context, ActivityThread aThread,
Instrumentation instr, IBinder token, int ident,
Application application, Intent intent, ActivityInfo info,
CharSequence title, Activity parent, String id,
NonConfigurationInstances lastNonConfigurationInstances,
Configuration config) {
attachBaseContext(context);
mFragments.attachActivity(this, mContainer, null);
mWindow = PolicyManager.makeNewWindow(this); //创建mWindow对象
mWindow.setCallback(this);
mWindow.getLayoutInflater().setPrivateFactory(this);
if (info.softInputMode != WindowManager.LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED) {
mWindow.setSoftInputMode(info.softInputMode);
}
if (info.uiOptions != 0) {
mWindow.setUiOptions(info.uiOptions);
}
mUiThread = Thread.currentThread();
mMainThread = aThread;
mInstrumentation = instr;
mToken = token;
mIdent = ident;
mApplication = application;
mIntent = intent;
mComponent = intent.getComponent();
mActivityInfo = info;
mTitle = title;
mParent = parent;
mEmbeddedID = id;
mLastNonConfigurationInstances = lastNonConfigurationInstances;
//创建WindowManager对象
mWindow.setWindowManager(
(WindowManager)context.getSystemService(Context.WINDOW_SERVICE),
mToken, mComponent.flattenToString(),
(info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);
if (mParent != null) {
mWindow.setContainer(mParent.getWindow());
}
mWindowManager = mWindow.getWindowManager();
mCurrentConfig = config;
}
先看mWindow的初始化，PolicyManager是一个final类，
public final class PolicyManager {
private static final String POLICY_IMPL_CLASS_NAME =
"com.android.internal.policy.impl.Policy";
private static final IPolicy sPolicy;
static {
// Pull in the actual implementation of the policy at run-time
try {
Class policyClass = Class.forName(POLICY_IMPL_CLASS_NAME); //加载类Policy
sPolicy = (IPolicy)policyClass.newInstance(); //创建sPolicy
} catch (ClassNotFoundException ex) {
throw new RuntimeException(
POLICY_IMPL_CLASS_NAME + " could not be loaded", ex);
} catch (InstantiationException ex) {
throw new RuntimeException(
POLICY_IMPL_CLASS_NAME + " could not be instantiated", ex);
} catch (IllegalAccessException ex) {
throw new RuntimeException(
POLICY_IMPL_CLASS_NAME + " could not be instantiated", ex);
}
}
// Cannot instantiate this class
private PolicyManager() {}
// The static methods to spawn new policy-specific objects
public static Window makeNewWindow(Context context) {
return sPolicy.makeNewWindow(context); //真正调用的地方是
//com.android.internal.policy.impl.Policy中的方法
}
public static LayoutInflater makeNewLayoutInflater(Context context) {
return sPolicy.makeNewLayoutInflater(context);
}
public static WindowManagerPolicy makeNewWindowManager() {
return sPolicy.makeNewWindowManager();
}
public static FallbackEventHandler makeNewFallbackEventHandler(Context context) {
return sPolicy.makeNewFallbackEventHandler(context);
}
}
在com.android.internal.policy.Policy类中，
Policy实现接口IPolicy，
public class Policy implements IPolicy {
private static final String TAG = "PhonePolicy";
private static final String[] preload_classes = {
"com.android.internal.policy.impl.PhoneLayoutInflater",
"com.android.internal.policy.impl.PhoneWindow",
"com.android.internal.policy.impl.PhoneWindow$1",
"com.android.internal.policy.impl.PhoneWindow$DialogMenuCallback",
"com.android.internal.policy.impl.PhoneWindow$DecorView",
"com.android.internal.policy.impl.PhoneWindow$PanelFeatureState",
"com.android.internal.policy.impl.PhoneWindow$PanelFeatureState$SavedState",
};
static {
// For performance reasons, preload some policy specific classes when
// the policy gets loaded.
for (String s : preload_classes) {
try {
Class.forName(s); //加载类
} catch (ClassNotFoundException ex) {
Log.e(TAG, "Could not preload class for phone policy: " + s);
}
}
}
public Window makeNewWindow(Context context) {
return new PhoneWindow(context); //创建一个PhoneWindow，是Window的子类
}
public LayoutInflater makeNewLayoutInflater(Context context) {
return new PhoneLayoutInflater(context);
}
public WindowManagerPolicy makeNewWindowManager() {
return new PhoneWindowManager();
}
public FallbackEventHandler makeNewFallbackEventHandler(Context context) {
return new PhoneFallbackEventHandler(context);
}
}
再看WindowManager，
mWindow.setWindowManager(
(WindowManager)context.getSystemService(Context.WINDOW_SERVICE),
mToken, mComponent.flattenToString(),
(info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);
在Window中，
public void setWindowManager(WindowManager wm, IBinder appToken, String appName,
boolean hardwareAccelerated) {
mAppToken = appToken;
mAppName = appName;
mHardwareAccelerated = hardwareAccelerated
|| SystemProperties.getBoolean(PROPERTY_HARDWARE_UI, false);
if (wm == null) {
wm = (WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE);
}
mWindowManager = ((WindowManagerImpl)wm).createLocalWindowManager(this); //关键
}
WindowManager是接口，
WindowManagerImpl实现了它。
（基本带Impl的类都是实现类）
public final class WindowManagerImpl implements WindowManager
在WindowManagerImpl中，函数createLocalWindowManager创建了一个
WindowManagerImpl对象，
public WindowManagerImpl createLocalWindowManager(Window parentWindow) {
return new WindowManagerImpl(mDisplay, parentWindow);
}private WindowManagerImpl(Display display, Window parentWindow) {
mDisplay = display;
mParentWindow = parentWindow;
}
在setContentView方法中，
getWindow().setContentView(layoutResID); //实际调用的是PhoneWindow中的setContentView
在PhoneWindow中，
public void setContentView(int layoutResID) {
if (mContentParent == null) { //初始值为null
installDecor();
} else {
mContentParent.removeAllViews();
}
mLayoutInflater.inflate(layoutResID, mContentParent);
final Callback cb = getCallback();
if (cb != null && !isDestroyed()) {
cb.onContentChanged();
}
}// This is the view in which the window contents are placed. It is either
// mDecor itself, or a child of mDecor where the contents go.
private ViewGroup mContentParent; //最终我们的layout就是显示在这个容器中// This is the top-level view of the window, containing the window decor.
private DecorView mDecor; //顶层Viewprivate void installDecor() {
if (mDecor == null) {
mDecor = generateDecor(); //创建mDecor
...
}
if (mContentParent == null) {
mContentParent = generateLayout(mDecor); //得到mContentParent
// Set up decor part of UI to ignore fitsSystemWindows if appropriate.
mDecor.makeOptionalFitsSystemWindows();
mTitleView = (TextView)findViewById(com.android.internal.R.id.title); //标题栏
...
}
}
其中创建mDecor为：
protected DecorView generateDecor() {
return new DecorView(getContext(), -1);
}
其中，DecorView继承了FrameLayout：
private final class DecorView extends FrameLayout implements RootViewSurfaceTaker
得到mContentParent：
protected ViewGroup generateLayout(DecorView decor){
// Apply data from current theme.
TypedArray a = getWindowStyle();
//开始判断一系列的窗口风格
...
...
// Inflate the window decor.
int layoutResource;
int features = getLocalFeatures();
if ((features & ((1 << FEATURE_LEFT_ICON) | (1 << FEATURE_RIGHT_ICON))) != 0) {
if (mIsFloating) {
TypedValue res = new TypedValue();
getContext().getTheme().resolveAttribute(
com.android.internal.R.attr.dialogTitleIconsDecorLayout, res, true);
layoutResource = res.resourceId;
} else {
layoutResource = com.android.internal.R.layout.screen_title_icons;
}
// XXX Remove this once action bar supports these features.
removeFeature(FEATURE_ACTION_BAR);
} else if ((features & ((1 << FEATURE_PROGRESS) | (1 << FEATURE_INDETERMINATE_PROGRESS))) != 0
&& (features & (1 << FEATURE_ACTION_BAR)) == 0) {
// Special case for a window with only a progress bar (and title).
// XXX Need to have a no-title version of embedded windows.
layoutResource = com.android.internal.R.layout.screen_progress;
} else if ((features & (1 << FEATURE_CUSTOM_TITLE)) != 0) {
// Special case for a window with a custom title.
// If the window is floating, we need a dialog layout
if (mIsFloating) {
TypedValue res = new TypedValue();
getContext().getTheme().resolveAttribute(
com.android.internal.R.attr.dialogCustomTitleDecorLayout, res, true);
layoutResource = res.resourceId;
} else {
layoutResource = com.android.internal.R.layout.screen_custom_title;
}
// XXX Remove this once action bar supports these features.
removeFeature(FEATURE_ACTION_BAR);
} else if ((features & (1 << FEATURE_NO_TITLE)) == 0) {
// If no other features and not embedded, only need a title.
// If the window is floating, we need a dialog layout
if (mIsFloating) {
TypedValue res = new TypedValue();
getContext().getTheme().resolveAttribute(
com.android.internal.R.attr.dialogTitleDecorLayout, res, true);
layoutResource = res.resourceId;
} else if ((features & (1 << FEATURE_ACTION_BAR)) != 0) {
layoutResource = com.android.internal.R.layout.screen_action_bar;
} else {
layoutResource = com.android.internal.R.layout.screen_title;
}
} else if ((features & (1 << FEATURE_ACTION_MODE_OVERLAY)) != 0) {
layoutResource = com.android.internal.R.layout.screen_simple_overlay_action_mode;
} else {
// Embedded, so no decoration is needed.
layoutResource = com.android.internal.R.layout.screen_simple;
}
mDecor.startChanging();
View in = mLayoutInflater.inflate(layoutResource, null);
//加入标题栏
decor.addView(in, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));
//ID_ANDROID_CONTENT = com.android.internal.R.id.content;
ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);
if (contentParent == null) {
throw new RuntimeException("Window couldn't find content container view");
}
if ((features & (1 << FEATURE_INDETERMINATE_PROGRESS)) != 0) {
ProgressBar progress = getCircularProgressBar(false);
if (progress != null) {
progress.setIndeterminate(true);
}
}
// Remaining setup -- of background and title -- that only applies
// to top-level windows.
if (getContainer() == null) {
Drawable drawable = mBackgroundDrawable;
if (mBackgroundResource != 0) {
drawable = getContext().getResources().getDrawable(mBackgroundResource);
}
mDecor.setWindowBackground(drawable);
drawable = null;
if (mFrameResource != 0) {
drawable = getContext().getResources().getDrawable(mFrameResource);
}
mDecor.setWindowFrame(drawable);
if (mTitleColor == 0) {
mTitleColor = mTextColor;
}
if (mTitle != null) {
setTitle(mTitle);
}
setTitleColor(mTitleColor);
}
mDecor.finishChanging();
return contentParent; //由findViewById返回
}
接着看findViewById方法，是由getDecorView()在调用，所以contentParent是属于DecorView的一部分。
public View findViewById(int id) {
//getDecorView返回的是mDevor
return getDecorView().findViewById(id);
}
再回到setContentView当中来，
public void setContentView(int layoutResID) {
if (mContentParent == null) { //初始值为null
installDecor(); //mDecor=null，则创建一个mDecor
} else {
mContentParent.removeAllViews(); //否则，就把当前mDecor上的所有View都移除
}
mLayoutInflater.inflate(layoutResID, mContentParent);//根据layoutResID，inflate出来
//父窗口为mContentParent，相当于：
// mContentParent.addView(view, params);
final Callback cb = getCallback();
if (cb != null && !isDestroyed()) {
cb.onContentChanged(); //没有找到具体的实现。
}
}
到此，setContentView就完成了layout，但是还没有显示哦~
PS：邓凡平先生的《深入理解Android卷I》真是好书好书好书啊！可惜在网上都买不到，几大网站上都是没货了~还好弄到电子版的~
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