android Window(一)从setConetView说起

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Activity的源码

首先从setContentView这里调用的mWindow的 setConetView()

private Window mWindow;
public void setContentView(View view) {
getWindow().setContentView(view);
initWindowDecorActionBar();
}public Window getWindow() {
return mWindow;
}

那么这mWindow什么时候初始化？

final void attach(...) {
attachBaseContext(context);
mFragments.attachHost(null /*parent*/);
mWindow = new PhoneWindow(this, window, activityConfigCallback);
mWindow.setWindowControllerCallback(this);
mWindow.setCallback(this);
mWindow.setOnWindowDismissedCallback(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);
}
//...
//给window设置windowManger
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; mWindow.setColorMode(info.colorMode);
}

可以看到这个mWindow 其实是一个PhoneWindow的实例，那么phoneWindow干了什么

可以查看PhoneWindow的源码

152 // This is the view in which the window contents are placed. It is either
153 // mDecor itself, or a child of mDecor where the contents go.
154 private ViewGroup mContentParent;390 @Override
391 public void setContentView(View view, ViewGroup.LayoutParams params) {
392 // Note: FEATURE_CONTENT_TRANSITIONS may be set in the process of installing the window
393 // decor, when theme attributes and the like are crystalized. Do not check the feature
394 // before this happens.
395 if (mContentParent == null) {
396 installDecor();
397 } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
398 mContentParent.removeAllViews();
399 }
400
401 if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
402 view.setLayoutParams(params);
403 final Scene newScene = new Scene(mContentParent, view);
404 transitionTo(newScene);
405 } else {
406 mContentParent.addView(view, params);
407 }
408 final Callback cb = getCallback();
409 if (cb != null && !isDestroyed()) {
410 cb.onContentChanged();
411 }
412 }

这里setContentView 主要是先判断mContentParent是否初始化如果没有初始化调用installDecor 。然后将view添加到mContentParent的ViewGroup中

那么 installDecor 做了些什么

private DecorView mDecor;
3551 private void installDecor() {
3552 if (mDecor == null) {
3553 mDecor = generateDecor();
3554 mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
3555 mDecor.setIsRootNamespace(true);
3556 if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {
3557 mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);
3558 }
3559 }
3560 if (mContentParent == null) {
3561 mContentParent = generateLayout(mDecor);
3562
3563 // Set up decor part of UI to ignore fitsSystemWindows if appropriate.
3564 mDecor.makeOptionalFitsSystemWindows();
3565
3566 final DecorContentParent decorContentParent = (DecorContentParent) mDecor.findViewById(
3567 R.id.decor_content_parent);
3568
3569 if (decorContentParent != null) {
3570 mDecorContentParent = decorContentParent;
3571 mDecorContentParent.setWindowCallback(getCallback());
3572 if (mDecorContentParent.getTitle() == null) {
3573 mDecorContentParent.setWindowTitle(mTitle);
3574 }
3575
3576 final int localFeatures = getLocalFeatures();
3577 for (int i = 0; i < FEATURE_MAX; i++) {
3578 if ((localFeatures & (1 << i)) != 0) {
3579 mDecorContentParent.initFeature(i);
3580 }
3581 }3582
3583 mDecorContentParent.setUiOptions(mUiOptions);
3584
//setIcon,setLogo ...
3608 } else {
//setTitle ...3627
}
//...
}
3686 }

installDecor 主要干两件事情

如果mDecor没有初始化generateDecor()初始化
如果mContentParent 没有初始化generateLayout()初始化

generateDecor 就是返回一个新的DecorView

3199 protected DecorView generateDecor() {
3200 return new DecorView(getContext(), -1);
3201 }

这里实例化了DecorView，而DecorView则是PhoneWindow类的一个内部类，继承于FrameLayout，由此可知它也是一个ViewGroup。
那么DecroView到底充当了什么样的角色呢？
其实，DecorView是整个ViewTree的最顶层View，它是一个FrameLayout布局，代表了整个应用的界面。在该布局下面，有标题view和内容view这两个子元素，而内容view则是上面提到的mContentParentDecorView

private final class DecorView extends FrameLayout implements RootViewSurfaceTaker{
//...
}

generateLayout()给activity的根布设置各种属性

protected ViewGroup generateLayout(DecorView decor) {
// Apply data from current theme.
// 从主题文件中获取样式信息
TypedArray a = getWindowStyle(); //... if (a.getBoolean(R.styleable.Window_windowNoTitle, false)) {
requestFeature(FEATURE_NO_TITLE);
} else if (a.getBoolean(R.styleable.Window_windowActionBar, false)) {
// Don't allow an action bar if there is no title.
requestFeature(FEATURE_ACTION_BAR);
} if(...){
...
} // Inflate the window decor.
// 加载窗口布局
int layoutResource;
int features = getLocalFeatures();
// System.out.println("Features: 0x" + Integer.toHexString(features));
if ((features & (1 << FEATURE_SWIPE_TO_DISMISS)) != 0) {
layoutResource = R.layout.screen_swipe_dismiss;
} else if(...){
...
} View in = mLayoutInflater.inflate(layoutResource, null); //加载layoutResource
decor.addView(in, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT)); //往DecorView中添加子View，即mContentParent
mContentRoot = (ViewGroup) in; ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT); // 这里获取的就是mContentParent
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);
}
} if ((features & (1 << FEATURE_SWIPE_TO_DISMISS)) != 0) {
registerSwipeCallbacks();
} // Remaining setup -- of background and title -- that only applies
// to top-level windows.
//... return contentParent;
}

根据设置的主题样式来设置DecorView的风格，比如说有没有titlebar之类的，接着为DecorView添加子View，而这里的子View则是上面提到的mContentParent，如果上面设置了FEATURE_NO_ACTIONBAR，那么DecorView就只有mContentParent一个子View，所以mContentParent是DecorView本身或者是DecorView的一个子元素。

用一幅图来表示DecorView的结构如下：

小结：DecorView是顶级View，内部有titlebar和contentParent两个子元素，contentParent的id是content，而我们设置的main.xml布局则是contentParent里面的一个子元素。

setConetViewz就是把view 添加到顶层的DecorView里面的contentParent里面

将DecorView添加至Window

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。上文分析了创建DecorView的过程，现在则要把DecorView添加到Window对象中。而要了解这个过程，我们首先要简单先了解一下Activity的创建过程：
首先，在ActivityThread#handleLaunchActivity中启动Activity，在这里面会调用到Activity#onCreate方法，从而完成上面所述的DecorView创建动作，当onCreate()方法执行完毕，在handleLaunchActivity方法会继续调用到ActivityThread#handleResumeActivity方法，我们看看这个方法的源码：

ActivityThread.java

final void handleResumeActivity(IBinder token, boolean clearHide, boolean isForward) {
//...
ActivityClientRecord r = performResumeActivity(token, clearHide); // 这里会调用到onResume()方法 if (r != null) {
final Activity a = r.activity; //...
if (r.window == null && !a.mFinished && willBeVisible) {
r.window = r.activity.getWindow(); // 获得window对象
View decor = r.window.getDecorView(); // 获得DecorView对象
decor.setVisibility(View.INVISIBLE);
ViewManager wm = a.getWindowManager(); // 获得windowManager对象
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); // 调用addView方法
}
//...
}
}
}