Window的创建过程

Window是View的直接管理者

图片源自https://mp.weixin.qq.com/s/IrwjQqlDoLp3xQZbthncVg

Activity的Window创建过程

Activity的启动最终会通过ActivityThread#performLaunchActivity()来完成。

ActivityThread#performLaunchActivity()

private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) { //... //通过类加载器创建Activity实例 java.lang.ClassLoader cl = r.packageInfo.getClassLoader(); activity = mInstrumentation.newActivity( cl, component.getClassName(), r.intent); //... Application app = r.packageInfo.makeApplication(false, mInstrumentation); Context appContext = createBaseContextForActivity(r, activity); CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager()); Configuration config = new Configuration(mCompatConfiguration); //关联运行过程中所依赖的一系列上下文环境变量 activity.attach(appContext, this, getInstrumentation(), r.token, r.ident, app, r.intent, r.activityInfo, title, r.parent, r.embeddedID, r.lastNonConfigurationInstances, config, r.voiceInteractor); mActivities.put(r.token, r); return activity; }

在attach方法里，系统会创建Activity所属的Window对象并为其设置回调接口。

Activity#attach()

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, IVoiceInteractor voiceInteractor) { attachBaseContext(context); mFragments.attachActivity(this, mContainer, null); //创建Window对象 mWindow = PolicyManager.makeNewWindow(this); //设置回调 比如我们熟悉的onAttachedToWindow、onDetachedFromWindow、dispatchTouchEvent //[重要] 当Window接收到外界的状态改变时就会调用Activity实现的回调 mWindow.setCallback(this); mWindow.setOnWindowDismissedCallback(this); //赋值 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; //... //设置WindowManager 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; }

再来看 PolicyManager.makeNewWindow(this)，PilicyManager的真正实现类是Policy类。 位于source\frameworks\base\policy\src\com\android\internal\policy\impl\Policy.java

public Window makeNewWindow(Context context) { return new PhoneWindow(context); }

可以发现Window的实现类确实是PhoneWindow。

Window初始完毕后，再来看Activity的视图是如何依附在Window上的。Activity的视图通过setContent方法提供。

public void setContentView(int layoutResID) { getWindow().setContentView(layoutResID); initWindowDecorActionBar(); }

可以发现，Activity的setContentView将具体实现交由Window处理。

phoneWindow#setContentView()

@Override public void setContentView(int layoutResID) { // 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. //1.创建DecorView (如果没有创建的话) if (mContentParent == null) { installDecor(); } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) { mContentParent.removeAllViews(); } if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) { final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID, getContext()); transitionTo(newScene); //2.将View添加到DecorView的mContentParent中 mLayoutInflater.inflate(layoutResID, mContentParent); } //3.回调Activity的onContentChanged()通知Activity视图已经发生改变 final Callback cb = getCallback(); if (cb != null && !isDestroyed()) { cb.onContentChanged(); } }

经过setContentView方法，DecorView已经被创建并初始化完毕，Activity的布局文件也已经成功添加到DecorView的mContentParent中，但这个时候DecorView还没有被WindowManager添加到Window中。 (在添加之前)

#

Activity的attach()中，Window被创建并初始化 在Activity的setContentView中 (PhoneWindow#setContentView)，DecorView被创建 (如果没被创建的话) 而在ActivityThread#handleResumeActivity首先会调用Activity的onResume方法中，接着会先将DecorView设为不可见(INVISIBLE)，然后会调用Activity的makeVisible()，在makeVisible()中，将DecorView添加到Window并置为Visible。

#

void makeVisible() { //将DecorView添加到Window if (!mWindowAdded) { ViewManager wm = getWindowManager(); wm.addView(mDecor, getWindow().getAttributes()); mWindowAdded = true; } //将Activity的显示置为Visible mDecor.setVisibility(View.VISIBLE); }

Dialog的window创建过程

Dialog的Window创建过程和Activity类似

Dialog#构造方法

Dialog(Context context, int theme, boolean createContextThemeWrapper) { //... mContext = context; mWindowManager = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE); //创建Window对象 Window w = PolicyManager.makeNewWindow(mContext); mWindow = w; w.setCallback(this); w.setOnWindowDismissedCallback(this); w.setWindowManager(mWindowManager, null, null); w.setGravity(Gravity.CENTER); mListenersHandler = new ListenersHandler(this); }

再来看Dialog#setContentView()

public void setContentView(int layoutResID) { mWindow.setContentView(layoutResID); }

同样是交由Window处理。

当Dialog dismiss时，会通过WindowManager来移除DecorView

@Override public void dismiss() { if (Looper.myLooper() == mHandler.getLooper()) { dismissDialog(); } else { mHandler.post(mDismissAction); } } void dismissDialog() { //... //移除DecorView mWindowManager.removeViewImmediate(mDecor); //... }

注意

普通Dialog需要使用Activity的Content 因为Window需要应用token，而应用token一般只有Activity才拥有。 系统Window比较特殊，它可以不需要token。

Toast的Window创建过程

Toast属于系统Window Toast内部有两类IPC过程

Toast访问NotifationManagerServiceNotificationManagerService回调Toast的TN接口

Toast提供了show和cancel分别用于显示和隐藏Toast [都是IPC过程]

public void show() { if (mNextView == null) { throw new RuntimeException("setView must have been called"); } INotificationManager service = getService(); String pkg = mContext.getOpPackageName(); TN tn = mTN; tn.mNextView = mNextView; try { service.enqueueToast(pkg, tn, mDuration); } catch (RemoteException e) { // Empty } } public void cancel() { mTN.hide(); try { getService().cancelToast(mContext.getPackageName(), mTN); } catch (RemoteException e) { // Empty } }

主要来看enqueueToast()

//参数一:当前应用的包名 //参数二:远程回调 //参数三:Toast的时长 //enqueueToast首先将Toast封装为ToastRecord对象并将其添加到一个名为mToastQueue的队列中 service.enqueueToast(pkg, tn, mDuration);

当ToastRecord被添加到mToastQueue中后，Inotifacationmanager就会通过showNextToastLacked方法来显示当前的Toast。

NotificationManagerService#showNextToastLocked()

void showNextToastLocked() { //获取下一个ToastRecord ToastRecord record = mToastQueue.get(0); while (record != null) { if (DBG) Slog.d(TAG, "Show pkg=" + record.pkg + " callback=" + record.callback); try { //record.callback就是Toast.java类中的TN (Binder) 对象 record.callback.show(); //发送延迟消息来移除toast //scheduleTimeoutLocked -> mHandler.sendMessageDelayed -> cancelToastLocked -> record.callback.hide(); scheduleTimeoutLocked(record); return; } catch (RemoteException e) { Slog.w(TAG, "Object died trying to show notification " + record.callback + " in package " + record.pkg); // remove it from the list and let the process die int index = mToastQueue.indexOf(record); if (index >= 0) { mToastQueue.remove(index); } keepProcessAliveLocked(record.pid); if (mToastQueue.size() > 0) { record = mToastQueue.get(0); } else { record = null; } } } }

可以发现，Toast的显示和移除都是通过Toast的TN类(Binder对象)来完成的。

Toast内部类TN

private static class TN extends ITransientNotification.Stub { final Runnable mShow = new Runnable() { @Override public void run() { handleShow(); } }; final Runnable mHide = new Runnable() { @Override public void run() { handleHide(); // Don't do this in handleHide() because it is also invoked by handleShow() mNextView = null; } }; @Override public void show() { if (localLOGV) Log.v(TAG, "SHOW: " + this); mHandler.post(mShow); } @Override public void hide() { if (localLOGV) Log.v(TAG, "HIDE: " + this); mHandler.post(mHide); } //... }

真正的显示

public void handleShow() { //... mWM = (WindowManager)context.getSystemService //... if (mView.getParent() != null) { mWM.removeView(mView); } mWM.addView(mView, mParams); //... } }

真正的隐藏

public void handleHide() { if (mView != null) { if (mView.getParent() != null) { mWM.removeView(mView); } mView = null; } }

相关

PhoneWindow伪代码