Dialog、Toast的Window和ViewRootImpl

本文主要是介绍Dialog、Toast的Window和ViewRootImpl，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

文章目录

前言
Dialog
- Dialog的构造
- Dialog添加View
- Dialog的展现
Toast
- Toast的构造
- Toast添加View
- Toast的展示
- Toast的消失
Dialog和Toast在异步线程的展现
总结

前言

文章Activity中的Window的setContentView、遇见LayoutInflater&Factory、ViewRootImpl的独白，我不是一个View(布局篇) 分别讲述了Activity的setContentView添加View、LayoutInflater布局解析以及添加Window。文章内容都是站在Activity的角度来进行代码解析的，因此我们不再对Dialog和Toast与Activity做具体分析，主要来看看它们与Activity有什么不同之处源码:android-22。

Dialog

Dialog的构造

public class Dialog implements DialogInterface, Window.Callback,KeyEvent.Callback, OnCreateContextMenuListener,Window.OnWindowDismissedCallback{//只有Activity的Context可以启动Dialog，因为Dialog展示的时候需要主题资源也就是ContextThemeWrapper。Dialog(Context context, int theme, boolean createContextThemeWrapper) {if (createContextThemeWrapper) {if (theme == 0) {TypedValue outValue = new TypedValue();context.getTheme().resolveAttribute(com.android.internal.R.attr.dialogTheme,outValue, true);theme = outValue.resourceId;}mContext = new ContextThemeWrapper(context, theme);} else {mContext = context;}//因为每个上下文环境获取的系统服务都是相同的实例，这里获取的WindowManager是Activity的WindowManager。mWindowManager = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);//创建Dialog的PhoneWindow对象。Window w = PolicyManager.makeNewWindow(mContext);mWindow = w;w.setCallback(this);w.setOnWindowDismissedCallback(this);w.setWindowManager(mWindowManager, null, null);w.setGravity(Gravity.CENTER);//Handler中的Looper默认为当前线程的LoopermListenersHandler = new ListenersHandler(this);}
}

Dialog添加View

和Activity相同通过setContentView初始化 Window 中的 DecorView，并对页面 View 进行add。详细讲述请移动到Activity中的Window的setContentView

public class Dialog implements DialogInterface, Window.Callback,KeyEvent.Callback, OnCreateContextMenuListener,Window.OnWindowDismissedCallback{/*** Set the screen content from a layout resource.  The resource will be* inflated, adding all top-level views to the screen.* * @param layoutResID Resource ID to be inflated.*/public void setContentView(int layoutResID) {mWindow.setContentView(layoutResID);}
}

Dialog的展现

Dialog 的展现和 Activity 不同是因为两者的声明周期不同，Activity 的声明周期是有 AMS 调用而 Dialog 是应用程序自己调用的。ViewRootImpl的初始化在 Activity 会在onResume()方法之后，而是 Dialog 被调用show方法时触发的。

public class Dialog implements DialogInterface, Window.Callback,KeyEvent.Callback, OnCreateContextMenuListener,Window.OnWindowDismissedCallback{/*** Start the dialog and display it on screen.  The window is placed in the* application layer and opaque.  Note that you should not override this* method to do initialization when the dialog is shown, instead implement* that in {@link #onStart}.*/public void show() {if (mShowing) {if (mDecor != null) {if (mWindow.hasFeature(Window.FEATURE_ACTION_BAR)) {mWindow.invalidatePanelMenu(Window.FEATURE_ACTION_BAR);}mDecor.setVisibility(View.VISIBLE);}return;}mCanceled = false;//判断是否调用onCreate方法if (!mCreated) {dispatchOnCreate(null);}//调用onStart方法onStart();//获取DecorView对象实例mDecor = mWindow.getDecorView();if (mActionBar == null && mWindow.hasFeature(Window.FEATURE_ACTION_BAR)) {final ApplicationInfo info = mContext.getApplicationInfo();mWindow.setDefaultIcon(info.icon);mWindow.setDefaultLogo(info.logo);mActionBar = new WindowDecorActionBar(this);}//更新Window属性参数WindowManager.LayoutParams l = mWindow.getAttributes();if ((l.softInputMode& WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) == 0) {WindowManager.LayoutParams nl = new WindowManager.LayoutParams();nl.copyFrom(l);nl.softInputMode |=WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION;l = nl;}try {//Windowmanger添加Window、ViewRootImpl初始化并绑定WindowmWindowManager.addView(mDecor, l);mShowing = true;//OnShowListener监听回调sendShowMessage();} finally {}}
}

Toast

Toast的构造

public class Toast {final Context mContext;final TN mTN;//int mDuration;//展示时间View mNextView;//所展示的View/*** Construct an empty Toast object.  You must call {@link #setView} before you* can call {@link #show}.** @param context  The context to use.  Usually your {@link android.app.Application}*                 or {@link android.app.Activity} object.*///Context可以为Application也可以为Activity，public Toast(Context context) {mContext = context;mTN = new TN();mTN.mY = context.getResources().getDimensionPixelSize(com.android.internal.R.dimen.toast_y_offset);mTN.mGravity = context.getResources().getInteger(com.android.internal.R.integer.config_toastDefaultGravity);}//NotificationManagerService的客户端IBinder对private static INotificationManager sService;private static class TN extends ITransientNotification.Stub {/***部分代码省略***/private final WindowManager.LayoutParams mParams = new WindowManager.LayoutParams();//Handler中的Looper默认为当前线程的Looperfinal Handler mHandler = new Handler(); TN() {// XXX This should be changed to use a Dialog, with a Theme.Toast// defined that sets up the layout params appropriately.final WindowManager.LayoutParams params = mParams;params.height = WindowManager.LayoutParams.WRAP_CONTENT;params.width = WindowManager.LayoutParams.WRAP_CONTENT;params.format = PixelFormat.TRANSLUCENT;params.windowAnimations = com.android.internal.R.style.Animation_Toast;//设置Window类型为Toastparams.type = WindowManager.LayoutParams.TYPE_TOAST;params.setTitle("Toast");params.flags = WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON| WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE;}}   
}

transient_notification.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"android:background="?android:attr/toastFrameBackground"><TextViewandroid:id="@android:id/message"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_weight="1"android:layout_gravity="center_horizontal"android:textAppearance="@style/TextAppearance.Toast"android:textColor="@color/bright_foreground_dark"android:shadowColor="#BB000000"android:shadowRadius="2.75"/></LinearLayout>

Toast添加View

从Toast的调用我们开始分析Toast.makeText(MainActivity.this , "Hello World" , Toast.LENGTH_SHORT);我们主要看makeText方法。

public class Toast {/*** Make a standard toast that just contains a text view.** @param context  The context to use.  Usually your {@link android.app.Application}*                 or {@link android.app.Activity} object.* @param text     The text to show.  Can be formatted text.* @param duration How long to display the message.  Either {@link #LENGTH_SHORT} or*                 {@link #LENGTH_LONG}**/public static Toast makeText(Context context, CharSequence text, @Duration int duration) {Toast result = new Toast(context);//获取布局解析器LayoutInflater inflate = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);//解析transient_notification.xml生成对应的ViewView v = inflate.inflate(com.android.internal.R.layout.transient_notification, null);//找到View中的id为message的TextViewTextView tv = (TextView)v.findViewById(com.android.internal.R.id.message);//对Textview进行文字赋值tv.setText(text);//展示的Toast所用的Viewresult.mNextView = v;//设置间隔时间result.mDuration = duration;return result;}
}

主要是对Toast内部成员变量mNextView和mDuration进行初始化。

Toast的展示

toast

将 Toast 内部的 TN ( ITransientNotification 客户端对象)加入到 INotificationManager 服务端的 Binder 兑现的 mToastQueue 队列中。再由服务端循环遍历 mToastQueue 队列中ToastRecord对象，处理一个移除一个，每次处理的都是 List 的第一个ToastRecord对象。

public class Toast {//INotificationManager的客户端的Binder对象private static INotificationManager sService;static private INotificationManager getService() {if (sService != null) {return sService;}//获取INotificationManager的客户端的Binder对象sService = INotificationManager.Stub.asInterface(ServiceManager.getService("notification"));return sService;}/*** Show the view for the specified duration.*/public void show() {//mNextView不能为空if (mNextView == null) {throw new RuntimeException("setView must have been called");}//service初始哈INotificationManager service = getService();//获取当前Context对应的包名String pkg = mContext.getOpPackageName();TN tn = mTN;tn.mNextView = mNextView;try {//将TN加入INotificationManager中的mToastQueue队列service.enqueueToast(pkg, tn, mDuration);} catch (RemoteException e) {// Empty}}
}

NotificationManagerService在服务端处理ITransientNotification客户端传过来的enqueueToast事件。

public class NotificationManagerService extends SystemService {//是否是系统调用private static boolean isCallerSystem() {return isUidSystem(Binder.getCallingUid());}private final IBinder mService = new INotificationManager.Stub() {@Overridepublic void enqueueToast(String pkg, ITransientNotification callback, int duration){if (DBG) {Slog.i(TAG, "enqueueToast pkg=" + pkg + " callback=" + callback+ " duration=" + duration);}if (pkg == null || callback == null) {Slog.e(TAG, "Not doing toast. pkg=" + pkg + " callback=" + callback);return ;}//判断是否是系统调动或者是Android系统应用程序进行调用final boolean isSystemToast = isCallerSystem() || ("android".equals(pkg));//Toast或者通知权限被禁用if (ENABLE_BLOCKED_TOASTS && !noteNotificationOp(pkg, Binder.getCallingUid())) {if (!isSystemToast) {Slog.e(TAG, "Suppressing toast from package " + pkg + " by user request.");return;}}//mToastQueue加锁synchronized (mToastQueue) {int callingPid = Binder.getCallingPid();long callingId = Binder.clearCallingIdentity();try {ToastRecord record;//寻找当前callback在mToastQueue中的索引，没找到则返回-1int index = indexOfToastLocked(pkg, callback);// If it's already in the queue, we update it in place, we don't// move it to the end of the queue.//index>=0表示mToastQueue中有该callback的索引，record进行更新展示时间if (index >= 0) {record = mToastQueue.get(index);record.update(duration);} else {// Limit the number of toasts that any given package except the android// package can enqueue.  Prevents DOS attacks and deals with leaks.//不是系统的Toastif (!isSystemToast) {int count = 0;final int N = mToastQueue.size();for (int i=0; i<N; i++) {final ToastRecord r = mToastQueue.get(i);//判断当前的Toast是不是同一个包发出的if (r.pkg.equals(pkg)) {count++;//当前包的需要展示的Toast缓存数量>=50if (count >= MAX_PACKAGE_NOTIFICATIONS) {Slog.e(TAG, "Package has already posted " + count+ " toasts. Not showing more. Package=" + pkg);return;}}}}//根据callback等信息构造ToastRecord对象record = new ToastRecord(callingPid, pkg, callback, duration);//将新的ToastRecord对象加入到队列总mToastQueue.add(record);//加入之后当前的索引是lenth-1index = mToastQueue.size() - 1;//将当前包对应的线程切换为前台线程keepProcessAliveLocked(callingPid);}// If it's at index 0, it's the current toast.  It doesn't matter if it's// new or just been updated.  Call back and tell it to show itself.// If the callback fails, this will remove it from the list, so don't// assume that it's valid after this.//如果之前队列中没有正在处理的消息，那么处理当前这个ToastRecordif (index == 0) {showNextToastLocked();}} finally {Binder.restoreCallingIdentity(callingId);}}}}
}

NotificationManagerService使用先进先出（FIFO）的方式处理 mToastQueue 队列中的消息。

服务端的处理

public class NotificationManagerService extends SystemService {void showNextToastLocked() {//获取队列第一个ToastRecordToastRecord record = mToastQueue.get(0);while (record != null) {if (DBG) Slog.d(TAG, "Show pkg=" + record.pkg + " callback=" + record.callback);try {//调用客户端Binder对应的TN.show方法。record.callback.show();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//当前Toast客户端Binder方法调用抛出异常//移除当前ToastRecordint index = mToastQueue.indexOf(record);if (index >= 0) {mToastQueue.remove(index);}//切换当前ToastRecord进程keepProcessAliveLocked(record.pid);//遍历对象变为列表下一个oastRecord对象if (mToastQueue.size() > 0) {record = mToastQueue.get(0);} else {record = null;}}}}
}

客户端的处理

private static class TN extends ITransientNotification.Stub {/*** schedule handleShow into the right thread*/@Overridepublic void show() {if (localLOGV) Log.v(TAG, "SHOW: " + this);mHandler.post(mShow);//利用Handler执行mShow}final Runnable mShow = new Runnable() {@Overridepublic void run() {handleShow();}};//展示Toastpublic void handleShow() {if (localLOGV) Log.v(TAG, "HANDLE SHOW: " + this + " mView=" + mView+ " mNextView=" + mNextView);//判断mNextView是否展示过if (mView != mNextView) {// remove the old view if necessary//移除当前展示的ToasthandleHide();mView = mNextView;//获取当前的应用程序的上下文环境Context context = mView.getContext().getApplicationContext();//获取当前包名String packageName = mView.getContext().getOpPackageName();if (context == null) {context = mView.getContext();}//获取上下文环境的WindowManagerImplmWM = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);// We can resolve the Gravity here by using the Locale for getting// the layout directionfinal Configuration config = mView.getContext().getResources().getConfiguration();final int gravity = Gravity.getAbsoluteGravity(mGravity, config.getLayoutDirection());//设置参数的重力防线mParams.gravity = gravity;if ((gravity & Gravity.HORIZONTAL_GRAVITY_MASK) == Gravity.FILL_HORIZONTAL) {mParams.horizontalWeight = 1.0f;}if ((gravity & Gravity.VERTICAL_GRAVITY_MASK) == Gravity.FILL_VERTICAL) {mParams.verticalWeight = 1.0f;}//设置参数的坐标和偏移量mParams.x = mX;mParams.y = mY;mParams.verticalMargin = mVerticalMargin;mParams.horizontalMargin = mHorizontalMargin;mParams.packageName = packageName;//如果mView添加过，那么先把mView从WindowManager中移除。if (mView.getParent() != null) {if (localLOGV) Log.v(TAG, "REMOVE! " + mView + " in " + this);mWM.removeView(mView);}if (localLOGV) Log.v(TAG, "ADD! " + mView + " in " + this);//把需要展示的View添加在WindowManager中mWM.addView(mView, mParams);trySendAccessibilityEvent();}}
}

Toast的消失

系统的 Toast 的 hide 都是在 INotificationManager 的服务端 Binder 中发起的，但最终的执行都是在 INotificationManager 的客户端 Binder 中执行的。

服务端

public class NotificationManagerService extends SystemService {private final class WorkerHandler extends Handler{@Overridepublic void handleMessage(Message msg){switch (msg.what){case MESSAGE_TIMEOUT://调用当前的Toast的hidehandleTimeout((ToastRecord)msg.obj);break;case MESSAGE_SAVE_POLICY_FILE:handleSavePolicyFile();break;case MESSAGE_SEND_RANKING_UPDATE:handleSendRankingUpdate();break;case MESSAGE_LISTENER_HINTS_CHANGED:handleListenerHintsChanged(msg.arg1);break;case MESSAGE_LISTENER_NOTIFICATION_FILTER_CHANGED:handleListenerInterruptionFilterChanged(msg.arg1);break;}}}//让当前Toast展示一段时间后消失private void scheduleTimeoutLocked(ToastRecord r){//移除mHandler关于这个TaostRecord的所有MessagemHandler.removeCallbacksAndMessages(r);Message m = Message.obtain(mHandler, MESSAGE_TIMEOUT, r);long delay = r.duration == Toast.LENGTH_LONG ? LONG_DELAY : SHORT_DELAY;//发送一个delayed=duration的MESSAGE_TIMEOUT事件mHandler.sendMessageDelayed(m, delay);}//使Toast消失private void handleTimeout(ToastRecord record){if (DBG) Slog.d(TAG, "Timeout pkg=" + record.pkg + " callback=" + record.callback);synchronized (mToastQueue) {//找当前ToastRecord在mToastQueue队列中的索引int index = indexOfToastLocked(record.pkg, record.callback);if (index >= 0) {cancelToastLocked(index);}}}//调用当前索引=index的ToastRecord.callback.hidevoid cancelToastLocked(int index) {ToastRecord record = mToastQueue.get(index);try {调用客户端Binder对应的TN.hide方法。record.callback.hide();} catch (RemoteException e) {Slog.w(TAG, "Object died trying to hide notification " + record.callback+ " in package " + record.pkg);// don't worry about this, we're about to remove it from// the list anyway}//移除处理完的ToastRecordmToastQueue.remove(index);keepProcessAliveLocked(record.pid);if (mToastQueue.size() > 0) {// Show the next one. If the callback fails, this will remove// it from the list, so don't assume that the list hasn't changed// after this point.//处理队列中的下一个ToastRecordshowNextToastLocked();}}
}

客户端

private static class TN extends ITransientNotification.Stub {/*** schedule handleHide into the right thread*/@Overridepublic void hide() {if (localLOGV) Log.v(TAG, "HIDE: " + this);mHandler.post(mHide);//利用Handler执行mHide}final Runnable mHide = new Runnable() {@Overridepublic void run() {handleHide();// Don't do this in handleHide() because it is also invoked by handleShow()mNextView = null;}};public void handleHide() {if (localLOGV) Log.v(TAG, "HANDLE HIDE: " + this + " mView=" + mView);if (mView != null) {// note: checking parent() just to make sure the view has// been added...  i have seen cases where we get here when// the view isn't yet added, so let's try not to crash.if (mView.getParent() != null) {if (localLOGV) Log.v(TAG, "REMOVE! " + mView + " in " + this);//调用WindowManager的removeView移除mViewmWM.removeView(mView);}mView = null;}}
}

Dialog和Toast在异步线程的展现

ViewRootImpl的独白，我不是一个View(布局篇) 这篇文章说明了为什么我们一般禁止在非 UI线程 中刷新 View ，以及怎么安全的在异步线程操作UI。

发生了对任务执行线程的校验，而且当前执行任务的线程与创建 ViewRootImpl 的线程不一样；。

那么 Toast 、 Dialog 和 View 的异步展现，与异步操作UI是否一致呢？

首先测试一下异步展现 Dialog 和 Toast :

//Toast展现
new Thread(new Runnable() {@Overridepublic void run() {//Looper.prepare();Toast.makeText(TestActivity.this, "test", Toast.LENGTH_SHORT).show();//Looper.loop();}
}).start();
//Dialog的展现
new Thread(new Runnable() {@Overridepublic void run() {//Looper.prepare();new MyDialog(TestActivity.this, "test").show();//Looper.loop();}
}).start();

崩溃日志：

//Toast崩溃日志
17:30:04.211#[androidcode@]#30824#E#AndroidRuntime #FATAL EXCEPTION: Thread-2Process: com.tzx.androidcode, PID: 30513java.lang.RuntimeException: Can't toast on a thread that has not called Looper.prepare()at android.widget.Toast$TN.<init>(Toast.java:394)at android.widget.Toast.<init>(Toast.java:114)at android.widget.Toast.makeText(Toast.java:277)at android.widget.Toast.makeText(Toast.java:267)at com.tzx.androidcode.activity.TestActivity$1.run(TestActivity.java:72)at java.lang.Thread.run(Thread.java:764)
//Dialog的崩溃日志
17:33:07.961#[androidcode@]#31514#E#AndroidRuntime #FATAL EXCEPTION: Thread-2Process: com.tzx.androidcode, PID: 31438java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()at android.os.Handler.<init>(Handler.java:203)at android.os.Handler.<init>(Handler.java:117)at android.app.Dialog.<init>(Dialog.java:123)at android.app.Dialog.<init>(Dialog.java:149)at com.tzx.rollaction.test.BaseDailog.<init>(BaseDailog.java:23)at com.tzx.rollaction.test.MyDialog.<init>(MyDialog.java:20)at com.tzx.androidcode.activity.TestActivity$2.run(TestActivity.java:86)at java.lang.Thread.run(Thread.java:764)

我们可以看到都是提示 当前的Handler的Looper没有调用prepare。
我们在上面进行源码阅读的时候都看到了 Toast.TN 和 Dialog 构造的时候的 Handler 都是默认当前线程的 Looper 。
如果当前线程的 Looper 没有 prepare 那么必定会抛异常，如果仅仅执行了 prepare 那么崩溃不会产生了，但是依旧不展示。因为整个 Looper 还没有开始，里面的 Message 都未进行处理。最后我们将代码中注释的 Looper.prepare(); 和 Looper.loop(); 打开就可以正常在异步线程进行 Toast 和 Dialog 的展现。

所以 Toast 和 Dialog 的异步展现其实主要是与其线程的 Looper 队列有关。 Toast 和 Dialog 展示的时候进行的 ViewRootImpl 的创建，这个执行UI操作的也是这个线程，所以展现不会发现异常。如果对 Dialog 进行异步刷新UI ，那么他的限制和 View 的异步刷新是相同的。