深入理解Android(安卓)Notifiction机制
framework/base/services/java/com/android/server/NotificationManagerService.java{@hide} extends INotificationManager.Stub
framework/base/services/java/com/android/server/StatusBarManagerService.javaextends IStatusBarService.Stub
framework/base/core/java/com/android/internal/statusbar/StatusBarNotificationimplements Parcelable
framework/base/core/java/com/android/internal/statusbar/IStatusBar.aidl
framework/base/core/java/com/android/internal/statusbar/IStatusBarService.aidl
framework/base/core/java/com/android/internal/statusbar/StatusBarNotification.aidl
framework/base/packages/SystemUI/src/com/android/systemui/statusbar/StatusBarService.java extends Service implements CommandQueue.Callbacks
framework/base/packages/SystemUI/src/com/android/systemui/statusbar/CommandQueue.java extends IStatusBar.Stub
1>.系统启动的时候：framework/base/services/java/com/android/server/SystemServer.java中：?
| 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 | try { Slog.i(TAG, "Status Bar" ); statusBar = new StatusBarManagerService(context); ServiceManager.addService(Context.STATUS_BAR_SERVICE, statusBar); } catch (Throwable e) { Slog.e(TAG, "Failure starting StatusBarManagerService" , e); } try { Slog.i(TAG, "Notification Manager" ); notification = new NotificationManagerService(context, statusBar, lights); ServiceManager.addService(Context.NOTIFICATION_SERVICE, notification); } catch (Throwable e) { Slog.e(TAG, "Failure starting Notification Manager" , e); } |
这段代码是 注册状态栏管理和通知管理这两个服务。
2>.在StatusBarManagerService.java中，有addNotification，removeNotification,updateNotification等方法用于管理传递给他的通知对象。这个类是一些管理方法，实际执行相关动作的是在IStatusBar.java里面，这个是framework/base/core/java/com/android/internal/statusbar/IStatusBar.aidl自动生成的用于IPC的类。
拿addNotification方法示范：
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| 01 02 03 04 05 06 07 08 09 10 11 12 13 | public IBinder addNotification(StatusBarNotification notification) { synchronized (mNotifications) { IBinder key = new Binder(); mNotifications.put(key, notification); if (mBar != null ) { try { mBar.addNotification(key, notification); } catch (RemoteException ex) { } } return key; } } |
这里的mBar其实就是IStatusBar的实例
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| 01 | volatile IStatusBar mBar; |
为了防止NPE，每次使用mBar都先判断是否为null，mBar是在方法registerStatusBar中传递进来的。
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| 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 | public void registerStatusBar(IStatusBar bar, StatusBarIconList iconList, List<IBinder> notificationKeys, List<StatusBarNotification> notifications) { enforceStatusBarService(); Slog.i(TAG, "registerStatusBar bar=" + bar); mBar = bar; synchronized (mIcons) { iconList.copyFrom(mIcons); } synchronized (mNotifications) { for (Map.Entry<IBinder,StatusBarNotification> e: mNotifications.entrySet()) { notificationKeys.add(e.getKey()); notifications.add(e.getValue()); } } } |
framework/base/packages/SystemUI/src/com/android/systemui/statusbar/CommandQueue.java实现IStatusBar.java接口，
framework/base/packages/SystemUI/src/com/android/systemui/statusbar/StatusBarService.java提供IStatusBar相关服务。
CommandQueue.java中，IStatusBar.java里面对应的方法是用callback的形式调用的，callback的实现当然就在对应的服务提供类也就是StatusBarService.java中提供的啦。
CommandQueue.java中：
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| 01 02 03 04 05 06 07 08 09 10 11 12 | public void addNotification(IBinder key, StatusBarNotification notification) { synchronized (mList) { NotificationQueueEntry ne = new NotificationQueueEntry(); ne.key = key; ne.notification = notification; mHandler.obtainMessage(MSG_ADD_NOTIFICATION, 0 , 0 , ne).sendToTarget(); //这句话对应的mHandler执行语句是： //final NotificationQueueEntry ne = (NotificationQueueEntry)msg.obj; // mCallbacks.addNotification(ne.key, ne.notification); //也就是调用回调函数里面的addNotification。 } } |
在StatusBarService.java中：
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| 01 02 03 04 05 06 07 08 09 | mCommandQueue = new CommandQueue( this , iconList); //StatusBarService实现了CommandQueue中的CommandQueue.Callbacks接口 mBarService = IStatusBarService.Stub.asInterface( ServiceManager.getService(Context.STATUS_BAR_SERVICE)); try { //将IStatusBar实现类的对象传递到StatusBarManagerService.java中，这里的mCommandQueue就是上面对应的mBar啦。 mBarService.registerStatusBar(mCommandQueue, iconList, notificationKeys, notifications); } catch (RemoteException ex) { // If the system process isn't there we're doomed anyway. } |
最终执行状态栏更新通知等事件都是在实现的CommandQueue.Callbacks里面执行。还是以addNotification为例：
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| 01 02 03 04 05 06 07 08 09 10 11 12 13 14 | public void addNotification(IBinder key, StatusBarNotification notification) { boolean shouldTick = true ; if (notification.notification.fullScreenIntent != null ) { shouldTick = false ; Slog.d(TAG, "Notification has fullScreenIntent; sending fullScreenIntent" ); try { notification.notification.fullScreenIntent.send(); } catch (PendingIntent.CanceledException e) { } } StatusBarIconView iconView = addNotificationViews(key, notification); if (iconView == null ) return ; //。。。以下省略N字。 |
大致流程就是:调用StatusBarManagerService.java中的addNotification方法->（mBar不为空的话）执行mBar.addNotification(key, notification);->对应的是CommandQueue中的addNotification(IBinder key, StatusBarNotification notification)->CommandQueue中的mCallbacks.addNotification(ne.key, ne.notification);->StatusBarService中的addNotification。
3>.上面是提供相关功能的一些类，具体的notification的管理类是framework/base/services/java/com/android/server/NotificationManagerService.java，从该类的定义public class NotificationManagerService extends INotificationManager.Stub可以知道
他是用来实现接口中INotificationManager中定义的相关方法并向外部提供服务的类。主要向外提供public void enqueueNotificationWithTag(String pkg, String tag, int id, Notification notification,int[] idOut)方法。该方法实际上是调用public void enqueueNotificationInternal(String pkg, int callingUid, int callingPid,String tag, int id, Notification notification, int[] idOut)，他里面提供了notification的具体处理方法。
摘取部分代码片段看看：
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| 01 02 03 04 05 06 07 08 09 10 11 12 13 14 | if (notification.icon != 0 ) { StatusBarNotification n = new StatusBarNotification(pkg, id, tag, r.uid, r.initialPid, notification); if (old != null && old.statusBarKey != null ) { r.statusBarKey = old.statusBarKey; long identity = Binder.clearCallingIdentity(); try { mStatusBar.updateNotification(r.statusBarKey, n); } finally { Binder.restoreCallingIdentity(identity); } } else { //省略。。。 |
当判断好需要更新通知的时候调用mStatusBar.updateNotification(r.statusBarKey, n);方法，这个就是StatusBarManagerService.java中的addNotification方法，这样就进入上面所说的处理流程了。
4>. 在3中的NotificationManagerService.java是管理notification的服务，服务嘛就是用来调用的，调用他的就是大家熟悉的NotificationManager了。
在NotificationManager.java中，有一个隐藏方法，用来得到INotificationManager接口对应的服务提供类，也就是NotificationManagerService了。
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| 01 02 03 04 05 06 07 08 09 10 | /** @hide */ static public INotificationManager getService() { if (sService != null ) { return sService; } IBinder b = ServiceManager.getService( "notification" ); sService = INotificationManager.Stub.asInterface(b); return sService; } |
再看看更熟悉的notify方法，其实是执行：
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| 01 02 03 04 05 06 07 08 09 10 11 12 13 14 | public void notify(String tag, int id, Notification notification) { int [] idOut = new int [ 1 ]; INotificationManager service = getService(); String pkg = mContext.getPackageName(); if (localLOGV) Log.v(TAG, pkg + ": notify(" + id + ", " + notification + ")" ); try { service.enqueueNotificationWithTag(pkg, tag, id, notification, idOut); if (id != idOut[ 0 ]) { Log.w(TAG, "notify: id corrupted: sent " + id + ", got back " + idOut[ 0 ]); } } catch (RemoteException e) { } } |
ervice.enqueueNotificationWithTag(pkg, tag, id, notification, idOut);也就是3中提到的那个对外公开的服务方法了，这样就进入了上面提到的处理流程了。
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