深入理解Android Notifiction机制

framework/base/core/java/android/app/NotificationManager.java

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：

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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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