深刻理解Notification機制

時間 2021-08-13

標籤 html java android app ide 函數工具 this spa 欄目 HTML 简体版

原文原文鏈接

Android藍牙控制遙控器的源碼
http://www.eoeandroid.com/thread-195605-1-1.htmlhtml

基於Android 砸蛋的遊戲
http://www.eoeandroid.com/thread-195603-1-1.htmljava

Android下瀏覽其文件系統的工具
http://www.eoeandroid.com/thread-195591-1-1.htmlandroid

先貼上這些源碼裏面相關的文件：app

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

framework/base/services/java/com/android/server/NotificationManagerService.java{@hide} extends INotificationManager.Stubide

framework/base/services/java/com/android/server/StatusBarManagerService.java extends IStatusBarService.Stub函數

framework/base/core/java/com/android/internal/statusbar/StatusBarNotification implements Parcelable工具

framework/base/core/java/com/android/internal/statusbar/IStatusBar.aidlui

framework/base/core/java/com/android/internal/statusbar/IStatusBarService.aidlthis

framework/base/core/java/com/android/internal/statusbar/StatusBarNotification.aidl spa

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>.系統啓動的時候：framework/base/services/java/com/android/server/SystemServer.java中：

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);     }

這段代碼是註冊狀態欄管理和通知管理這兩個服務。

2>.在StatusBarManagerService.java中，有addNotification，removeNotification,updateNotification等方法用於管理傳遞給他的通知對象。這個類是一些管理方法，實際執行相關動做的是在IStatusBar.java裏面，這個是framework/base/core/java/com/android/internal/statusbar/IStatusBar.aidl自動生成的用於IPC的類。

拿addNotification方法示範：

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;             }           }

這裏的mBar其實就是IStatusBar的實例

volatile IStatusBar mBar;

爲了防止NPE，每次使用mBar都先判斷是否爲null，mBar是在方法registerStatusBar中傳遞進來的。

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實現IStatusBar.java接口，

framework/base/packages/SystemUI/src/com/android/systemui/statusbar/StatusBarService.java提供IStatusBar相關服務。

CommandQueue.java中，IStatusBar.java裏面對應的方法是用callback的形式調用的，callback的實現固然就在對應的服務提供類也就是StatusBarService.java中提供的啦。

CommandQueue.java中：

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();                     //這句話對應的mHandler執行語句是：                     //  final NotificationQueueEntry ne = (NotificationQueueEntry)msg.obj;                 // mCallbacks.addNotification(ne.key, ne.notification);                     //也就是調用回調函數裏面的addNotification。             }         }

在StatusBarService.java中：

mCommandQueue = new CommandQueue(this, iconList);//StatusBarService實現了CommandQueue中的CommandQueue.Callbacks接口             mBarService = IStatusBarService.Stub.asInterface(                     ServiceManager.getService(Context.STATUS_BAR_SERVICE));             try {                     //將IStatusBar實現類的對象傳遞到StatusBarManagerService.java中，這裏的mCommandQueue就是上面對應的mBar啦。                 mBarService.registerStatusBar(mCommandQueue, iconList, notificationKeys, notifications);             } catch (RemoteException ex) {                 // If the system process isn't there we're doomed anyway.             }

最終執行狀態欄更新通知等事件都是在實現的CommandQueue.Callbacks裏面執行。仍是以addNotification爲例：

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;               //。。。如下省略N字。

大體流程就是:調用StatusBarManagerService.java中的addNotification方法->（mBar不爲空的話）執行mBar.addNotification(key, notification);->對應的是CommandQueue中的addNotification(IBinder key, StatusBarNotification notification)->CommandQueue中的mCallbacks.addNotification(ne.key, ne.notification);->StatusBarService中的addNotification。

3>.上面是提供相關功能的一些類，具體的notification的管理類是framework/base/services/java/com/android/server/NotificationManagerService.java，從該類的定義public class NotificationManagerService extends INotificationManager.Stub能夠知道

他是用來實現接口中INotificationManager中定義的相關方法並向外部提供服務的類。主要向外提供public void enqueueNotificationWithTag(String pkg, String tag, int id, Notification notification,int[] idOut)方法。該方法其實是調用public void enqueueNotificationInternal(String pkg, int callingUid, int callingPid,String tag, int id, Notification notification, int[] idOut)，他裏面提供了notification的具體處理方法。

摘取部分代碼片斷看看：

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。。。

當判斷好須要更新通知的時候調用mStatusBar.updateNotification(r.statusBarKey, n);方法，這個就是StatusBarManagerService.java中的addNotification方法，這樣就進入上面所說的處理流程了。

4>. 在3中的NotificationManagerService.java是管理notification的服務，服務嘛就是用來調用的，調用他的就是你們熟悉的NotificationManager了。

在NotificationManager.java中，有一個隱藏方法，用來獲得INotificationManager接口對應的服務提供類，也就是NotificationManagerService了。

/** @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，實際上是執行：

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) {             }         }