SystemUI之USB2（Framework UEvent -> SystemUI）

第二节  Framework UEvent -> SystemUI

逻辑主要在Framework里面的NotificationManagerService.java

UsbDeviceManager.java 到framework的NotificationManagerService.java，这里面涉及到通知的分类和排序，通知的显示风格等等，然后通过NotificationListenerService来通知SystemUI.

在SystemUI注册服务，然后在framework层回调，贯通SystemUI以及Framework。

UsbDeviceManager.java中——》
mNotificationManager.notifyAsUser(null, id, notification,
                            UserHandle.ALL);
调用NotificationManager的notifyAsUser（）往上上传notification，跟到方法里面看下，
路径：framework/base/core/java/android/app/NotificationManager.java
 INotificationManager service = getService();//获取IBinder对象
我们看下Notification的addFieldsFromContext方法做了哪些事情：

路径：frameworks/base/core/java/android/app/Notification.java

public static void addFieldsFromContext(Context context, Notification notification) {  
    addFieldsFromContext(context.getApplicationInfo(), context.getUserId(), notification);  
}  
  
/** 
 * @hide 
 */  
public static void addFieldsFromContext(ApplicationInfo ai, int userId,  
        Notification notification) {  
    notification.extras.putParcelable(EXTRA_BUILDER_APPLICATION_INFO, ai);//"android.appinfo"  
    notification.extras.putInt(EXTRA_ORIGINATING_USERID, userId);//"android.originatingUserId"  
}  

addFieldsFromContext方法主要实现将当前应用的ApplicationInfo对象保存到“android.appinfo”字段，将当前的userId保存到“android.originatingUserId”字段中。

fixLegacySmalIcon，notify函数会判断notification是否有small icon，如果没有设icon或small icon，用notify方法时会抛出异常。fixLegacySmallIcon方法如下：

    private void fixLegacySmallIcon(Notification n, String pkg) {  
        if (n.getSmallIcon() == null && n.icon != 0) {  
            n.setSmallIcon(Icon.createWithResource(pkg, n.icon));  
        }  
    }  

完成上面的操作后，调用通知管理类NotificationManagerService的enqueueNotificationWithTag方法，

    @Override  
    public void enqueueNotificationWithTag(String pkg, String opPkg, String tag, int id,  
            Notification notification, int[] idOut, int userId) throws RemoteException {  
        enqueueNotificationInternal(pkg, opPkg, Binder.getCallingUid(),  
                Binder.getCallingPid(), tag, id, notification, idOut, userId);  
    } 

我们看到在enqueueNotificationWithTag方法中调用了enqueueNotificationInternal方法，这里就是通知处理的核心了。


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在CODE上查看代码片派生到我的代码片


    void enqueueNotificationInternal(final String pkg, final String opPkg, final int callingUid,  
            final int callingPid, final String tag, final int id, final Notification notification,  
            int[] idOut, int incomingUserId) {  
        if (DBG) {  
            Slog.v(TAG, "enqueueNotificationInternal: pkg=" + pkg + " id=" + id  
                    + " notification=" + notification);  
        }  
        checkCallerIsSystemOrSameApp(pkg);  
        // 校验UID  
        final boolean isSystemNotification = isUidSystem(callingUid) || ("android".equals(pkg));  
        final boolean isNotificationFromListener = mListeners.isListenerPackage(pkg);  
      
        final int userId = ActivityManager.handleIncomingUser(callingPid,  
                callingUid, incomingUserId, true, false, "enqueueNotification", pkg);  
        final UserHandle user = new UserHandle(userId);  
      
        // Fix the notification as best we can.  
        try {  
            final ApplicationInfo ai = getContext().getPackageManager().getApplicationInfoAsUser(  
                    pkg, PackageManager.MATCH_DEBUG_TRIAGED_MISSING,  
                    (userId == UserHandle.USER_ALL) ? UserHandle.USER_SYSTEM : userId);  
            Notification.addFieldsFromContext(ai, userId, notification);  
        } catch (NameNotFoundException e) {  
            Slog.e(TAG, "Cannot create a context for sending app", e);  
            return;  
        }  
      
        mUsageStats.registerEnqueuedByApp(pkg);  
      
        // Limit the number of notifications that any given package except the android  
        // package or a registered listener can enqueue.  Prevents DOS attacks and de