Question

我想知道如何使用NotificationCompat.Builder检测通知是否已启用.cancelAll（）。

停止/的onDestroy：

08-15 14:38:50.315  25990-25990/? E/dalvikvm﹕ >>>>> Normal User
08-15 14:38:50.315  25990-25990/? E/dalvikvm﹕ >>>>> com.myapptest [ userId:0 | appId:10223 ]
08-15 14:39:06.492  25990-25990/? E/MediaPlayer﹕ Should have subtitle controller already set
08-15 14:39:33.051  25990-25990/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.myapptest, PID: 25990
    java.lang.RuntimeException: Unable to stop service com.myapptest.MyMPServ@423a8fd0: java.lang.NullPointerException
            at android.app.ActivityThread.handleStopService(ActivityThread.java:3036)
            at android.app.ActivityThread.access$2300(ActivityThread.java:174)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1409)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:146)
            at android.app.ActivityThread.main(ActivityThread.java:5593)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.myapptest.MyMPServ.stopMediaPlayer(MyMPServ.java:225)
            at com.myapptest.MyMPServ.onDestroy(MyMPServ.java:114)
            at android.app.ActivityThread.handleStopService(ActivityThread.java:3019)
            at android.app.ActivityThread.access$2300(ActivityThread.java:174)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1409)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:146)
            at android.app.ActivityThread.main(ActivityThread.java:5593)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
            at dalvik.system.NativeStart.main(Native Method)

通知

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我使用SharedPreferences，仅在以下情况下调用我的通知：

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logcat的：

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Answer 1

好的 - 看起来当您的服务停止时，notificationManager尚未初始化。看起来您只是在调用showNotification()时初始化notificationManager：

notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);

如果您的服务从不调用showNotification()，则notificationManager将具有null值，以及当您的服务停止时导致NullPointerException（NPE）的原因。

将系统服务的价值保存为班级中的字段通常不是一个好主意。相反，删除NotificationManager字段，只需在每个需要使用它的方法中创建一个新的NotificationManager变量。像这样：

public void stopMediaPlayer() {
    NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
    notificationManager.cancelAll();
    mMediaPlayer.release();
}

public void showNotification(){

    builder = new NotificationCompat.Builder(this);

    builder.setTicker("Hello");
    builder.setContentTitle("Helloo");
    builder.setContentText("Helloooo");
    builder.setOngoing(true);

    NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);

    // Will display the notification in the notification bar
    notificationManager.notify(NOTIFICATION_ID, builder.build());

}

如何检测是否在通知之前显示？

1 个答案: