Android AlarmManager 使用默认的闹铃音

Question

我正在尝试在 Android 中使用警报管理器。我想要的是当闹钟响起时，它应该播放我为安卓时钟设置的默认闹钟铃声。我使用了以下代码

Uri uri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_ALARM);
    mp = MediaPlayer.create(context, uri);
    mp.start();

但是，我得到以下异常

java.lang.RuntimeException: Unable to start receiver com.example.user.alarmmanager.MyBroadcastReceiver: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.start()' on a null object reference
        at android.app.ActivityThread.handleReceiver(ActivityThread.java:2732)
        at android.app.ActivityThread.-wrap14(ActivityThread.java)
        at 

android.app.ActivityThread$H.handleMessage(ActivityThread.java:1421)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:148)
            at android.app.ActivityThread.main(ActivityThread.java:5417)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.start()' on a null object reference
            at com.example.user.alarmmanager.MyBroadcastReceiver.onReceive(MyBroadcastReceiver.java:25)
            at android.app.ActivityThread.handleReceiver(ActivityThread.java:2725)
            at android.app.ActivityThread.-wrap14(ActivityThread.java)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1421)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:148)
            at android.app.ActivityThread.main(ActivityThread.java:5417)

请帮忙

Answer 1

嘿伙计们，如果没有警报音，则可能会发生崩溃。