java - 通过通知中的按钮播放上一首/下一首歌曲

Question

我有一个播放器，当用户选择一首歌曲时，播放器会通过 3 个按钮发出通知:上一首、播放、下一首。在背景模式下选择歌曲需要此按钮。但是当我点击这个按钮时什么也没有发生。这是通知代码:

Intent intentPrev = new Intent(this, NotificationReceiver.class);
        intentPrev.setAction(ACTION_PREV);
        LocalBroadcastManager.getInstance(this).sendBroadcast(intentPrev);
        PendingIntent pendingIntentPrev = PendingIntent.getActivity(this, 0, intentPrev, PendingIntent.FLAG_UPDATE_CURRENT);

        Intent intentPlay = new Intent(this, NotificationReceiver.class);
        intentPlay.setAction(ACTION_PLAY);
        LocalBroadcastManager.getInstance(this).sendBroadcast(intentPlay);
        PendingIntent pendingIntentPlay = PendingIntent.getActivity(this, 0, intentPlay, PendingIntent.FLAG_UPDATE_CURRENT);

        Intent intentNext = new Intent(this, NotificationReceiver.class);
        intentNext.setAction(ACTION_NEXT);
        LocalBroadcastManager.getInstance(this).sendBroadcast(intentNext);
        PendingIntent pendingIntentNext = PendingIntent.getActivity(this, 0, intentNext, PendingIntent.FLAG_UPDATE_CURRENT);

        NotificationCompat.Builder builder = new NotificationCompat.Builder(this).setSmallIcon(R.drawable.notification).
                setContentTitle(songs.get(songPos).getTitle()).setContentText(songs.get(songPos).getArtist()).
                addAction(R.drawable.previous, "Previous", pendingIntentPrev).addAction(R.drawable.pause, "Pause", pendingIntentPlay).
                addAction(R.drawable.next, "Next", pendingIntentNext);
        Notification notification = builder.build();
        NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        notificationManager.notify(1, notification);

Receiver 的代码如下:

package asus.example.com.player;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

import java.util.Objects;

public class NotificationReceiver extends BroadcastReceiver {

    private final String    ACTION_PREV = "PREVIOUS";
    private final String    ACTION_PLAY = "PLAY";
    private final String    ACTION_NEXT = "NEXT";
    private final MyService service     = new MyService();

    @Override
    public void onReceive(Context context, Intent intent) {
        if (Objects.equals(intent.getAction(), ACTION_PREV)){
            service.playPrev();
        }
        else if (Objects.equals(intent.getAction(), ACTION_NEXT)){
            service.playNext();
        }
    }
}

我还向 Manifest 添加了接收器:

<receiver
            android:name=".NotificationReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="PREVIOUS"/>
                <action android:name="PLAY"/>
                <action android:name="NEXT"/>
            </intent-filter>
        </receiver>

当我在调试器中观察时，我看到没有使用 Receiver 类，但我不明白为什么

Answer 1

现在，您正在立即发送广播，其中包含如下语句:

LocalBroadcastManager.getInstance(this).sendBroadcast(intentNext);

你说你想稍后开始一个Activity:

PendingIntent pendingIntentNext = PendingIntent.getActivity(this, 0, intentNext, PendingIntent.FLAG_UPDATE_CURRENT);

(旁注:这无论如何都行不通，因为在 intentNext 中，您指定了一个从 BroadcastReceiver 而不是 Activity 扩展的类)

应该是 getBroadcast() 而不是 getActivity():

Intent intentNext = new Intent(this, NotificationReceiver.class);
intentNext.setAction(ACTION_NEXT);
PendingIntent pendingIntentNext = PendingIntent.getBroadcast(this, 0, intentNext, PendingIntent.FLAG_UPDATE_CURRENT);

另一件事:您在所有 PendingIntent 中使用“0”作为请求代码(第二个参数)。您必须对请求代码使用不同的值，因为共享相同请求代码的两个 Intent 被认为是相同的 Intent，因此您最终所有三个通知 Button 都会触发相同的操作。