java无法理解如何创建用于响铃报警的取消按钮

Question

即使在按下停止报警按钮后，我仍无法停止报警。我不知道如何访问同一个Ringtone实例和call stop（）

这是MainActivity java类中的启动报警开关

public void switchClicked(View view) {
    if (((Switch) view).isChecked()) {
        Log.d("MainActivity", "Alarm On");
        Calendar calendar = Calendar.getInstance();
        calendar.set(Calendar.HOUR_OF_DAY, alarmTimePicker.getHour());
        calendar.set(Calendar.MINUTE, alarmTimePicker.getMinute());
        Intent myIntent = new Intent(MainActivity.this, AlarmReceiver.class);
        pendingIntent = PendingIntent.getBroadcast(MainActivity.this, 0, myIntent, 0);
        alarmManager.set(AlarmManager.RTC, calendar.getTimeInMillis(), pendingIntent);
        setAlarmText("ON");


    } else {
        alarmManager.cancel(pendingIntent);
        setAlarmText("OFF");
        Log.d("MainActivity", "Alarm Off");
    }
}

public void setAlarmText(String alarmText) {
    alarmTextView.setText(alarmText);
}

这是我在MainActivity java类中的StopAlarm按钮

public void stopAlarm(View view) {
        setAlarmText("Alarm stopped");
        Intent myIntent = new Intent(MainActivity.this, AlarmReceiver.class);
        pendingIntent = PendingIntent.getBroadcast(MainActivity.this, 0, myIntent, PendingIntent.FLAG_UPDATE_CURRENT);
        alarmManager.cancel(pendingIntent);
    }

这是AlarmReceiver java类

public class AlarmReceiver extends BroadcastReceiver {
@Override
public void onReceive(final Context context, Intent intent) {

    MainActivity inst = MainActivity.instance();
    inst.setAlarmText("Alarm! Wake up! Wake up!");
    Uri alarmUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_ALARM);
    if (alarmUri == null) {
        alarmUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
    }
    Ringtone ringtone = RingtoneManager.getRingtone(context, alarmUri);
    ringtone.play();
}
}

Answer 1

步骤：

将RingtonePlayingService添加到项目中（别忘了在清单中声明它）

public class RingtonePlayingService extends Service{

    private Ringtone ringtone = null;

    @Override
    public int onStartCommand(Intent intent, int flags, int startId){
        Uri alarmUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_ALARM);
        if (alarmUri == null) 
            alarmUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);

        this.ringtone = RingtoneManager.getRingtone(this, alarmUri);
        ringtone.play();

        return START_STICKY;
    }

    @Override
    public IBinder onBind(Intent intent){
        return null;
    }

    @Override
    public void onDestroy(){
        super.onDestroy();
        shutUpRingtone();
    }

    private void shutUpRingtone(){
        if(ringtone != null)
            ringtone.stop();
        ringtone = null;
    }
}

删除onReceive中的代码，并将其放入：

@Override
public void onReceive(final Context context, Intent intent) {
    Intent startIntent = new Intent(context, RingtonePlayingService.class);
    context.startService(startIntent);
}

现在RingtonePlayingService正在处理铃声播放，并不断引用它。您的stopAlarm方法只是取消潜在的挂起报警，因此，如果它在单击停止按钮之前尚未触发，它将永远不会触发。但当它已经开始响铃时，您应该停止启动服务持有的ringtone实例。在方法末尾添加：

public void stopAlarm(View view) {
    ...
    Intent stopIntent = new Intent(context, RingtonePlayingService.class);
    stopService(stopIntent);
}

现在stopAlarm两个都做：取消挂起的报警（如果有）并停止服务（如果是活动的），这可能会播放铃声

同时删除MainActivity.instance()模式，这是非常糟糕的。。。当你设置未来报警（例如，现在+1h）并且系统（或用户）在启动应用程序之前从内存中删除应用程序时，你将得到NullPointerException，因为.instance()是null，你正在立即尝试访问inst.setAlarmText方法。您可以使用Local Broadcasting或service binding更新您的用户界面-从工作状态RingtonePlayingService向您的Activity发送广播/消息，并保持开始/停止/当前状态