为什么加速度计没有按时启动或正常检索数据？

Question

我编写了一个应用程序，计划每 15 秒启动一次加速度计并运行 10 秒以检索传感器数据。我使用 AlarmManager 启动加速度计，并在屏幕关闭时通过唤醒锁保持其运行。但我发现有时：

1. 加速度计在一段时间后无法检索数据。我的意思是它已经根据logcat启动了，但是没有任何传感器数据，然后它被关闭并在没有数据的情况下再次启动。
2. 我不知道为什么加速度计在一段时间后不再启动，而之前一切都很好。我发现 logcat 说“带有绑定器 android.os.BinderProxy 的监听器不存在加速计”。我不知道为什么。

以下是内核代码：

Activity.java

Intent intent = new Intent(getApplicationContext(),SensorService.class);
PendingIntent pendingIntent = PendingIntent.getService(getApplicationContext(), 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
long curTime = Calendar.getInstance().getTimeInMillis();
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, curTime, _intervalTime, pendingIntent);  

SensorService.java

public void onStart(Intent intent, int startId) {

        new Thread(new Runnable(){

            public void run() {
                // TODO Auto-generated method stub
                wl.acquire();
                Log.d(TAG,"I'm bright!");
                try {
                    Thread.sleep(_delayClose);// kill self after _delayClose ms
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                stopSelf();// SensorService.this.stopSelf()
            }

        }).start();

        this.mSensorManager.registerListener( _sensorHandle, 
                accSensor, 
                sensorDelay)
}
public void onDestroy() {
    // TODO Auto-generated method stub
    super.onDestroy();
    this.mSensorManager.unregisterListener(_sensorHandle);
    Log.d(TAG,"TIEM UP");
    if(wl.isHeld())
    {
        wl.release();   
    }
}

Answer 1

我猜测经常注册和取消注册传感器侦听器一定会产生相当大的开销，再加上alarmManager的开销。

考虑到您经常需要传感器数据，那么如何让您的侦听器注册并让它在内部管理它何时应该和不应该对它接收的样本执行一些有用的操作？

public class SensorSamplrActivity extends Activity {
    private final static String TAG = "samplr";
    private final static int SAMPLE_INTERVAL_SECS = 15;
    private final static int SAMPLE_DURATION_SECS = 10;

    private SensorManager mSensorManager;
    private long whenToStartSample = System.currentTimeMillis();
    private long whenToEndSample = System.currentTimeMillis() + SAMPLE_DURATION_SECS;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mSensorManager = (SensorManager)getSystemService(Context.SENSOR_SERVICE);
        mSensorManager.registerListener(mSensorListener, mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),SensorManager.SENSOR_DELAY_GAME);
    }

    private SensorEventListener mSensorListener = new SensorEventListener() {

        @Override
        public void onAccuracyChanged(Sensor arg0, int arg1) {
            // TODO Auto-generated method stub
        }

        @Override
        public void onSensorChanged(SensorEvent event) {
            long now = System.currentTimeMillis();
            if (now < whenToStartSample){
                // ignore the event & wait for next time to sample
                Log.d(TAG,"ignoring events for " + (whenToStartSample - now) + "ms");
                return;
            }

            if (whenToStartSample <= now && whenToEndSample > now){
                Log.d(TAG,"Do something with this event @ " + now);
            }
            else {
                // we've gone past whenToEndSample so reset timers
                whenToStartSample = now + (SAMPLE_INTERVAL_SECS * 1000);
                whenToEndSample = whenToStartSample + (SAMPLE_DURATION_SECS * 1000) ;
            }
        }
    };

    @Override
    public void onDestroy(){
        super.onDestroy();
        mSensorManager.unregisterListener(mSensorListener);
    }
}