Android-确定指南针中的内存泄漏（SensorManager）

Question

I implemented a simple compass class using a singleton pattern. Once I registered the accelerometer and magnetometer listener with the sensor manager the memory consumption is increasing. My GPS class is very similar to the compass class and there I have no problems regarding memory leaks.I placed a breakpoint in the onSensorChanged method and the the allocated memory is increases by 0,01 MB every 5 calls. I will add the corresponding code below. Maybe anyone got an idea what is going wrong. Maybe there is no problem and its normal, that the memory is slightly increasing?

Main Activity

public class MainActivity extends ActionBarActivity {
    [...]
    protected void onCreate( Bundle savedInstanceState ) {
        super.onCreate( savedInstanceState );
        setContentView( R.layout.activity_main );

        this.mGPS = GPSTracker.getInstance();
        this.mGPS.start( MainActivity.this );
        this.mLocation = this.mGPS.getLatLng();

        this.mCompass = CompassTracker.getInstance();
        // uncomment the following line will stop the memory leak
        this.mCompass.start( MainActivity.this );
    }
    [...]
}

Compass Class

public class CompassTracker implements SensorEventListener {
    [...]
    /**
     * The minimum time between updates in milliseconds.
     */
    private static final int MIN_TIME_BW_UPDATES = 500; //  1 * 60 * 1000 -> 1 Minute

    private void start( Context context ) {
        this.mSensorManager = (SensorManager) context.getSystemService( Context.SENSOR_SERVICE );

        this.mAccelerometer = this.mSensorManager.getDefaultSensor( Sensor.TYPE_ACCELEROMETER );
        this.mMagnetometer = this.mSensorManager.getDefaultSensor( Sensor.TYPE_MAGNETIC_FIELD );

        boolean enAcc = this.mSensorManager.registerListener( this, this.mAccelerometer, MIN_TIME_BW_UPDATES );
        boolean enMag = this.mSensorManager.registerListener( this, this.mMagnetometer, MIN_TIME_BW_UPDATES );

        if ( enAcc && enMag ) {
            this.mStatus = States.ENABLED;
        } else {
            this.mStatus = States.NOT_AVAILABLE;
            this.stop();
        }
    }

    @Override
    public void onSensorChanged( SensorEvent event ) {
        final float alpha = 0.97f;

        if ( event.sensor.getType() == Sensor.TYPE_ACCELEROMETER ) {
            this.mGravity[0] = alpha * this.mGravity[0] + ( 1 - alpha ) * event.values[0];
            this.mGravity[1] = alpha * this.mGravity[1] + ( 1 - alpha ) * event.values[1];
            this.mGravity[2] = alpha * this.mGravity[2] + ( 1 - alpha ) * event.values[2];
        }

        if ( event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD ) {
            this.mGeomagnetic[0] = alpha * this.mGeomagnetic[0] + ( 1 - alpha ) * event.values[0];
            this.mGeomagnetic[1] = alpha * this.mGeomagnetic[1] + ( 1 - alpha ) * event.values[1];
            this.mGeomagnetic[2] = alpha * this.mGeomagnetic[2] + ( 1 - alpha ) * event.values[2];
        }

        float R[] = new float[9];
        float I[] = new float[9];

        if ( SensorManager.getRotationMatrix( R, I, mGravity, mGeomagnetic ) ) {
            this.mOrientation = SensorManager.getOrientation( R, this.mOrientation );
        }

        // inform the listener
        if( this.orientationChangedListener != null )
            this.orientationChangedListener.onOrientationChanged( this.mOrientation );
    }


    /**
     * Orientation listener
     * @param orientationChangedListener
     */
    public void setOrientationChangedListener( OrientationChangedListener orientationChangedListener ) {
        this.orientationChangedListener = orientationChangedListener;
    }
    [...]
}

Thanks in Advance!

Answer 1

Each time

this.mSensorManager = (SensorManager) context.getSystemService( Context.SENSOR_SERVICE );

gets called, the instance of your current MainActivity gets tied to your singleton class. Probably your GPS class would cause the same Memory leak but not as fast as this one.

What you do here is bad design. Especially using the singleton class in an Activity. Refactor your code like this:

1. Learn about Service in Androids documentation
2. Put the sensor stuff in a service.
3. In your service's onCreate method, use its context to get the system services for GPS and compass
4. Unbind the system services in the onDestroy method of your service
5. Use Broadcasting like the LocalBroadcastManager to pass data to other components like to your Activities