Fetching direction from Accelerometer using shake

问题:

I have made android app that plays next song when shake once using Accelerometer.

Now what i want my in app if a shake the phone in right side it should play the next song in line or if shake in left play previous, can i do it with the logic of axis found at time of shake action if that is possible how can I put axis to the methods of motion detection to know the direction in which the mobile is shaked. If any one have a logic for this please help i am stuck here.

回答1:

I did some digging into this and was able to resolve it myself. but while posting the answer I found this answer by Basil which explains better than my implementation. So, i found it more helpful.

what he did

In the onSensorChanged whenever the device receives new value it store the values into variables after some delay. After that compares the new value with previous values beautifully. Which leads to calculate into direction the device has shakes. If the answer is still unclear let me know.

public class ShakeActivity extends Activity implements SensorListener {
// For shake motion detection.
private SensorManager sensorMgr;
private long lastUpdate = -1;
private float x, y, z;
private float last_x, last_y, last_z;
private static final int SHAKE_THRESHOLD = 800;

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

setContentView(R.layout.main);
// start motion detection
sensorMgr = (SensorManager) getSystemService(SENSOR_SERVICE);
boolean accelSupported = sensorMgr.registerListener(this,
    SensorManager.SENSOR_ACCELEROMETER,
    SensorManager.SENSOR_DELAY_GAME);

    if (!accelSupported) {
        // on accelerometer on this device
        sensorMgr.unregisterListener(this,
                SensorManager.SENSOR_ACCELEROMETER);
    }
}

protected void onPause() {
    if (sensorMgr != null) {
        sensorMgr.unregisterListener(this,
                SensorManager.SENSOR_ACCELEROMETER);
        sensorMgr = null;
    }
    super.onPause();
}

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

public void onSensorChanged(int sensor, float[] values) {
    if (sensor == SensorManager.SENSOR_ACCELEROMETER) {
        long curTime = System.currentTimeMillis();
        // only allow one update every 100ms.
        if ((curTime - lastUpdate) > 100) {
        long diffTime = (curTime - lastUpdate);
        lastUpdate = curTime;

        x = values[SensorManager.DATA_X];
        y = values[SensorManager.DATA_Y];
        z = values[SensorManager.DATA_Z];

        if(Round(x,4)>10.0000){
            Log.d("sensor", "X Right axis: " + x);
            Toast.makeText(this, "Right shake detected", Toast.LENGTH_SHORT).show();
        }
        else if(Round(x,4)<-10.0000){
            Log.d("sensor", "X Left axis: " + x);
            Toast.makeText(this, "Left shake detected", Toast.LENGTH_SHORT).show();
        }

        float speed = Math.abs(x+y+z - last_x - last_y - last_z) / diffTime * 10000;

        // Log.d("sensor", "diff: " + diffTime + " - speed: " + speed);
        if (speed > SHAKE_THRESHOLD) {
            //Log.d("sensor", "shake detected w/ speed: " + speed);
            //Toast.makeText(this, "shake detected w/ speed: " + speed, Toast.LENGTH_SHORT).show();
        }
        last_x = x;
        last_y = y;
        last_z = z;
        }
    }
}

public static float Round(float Rval, int Rpl) {
float p = (float)Math.pow(10,Rpl);
Rval = Rval * p;
float tmp = Math.round(Rval);
return (float)tmp/p;
}
}