制作简单的指南针

/***
 * 指南针简单制作
 **/
public class CompassActivity extends BaseActivity {
    private SensorManager sensorManager;
    @Bind(R.id.compass_img)
    ImageView compassImg;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_compass);
        ButterKnife.bind(this);
        sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
        Sensor magneticSensor = sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
        Sensor accelerometerSensor = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
        sensorManager.registerListener(listener, accelerometerSensor, SensorManager.SENSOR_DELAY_GAME);
        sensorManager.registerListener(listener, magneticSensor, SensorManager.SENSOR_DELAY_GAME);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
    }

    private SensorEventListener listener = new SensorEventListener() {
        float[] accelerometerValues = new float[3];
        float[] magneticValues = new float[3];
        private float lastRotateDegress;

        @Override
        public void onSensorChanged(SensorEvent event) {
            //判断当前是加速度传感器还是地磁传感器
            if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
                //注意赋值时要调用clone()方法
                accelerometerValues = event.values.clone();
            } else if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
                //注意赋值时要调用clone()方法
                magneticValues = event.values.clone();
            }
            float[] values = new float[3];
            float[] R = new float[9];
            SensorManager.getRotationMatrix(R, null, accelerometerValues, magneticValues);
            SensorManager.getOrientation(R, values);
            //将计算出的旋转角度取反，用于旋转指南针背景图
            float rotateDegree = -(float) Math.toDegrees(values[0]);
            if (Math.abs(rotateDegree - lastRotateDegress) > 1) {
                RotateAnimation animation = new RotateAnimation(lastRotateDegress, rotateDegree, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);
                animation.setFillAfter(true);
                compassImg.startAnimation(animation);
                lastRotateDegress = rotateDegree;
            }

        }

        @Override
        public void onAccuracyChanged(Sensor sensor, int accuracy) {

        }
    };
}