Android实现指南针功能

（1）布局文件如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:gravity="center"
    android:orientation="vertical" >

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/zn" />

</LinearLayout>

所需图片：

（2）MainActivity.java

import android.app.Activity;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.view.animation.Animation;
import android.view.animation.RotateAnimation;
import android.widget.ImageView;

public class MainActivity extends Activity {
    private ImageView imageView;
    private SensorManager manager;
    private SensorListener listener = new SensorListener();

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

        imageView = (ImageView) this.findViewById(R.id.imageView);
        imageView.setKeepScreenOn(true);
        manager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
    }

    @Override
    protected void onResume() {
        Sensor sensor = manager.getDefaultSensor(Sensor.TYPE_ORIENTATION);
        manager.registerListener(listener, sensor,
                SensorManager.SENSOR_DELAY_GAME);
        super.onResume();
    }

    @Override
    protected void onPause() {
        manager.unregisterListener(listener);
        super.onPause();
    }

    private final class SensorListener implements SensorEventListener {
        private float predegree = 0;

        public void onSensorChanged(SensorEvent event) {
            float degree = event.values[0];// 存放了方向值 90
            RotateAnimation animation = new RotateAnimation(predegree, -degree,
                    Animation.RELATIVE_TO_SELF, 0.5f,
                    Animation.RELATIVE_TO_SELF, 0.5f);
            animation.setDuration(200);
            imageView.startAnimation(animation);
            predegree = -degree;
        }

        public void onAccuracyChanged(Sensor sensor, int accuracy) {
        }
    }

}