android指南针

布局文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <ImageView
        android:id="@+id/iv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:src="@drawable/lv" />

</RelativeLayout>

类文件：

package com.example.chuanganqi;

import android.app.Activity;
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 SensorManager sensorManager;
	private MyListener listener;
	private ImageView iv;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);// 获取他的Api
		Sensor sensor = sensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION);// 得到设备上方向的传感器
		listener = new MyListener();
		iv = (ImageView) this.findViewById(R.id.iv);
		sensorManager.registerListener(listener, sensor,
				SensorManager.SENSOR_DELAY_UI);
	}

	private class MyListener implements SensorEventListener {

		float anglestart = 0;

		// 传感器数据变化的时候
		@Override
		public void onSensorChanged(SensorEvent event) {
			float[] values = event.values;
			float angle = values[0];// 与正北的角度
			System.out.println("与正北的夹角：" + angle);
			RotateAnimation ra = new RotateAnimation(0, angle,
					Animation.RELATIVE_TO_SELF, 0.5f,
					Animation.RELATIVE_TO_SELF, 0.5f);
			ra.setDuration(100);
			iv.startAnimation(ra);
			anglestart = -angle;
		}

		// 传感器精确度变化时调用的方法
		@Override
		public void onAccuracyChanged(Sensor sensor, int accuracy) {

		}

	}

	@Override
	protected void onDestroy() {
		sensorManager.unregisterListener(listener);
		listener = null;
		super.onDestroy();
	}
}