轻松实现Android指南针功能

<?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>

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) {
    }
  }

}