轻松实现Android指南针功能

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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) {
    }
  }

}