public class ShapeDrawableActivity extends AppCompatActivity {
 private ImageView ivLightbeam;

 private ObjectAnimator radarScanAnim; // 扫描动画

 private int width;
 private int height;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);

  setContentView(R.layout.activity_shape_drawable);
  ivLightbeam = (ImageView) findViewById(R.id.ivLightbeam);
 }


 @Override
 protected void onResume() {
  super.onResume();
  startScan();
 }

 @Override
 public void onWindowFocusChanged(boolean hasFocus) {
  super.onWindowFocusChanged(hasFocus);
  if (height == 0 || width == 0) {   //获取屏幕长、宽
   width = ScreenUtils.getScreenWidth(this);
   height = ScreenUtils.getScreenHeight(this);   //根据屏幕长、宽计算扫描圆的直径
   int diameter = (int) Math.sqrt(Math.pow(height, 2) + Math.pow(width, 2));   //修改光束的大小，使光束可以扫描到整个屏幕
   FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(diameter, diameter);
   ivLightbeam.setLayoutParams(layoutParams);   //将扫描光束的中心移至屏幕内容中心
   int offsetX = (width - diameter) / 2;
   int offsetY = (height - diameter) / 2 + ScreenUtils.getStatusHeight(this) / 2;
   ivLightbeam.setX(offsetX);
   ivLightbeam.setY(offsetY);
  }
 }

 @Override
 protected void onPause() {
  super.onPause();
  stopScan();
 } // 开始扫描

 private void startScan() {
  radarScanAnim = ObjectAnimator.ofFloat(ivLightbeam, "rotation", 0f, 360f);
  radarScanAnim.setDuration(2000); //2秒扫描一圈
  radarScanAnim.setInterpolator(new LinearInterpolator());
  radarScanAnim.setRepeatCount(ObjectAnimator.INFINITE);//循环扫描

  ivLightbeam.setVisibility(View.VISIBLE);
  radarScanAnim.start();
 } // 停止扫描

 private void stopScan() {
  ivLightbeam.setVisibility(View.GONE);
  radarScanAnim.end();
 }
}