Android实现绕球心旋转的引导页效果

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/activity_main"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:background="#440000ff">

  <ImageView
    android:layout_width="match_parent"
    android:layout_height="230dp"
    android:layout_alignParentBottom="true"
    android:background="@mipmap/guide_bg" />

  <RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ViewFlipper
      android:id="@+id/vf"
      android:layout_width="match_parent"
      android:layout_height="match_parent">

      <fragment
        class="com.example.dell.guide.GuideOneFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

      <fragment
        class="com.example.dell.guide.GuideTwoFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

      <fragment
        class="com.example.dell.guide.GuideThreeFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
    </ViewFlipper>
  </RelativeLayout>
</RelativeLayout>

public class MainActivity extends AppCompatActivity {
  //处理手势监听
  private GestureDetector detector;

  private ViewFlipper flipper;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    flipper = (ViewFlipper) findViewById(R.id.vf);

    detector = new GestureDetector(this, new GestureDetector.SimpleOnGestureListener() {
      @Override
      public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        if (e1.getX() - e2.getX() > 120.0F) { //从右向左滑动
          flipper.setInAnimation(MainActivity.this, R.anim.tip_left_in);
          flipper.setOutAnimation(MainActivity.this, R.anim.tip_left_out);
          if (flipper.getDisplayedChild() < 2) {
            flipper.showNext();
          }
        } else if (e1.getX() - e2.getX() < -120.0F) { //从左向右滑动
          flipper.setInAnimation(MainActivity.this, R.anim.tip_right_in);
          flipper.setOutAnimation(MainActivity.this, R.anim.tip_right_out);
          if (flipper.getDisplayedChild() > 0) {
            flipper.showPrevious();
          }
        }
        return false;
      }
    });
  }

  @Override
  public boolean onTouchEvent(MotionEvent event) {
    if (detector != null) {
      return detector.onTouchEvent(event);
    }
    return super.onTouchEvent(event);
  }
}

detector = new GestureDetector(this, new GestureDetector.SimpleOnGestureListener() {
      @Override
      public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        //省略......
        return false;
      }
    });