public class LoadingView extends View {  private final static String TAG = "LoadingView";  private final static int LEFT_BALL_DOWN = 1;  private final static int LEFT_BALL_UP = 2;  private final static int RIGHT_BALL_DOWN = 3;  private final static int RIGHT_BALL_UP = 4;  private Paint paint1, paint2, paint3, paint4, paint5;  private int mCurrentAnimatorValue;  private int circleRadius = 10; //小球的半徑  private int distance = 60; //小球開始下落到最低點的距離  private int mCurrentState = LEFT_BALL_DOWN;  public LoadingView(Context context) {    super(context);    init(context);  }  public LoadingView(Context context, @Nullable AttributeSet attrs) {    super(context, attrs);    init(context);  }  public LoadingView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {    super(context, attrs, defStyleAttr);    init(context);  }  private void init(Context context) {    paint1 = getPaint(Color.RED);    paint2 = getPaint(Color.YELLOW);    paint3 = getPaint(Color.GREEN);    paint4 = getPaint(Color.BLUE);    paint5 = getPaint(Color.CYAN);    ValueAnimator animator = ValueAnimator.ofInt(0, 90);    animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {      @Override      public void onAnimationUpdate(ValueAnimator animation) {        mCurrentAnimatorValue = (int) animation.getAnimatedValue();        Log.e(TAG, "onAnimationUpdate : mCurrentAnimatorValue = " + mCurrentAnimatorValue);        invalidate();      }    });    animator.addListener(new Animator.AnimatorListener() {      @Override      public void onAnimationStart(Animator animation) {      }      @Override      public void onAnimationEnd(Animator animation) {      }      @Override      public void onAnimationCancel(Animator animation) {      }      @Override      public void onAnimationRepeat(Animator animation) {        Log.e(TAG, "onAnimationRepeat : mCurrentAnimatorValue = " + mCurrentAnimatorValue);        switch (mCurrentState) {          case LEFT_BALL_DOWN:            mCurrentState = RIGHT_BALL_UP;            break;          case RIGHT_BALL_UP:            mCurrentState = RIGHT_BALL_DOWN;            break;          case RIGHT_BALL_DOWN:            mCurrentState = LEFT_BALL_UP;            break;          case LEFT_BALL_UP:            mCurrentState = LEFT_BALL_DOWN;            break;        }      }    });    animator.setStartDelay(500);    animator.setDuration(600);    animator.setRepeatCount(ValueAnimator.INFINITE);    animator.setInterpolator(new DecelerateInterpolator());    animator.start();  }  private Paint getPaint(int color) {    Paint paint = new Paint();    paint.setColor(color);    paint.setAntiAlias(true);    paint.setStyle(Paint.Style.FILL);    return paint;  }  @Override  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {    super.onMeasure(widthMeasureSpec, heightMeasureSpec);  }  @Override  protected void onDraw(Canvas canvas) {    super.onDraw(canvas);    int x, y;    double cosValue = Math.cos(PI * mCurrentAnimatorValue / 180);    double sinValue = Math.sin(PI * mCurrentAnimatorValue / 180);    drawFourBall(canvas);    switch (mCurrentState) {      case LEFT_BALL_DOWN://最左邊小球往下撞擊        x = circleRadius + (int) ((distance - circleRadius) * (1 - cosValue));        y = getHeight() - distance + (int) ((distance - circleRadius) * sinValue);        canvas.drawCircle(x, y, circleRadius, paint1);        break;      case RIGHT_BALL_UP://最右邊小球往上撞擊        x = distance + 8 * circleRadius + (int) ((distance - circleRadius) * sinValue);        y = getHeight() - distance + (int) (cosValue * (distance - circleRadius));        canvas.drawCircle(x, y, circleRadius, paint5);        break;      case RIGHT_BALL_DOWN://最右邊小球往下撞擊        x = distance + 8 * circleRadius + (int) ((distance - circleRadius) * (cosValue));        y = (getHeight() - distance) + (int) ((distance - circleRadius) * (sinValue));        canvas.drawCircle(x, y, circleRadius, paint5);        break;      case LEFT_BALL_UP://最左邊小球往上撞擊        x = distance - (int) ((distance - circleRadius) * sinValue);        y = getHeight() - distance + (int) ((distance - circleRadius) * cosValue);        canvas.drawCircle(x, y, circleRadius, paint1);        break;    }  }  private void drawFourBall(Canvas canvas) {    int y = getHeight() - circleRadius;    canvas.drawCircle(distance + 2 * circleRadius, y, circleRadius, paint2);    canvas.drawCircle(distance + 4 * circleRadius, y, circleRadius, paint3);    canvas.drawCircle(distance + 6 * circleRadius, y, circleRadius, paint4);    if (mCurrentState == LEFT_BALL_DOWN || mCurrentState == LEFT_BALL_UP) {//最左邊球運動的時候，要繪制最右邊的球      canvas.drawCircle(distance + 8 * circleRadius, y, circleRadius, paint5);    } else if (mCurrentState == RIGHT_BALL_UP || mCurrentState == RIGHT_BALL_DOWN) {//最右邊球運動的時候，要繪制最左邊的球      canvas.drawCircle(distance, y, circleRadius, paint1);    }  }}

<com.define_view.LoadingView    android:layout_marginTop="20px"    android:background="#999999"    android:layout_width="200px"    android:layout_height="200px" />