public class DancingView extends SurfaceView implements SurfaceHolder.Callback {  public static final int STATE_DOWN = 1;//向下狀態  public static final int STATE_UP = 2;//向上狀態  public static final int DEFAULT_POINT_RADIUS = 10;  public static final int DEFAULT_BALL_RADIUS = 13;  public static final int DEFAULT_LINE_WIDTH = 200;  public static final int DEFAULT_LINE_HEIGHT = 2;  public static final int DEFAULT_LINE_COLOR = Color.parseColor("#FF9800");  public static final int DEFAULT_POINT_COLOR = Color.parseColor("#9C27B0");  public static final int DEFAULT_BALL_COLOR = Color.parseColor("#FF4081");  public static final int DEFAULT_DOWN_DURATION = 600;//ms  public static final int DEFAULT_UP_DURATION = 600;//ms  public static final int DEFAULT_FREEDOWN_DURATION = 1000;//ms  public static final int MAX_OFFSET_Y = 50;//水平下降最大偏移距離  public int PONIT_RADIUS = DEFAULT_POINT_RADIUS;//小球半徑  public int BALL_RADIUS = DEFAULT_BALL_RADIUS;//小球半徑  private Paint mPaint;  private Path mPath;  private int mLineColor;  private int mPonitColor;  private int mBallColor;  private int mLineWidth;  private int mLineHeight;  private float mDownDistance;  private float mUpDistance;  private float freeBallDistance;  private ValueAnimator mDownController;//下落控制器  private ValueAnimator mUpController;//上彈控制器  private ValueAnimator mFreeDownController;//自由落體控制器  private AnimatorSet animatorSet;  private int state;  private boolean ismUpControllerDied = false;  private boolean isAnimationShowing = false;  private boolean isBounced = false;  private boolean isBallFreeUp = false;  public DancingView(Context context) {    super(context);    init(context, null);  }  public DancingView(Context context, AttributeSet attrs) {    super(context, attrs);    init(context, attrs);  }  public DancingView(Context context, AttributeSet attrs, int defStyleAttr) {    super(context, attrs, defStyleAttr);    init(context, attrs);  }  private void init(Context context, AttributeSet attrs) {    initAttributes(context, attrs);    mPaint = new Paint();    mPaint.setAntiAlias(true);    mPaint.setStrokeWidth(mLineHeight);    mPaint.setStrokeCap(Paint.Cap.ROUND);    mPath = new Path();    getHolder().addCallback(this);    initController();  }  private void initAttributes(Context context, AttributeSet attrs) {    TypedArray typeArray = context.obtainStyledAttributes(attrs, R.styleable.DancingView);    mLineColor = typeArray.getColor(R.styleable.DancingView_lineColor, DEFAULT_LINE_COLOR);    mLineWidth = typeArray.getDimensionPixelOffset(R.styleable.DancingView_lineWidth, DEFAULT_LINE_WIDTH);    mLineHeight = typeArray.getDimensionPixelOffset(R.styleable.DancingView_lineHeight, DEFAULT_LINE_HEIGHT);    mPonitColor = typeArray.getColor(R.styleable.DancingView_pointColor, DEFAULT_POINT_COLOR);    mBallColor = typeArray.getColor(R.styleable.DancingView_ballColor, DEFAULT_BALL_COLOR);    typeArray.recycle();  }  private void initController() {    mDownController = ValueAnimator.ofFloat(0, 1);    mDownController.setDuration(DEFAULT_DOWN_DURATION);    mDownController.setInterpolator(new DecelerateInterpolator());    mDownController.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {      @Override      public void onAnimationUpdate(ValueAnimator animation) {        mDownDistance = MAX_OFFSET_Y * (float) animation.getAnimatedValue();        postInvalidate();      }    });    mDownController.addListener(new Animator.AnimatorListener() {      @Override      public void onAnimationStart(Animator animation) {        state = STATE_DOWN;      }      @Override      public void onAnimationEnd(Animator animation) {      }      @Override      public void onAnimationCancel(Animator animation) {      }      @Override      public void onAnimationRepeat(Animator animation) {      }    });    mUpController = ValueAnimator.ofFloat(0, 1);    mUpController.setDuration(DEFAULT_UP_DURATION);    mUpController.setInterpolator(new DancingInterpolator());    mUpController.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {      @Override      public void onAnimationUpdate(ValueAnimator animation) {        mUpDistance = MAX_OFFSET_Y * (float) animation.getAnimatedValue();        if (mUpDistance >= MAX_OFFSET_Y) {          //進入自由落體狀態          isBounced = true;          if (!mFreeDownController.isRunning() && !mFreeDownController.isStarted() && !isBallFreeUp) {            mFreeDownController.start();          }        }        postInvalidate();      }    });    mUpController.addListener(new Animator.AnimatorListener() {      @Override      public void onAnimationStart(Animator animation) {        state = STATE_UP;      }      @Override      public void onAnimationEnd(Animator animation) {        ismUpControllerDied = true;      }      @Override      public void onAnimationCancel(Animator animation) {      }      @Override      public void onAnimationRepeat(Animator animation) {      }    });    mFreeDownController = ValueAnimator.ofFloat(0, 8f);    mFreeDownController.setDuration(DEFAULT_FREEDOWN_DURATION);    mFreeDownController.setInterpolator(new DecelerateInterpolator());    mFreeDownController.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {      @Override      public void onAnimationUpdate(ValueAnimator animation) {        //該公式解決上升減速 和 下降加速        float t = (float) animation.getAnimatedValue();        freeBallDistance = 40 * t - 5 * t * t;        if (ismUpControllerDied) {//往上拋,到臨界點          postInvalidate();        }      }    });    mFreeDownController.addListener(new Animator.AnimatorListener() {      @Override      public void onAnimationStart(Animator animation) {        isBallFreeUp = true;      }      @Override      public void onAnimationEnd(Animator animation) {        isAnimationShowing = false;        //循環第二次        startAnimations();      }      @Override      public void onAnimationCancel(Animator animation) {      }      @Override      public void onAnimationRepeat(Animator animation) {      }    });    animatorSet = new AnimatorSet();    animatorSet.play(mDownController).before(mUpController);    animatorSet.addListener(new Animator.AnimatorListener() {      @Override      public void onAnimationStart(Animator animation) {        isAnimationShowing = true;      }      @Override      public void onAnimationEnd(Animator animation) {      }      @Override      public void onAnimationCancel(Animator animation) {      }      @Override      public void onAnimationRepeat(Animator animation) {      }    });  }  /**   * 啟動動畫,外部調用   */  public void startAnimations() {    if (isAnimationShowing) {      return;    }    if (animatorSet.isRunning()) {      animatorSet.end();      animatorSet.cancel();    }    isBounced = false;    isBallFreeUp = false;    ismUpControllerDied = false;    animatorSet.start();  }  @Override  protected void onDraw(Canvas canvas) {    super.onDraw(canvas);    // 一條繩子用左右兩部分的二階貝塞爾曲線組成    mPaint.setColor(mLineColor);    mPath.reset();    //起始點    mPath.moveTo(getWidth() / 2 - mLineWidth / 2, getHeight() / 2);    if (state == STATE_DOWN) {//下落      /**************繪制繩子開始*************/      //左部分 的貝塞爾      mPath.quadTo((float) (getWidth() / 2 - mLineWidth / 2 + mLineWidth * 0.375), getHeight() / 2 + mDownDistance,          getWidth() / 2, getHeight() / 2 + mDownDistance);      //右部分 的貝塞爾      mPath.quadTo((float) (getWidth() / 2 + mLineWidth / 2 - mLineWidth * 0.375), getHeight() / 2 + mDownDistance,          getWidth() / 2 + mLineWidth / 2, getHeight() / 2);      mPaint.setStyle(Paint.Style.STROKE);      canvas.drawPath(mPath, mPaint);      /**************繪制繩子結束*************/      /**************繪制彈跳小球開始*************/      mPaint.setStyle(Paint.Style.FILL);      mPaint.setColor(mBallColor);      canvas.drawCircle(getWidth() / 2, getHeight() / 2 + mDownDistance - BALL_RADIUS, BALL_RADIUS, mPaint);      /**************繪制彈跳小球結束*************/    } else if (state == STATE_UP) { //向上彈      /**************繪制繩子開始*************/      //左部分的貝塞爾      mPath.quadTo((float) (getWidth() / 2 - mLineWidth / 2 + mLineWidth * 0.375), getHeight() / 2 + 50 - mUpDistance,          getWidth() / 2,          getHeight() / 2 + (50 - mUpDistance));      //右部分的貝塞爾      mPath.quadTo((float) (getWidth() / 2 + mLineWidth / 2 - mLineWidth * 0.375), getHeight() / 2 + 50 - mUpDistance,          getWidth() / 2 + mLineWidth / 2,          getHeight() / 2);      mPaint.setStyle(Paint.Style.STROKE);      canvas.drawPath(mPath, mPaint);      /**************繪制繩子結束*************/      mPaint.setStyle(Paint.Style.FILL);      mPaint.setColor(mBallColor);      //彈性小球,自由落體      if (!isBounced) {        //上升        canvas.drawCircle(getWidth() / 2, getHeight() / 2 + (MAX_OFFSET_Y - mUpDistance) - BALL_RADIUS, BALL_RADIUS, mPaint);      } else {        //自由落體        canvas.drawCircle(getWidth() / 2, getHeight() / 2 - freeBallDistance - BALL_RADIUS, BALL_RADIUS, mPaint);      }    }    mPaint.setColor(mPonitColor);    mPaint.setStyle(Paint.Style.FILL);    canvas.drawCircle(getWidth() / 2 - mLineWidth / 2, getHeight() / 2, PONIT_RADIUS, mPaint);    canvas.drawCircle(getWidth() / 2 + mLineWidth / 2, getHeight() / 2, PONIT_RADIUS, mPaint);  }  @Override  public void surfaceCreated(SurfaceHolder holder) {    Canvas canvas = holder.lockCanvas();//鎖定整個SurfaceView對象,獲取該Surface上的Canvas.    draw(canvas);    holder.unlockCanvasAndPost(canvas);//釋放畫布，提交修改  }  @Override  public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {  }  @Override  public void surfaceDestroyed(SurfaceHolder holder) {  }}

 public class DancingInterpolator implements Interpolator {  @Override  public float getInterpolation(float input) {    return (float) (1 - Math.exp(-3 * input) * Math.cos(10 * input));  }}

<declare-styleable name="DancingView">    <attr name="lineWidth" format="dimension" />    <attr name="lineHeight" format="dimension" />    <attr name="pointColor" format="reference|color" />    <attr name="lineColor" format="reference|color" />    <attr name="ballColor" format="reference|color" /></declare-styleable>