Android贝塞尔曲线实现消息拖拽消失

写在前头

写消息拖拽效果的文章不少，但是大部分都把自定义View写死了，我们要实现的是传入一个View，每个View都可以实现拖拽消失爆炸的效果，当然我也是站在巨人的肩膀上来学习的。但个人觉得程序员本就应该敢于学习和借鉴。

源码地址：源码Github地址

效果图

分析（用到的知识点）： 

（1）ValueAnimator （数值生成器） 用于生成数值，可以设置差值器来改变数字的变化幅度。

（2）ObjectAnimator （动画生成器） 用于生成各种属性，布局动画，同样也可以设置差值器来改变效果。

（3）贝塞尔一阶曲线

（4）自定义View的基础知识

（5）WindowManager 使view拖拽能显示在整个屏幕的任何地方，而不是局限于父布局内

具体实现方法

一、首先我们要实现基础效果

基础效果是点击屏幕任意一点能出现消息拖拽的效果，但是此时我们不用管我们拖动的View，只需要完成大致模型。该部分的难点在于贝塞尔一阶曲线的怎么实现。

基础效果图

分析：

（1）点击任意一点画出两个圆，和一个有贝塞尔曲线组成的path路径

（2）随着拖动距离的增加原点的圆半径逐渐缩小，当距离达到一定大以后原点的圆和贝塞尔曲线组成的path不再显示

贝塞尔曲线的画法

首先我们需要求出角a的大小，根据角a来求到A,B,C,D的坐标位子，然后求到控制点E点的坐标，通过Path.quadTo()方法来连接A,B和C,D两条贝塞尔曲线。

各点坐标

A（c1.x+sina*c1半径，c1.y-cina*c1半径）

B（c2.x+sina*c2半径，c2.y-cina*c2半径）

C（c2.x-sina*c1半径，c2.y+cina*c1半径）

D（c1.x-sina*c2半径，c1.y+cina*c2半径）

E ((c1.x+c2.x)/2,(c1.y+c2.y)/2)

贝塞尔曲线的path代码

private Path getBezeierPath() {
  double distance = getDistance(mBigCirclePoint,mLittleCirclePoint);

  mLittleCircleRadius = (int) (mLittleCircleRadiusMax - distance / 10);
  if (mLittleCircleRadius < mLittleCircleRadiusMin) {
   // 超过一定距离 贝塞尔和固定圆都不要画了
   return null;
  }

  Path bezeierPath = new Path();

  // 求角 a
  // 求斜率
  float dy = (mBigCirclePoint.y-mLittleCirclePoint.y);
  float dx = (mBigCirclePoint.x-mLittleCirclePoint.x);
  float tanA = dy/dx;
  // 求角a
  double arcTanA = Math.atan(tanA);

  // A
  float Ax = (float) (mLittleCirclePoint.x + mLittleCircleRadius*Math.sin(arcTanA));
  float Ay = (float) (mLittleCirclePoint.y - mLittleCircleRadius*Math.cos(arcTanA));

  // B
  float Bx = (float) (mBigCirclePoint.x + mBigCircleRadius*Math.sin(arcTanA));
  float By = (float) (mBigCirclePoint.y - mBigCircleRadius*Math.cos(arcTanA));

  // C
  float Cx = (float) (mBigCirclePoint.x - mBigCircleRadius*Math.sin(arcTanA));
  float Cy = (float) (mBigCirclePoint.y + mBigCircleRadius*Math.cos(arcTanA));

  // D
  float Dx = (float) (mLittleCirclePoint.x - mLittleCircleRadius*Math.sin(arcTanA));
  float Dy = (float) (mLittleCirclePoint.y + mLittleCircleRadius*Math.cos(arcTanA));

  // 拼装 贝塞尔的曲线路径
  bezeierPath.moveTo(Ax,Ay); // 移动
  // 两个点
  PointF controlPoint = getControlPoint();
  // 画了第一条 第一个点（控制点,两个圆心的中心点），终点
  bezeierPath.quadTo(controlPoint.x,controlPoint.y,Bx,By);

  // 画第二条
  bezeierPath.lineTo(Cx,Cy); // 链接到
  bezeierPath.quadTo(controlPoint.x,controlPoint.y,Dx,Dy);
  bezeierPath.close();

  return bezeierPath;
 }

 二、完善代码

这部分我们需要完善所有代码，实现代码的分离，使得所用View都能被拖动，且需要创建一个监听器来监听View是否拖动结束了，结束后调用回调方法以便需要做其他处理。

需要完成的功能：

（1）将传入的View画出来

（2）在手指抬起时判断是爆炸还是回弹

（3）完成回弹和爆炸的代码部分

（4）回弹或者爆炸结束后调用回调通知动画结束

（5）使用WindowManager把自定义拖拽View加进去，隐藏原来得View实现View在任意地方拖动

完整代码部分

（1）自定义View的代码

public class MsgDrafitingView extends View{

 private PointF mLittleCirclePoint;
 private PointF mBigCirclePoint;
 private Paint mPaint;
 //大圆半径
 private int mBigCircleRadius = 10;
 //小圆半径
 private int mLittleCircleRadiusMax = 10;
 private int mLittleCircleRadiusMin = 2;
 private int mLittleCircleRadius;
 private Bitmap dragBitmap;
 private OnToucnUpListener mOnToucnUpListener;

 public MsgDrafitingView(Context context) {
  this(context,null);
 }

 public MsgDrafitingView(Context context, @Nullable AttributeSet attrs) {
  this(context, attrs,0);
 }

 public MsgDrafitingView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
  mBigCircleRadius = dip2px(mBigCircleRadius);
  mLittleCircleRadiusMax = dip2px(mLittleCircleRadiusMax);
  mLittleCircleRadiusMin = dip2px(mLittleCircleRadiusMin);
  mPaint = new Paint();
  mPaint.setColor(Color.RED);
  mPaint.setAntiAlias(true);
  mPaint.setDither(true);
 }

 private int dip2px(int dip) {
  return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,dip,getResources().getDisplayMetrics());
 }

 @Override
 protected void onDraw(Canvas canvas) {
  if (mBigCirclePoint == null || mLittleCirclePoint == null) {
   return;
  }
  //画大圆
  canvas.drawCircle(mBigCirclePoint.x, mBigCirclePoint.y, mBigCircleRadius, mPaint);
  //获得贝塞尔路径
  Path bezeierPath = getBezeierPath();
  if (bezeierPath!=null) {
   // 小到一定层度就不见了（不画了）
   canvas.drawCircle(mLittleCirclePoint.x, mLittleCirclePoint.y, mLittleCircleRadius, mPaint);
   // 画贝塞尔曲线
   canvas.drawPath(bezeierPath, mPaint);
  }
  // 画图片
  if (dragBitmap != null) {
   canvas.drawBitmap(dragBitmap, mBigCirclePoint.x - dragBitmap.getWidth() / 2,
     mBigCirclePoint.y - dragBitmap.getHeight() / 2, null);
  }
 }

 private Path getBezeierPath() {
  double distance = getDistance(mBigCirclePoint,mLittleCirclePoint);

  mLittleCircleRadius = (int) (mLittleCircleRadiusMax - distance / 10);
  if (mLittleCircleRadius < mLittleCircleRadiusMin) {
   // 超过一定距离 贝塞尔和固定圆都不要画了
   return null;
  }

  Path bezeierPath = new Path();

  // 求角 a
  // 求斜率
  float dy = (mBigCirclePoint.y-mLittleCirclePoint.y);
  float dx = (mBigCirclePoint.x-mLittleCirclePoint.x);
  float tanA = dy/dx;
  // 求角a
  double arcTanA = Math.atan(tanA);

  // A
  float Ax = (float) (mLittleCirclePoint.x + mLittleCircleRadius*Math.sin(arcTanA));
  float Ay = (float) (mLittleCirclePoint.y - mLittleCircleRadius*Math.cos(arcTanA));

  // B
  float Bx = (float) (mBigCirclePoint.x + mBigCircleRadius*Math.sin(arcTanA));
  float By = (float) (mBigCirclePoint.y - mBigCircleRadius*Math.cos(arcTanA));

  // C
  float Cx = (float) (mBigCirclePoint.x - mBigCircleRadius*Math.sin(arcTanA));
  float Cy = (float) (mBigCirclePoint.y + mBigCircleRadius*Math.cos(arcTanA));

  // D
  float Dx = (float) (mLittleCirclePoint.x - mLittleCircleRadius*Math.sin(arcTanA));
  float Dy = (float) (mLittleCirclePoint.y + mLittleCircleRadius*Math.cos(arcTanA));

  // 拼装 贝塞尔的曲线路径
  bezeierPath.moveTo(Ax,Ay); // 移动
  // 两个点
  PointF controlPoint = getControlPoint();
  // 画了第一条 第一个点（控制点,两个圆心的中心点），终点
  bezeierPath.quadTo(controlPoint.x,controlPoint.y,Bx,By);

  // 画第二条
  bezeierPath.lineTo(Cx,Cy); // 链接到
  bezeierPath.quadTo(controlPoint.x,controlPoint.y,Dx,Dy);
  bezeierPath.close();

  return bezeierPath;
 }
 /**
  * 获得控制点距离
  */
 public PointF getControlPoint() {
  return new PointF((mLittleCirclePoint.x+mBigCirclePoint.x)/2,(mLittleCirclePoint.y+mBigCirclePoint.y)/2);
 }

 /**
  * 获得两点之间的距离
  */
 private double getDistance(PointF point1, PointF point2) {
  return Math.sqrt((point1.x - point2.x) * (point1.x - point2.x) + (point1.y - point2.y) * (point1.y - point2.y));
 }

 /**
  * 绑定View
  */
 public static void attach(View view, MsgDrafitingListener.BubbleDisappearListener disappearListener) {
  view.setOnTouchListener(new MsgDrafitingListener(view.getContext(),disappearListener));
 }

 public void initPoint(float x, float y) {
  mBigCirclePoint = new PointF(x,y);
  mLittleCirclePoint = new PointF(x,y);
 }

 public void updatePoint(float x,float y)
 {
  mBigCirclePoint.x = x;
  mBigCirclePoint.y = y;
  invalidate();
 }

 public void setDragBitmap(Bitmap dragBitmap) {
  this.dragBitmap = dragBitmap;
 }

 public void setOnToucnUpListener(OnToucnUpListener listener)
 {
  mOnToucnUpListener = listener;
 }

 public interface OnToucnUpListener {
  // 还原
  void restore();
  // 消失爆炸
  void dismiss(PointF pointF);
 }

 /**
  * 处理手指抬起后的操作
  */
 public void OnTouchUp()
 {
  if (mLittleCircleRadius > mLittleCircleRadiusMin) {
   // 回弹 ValueAnimator 值变化的动画 0 变化到 1
   ValueAnimator animator = ObjectAnimator.ofFloat(1);
   animator.setDuration(250);
   final PointF start = new PointF(mBigCirclePoint.x, mBigCirclePoint.y);
   final PointF end = new PointF(mLittleCirclePoint.x, mLittleCirclePoint.y);
   animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
    @Override
    public void onAnimationUpdate(ValueAnimator animation) {
     float percent = (float) animation.getAnimatedValue();// 0 - 1
     PointF pointF = Utils.getPointByPercent(start, end, percent);
     //更新位子
     updatePoint(pointF.x, pointF.y);
    }
   });
   // 设置一个差值器 在结束的时候回弹
   animator.setInterpolator(new OvershootInterpolator(3f));
   animator.start();
   // 还要通知 TouchListener
   animator.addListener(new AnimatorListenerAdapter() {
    @Override
    public void onAnimationEnd(Animator animation) {
     if(mOnToucnUpListener != null){
      mOnToucnUpListener.restore();
     }
    }
   });
  } else {
   // 爆炸
   if(mOnToucnUpListener != null){
    mOnToucnUpListener.dismiss(mBigCirclePoint);
   }
  }
 }
}

（2）自定义OnTouchListenner的代码

public class MsgDrafitingListener implements View.OnTouchListener {

 private WindowManager mWindowManager;
 private WindowManager.LayoutParams params;
 private MsgDrafitingView mMsgDrafitingView;
 private Context context;
 // 爆炸动画
 private FrameLayout mBombFrame;
 private ImageView mBombImage;
 private BubbleDisappearListener mDisappearListener;

 public MsgDrafitingListener(Context context,BubbleDisappearListener disappearListener)
 {
  mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
  params = new WindowManager.LayoutParams();
  mMsgDrafitingView = new MsgDrafitingView(context);
  //背景透明
  params.format = PixelFormat.TRANSPARENT;
  this.context = context;

  mBombFrame = new FrameLayout(context);
  mBombImage = new ImageView(context);
  mBombImage.setLayoutParams(new FrameLayout.LayoutParams(Utils.dip2px(30,context),
    Utils.dip2px(30,context)));
  mBombFrame.addView(mBombImage);
  this.mDisappearListener = disappearListener;
 }

 @Override
 public boolean onTouch(final View view, MotionEvent motionEvent) {

  switch (motionEvent.getAction())
  {
   case MotionEvent.ACTION_DOWN:
    //隐藏自己
    view.setVisibility(View.INVISIBLE);
    mWindowManager.addView(mMsgDrafitingView,params);
    int[] location = new int[2];
    view.getLocationOnScreen(location);
    Bitmap bitmap = getBitmapByView(view);
    //y轴需要减去状态栏的高度
    mMsgDrafitingView.initPoint(location[0] + view.getWidth() / 2,
      location[1]+view.getHeight()/2 -Utils.getStatusBarHeight(context));
    // 给消息拖拽设置一个Bitmap
    mMsgDrafitingView.setDragBitmap(bitmap);
    //设置OnTouchUpListener
    mMsgDrafitingView.setOnToucnUpListener(new MsgDrafitingView.OnToucnUpListener() {
     @Override
     public void restore() {
      //还原位子
      // 把消息的View移除
      mWindowManager.removeView(mMsgDrafitingView);
      // 把原来的View显示
      view.setVisibility(View.VISIBLE);
     }

     @Override
     public void dismiss(PointF pointF) {
      //爆炸效果
      // 要去执行爆炸动画 （帧动画）
      //移除拖拽的view
      mWindowManager.removeView(mMsgDrafitingView);
      // 要在 mWindowManager 添加一个爆炸动画
      mWindowManager.addView(mBombFrame,params);
      mBombImage.setBackgroundResource(R.drawable.anim_bubble_pop);

      AnimationDrawable drawable = (AnimationDrawable) mBombImage.getBackground();
      mBombImage.setX(pointF.x-drawable.getIntrinsicWidth()/2);
      mBombImage.setY(pointF.y-drawable.getIntrinsicHeight()/2);
      drawable.start();
      // 等它执行完之后我要移除掉这个 爆炸动画也就是 mBombFrame
      mBombImage.postDelayed(new Runnable() {
       @Override
       public void run() {
        mWindowManager.removeView(mBombFrame);
        // 通知一下外面该消失
        if(mDisappearListener != null){
         mDisappearListener.dismiss(view);
        }
       }
      },getAnimationDrawableTime(drawable));
     }
    });
    break;
   case MotionEvent.ACTION_MOVE:
    mMsgDrafitingView.updatePoint(motionEvent.getRawX(),
      motionEvent.getRawY() - Utils.getStatusBarHeight(context));
    break;
   case MotionEvent.ACTION_UP:
    mMsgDrafitingView.OnTouchUp();
    break;
  }
  return true;
 }

 private Bitmap getBitmapByView(View view) {
  view.buildDrawingCache();
  Bitmap bitmap = view.getDrawingCache();
  return bitmap;
 }

 public interface BubbleDisappearListener {
  void dismiss(View view);
 }

 /**
  * 获取爆炸动画画的时间
  * @param drawable
  * @return
  */
 private long getAnimationDrawableTime(AnimationDrawable drawable) {
  int numberOfFrames = drawable.getNumberOfFrames();
  long time = 0;
  for (int i=0;i<numberOfFrames;i++){
   time += drawable.getDuration(i);
  }
  return time;
 }
}

（3）View的调用代码

public class MsgDrafitingViewActivity extends AppCompatActivity{
 private Button mButton;
 private TextView mText;
 @Override
 protected void onCreate(@Nullable Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.qq_msg_drafitingview_activity);
  mButton = findViewById(R.id.mBtn);
  mText = findViewById(R.id.mText);
  MsgDrafitingView.attach(mButton, new MsgDrafitingListener.BubbleDisappearListener() {
   @Override
   public void dismiss(View view) {

   }
  });
  MsgDrafitingView.attach(mText, new MsgDrafitingListener.BubbleDisappearListener() {
   @Override
   public void dismiss(View view) {

   }
  });
 }
}

源码地址：源码Github地址

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。