本篇文章为大家展示了怎么在Android中通过贝塞尔曲线实现消息拖拽消失，内容简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。
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) {
}
});
}
}上述内容就是怎么在Android中通过贝塞尔曲线实现消息拖拽消失，你们学到知识或技能了吗？如果还想学到更多技能或者丰富自己的知识储备，欢迎关注亿速云行业资讯频道。
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