IOS中qq消息拖动移除的粘性效果

QQ粘性效果

--思路

新建自定义UIButton

添加拖动手势

计算圆的变化

计算圆之间矩形并且填充

回弹

爆炸

--步骤

 先完成空间布局以及手势添加

 然后计算圆的变化，计算圆之间的矩形面积

 效果微调

预览代码结构图

详细步骤

- 在一个storyBoard里面拖一个UIButton进去，然后新建一个自定义UIBUtton类 如：ETBUtton类与之对应，好了，一切新建工作完毕，下面，我们只需要在自定义的UIButton类里面做功夫就好了，简单的代码直接上好

#import "ETStickBtn.h"

@interface ETStickBtn ()
@property (nonatomic, strong) UIView *smalCirView;
@property (nonatomic, assign) NSInteger oriRadius;
@property (nonatomic, strong) CAShapeLayer *shapeLayer;
@end
@implementation ETStickBtn

#pragma mark - 懒加载数据
- (UIView *)smalCirView{
    if (!_smalCirView) {
        //    新建一个圆
        UIView *smalCirView = [[UIView alloc] init];
//        smalCirView.frame = self.frame;
        smalCirView.backgroundColor = self.backgroundColor;
        [self.superview insertSubview:smalCirView belowSubview:self];
        _smalCirView = smalCirView;
    }
    return _smalCirView;
}

- (CAShapeLayer *)shapeLayer{
    if (!_shapeLayer) {
        CAShapeLayer *shapeLayer = [CAShapeLayer layer];
        shapeLayer.fillColor = self.backgroundColor.CGColor;
        [self.superview.layer insertSublayer:shapeLayer below:self.layer];
        _shapeLayer = shapeLayer;
    }
    return _shapeLayer;
}

#pragma mark - 系统初始化
- (id)initWithFrame:(CGRect)frame{
    self = [super initWithFrame:frame];
    if (self) {
        [self setUp];
    }
    return self;
}

- (void)awakeFromNib{
     [self setUp];
}

#pragma mark - 初始化视图
- (void)setUp{
    CGFloat w = self.bounds.size.width;
    self.layer.cornerRadius = w / 2;
    self.smalCirView.layer.cornerRadius = w/2;
//    记录半径
    _oriRadius = w/2;
    _smalCirView.frame = self.frame;
    UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
    [self addGestureRecognizer:pan];
}

• 在添加完Pan手势后当然我们要在自定义的Pan方法里面做功夫，先看看已经实现了拖动效果的Pan代码块吧。

  - (void)pan:(UIPanGestureRecognizer *)pan{
  
  //  移动
      CGPoint transPoint = [pan translationInView:self];
      CGPoint center = self.center;
      center.x += transPoint.x;
      center.y += transPoint.y;
      self.center = center;
      [pan setTranslation:CGPointZero inView:self];
      }

• 就这样，可以拖动啦，接下来你想做什么呢？我就想你不断拖动大圆的过程中，小圆的半径一直减少直到为0，具体思路是圆心距越大，小圆半径越小，这是奉上此时的Pan代码。

  - (void)pan:(UIPanGestureRecognizer *)pan{
  
  //  移动
      CGPoint transPoint = [pan translationInView:self];
      CGPoint center = self.center;
      center.x += transPoint.x;
      center.y += transPoint.y;
      self.center = center;
      [pan setTranslation:CGPointZero inView:self];
  
  //  设置小圆变化的值
      CGFloat cirDistance = [self distanceWithPointA:self.center andPointB:self.smalCirView.center];
      CGFloat smallCirRadius = _oriRadius - cirDistance/10.0;
      if(smallCirRadius<0) smallCirRadius = 0;
      _smalCirView.bounds = CGRectMake(0, 0, smallCirRadius * 2, smallCirRadius * 2);
      self.smalCirView.layer.cornerRadius = smallCirRadius;
      }
  
  #pragma mark - 获取圆心距离
  - (CGFloat)distanceWithPointA:(CGPoint)pointA  andPointB:(CGPoint)pointB{
      CGFloat offSetX = pointA.x - pointB.x;
      CGFloat offSetY = pointA.y - pointB.y;
      return sqrt(offSetX*offSetX + offSetY*offSetY);
  }

• 好了，现在小圆终于可以随着两圆心距的变大而变小了，之后重头戏来了，获取贝塞尔曲线路径，也就是绘制两圆之间的曲线部分
• 这个也不难，只是用到初中的知识，先上个原型图(手绘)
• 
• 咳咳，由于用铅笔画的，有点模糊，那就奉上一个根据原型图用电脑绘制的图吧!
• 至此，重要的点都已经计算出来的，也不难吧，把算式换成代码如下

  - (UIBezierPath *)getBezierPathWithSmallCir:(UIView *)smallCir andBigCir:(UIView *)bigCir{
  //    获取最小的圆
      if (bigCir.frame.size.width < smallCir.frame.size.width) {
          UIView *view = bigCir;
          bigCir = smallCir;
          smallCir = view;
      }
  //    获取小圆的信息
      CGFloat d = [self distanceWithPointA:smallCir.center andPointB:bigCir.center];
      CGFloat x1 = smallCir.center.x;
      CGFloat y1 = smallCir.center.y;
      CGFloat r1 = smallCir.bounds.size.width/2;
  
  //    获取大圆的信息
      CGFloat x2 = bigCir.center.x;
      CGFloat y2 = bigCir.center.y;
      CGFloat r2 = bigCir.bounds.size.width/2;
  
  //    获取三角函数
      CGFloat sinA = (y2 - y1)/d;
      CGFloat cosA = (x2 - x1)/d;
  
  //    获取矩形四个点
      CGPoint pointA = CGPointMake(x1 - sinA*r1, y1 + cosA * r1);
      CGPoint pointB = CGPointMake(x1 + sinA*r1, y1 - cosA * r1);
      CGPoint pointC = CGPointMake(x2 + sinA*r2, y2 - cosA * r2);
      CGPoint pointD = CGPointMake(x2 - sinA*r2, y2 + cosA * r2);
  
  //    获取控制点，以便画出曲线
      CGPoint pointO = CGPointMake(pointA.x + d / 2 * cosA , pointA.y + d / 2 * sinA);
      CGPoint pointP =  CGPointMake(pointB.x + d / 2 * cosA , pointB.y + d / 2 * sinA);
  
  //    创建路径
      UIBezierPath *path =[UIBezierPath bezierPath];
      [path moveToPoint:pointA];
      [path addLineToPoint:pointB];
      [path addQuadCurveToPoint:pointC controlPoint:pointP];
      [path addLineToPoint:pointD];
      [path addQuadCurveToPoint:pointA controlPoint:pointO];
      return path;
  }
  
  
  

  //    获取最小的圆
      if (bigCir.frame.size.width < smallCir.frame.size.width) {
          UIView *view = bigCir;
          bigCir = smallCir;
          smallCir = view;
      }

• 以上这段代码，由于我作图是小圆的圆心为x1 y1,所以如果把大圆小圆的位置调过来会导致曲线面积的中间鼓起来，所以为了防止别人传错值，也不用他们那么纠结了，我代码里面自己找出最小的圆就好了，所以一定要加上这一句，然后奉上此时的pan代码。

  - (void)pan:(UIPanGestureRecognizer *)pan{
  
  //  移动
      CGPoint transPoint = [pan translationInView:self];
      CGPoint center = self.center;
      center.x += transPoint.x;
      center.y += transPoint.y;
      self.center = center;
      [pan setTranslation:CGPointZero inView:self];
  
  //  设置小圆变化的值
      CGFloat cirDistance = [self distanceWithPointA:self.center andPointB:self.smalCirView.center];
      CGFloat smallCirRadius = _oriRadius - cirDistance/10.0;
      if(smallCirRadius<0) smallCirRadius = 0;
      _smalCirView.bounds = CGRectMake(0, 0, smallCirRadius * 2, smallCirRadius * 2);
      self.smalCirView.layer.cornerRadius = smallCirRadius;
        self.shapeLayer.path = [self getBezierPathWithSmallCir:self andBigCir:self.smalCirView].CGPath;
        }

• 好了接下来就是收尾部分了，只是我想做在超过一定距离后，按钮就完全被拖走了 依依不舍的走了。

  #pragma mark - 自定义方法
  #pragma mark - 手势触发方法
  #define MaxDistance 90
  - (void)pan:(UIPanGestureRecognizer *)pan{
  
  //  移动
      CGPoint transPoint = [pan translationInView:self];
      CGPoint center = self.center;
      center.x += transPoint.x;
      center.y += transPoint.y;
      self.center = center;
      [pan setTranslation:CGPointZero inView:self];
  
  //  设置小圆变化的值
      CGFloat cirDistance = [self distanceWithPointA:self.center andPointB:self.smalCirView.center];
      CGFloat smallCirRadius = _oriRadius - cirDistance/10.0;
      if(smallCirRadius<0) smallCirRadius = 0;
      _smalCirView.bounds = CGRectMake(0, 0, smallCirRadius * 2, smallCirRadius * 2);
      self.smalCirView.layer.cornerRadius = smallCirRadius;
  
   //    画图
      if (cirDistance > MaxDistance) {
          self.smalCirView.hidden = YES;
          [self.shapeLayer removeFromSuperlayer];
  //        self.smalCirView  = nil;
          self.shapeLayer = nil;
      }else if(self.smalCirView.hidden == NO && cirDistance > 0){
           self.shapeLayer.path = [self getBezierPathWithSmallCir:self andBigCir:self.smalCirView].CGPath;
      }

• 最后，我们判断在限定范围内放手就回弹，超过就爆炸消失

  #pragma mark - 自定义方法
  #pragma mark - 手势触发方法
  #define MaxDistance 90
  - (void)pan:(UIPanGestureRecognizer *)pan{
  
  //  移动
      CGPoint transPoint = [pan translationInView:self];
      CGPoint center = self.center;
      center.x += transPoint.x;
      center.y += transPoint.y;
      self.center = center;
      [pan setTranslation:CGPointZero inView:self];
  
  //  设置小圆变化的值
      CGFloat cirDistance = [self distanceWithPointA:self.center andPointB:self.smalCirView.center];
      CGFloat smallCirRadius = _oriRadius - cirDistance/10.0;
      if(smallCirRadius<0) smallCirRadius = 0;
      _smalCirView.bounds = CGRectMake(0, 0, smallCirRadius * 2, smallCirRadius * 2);
      self.smalCirView.layer.cornerRadius = smallCirRadius;
  
   //    画图
      if (cirDistance > MaxDistance) {
          self.smalCirView.hidden = YES;
          [self.shapeLayer removeFromSuperlayer];
  //        self.smalCirView  = nil;
          self.shapeLayer = nil;
      }else if(self.smalCirView.hidden == NO && cirDistance > 0){
           self.shapeLayer.path = [self getBezierPathWithSmallCir:self andBigCir:self.smalCirView].CGPath;
      }
  //    爆炸或还原
      if(pan.state == UIGestureRecognizerStateBegan){
          NSLog(@"%@",NSStringFromCGRect(self.frame));
      }
      if (pan.state == UIGestureRecognizerStateEnded) {
          if (cirDistance > MaxDistance){
  //            这是动画的爆炸效果
              UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.bounds];
              NSLog(@"%@",NSStringFromCGRect(self.frame));
              NSMutableArray *imageArr = [NSMutableArray array];
              for (int i = 1 ; i < 9; i++) {
                  UIImage *image = [UIImage imageNamed:[NSString stringWithFormat:@"%d",i]];
                  [imageArr addObject:image];
              }
              imageView.animationImages = imageArr;
              imageView.animationDuration = 0.5;
              imageView.animationRepeatCount = 1;
              [imageView startAnimating];
              [self addSubview:imageView];
  
              dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.4 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
  //                移除控件
                  [self removeFromSuperview];
              });
          }else{
  //            回弹
              [self.shapeLayer removeFromSuperlayer];
              self.shapeLayer = nil;
              [UIView animateWithDuration:0.5 delay:0 usingSpringWithDamping:0.2 initialSpringVelocity:0 options:UIViewAnimationOptionCurveLinear animations:^{
                  self.center = self.smalCirView.center;
              } completion:^(BOOL finished) {
                  self.smalCirView.hidden = NO;
              }];
          }
      }
  }

• 这时基本上已经可以宣告完成的了，但是在爆炸效果释放的时候你会发现，爆炸效果不在我们当前的位置爆炸，而是在初始位置爆炸，这是因为苹果官方自动给StoryBoard添加了自动布局约束，这是只需要把约束渲染设为NO就好了，就是在ViewController里面加上一句代码

  - (void)viewDidLoad {
      [super viewDidLoad];
      self.view.translatesAutoresizingMaskIntoConstraints = NO;
  }

• 最后奉上整个类的代码

  #import "ETStickBtn.h"
  
  @interface ETStickBtn ()
  @property (nonatomic, strong) UIView *smalCirView;
  @property (nonatomic, assign) NSInteger oriRadius;
  @property (nonatomic, strong) CAShapeLayer *shapeLayer;
  @end
  @implementation ETStickBtn
  
  #pragma mark - 懒加载数据
  - (UIView *)smalCirView{
      if (!_smalCirView) {
          //    新建一个圆
          UIView *smalCirView = [[UIView alloc] init];
  //        smalCirView.frame = self.frame;
          smalCirView.backgroundColor = self.backgroundColor;
          [self.superview insertSubview:smalCirView belowSubview:self];
          _smalCirView = smalCirView;
      }
      return _smalCirView;
  }
  
  - (CAShapeLayer *)shapeLayer{
      if (!_shapeLayer) {
          CAShapeLayer *shapeLayer = [CAShapeLayer layer];
          shapeLayer.fillColor = self.backgroundColor.CGColor;
          [self.superview.layer insertSublayer:shapeLayer below:self.layer];
          _shapeLayer = shapeLayer;
      }
      return _shapeLayer;
  }
  
  #pragma mark - 系统初始化
  - (id)initWithFrame:(CGRect)frame{
      self = [super initWithFrame:frame];
      if (self) {
          [self setUp];
      }
      return self;
  }
  
  - (void)awakeFromNib{
       [self setUp];
  }
  
  #pragma mark - 初始化视图
  - (void)setUp{
      CGFloat w = self.bounds.size.width;
      self.layer.cornerRadius = w / 2;
      self.smalCirView.layer.cornerRadius = w/2;
  //    记录半径
      _oriRadius = w/2;
      _smalCirView.frame = self.frame;
      UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
      [self addGestureRecognizer:pan];
  }
  
  
  #pragma mark - 自定义方法
  #pragma mark - 手势触发方法
  #define MaxDistance 90
  - (void)pan:(UIPanGestureRecognizer *)pan{
  
  //  移动
      CGPoint transPoint = [pan translationInView:self];
      CGPoint center = self.center;
      center.x += transPoint.x;
      center.y += transPoint.y;
      self.center = center;
      [pan setTranslation:CGPointZero inView:self];
  
  //  设置小圆变化的值
      CGFloat cirDistance = [self distanceWithPointA:self.center andPointB:self.smalCirView.center];
      CGFloat smallCirRadius = _oriRadius - cirDistance/10.0;
      if(smallCirRadius<0) smallCirRadius = 0;
      _smalCirView.bounds = CGRectMake(0, 0, smallCirRadius * 2, smallCirRadius * 2);
      self.smalCirView.layer.cornerRadius = smallCirRadius;
  
   //    画图
      if (cirDistance > MaxDistance) {
          self.smalCirView.hidden = YES;
          [self.shapeLayer removeFromSuperlayer];
  //        self.smalCirView  = nil;
          self.shapeLayer = nil;
      }else if(self.smalCirView.hidden == NO && cirDistance > 0){
           self.shapeLayer.path = [self getBezierPathWithSmallCir:self andBigCir:self.smalCirView].CGPath;
      }
  //    爆炸或还原
      if(pan.state == UIGestureRecognizerStateBegan){
          NSLog(@"%@",NSStringFromCGRect(self.frame));
      }
      if (pan.state == UIGestureRecognizerStateEnded) {
          if (cirDistance > MaxDistance){
  //            这是动画的爆炸效果
              UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.bounds];
              NSLog(@"%@",NSStringFromCGRect(self.frame));
              NSMutableArray *imageArr = [NSMutableArray array];
              for (int i = 1 ; i < 9; i++) {
                  UIImage *image = [UIImage imageNamed:[NSString stringWithFormat:@"%d",i]];
                  [imageArr addObject:image];
              }
              imageView.animationImages = imageArr;
              imageView.animationDuration = 0.5;
              imageView.animationRepeatCount = 1;
              [imageView startAnimating];
              [self addSubview:imageView];
  
              dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.4 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
  //                移除控件
                  [self removeFromSuperview];
              });
          }else{
  //            回弹
              [self.shapeLayer removeFromSuperlayer];
              self.shapeLayer = nil;
              [UIView animateWithDuration:0.5 delay:0 usingSpringWithDamping:0.2 initialSpringVelocity:0 options:UIViewAnimationOptionCurveLinear animations:^{
                  self.center = self.smalCirView.center;
              } completion:^(BOOL finished) {
                  self.smalCirView.hidden = NO;
              }];
          }
      }
  }
  
  #pragma mark - 获取圆心距离
  - (CGFloat)distanceWithPointA:(CGPoint)pointA  andPointB:(CGPoint)pointB{
      CGFloat offSetX = pointA.x - pointB.x;
      CGFloat offSetY = pointA.y - pointB.y;
      return sqrt(offSetX*offSetX + offSetY*offSetY);
  }
  
  #pragma mark - 获取贝塞尔曲线
  - (UIBezierPath *)getBezierPathWithSmallCir:(UIView *)smallCir andBigCir:(UIView *)bigCir{
  //    获取最小的圆
      if (bigCir.frame.size.width < smallCir.frame.size.width) {
          UIView *view = bigCir;
          bigCir = smallCir;
          smallCir = view;
      }
  //    获取小圆的信息
      CGFloat d = [self distanceWithPointA:smallCir.center andPointB:bigCir.center];
      CGFloat x1 = smallCir.center.x;
      CGFloat y1 = smallCir.center.y;
      CGFloat r1 = smallCir.bounds.size.width/2;
  
  //    获取大圆的信息
      CGFloat x2 = bigCir.center.x;
      CGFloat y2 = bigCir.center.y;
      CGFloat r2 = bigCir.bounds.size.width/2;
  
  //    获取三角函数
      CGFloat sinA = (y2 - y1)/d;
      CGFloat cosA = (x2 - x1)/d;
  
  //    获取矩形四个点
      CGPoint pointA = CGPointMake(x1 - sinA*r1, y1 + cosA * r1);
      CGPoint pointB = CGPointMake(x1 + sinA*r1, y1 - cosA * r1);
      CGPoint pointC = CGPointMake(x2 + sinA*r2, y2 - cosA * r2);
      CGPoint pointD = CGPointMake(x2 - sinA*r2, y2 + cosA * r2);
  
  //    获取控制点，以便画出曲线
      CGPoint pointO = CGPointMake(pointA.x + d / 2 * cosA , pointA.y + d / 2 * sinA);
      CGPoint pointP =  CGPointMake(pointB.x + d / 2 * cosA , pointB.y + d / 2 * sinA);
  
  //    创建路径
      UIBezierPath *path =[UIBezierPath bezierPath];
      [path moveToPoint:pointA];
      [path addLineToPoint:pointB];
      [path addQuadCurveToPoint:pointC controlPoint:pointP];
      [path addLineToPoint:pointD];
      [path addQuadCurveToPoint:pointA controlPoint:pointO];
      return path;
  }
  @end