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仿手机iPhone QQ消息小红点动画1

偶然发现iPhone QQ 显示消息条数的小红点可以响应动作事件,也有人问我这样的动画该怎么做,这里就把实现的思路简单的描述一下。在实现的过程中,同样发现该功能并没有看到的那么简单,要做一个完备的动画效果需要有一定的功底。因此,本篇会先侧重于实现思路,并不会实现一个一模一样的效果。

下面是iPhone QQ小红点的动作交互效果:

仿手机iPhone QQ消息小红点动画1

分析

首先我们分析拖拽时候的表现:

  1. 原先的小红点顺着手指移动,并与原来所处位置通过一个小尾巴(即移动的轨迹)连接
  2. 与原先位置在一定范围内时,小尾巴出现;超过一定范围时,小尾巴不出现
  3. 释放手指,小红点回到原先位置,并有弹簧动画效果
  4. 释放手指时离原先位置超过一定范围则不返回原点,而是有消失的泡沫动画

抛开细节,抓住要点,我归纳了几个要点:

  1. 小原点随手指移动
  2. 小尾巴分情况出现
  3. 手指释放后,小红点弹回原先位置

除此之外,红点上的文字,消失等情形的处理不是主要问题,我们先缓一缓。

实现

红点的移动

首先实现一个圆形的view,并且可以随手指移动。在一定移动范围内,手指离开后,view返回原处并带有弹簧效果;超出范围,view则停留在手指离开处。我们通过drawRect:来画一个圆;设置一个CGPoint的对象来记录开始触摸时的位置;接着就是实现相关的touchEvent:。因为都是很基本的内容,直接上代码。

仿手机iPhone QQ消息小红点动画1
//头文件 @interface ZZSpringView : UIView - (instancetype)initWithSquareLength:(CGFloat)length originPoint:(CGPoint)oPoint; @end //类文件 const CGFloat kOffset = 100.0;//拖拽的范围限制 @interface ZZSpringView () {  CGPoint pointOriginCenter; } @end @implementation ZZSpringView - (instancetype)initWithFrame:(CGRect)frame {  if (self = [super initWithFrame:frame])  {   pointOriginCenter = self.center;      self.backgroundColor = [UIColor clearColor];  }  return self; } - (instancetype)initWithSquareLength:(CGFloat)length originPoint:(CGPoint)oPoint {  if (self = [self initWithFrame:CGRectMake(oPoint.x, oPoint.y, length, length)])  {  }  return self; } // Only override drawRect: if you perform custom drawing. // An empty implementation adversely affects performance during animation. - (void)drawRect:(CGRect)rect {  // Drawing code  CGContextRef context = UIGraphicsGetCurrentContext();  CGContextSetAllowsAntialiasing(context, true);  CGContextSetShouldAntialias(context, true);  CGContextAddEllipseInRect(context, rect);  CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor);  CGContextFillPath(context); } - (BOOL)_isDistanceEnough:(CGPoint)point {  CGFloat distance = (point.x - pointOriginCenter.x)*(point.x - pointOriginCenter.x) + (point.y - pointOriginCenter.y)*(point.y - pointOriginCenter.y);  if (distance > kOffset * kOffset)  {   return YES;  }  return NO; } //touch event - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {  UITouch *touch =  [touches anyObject];  pointOriginCenter = [touch locationInView:self.superview];  [UIView animateWithDuration:.3 animations:^{   self.center = pointOriginCenter;  }]; } - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event { } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {  UITouch *touch =  [touches anyObject];  CGPoint pointMove = [touch locationInView:self.superview];  self.center = pointMove;  }  - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {  UITouch *touch =  [touches anyObject];  CGPoint pointEnd = [touch locationInView:self.superview];  CGFloat distance = (pointEnd.x - pointOriginCenter.x)*(pointEnd.x - pointOriginCenter.x) + (pointEnd.y - pointOriginCenter.y)*(pointEnd.y - pointOriginCenter.y);  if ([self _isDistanceEnough:pointEnd])  {   //may be destory self animation   self.center = pointEnd;   pointOriginCenter = self.center;  }  else  {   [UIView animateWithDuration:1.0          delay:.0     usingSpringWithDamping:0.1      initialSpringVelocity:.0        options:0        animations:^{    self.center = pointOriginCenter;   }        completion:^(BOOL finished) {   }];  } } 
ZZSrpingView

在touchBegin事件中,因为点击小红点的位置与中心会有偏移,通过UIView animation做一个平滑的过度。而在touchEnd事件中,返回弹簧震荡的效果是使用UIView的Spring animation。

添加小尾巴(轨迹)

我画了一张简化的模拟拖拽过程的图:

仿手机iPhone QQ消息小红点动画1

虚线圆是view原来的位置,P0是其圆点;实线圆是移动的位置,P1是圆点。设置两圆的切线(红色),把封闭的部分都填充为同一个颜色的话,就能大致模拟出相似的效果。这里隐含了几个前提:

  1. 实际的轨迹是带有弧度的曲线,这里使用了切线来代替(红色的切线)
  2. 拖拽的时候,原先位置的圆形view会随拖拽距离变小,这里设置为一个固定大小的圆(半径为原来的一半)

鉴于此,我们需要求出的是两对切点的位置,使之成为一个封闭图形进行填充。同时,虚线位置的小圆也进行填充。这样,就基本完成类似的功能。

首先我们需要扩展当前context的范围,为了简便,通过添加尾巴的子view来实线,这样可以利用原先的红点view。现在我们已知P0,P1,以及各自的半径,然后求外围矩形的位置和长度。因为可以按任意方向拖拽,按当前的计算方式,需要分四种情况讨论。按笛卡尔坐标系的划分,图例是第一象限的情形。同理还有二三四的可能。为了迅速验证方案的可行性,这里只对第一象限进行讨论和模拟。

定义新view:

仿手机iPhone QQ消息小红点动画1
typedef enum : NSUInteger {  ZZLineDirection1=1,//northease  ZZLineDirection2,//northwest  ZZLineDirection3,//southwest  ZZLineDirection4//southeast } ZZLineDirection; @interface ZZSpringTailView : UIView @property (nonatomic, assign) ZZLineDirection lineDirection; @property (nonatomic, assign) CGFloat radius;//centerradius @property (nonatomic, assign) CGFloat moveRadius; @end 
ZZSpringTailView

ZZLineDirection代表的是某象限,radius是P0的半径,moveRadius为P1半径。 我们在touchMove事件中添加一个view,在此之前,我们会在ZZSpringView中添加一个ZZSpringTailView实例,用于内部访问。touchMove的实现更新为:

仿手机iPhone QQ消息小红点动画1
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {  UITouch *touch =  [touches anyObject];  CGPoint pointMove = [touch locationInView:self.superview];  if ([self _isDistanceEnough:pointMove])  {   //beyond the offset, hide the view   if (tailView)   {    tailView.hidden = YES;   }  }  else  {   //redraw the view   self.center = pointMove;   if (!tailView)   {    tailView = [[ZZSpringTailView alloc] init];    [self addSubview:tailView];   }   CGFloat widthHalf = self.bounds.size.width/2.0;   CGFloat minX = 0;//= MIN(pointMove.x, pointOriginCenter.x);   CGFloat minY = 0;//= MIN(pointMove.y, pointOriginCenter.y);   CGFloat radius = widthHalf;   //the width: the distance betweent two points and the origin size's width/2   CGRect frameInSuper = CGRectMake(minX, minY, fabsf(pointMove.x - pointOriginCenter.x)  + widthHalf + radius, fabsf(pointMove.y - pointOriginCenter.y)  + widthHalf + radius);   tailView.radius = radius/2;   tailView.moveRadius = radius;   if (pointMove.x >= pointOriginCenter.x && pointMove.y <= pointOriginCenter.y)   {    NSLog(@"direnction1");    tailView.lineDirection = ZZLineDirection1;    frameInSuper.origin.x = pointOriginCenter.x - radius;    frameInSuper.origin.y = pointMove.y - radius;   }   else if (pointMove.x <= pointOriginCenter.x && pointMove.y <= pointOriginCenter.y)   {    NSLog(@"direnction2");    tailView.lineDirection = ZZLineDirection2;    frameInSuper.origin.x = pointMove.x ;    frameInSuper.origin.y = pointMove.y;   }   else if (pointMove.x <= pointOriginCenter.x && pointMove.y >= pointOriginCenter.y)   {    NSLog(@"direnction3");    tailView.lineDirection = ZZLineDirection3;    frameInSuper.origin.x = pointMove.x - radius;    frameInSuper.origin.y = pointOriginCenter.y;   }   else   {    NSLog(@"direnction4");    tailView.lineDirection = ZZLineDirection4;    frameInSuper.origin.x = pointOriginCenter.x - radius;    frameInSuper.origin.y = pointOriginCenter.y - radius;   }   tailView.frame = [self convertRect:frameInSuper fromView:self.superview];   [tailView setNeedsDisplay];  } } 
touchMoveEvent:

这里的实现是把tailview添加到springview之上,通常情况下,clipToBouds默认是NO的,因此这种添加超出父view bound 的子view方案是可行的。需要注意的是,上述的两个point是在spring view的父view内的,因此,在最后确定tailView frame的时候需要转换到springView的坐标系。接下来就是tailView的drawRect实现。这里主要需要做2件事情:

  1. 绘制P0为圆心的圆
  2. 绘制2对切点构成的封闭图形

drawRect的部分实现:

仿手机iPhone QQ消息小红点动画1
- (void)drawRect:(CGRect)rect {  CGContextRef context = UIGraphicsGetCurrentContext();  CGContextSetAllowsAntialiasing(context, true);  CGContextSetShouldAntialias(context, true);  CGContextSetStrokeColorWithColor(context, [UIColor greenColor].CGColor);  CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor);  CGContextSetLineWidth(context, 2);  CGPoint pointStart, pointEnd;//center   CGPoint movePoint1, movePoint2;//移动圆的2个切点  CGPoint centerPoint1, centerPoint2;//原有圆的2个切点  CGFloat moveRadius = _moveRadius;//移动圆 弧的半径   CGFloat sinval = 0, csinval = 0;  CGFloat distance = 0;  switch (_lineDirection) {   case ZZLineDirection1:   {    pointStart = CGPointMake(rect.size.width - moveRadius, 0 + moveRadius);    pointEnd = CGPointMake(0 + _radius, rect.size.height - _radius);    distance = CGRectGetHeight(rect) * CGRectGetHeight(rect) + CGRectGetWidth(rect) * CGRectGetWidth(rect);    sinval = CGRectGetHeight(rect) * CGRectGetHeight(rect)/distance;    csinval = CGRectGetWidth(rect) * CGRectGetWidth(rect)/distance;    movePoint2 = CGPointMake(pointStart.x - moveRadius * sinval, pointStart.y - moveRadius*csinval);    movePoint1 = CGPointMake(pointStart.x + moveRadius*sinval, pointStart.y + moveRadius*csinval);    centerPoint2 = CGPointMake(pointEnd.x + _radius*sinval, pointEnd.y + _radius*csinval);    centerPoint1 = CGPointMake(pointEnd.x - _radius * sinval, pointEnd.y - _radius*csinval);    break;   }   case ZZLineDirection2:   {    break;   }   case ZZLineDirection3:   {    break;   }   case ZZLineDirection4:   {    break;   }  }  CGContextMoveToPoint(context, movePoint1.x, movePoint1.y);  CGContextAddLineToPoint(context, movePoint2.x, movePoint2.y);  CGContextAddLineToPoint(context, centerPoint1.x, centerPoint1.y);  CGContextAddLineToPoint(context, centerPoint2.x, centerPoint2.y);  CGContextClosePath(context);  CGContextFillPath(context);  CGContextStrokePath(context);  CGContextAddArc(context, pointEnd.x, pointEnd.y, _radius, 0, 2*M_PI, 0);  CGContextFillPath(context); } 
ZZSpringTailView

计算过程就不详细描述了,初中数学的知识就够了。接着运行下,看看效果。

仿手机iPhone QQ消息小红点动画1

从运行效果看,还是差强人意的。这显示了方案的可行性。那么相应二三四象限的情况也能做类似的处理,这里就不贴代码了。

由于时间的关系,暂时研究到此,下一篇会把功能逐步完善。主要会包含添加文字的情形等内容,敬请期待。如果有更好的实现方式,也请大家赐教!

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