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:
首先我们分析拖拽时候的表现:
抛开细节,抓住要点,我归纳了几个要点:
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。
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。
//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。
我画了一张简化的模拟拖拽过程的图:
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:
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:
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; @endZZSpringTailView
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:
- (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:
drawRect的部分实现:
- (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。
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!