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iOS - 图片实现多层折叠效果

本文是投稿文章，作者： Resory

序

在网上能找到挺多图片折叠效果的教程，但大多数是一层折叠，在他们的教程的基础上，我试着实现了一下多层折叠的效果。操作如下~

效果

iOS - 图片实现多层折叠效果

Demo

Demo地址： https://github.com/Resory/RYMutipleFoldImageView

如果官人喜欢的话不妨给个星星吧。

逻辑

在做图片折叠效果的时候，我们可以理解为把图片分成几部分，然后分别对各部分做动效来实现折叠效果。
根据动态图,可以看到这是一张大图"分成"4个小imageView。从上至下，我们分别命名为one,two,three,four
对one,two,three,four这四个小imageView进行旋转+移动。旋转的时候，关键是看各个imageView的anchorPoint是多少.而我们这里,可看p1图中的红点。

1.a1代表one的anchorPoint为(0.5,0.0)

2.a2代表two的anchorPoint为(0.5,1.0)

3.a3代表three的anchorPoint为(0.5,0.0)

4.a4代表four的anchorPoint为(0.5,1.0)

iOS - 图片实现多层折叠效果

旋转：我们这里的imageView都是旋转45°或者是-45°,这个用CATransform3DRotate即可完成。
移动（关键）：

1.旋转后，各个imageView都会变形并且都一样大小，只有位置不一样，我们要根据这个旋转后的imageView高度来进行移动。

2.比如two要和one对接。根据动态图,one只有旋转，没有移动。而two则旋转和移动了。那么移动了多少呢。在没有折叠前，所有的imageView高度都是50px。也就是one和two总共加起来是100px。而折叠后。one和two都变小了。就是因为他们两个都变小了。所以中间就出现了缝隙，这个缝隙就是我们要移动的距离。而我们知道在二维空间中，总长度是100px,one,two的高度在旋转后是可以算出来的,也就是说缝隙的二维空间距离是:100-2*(one.frame.size.height)。,然后再经过CATransform3DMakeAffineTransform方法的转换得到真实地三维空间移动的距离。

实现

初始化4个小imageView(contentsRect的运用)

- (void)configFourFoldImage {     UIView *bgView = [[UIView alloc] initWithFrame:CGRectMake(10, 100, 300, IMAGE_PER_HEIGIT*4)];     [self.view addSubview:bgView];          // 把kiluya这张图，分成平均分成4个部分的imageview     _one = [[UIImageView alloc] init];     _one.image = [UIImage imageNamed:@"Kiluya.jpg"];     _one.layer.contentsRect = CGRectMake(0, 0, 1, 0.25);     _one.layer.anchorPoint = CGPointMake(0.5, 0.0);     _one.frame = CGRectMake(0, 0, 300, IMAGE_PER_HEIGIT);          _two = [[UIImageView alloc] init];     _two.image = [UIImage imageNamed:@"Kiluya.jpg"];     _two.layer.contentsRect = CGRectMake(0, 0.25, 1, 0.25);     _two.layer.anchorPoint = CGPointMake(0.5, 1.0);     _two.frame = CGRectMake(0, IMAGE_PER_HEIGIT, 300, IMAGE_PER_HEIGIT);          _three = [[UIImageView alloc] init];     _three.image = [UIImage imageNamed:@"Kiluya.jpg"];     _three.layer.contentsRect = CGRectMake(0, 0.5, 1, 0.25);     _three.layer.anchorPoint = CGPointMake(0.5, 0.0);     _three.frame = CGRectMake(0, IMAGE_PER_HEIGIT*2, 300, IMAGE_PER_HEIGIT);          _four = [[UIImageView alloc] init];     _four.image = [UIImage imageNamed:@"Kiluya.jpg"];     _four.layer.contentsRect = CGRectMake(0, 0.75, 1, 0.25);     _four.layer.anchorPoint = CGPointMake(0.5, 1.0);     _four.frame = CGRectMake(0, IMAGE_PER_HEIGIT*3, 300, IMAGE_PER_HEIGIT);          [bgView addSubview:_one];     [bgView addSubview:_two];     [bgView addSubview:_three];     [bgView addSubview:_four];          // 给第一张和第三张添加阴影     _oneShadowView = [[UIView alloc] initWithFrame:_one.bounds];     _oneShadowView.backgroundColor = [UIColor blackColor];     _oneShadowView.alpha = 0.0;          _threeShadowView = [[UIView alloc] initWithFrame:_three.bounds];     _threeShadowView.backgroundColor = [UIColor blackColor];          _threeShadowView.alpha = 0.0;     [_one addSubview:_oneShadowView];     [_three addSubview:_threeShadowView]; }

生成折叠动效需要的CATransform3D

- (CATransform3D)config3DTransformWithRotateAngle:(double)angle andPositionY:(double)y {     CATransform3D transform = CATransform3DIdentity;     // 立体     transform.m34 = -1/1000.0;     // 旋转     CATransform3D rotateTransform = CATransform3DRotate(transform, M_PI*angle/180, 1, 0, 0);     // 移动(这里的y坐标是平面移动的的距离,我们要把他转换成3D移动的距离.这是关键,没有它,图片就没办法很好地对接。)     CATransform3D moveTransform = CATransform3DMakeAffineTransform(CGAffineTransformMakeTranslation(0, y));     // 合并     CATransform3D concatTransform = CATransform3DConcat(rotateTransform, moveTransform);     return concatTransform; }

折叠

// 动效是否执行中 static bool isFolding = NO;  - (IBAction)fold:(id)sender {     if(!isFolding)     {         isFolding = YES;                  [UIView animateWithDuration:1.0                               delay:0              usingSpringWithDamping:1.0               initialSpringVelocity:0                             options:UIViewAnimationOptionCurveLinear                          animations:^{                                       // 阴影显示             _oneShadowView.alpha = 0.2;             _threeShadowView.alpha = 0.2;                          // 折叠             _one.layer.transform = [self config3DTransformWithRotateAngle:-45.0                                                              andPositionY:0];             _two.layer.transform = [self config3DTransformWithRotateAngle:45.0                                                              andPositionY:-100+2*_one.frame.size.height];             _three.layer.transform = [self config3DTransformWithRotateAngle:-45.0                                                                andPositionY:-100+2*_one.frame.size.height];             _four.layer.transform = [self config3DTransformWithRotateAngle:45.0                                                               andPositionY:-200+4*_one.frame.size.height];         } completion:^(BOOL finished) {             if(finished)             {                 isFolding = NO;             }         }];     } }

恢复

- (IBAction)reset:(id)sender {     isFolding = NO;     [UIView animateWithDuration:1.0                           delay:0          usingSpringWithDamping:1.0           initialSpringVelocity:0                         options:UIViewAnimationOptionCurveLinear                      animations:^{                               // 阴影隐藏         _oneShadowView.alpha = 0.0;         _threeShadowView.alpha = 0.0;                  // 图片恢复原样         _one.layer.transform = CATransform3DIdentity;         _two.layer.transform = CATransform3DIdentity;         _three.layer.transform = CATransform3DIdentity;         _four.layer.transform = CATransform3DIdentity;              } completion:^(BOOL finished) {          }]; }