前言
之前流行过一种图片展示视图——photo stack,即照片叠放视图。大致上是这个样子的:
(图片出自code4app)
现在我们已经能够使用UICollectionViewLayout来实现这种视图了。Apple给的示例代码中就有这样一个layout,并且示例代码中不仅仅是展示这样的视图,还有非常棒的layout过度动画(结合手势)。在这之前,也有非常多的开源代码能实现这样的效果。本文正是借鉴了开源的源代码“PhotoStackView”,使用Objective-C实现,并且带手势移动图片的功能。由于这是上一学期课设的时候拿来用的库,结果现在找不到了,无法给出链接,还望见谅。
最后的效果图如下
这样重复造轮子的目的是什么呢?一方面,不使用UICollectionViewLayout而是纯粹的用UIView来实现,提高灵活性,方便“私人订制”。另一方面,学习大神的源代码,从中学习一下自定义库的书写方式等。最后,swift。。天杀的swift,是谁说swift对新手友好来着
当然,这里也不是简单的对源代码的搬运、抄袭与翻译,我还根据自己的需要给他改了一个bug,添加了一些功能,比如全屏展示与返回等。示例图如下:
- 全屏展示
(图片有些卡,测试运行时还是非常流畅的)
思路
- 使用若干和自己一样大的view来装载图片,每次添加新图片到视图上时为其随机旋转一定角度,把最前面的这张旋转角度设为0。
- “view装载图片”的意思是,view里面放一个imageView,为什么不直接用imageVIew呢?因为我们要放边框,边框可以是图片,另外在highlighted状态下也可以用图片或自定义颜色铺在图片上,因此使用一个view统一管理
- 添加pan手势,当手指移动时让view跟着做相应平移,手指松开时根据velocity决定返回还是移到最后
- 综上,我们还需要不少辅助方法,例如获取顶部图片和其下标、使用动画移动view、让view旋转到某一度数等
代码
computed property & stored property
oc中可以声明属性然后覆写setter或getter,从而实现赋值或取值时进行一些操作的功能,如下代码
- @property(strong,nonatomic) NSString *someString
-
- - (void)setSomeString() {...}
- - (NSString *)someString() {...}
swift中相对应的写法,目前我知道的有两种,一种是使用computed property 的set和get,缺点是必须同时声明一个stored property(?可以不用吗,求科普),很像oc2.0之前的属性。另一种是使用监听器(didSet和willSet),缺点是只能对setter操作,不能对getter操作。
但是,要想实现重写父类的setSomeThing这样的功能,只能通过监听器的方法。否则会报错
由上,该类用到的属性如下(部分):
- //MARK: computed property
-
- var s_rotationOffset: CGFloat = 0.0
- /// the scope of offset of rotation on every photo except the first one. default is 4.0.
- /// ie,4.0 means rotate iamge with degree between (-4.0,4.0)
- var rotationOffset: CGFloat {
- set {
- if s_rotationOffset == newValue {
- return
- }
-
- s_rotationOffset = newValue
- reloadData()
- }
- get {
- return s_rotationOffset
- }
- }
-
- var s_photoImages: [UIView]?
- var photoImages: [UIView]? {
- set {
- //remove all subview and prepare to re-add all images from data source
- for view in subviews {
- view.removeFromSuperview()
- }
-
- if let images = newValue {
- for view in images {
- //keep the original transfrom for the existing images
- if let index = find(images,view),count = s_photoImages?.count where index < count {
- let existingView = s_photoImages![index]
- view.transform = existingView.transform
- } else {
- makeCrooked(view,animated: false)
- }
-
- insertSubview(view,atIndex: 0)
- }
- }
-
- s_photoImages = newValue
- }
- get {
- return s_photoImages
- }
- }
-
- override var highlighted: Bool {
- didSet {
- let photo = self.topPhoto()?.subviews.last as! UIImageView
- if highlighted {
- let view = UIView(frame: self.bounds)
- view.backgroundColor = self.highlightColor
- photo.addSubview(view)
- photo.bringSubviewToFront(view)
- } else {
- photo.subviews.last?.removeFromSuperview()
- }
- }
- }
-
- override var frame: CGRect {
- didSet {
- if CGRectEqualToRect(oldValue,self.frame) {
- return
- }
-
- reloadData()
- }
- }
上面大部分还有其他省略的大都是一样的思路:设置新值时调用reloadData刷新,主要是上面那个photoImage数组的setter:首先移除当前所有的子视图,接下来遍历新数组,那句判断if let index = find(images,count = s_photoImages?.count where index < count
的作用是判断此次循环中view是否是之前已经添加到界面上的,如果是,则保留其transform不变,否则为其重新生产一个旋转角度(产生照片堆效果),这样做保证了添加照片时原先的照片形状不会变。
Set up & Touches
初始化的工作非常简单,一方面为属性设置默认值,另一方面添加手势监听。
- //MARK: Set up
-
- override init(frame: CGRect) {
- super.init(frame: frame)
- setup()
- }
-
- required init(coder aDecoder: NSCoder) {
- super.init(coder: aDecoder)
- setup()
- }
-
- func setup() {
- //default value
- borderWidth = 5.0
- showBorder = true
- rotationOffset = 4.0
-
- let panGR = UIPanGestureRecognizer(target: self,action: Selector("handlePan:"))
- addGestureRecognizer(panGR)
-
- let tapGR = UITapGestureRecognizer(target: self,action: Selector("handleTap:"))
- addGestureRecognizer(tapGR)
-
- reloadData()
- }
-
- override func sendActionsForControlEvents(controlEvents: UIControlEvents) {
- super.sendActionsForControlEvents(controlEvents)
- highlighted = (controlEvents == .TouchDown)
- }
sendActionsForControlEvents
是自定义UIControl时可能会使用或重写的方法,作用是发送事件。为了说明这一点,这里顺带附上view的触摸方法:
- //MARK: Touch Methods
-
- override func touchesBegan(touches: Set<NSObject>,withEvent event: UIEvent) {
- super.touchesBegan(touches,withEvent: event)
-
- sendActionsForControlEvents(.TouchDown)
- }
-
- override func touchesMoved(touches: Set<NSObject>,withEvent event: UIEvent) {
- super.touchesMoved(touches,withEvent: event)
-
- sendActionsForControlEvents(.TouchDragInside)
- }
-
- override func touchesEnded(touches: Set<NSObject>,withEvent event: UIEvent) {
- super.touchesEnded(touches,withEvent: event)
-
- sendActionsForControlEvents(.TouchCancel)
- }
例如,当用户点击该控件时,发送UIControlEventTouchDown事件,这样使用该控件的人就可以通过addTarget:selector:forControlEvent:方法对此事件添加监听了。我们平时最经常使用的button不就是对TouchUpInside事件进行监听的吗。
reloadData
刷新视图时,要做的事情有:重新获取size,计算frame,添加border,设置images
- /** use this method to reload photo stack view when data has changed */
- func reloadData() {
- if dataSource == nil {
- photoImages = nil
- return
- }
-
- if let number = dataSource?.numberOfPhotosInStackView(self) {
- var images = [UIView]()
- let border = borderImage?.resizableImageWithCapInsets(UIEdgeInsets(top: borderWidth,left: borderWidth,bottom: borderWidth,right: borderWidth))
- let topIndex = indexOfTopPhoto()
-
- for i in 0..<number {
- if let image = dataSource?.stackView(self,imageAtIndex: i) {
-
- //add image view for every image
- let imageView = UIImageView(image: image)
- var viewFrame = CGRectMake(0,0,image.size.width,image.size.height)
-
- if let ds = dataSource where ds.respondsToSelector(Selector("stackView:sizeOfPhotoAtIndex:")) {
- let size = ds.stackView!(self,sizeOfPhotoAtIndex: i)
- viewFrame.size = size
- }
-
- imageView.frame = viewFrame
-
- let view = UIView(frame: viewFrame)
-
- //add border for view
- if showBorder {
- if let b = border {
- viewFrame.origin = CGPoint(x: borderWidth,y: borderWidth)
- imageView.frame = viewFrame
- view.frame = CGRect(x: 0,y: 0,width: imageView.frame.width + 2 * borderWidth,height: imageView.frame.height + 2 * borderWidth)
-
- let backgroundImage = UIImageView(image: b)
- backgroundImage.frame = view.frame
- view.addSubview(backgroundImage)
- } else {
- view.layer.borderWidth = borderWidth
- view.layer.borderColor = UIColor.whiteColor().CGColor
- }
-
- }
- view.addSubview(imageView)
-
- //add view to array
- images.append(view)
- view.tag = i
- view.center = CGPoint(x: CGRectGetMidX(bounds),y: CGRectGetMidY(bounds))
- }
- }
-
- photoImages = images
- goToImageAtIndex(topIndex)
- }
-
- }
这里要干的仅有前三件事,添加photos的任务交给photoImages的setter去做,这个之前已经说过了。
逻辑相关
在谈这个之前,让我们先来了解一下view的组织方式。如果一个view内有若干个subview,你知道subviews.lastObject和subviews.firstObject分别指哪个吗?
事实上,越是靠近我们的,下标识越小。换句话说,subviews[0]指的是子视图中位于最底层的,被其他子视图遮住了的那一个,而subviews.lastObject指的则是最顶层的,能被我们看到(一般来说)的。
这样,很容易能得出下面几个函数
- /** find the index of top photo :returns: index of top photo */
- func indexOfTopPhoto() -> Int {
- if let images = photoImages,let photo = topPhoto() {
- if let index = find(images,photo) {
- return index
- }
- }
- return 0
- }
-
- /** get the top photo on photo stack :returns: current first photo */
- func topPhoto() -> UIView? {
- if subviews.count == 0 {
- return nil
- }
- return subviews[subviews.count - 1] as? UIView
- }
-
- /** jump to photo at index */
- func goToImageAtIndex(index: Int) {
- if let photos = photoImages {
- for view in photos {
- if let idx = find(photos,view) where idx < index {
- sendSubviewToBack(view)
- }
- }
- }
- makeStraight(topPhoto()!,animated: false)
- }
swift知识补充:swift中没有indexForObject:这样的方法,众所周知,swift更多的是“函数式编程”,因此Int、Float甚至Array、Dictionary都是结构体(虽然和类挺相似),我们也是使用一些函数来对这些结构体操作。例如这里取代上述方法的是find()函数
有了这些方法,我们就能使用动画后处理view的层级关系了。
动画相关
这里用到的动画相关的都非常简单,所以直接上代码:
- //MARK: Animations
-
- func returnToCenter(view: UIView) {
- UIView.animateWithDuration(0.2,animations: { () -> Void in view.center = CGPoint(x: CGRectGetMidX(self.bounds),y: CGRectGetMidY(self.bounds)) }) } func flickAway(view: UIView,withVelocity velocity: CGPoint) { if let del = delegate where del.respondsToSelector(Selector("stackView:willFlickAwayPhotoFromIndex:toIndex:")) { let from = indexOfTopPhoto() var to = from + 1 if let number = dataSource?.numberOfPhotosInStackView(self) where to >= number { to = 0 } del.stackView!(self,willFlickAwayPhotoFromIndex: from,toIndex: to) } let width = CGRectGetWidth(bounds) let height = CGRectGetHeight(bounds) var xPosition: CGFloat = CGRectGetMidX(bounds) var yPosition: CGFloat = CGRectGetMidY(bounds) if velocity.x > 0 { xPosition = CGRectGetMidX(bounds) + width } else if velocity.x < 0 { xPosition = CGRectGetMidX(bounds) - width } if velocity.y > 0 { yPosition = CGRectGetMidY(bounds) + height } else if velocity.y < 0 { yPosition = CGRectGetMidY(bounds) - height } UIView.animateWithDuration(0.1,animations: { () -> Void in view.center = CGPoint(x: xPosition,y: yPosition) }) { (finished) -> Void in
- self.makeCrooked(view,animated: true)
- self.sendSubviewToBack(view)
- self.makeStraight(self.topPhoto()!,animated: true)
- self .returnToCenter(view)
-
- if let del = self.delegate where del.respondsToSelector("stackView:didRevealPhotoAtIndex:") {
- del.stackView!(self,didRevealPhotoAtIndex:self.indexOfTopPhoto())
- }
- }
- }
-
- func rotate(degree: Int,onView view: UIView,animated: Bool) {
- let radian = CGFloat(degree) * CGFloat(M_PI) / 180
-
- if animated {
- UIView.animateWithDuration(0.2,animations: { () -> Void in view.transform = CGAffineTransformMakeRotation(radian) }) } else { view.transform = CGAffineTransformMakeRotation(radian) } } func makeCrooked(view: UIView,animated: Bool) { let min = Int(-rotationOffset) let max = Int(rotationOffset) let scope = UInt32(max - min - 1) let randomDegree = Int(arc4random_uniform(scope)) let degree: Int = min + randomDegree rotate(degree,onView: view,animated: animated) } func makeStraight(view: UIView,animated: Bool) { rotate(0,animated: animated) }
swift相关:一直不是太明白swift中可选值的意义是什么。到是给我们带来了不少麻烦,因为不怎么想全都用强解(!),所以用了大量if let解包的方式。其中oc中很简单就能完成的操作:
- if (self.delegate responseToSelector:@selector(@"someMethod")) {
- [self.delegate someMethod];
- }
到了swift中
- if let del = delegate where del.responseToSelector(Selector("someMethod") {
- del.someMethod()
- }
且不说swift的Selector机制,每次都这样写可真是要累死人了:[
手势
和之前说的一样,pan手势中要做的就是通知代理,让view随手指移动,释放手指后根据velocity将view归位或切换到最后一张。
- //MARK: Gesture Recognizer
-
- func handlePan(recognizer: UIPanGestureRecognizer) {
- if let topPhoto = self.topPhoto() {
- let velocity = recognizer.velocityInView(recognizer.view)
- let translation = recognizer.translationInView(recognizer.view!)
-
- if recognizer.state == .Began {
- sendActionsForControlEvents(.TouchCancel)
-
- if let del = delegate where del.respondsToSelector(Selector("stackView:willBeginDraggingPhotoAtIndex")) {
- del.stackView!(self,willBeginDraggingPhotoAtIndex: self.indexOfTopPhoto())
- }
- } else if recognizer.state == .Changed {
- topPhoto.center = CGPoint(x: topPhoto.center.x + translation.x,y: topPhoto.center.y + translation.y)
- recognizer.setTranslation(CGPoint.zeroPoint,inView: recognizer.view)
- } else if recognizer.state == .Ended || recognizer.state == .Cancelled {
- if abs(velocity.x) > 200 {
- flickAway(topPhoto,withVelocity: velocity)
- } else {
- returnToCenter(topPhoto)
- }
- }
-
- }
-
- }
-
- func handleTap(recognizer: UIGestureRecognizer) {
- sendActionsForControlEvents(.TouchUpInside)
-
- if let del = delegate where del.respondsToSelector(Selector("stackView:didSelectPhotoAtIndex:")) {
- del.stackView!(self,didSelectPhotoAtIndex: self.indexOfTopPhoto())
- }
- }
Show All Images
创建一层黑色的遮罩(view),然后将每个view从自己原来的位置移到计算好的新位置,为了产生顺序关系,为每个view 的动画设置各自的delay。点击黑色遮罩后所有view回位,view消失。
- func showAllPhotos() {
- let screenBounds = UIScreen.mainScreen().bounds
- let maskView = UIView(frame: screenBounds)
- maskView.backgroundColor = UIColor.blackColor()
- maskView.alpha = 0
- UIApplication.sharedApplication().keyWindow?.addSubview(maskView)
-
- UIView.animateWithDuration(0.1,delay: 0.0,options: nil,animations: { () -> Void in maskView.alpha = 1.0 }) { (_) -> Void in
-
- }
-
-
- let column = 3
- let imageWidth = 80
- let padding = (Int(screenBounds.width) - column * imageWidth) / (column + 1)
-
- if let photos = photoImages {
- for view in photos {
-
- //set the initial location
- view.removeFromSuperview()
- maskView.addSubview(view)
- view.frame = frame
-
- if let index = find(photos,view) {
- UIView.animateWithDuration(0.1,delay: NSTimeInterval(Double(index) * 0.1),animations: { () -> Void in view.frame = CGRect(x: padding + (index % column) * (imageWidth + padding),y: padding + (index / column) * (padding + imageWidth),width: imageWidth,height: imageWidth) },completion: { (finished) -> Void in }) } } } let tapGR = UITapGestureRecognizer(target: self,action: Selector("removeMaskView:")) maskView.addGestureRecognizer(tapGR) }
- func removeMaskView(recognizer: UITapGestureRecognizer) {
- let maskView = recognizer.view!
- for i in stride(from: maskView.subviews.count - 1,through: 0,by: -1) {
- let photo = maskView.subviews[i] as? UIView
- UIView.animateWithDuration(0.25,animations: { () -> Void in photo?.frame = self.frame },completion: { (_) -> Void in }) } UIView.animateWithDuration(0.25,animations: { () -> Void in maskView.alpha = 0.0 }) { (_) -> Void in
- maskView.removeFromSuperview()
- self.reloadData()
- }
- }
源代码
总结
刚接触swift不久就直接写东西,确实不好写,swift为了安全做了很多努力,但却增加了一些注意事项。一个Int乘以一个Double都报错的“强类型“检查实在不习惯。但是不得不说这门语言确实有意思,省略小括号,不用分号,switch,where…以后多接触,说不定就能喜欢上这门语言了:]