应该使用什么方法在选择时动态更改 UICollectionViewCell 的大小? [英] What method should be used to dynamically change the size of UICollectionViewCell on selection?
问题描述
我需要做的是加宽选定单元格的宽度，同时缩短其余未选定单元格的宽度，以便一次性显示所有单元格.
What I need to do is to widen the width of a cell selected and at the same time shorten widths of the rest of the cells not selected so that all the cells are shown in one time.
我现在拥有的是:
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 30
}
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
return CGSize(width: collectionView.bounds.width / 30, height: collectionView.bounds.height)
}
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
var cell: UIDateSliderCell = collectionView.dequeueReusableCellWithReuseIdentifier("cell", forIndexPath: indexPath) as UIDateSliderCell
return cell
}
我在子类 UIView 中有一个 horizontal UICollectionView 设置，有 30 个单元格，它们平均分配.
I have a horizontal UICollectionView setup in subclassed UIView, with 30 cells and they're divided equally.
为了通过检测手势来选择单元格，我将 UIPanGestureRecognizer 添加到 collectionView.
To select a cell by detecting gestures, I have UIPanGestureRecognizer added to collectionView.
func pan(sender: UIPanGestureRecognizer) {
switch sender.state {
case .Began:
fallthrough
case .Changed:
_collectionView.selectItemAtIndexPath(_collectionView.indexPathForItemAtPoint(CGPointMake(sender.locationInView(_collectionView).x, 0.0)), animated: true, scrollPosition: nil)
case .Ended:
break
default:
break
}
}
此外，我将 UICollectionViewCell 子类化，我实际上可以通过以下代码更改所选单元格的宽度:
Additionally, I have UICollectionViewCell subclassed and I can actually change the width of selected cell by this code:
override var selected: Bool {
didSet {
if selected {
UIView.animateWithDuration(1.0,
delay: 0.0,
usingSpringWithDamping: 0.5,
initialSpringVelocity: 1.0,
options: .CurveEaseIn,
animations: { () -> Void in
self.frame = CGRectMake(self.frame.origin.x, self.frame.origin.y, self.frame.size.width*2, self.frame.size.height)
},
completion: { (finished: Bool) -> Void in
})
}
}
}
当然，它只能更改选定的单元格.我需要做的是改变选定的一个单元格的宽度，并根据选定的单元格重新计算其他单元格的宽度.
But of course with this it can only change a cell selected. What I need to do is to change the width of one cell selected and recalculate the widths of other cells according to the selected cell.
再次澄清我的问题，我想做的是:
To clarify my question again, what I'd like to do is this:
- 假设 UICollectionView.width 为 300
- 它有 30 个单元格，Cell.width 为 300/30 = 10
- 必须一次显示所有单元格，UICollectionView 不会滚动.
- 当一个单元格被选中时，它的宽度将为 20.
- 因此其他单元格的宽度将为 (300-20)/29.
我应该挂钩什么方法或函数?最好是简单的示例代码，非常感谢.
What method or functions should I hook? Preferbly simple sample codes please, thanks a lot in advance.
推荐答案
我觉得子类化 UICollectionViewFlowLayout 会更适合您的问题/可扩展的解决方案.
I feel like subclassing UICollectionViewFlowLayout would be a more suitable/scalable solution for your problem.
下面我在子类化UICollectionViewLayout时分享了一些小代码，这样你就会得到大致的想法.
Below I shared small code when subclassing UICollectionViewLayout So you'll get the general Idea.
将 totalItem 添加到您的子类.以及指示正在选择哪个单元格的索引路径.在您的 collectionview 上选择一个单元格调用 invalidatelayout 后
add totalItem to your subclass.
and a indexpath that indicates which cell is being selected.
after selecting a cell call invalidatelayout on your collectionview
在您的情况下，您希望每次都计算单元格的所有属性.
in your case you want to calculate all the cell's attributes every time.
这是粗略的草图，没有经过测试可能有一些计算错误
- (void)prepareLayout {
self.totalItems = (int)[self.collectionView numberOfItemsInSection:0];
}
- (CGSize)collectionViewContentSize
{
return self.collectionView.frame.size;
}
-(CGRect) rectForIndex:(int) index {
//Here you should calculate the sizes of all the cells
// The ones before the selected one , the selected one, and the ones after the selected
if (index<selected) {
//Regular calculating
frame=CGRectMake(0, height * index, width, height)
} else if (index>selected) {
//here the tricky part is the origin you ( assuming one is seleceted) you calculate the accumulated height of index-1 regular cells and 1 selected cell
frame=CGRectMake(0, (height* (selected-1) + sizeOfSelectedCell) +height * (index-selected), width, height)
} else {
frame=CGRectMake(0, (height* (index-selected)) , width, selectedHeight)
}
return frame;
}
- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
NSMutableArray *attributes = [NSMutableArray array];
for (int i = 0; i< self.totalItems; i++) {
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:i inSection:0];
[attributes addObject:[self layoutAttributesForItemAtIndexPath:indexPath]];
}
return attributes;
}
-(UICollectionViewLayoutAttributes *) layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath {
UICollectionViewLayoutAttributes *attributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
attributes.frame = [self rectForIndex:(int)indexPath.row];
return attributes;
}
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