UICollectionView
目录
1 布局从右到左
1.1 方式1
数据会从右到左排列
if #available(iOS 9.0, *) {
collectionView.semanticContentAttribute = .forceRightToLeft
}if (@available(iOS 9.0, *)) {
_collectionView.semanticContentAttribute = UISemanticContentAttributeForceRightToLeft;
}1.2 方式2
数据会从右到左排列
if #available(iOS 9.0, *) {
collectionView.transform = CGAffineTransform(scaleX: -1.0, y: 1.0)
}if (@available(iOS 9.0, *)) {
_collectionView.transform = CGAffineTransformMakeScale(-1.0, 1.0);
}cell中的内容也需要做相应的变换
cell.transform = CGAffineTransform(scaleX: -1.0, y: 1.0)cell.transform = CGAffineTransformMakeScale(-1.0, 1.0);1.3 方式3
自定义UICollectionViewFlowLayout,这种方式不会改变数据的排列方向，只是改变了cell的布局方向
比如一行有4个cell，那么第一个cell的x坐标为0，第二个cell的x坐标为第一个cell的x坐标加上第一个cell的宽度，以此类推，第四个cell的x坐标为第三个cell的x坐标加上第三个cell的宽度，这样就可以实现从右到左的布局
示例代码如下：
class RTLCollectionViewFlowLayout: UICollectionViewFlowLayout {
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
guard let attributesArray = super.layoutAttributesForElements(in: rect) else {
return nil
}
var newAttributesArray = [UICollectionViewLayoutAttributes]()
// 获取余数
let remainder = attributesArray.count % 4
// 获取collectionView的宽度
let collectionViewWidth = collectionViewContentSize.width
var currentX: CGFloat = sectionInset.left
if attributesArray.count < 4 {
// 只有一行
currentX = collectionViewWidth - sectionInset.right - CGFloat(remainder) * (itemSize.width + minimumInteritemSpacing)
}
var currentY: CGFloat = sectionInset.top
for (index,attributes) in attributesArray.enumerated() {
let newAttributes = attributes.copy() as! UICollectionViewLayoutAttributes
if newAttributes.frame.origin.y == currentY {
// 在同一行
newAttributes.frame.origin.x = currentX
} else {
// 开始新的一行
currentY = newAttributes.frame.origin.y
let last = attributesArray.count - index
if last < 4 {
let count = last % 4
currentX = collectionViewContentSize.width - sectionInset.right - CGFloat(count) * itemSize.width - CGFloat(count - 1) * minimumInteritemSpacing
} else {
currentX = sectionInset.left
}
newAttributes.frame.origin.x = currentX
}
currentX += newAttributes.frame.size.width + minimumInteritemSpacing
newAttributesArray.append(newAttributes)
}
return newAttributesArray
}
}@implementation RTLCollectionViewFlowLayout
- (NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect {
NSArray *attributesArray = [super layoutAttributesForElementsInRect:rect];
NSMutableArray *newAttributesArray = [NSMutableArray array];
// 获取余数
NSInteger remainder = attributesArray.count % 4;
// 获取collectionView的宽度
CGFloat collectionViewWidth = self.collectionViewContentSize.width;
CGFloat currentX = self.sectionInset.left;
if (attributesArray.count < 4) {
// 只有一行
currentX = collectionViewWidth - self.sectionInset.right - remainder * (self.itemSize.width + self.minimumInteritemSpacing);
}
CGFloat currentY = self.sectionInset.top;
for (NSInteger index = 0; index < attributesArray.count; index++) {
UICollectionViewLayoutAttributes *attributes = attributesArray[index];
UICollectionViewLayoutAttributes *newAttributes = [attributes copy];
if (newAttributes.frame.origin.y == currentY) {
// 在同一行
newAttributes.frame.origin.x = currentX;
} else {
// 开始新的一行
currentY = newAttributes.frame.origin.y;
NSInteger last = attributesArray.count - index;
if (last < 4) {
NSInteger count = last % 4;
currentX = collectionViewWidth - self.sectionInset.right - count * self.itemSize.width - (count - 1) * self.minimumInteritemSpacing;
} else {
currentX = self.sectionInset.left;
}
newAttributes.frame.origin.x = currentX;
}
currentX += newAttributes.frame.size.width + self.minimumInteritemSpacing;
[newAttributesArray addObject:newAttributes];
}
return newAttributesArray;
}
@end