UICollectionView 布局不一致，UICollectionViewFlowLayout

Posted 2023-02-23

【中文标题】UICollectionView 布局不一致，UICollectionViewFlowLayout

【英文标题】：UICollectionView not consistent layout, UICollectionViewFlowLayout

【发布时间】：2013-04-01 18:32:20

【问题描述】：

我无法以一致的方式在 UICollectionView 中显示单元格。单元格的初始显示是正确的，但是每次用户滚动过去然后返回到一组单元格时，显示都是不正确的。行应该只包含 2 或 1 个单元格。 2 个单元格各占显示宽度的一半，1 个单元格占全宽。

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath

    return [self preferredSizeForIndexPath:indexPath];


- (CGSize)preferredSizeForIndexPath:(NSIndexPath *)indexPath 

    BOOL isLastObjectInSection = NO;
    NSString *sectionKey = [[arrCollectionData[indexPath.section] allKeys] objectAtIndex:0];
    DLog(@"SectionKey: %@", sectionKey);
    NSArray *arrSection = [arrCollectionData[indexPath.section] objectForKey:sectionKey];
    DLog(@"ArrSection: %@", arrSection);

    if ( arrSection[indexPath.row] == arrSection.lastObject ) 
        if( arrSection.count % 2 != 0 ) 
            isLastObjectInSection = YES;
        
    

    CGSize cellSize = CGSizeZero;
    if (UIDeviceOrientationIsLandscape([[UIDevice currentDevice] orientation])) 
        if (isLastObjectInSection == YES) 
            cellSize = CGSizeMake(IPAD_BADGE_WIDTH_LANDSCAPE_WIDE, IPAD_BADGE_HEIGHT_LANDSCAPE_WIDE);
         else 
            cellSize = CGSizeMake(IPAD_BADGE_WIDTH_LANDSCAPE, IPAD_BADGE_HEIGHT_LANDSCAPE);
        
     else 
        if (isLastObjectInSection == YES) 
            cellSize = CGSizeMake(IPAD_BADGE_WIDTH_WIDE, IPAD_BADGE_HEIGHT_WIDE);
         else 
            cellSize = CGSizeMake(IPAD_BADGE_WIDTH, IPAD_BADGE_HEIGHT);
        
    
    DLog(@"CellSize: %@", NSStringFromCGSize(cellSize));
    return cellSize;

以下是收集数据的示例。

Printing description of self->arrCollectionData:
<__NSArrayI 0x94bbc40>(

    "March 12, 2013" =     (
        "<FMLeafTimelineContainer: 0x94b2430>",
        "<FMLeafTimelineContainer: 0x94b3670>"
    );
,

    "February 25, 2013" =     (
        "<FMLeafTimelineContainer: 0x94b4500>"
    );
,

    "February 14, 2013" =     (
        "<FMLeafTimelineContainer: 0x94b48f0>",
        "<FMLeafTimelineContainer: 0x94b3a60>"
    );
,

    "February 12, 2013" =     (
        "<FMLeafTimelineContainer: 0x94b3ce0>",
        "<FMLeafTimelineContainer: 0x94b2b00>"
    );
,

    "February 4, 2013" =     (
        "<FMCommunityTimelineContainer: 0x94b4e90>",
        "<FMCommunityTimelineContainer: 0x94b5050>",
        "<FMCommunityTimelineContainer: 0x94b5f70>"
    );
,

    "January 30, 2013" =     (
        "<FMCommunityTimelineContainer: 0x94b6ad0>",
        "<FMCommunityTimelineContainer: 0x94b5a90>"
    );
,

    "January 24, 2013" =     (
        "<FMCommunityTimelineContainer: 0x94b5d00>",
        "<FMCommunityTimelineContainer: 0x94b6d90>"
    );
,

    "January 22, 2013" =     (
        "<FMCommunityTimelineContainer: 0x94b6440>"
    );
,

    "January 21, 2013" =     (
        "<FMCommunityTimelineContainer: 0x94b6260>",
        "<FMCommunityTimelineContainer: 0x94b62e0>",
        "<FMCommunityTimelineContainer: 0x94b70c0>",
        "<FMCommunityTimelineContainer: 0x94b55a0>",
        "<FMCommunityTimelineContainer: 0x94b82d0>",
        "<FMCommunityTimelineContainer: 0x94b78b0>"
    );
,

    "December 20, 2012" =     (
        "<FMCommunityTimelineContainer: 0x94b53f0>"
    );
,

    "December 6, 2012" =     (
        "<FMCommunityTimelineContainer: 0x94b7200>"
    );
,

    "December 4, 2012" =     (
        "<FMCommunityTimelineContainer: 0x94b72b0>"
    );
,

    "November 19, 2012" =     (
        "<FMCommunityTimelineContainer: 0x94b7ae0>"
    );

)

下面的图片都展示了集合视图的同一部分。

【参考方案1】：

问题是由在实例化时分配了固定帧大小的父子视图引起的。 Overrode setFrame: 用于 UICollectionView 子类分配子视图帧的值，并且每次单元格出列和重新入队时调用 setFrame: 进行相应调整。

【参考方案2】：

您可以尝试动态计算项目宽度。

CGFloat fullItemWidth = self.collectionView.bounds.size.width;
NSInteger itemsPerRow = 2;
CGFloat itemWidth = (fullItemWidth - (itemsPerRow-1)*self.collectionView.collectionViewLayout.minimumInteritemSpacing)/itemsPerRow;
if (UIDeviceOrientationIsLandscape([[UIDevice currentDevice] orientation])) 
    if (isLastObjectInSection == YES) 
        cellSize = CGSizeMake(fullItemWidth, IPAD_BADGE_HEIGHT_LANDSCAPE_WIDE);
     else 
        cellSize = CGSizeMake(halfItemWidth, IPAD_BADGE_HEIGHT_LANDSCAPE);
    
 else 
    if (isLastObjectInSection == YES) 
        cellSize = CGSizeMake(fullItemWidth, IPAD_BADGE_HEIGHT_WIDE);
     else 
        cellSize = CGSizeMake(halfItemWidth, IPAD_BADGE_HEIGHT);