UICollectionView布局不一致,UICollectionViewFlowLayout

Question

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个或1个单元格.2个单元,每个显示宽度的一半,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相同部分.

Answer 1

问题是由于父视图的子视图在实例化时分配了固定的帧大小而引起的。重写 setFrame: 供 UICollectionView 子类分配子视图框架的值，并且每次单元格出队和重新排队时调用 setFrame: 进行相应调整。