UICollectionView佈局不一致，UICollectionViewFlowLayout

Question

我無法以一致的方式在UICollectionView中顯示單元格。單元的初始顯示是正確的，但是每次用戶滾動過去然後返回到一組單元時，顯示都不正確。行應該只包含2個或1個單元格。每個顯示寬度的一半爲2個單元，1個單元爲全寬。

- (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; 

} 

以下是收集數據的示例。

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>" 
    ); 
} 
) 

下面的圖片展示了集合視圖的同一部分。

Answer 1

問題是由具有在實例化分配了固定幀大小的父的子視圖引起的。 Overrode setFrame：用於UICollectionView子類來分配子視圖幀的值，並且每當一個單元出隊和重新排隊時調用setFrame：進行相應的調整。

Answer 2

您可以嘗試動態計算項目寬度。

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); 
    } 
}