为什么所有的背景消失在UITableViewCell选择？(Why do all backgrounds disappear on UITableViewCell select?)

 我当前的项目的UITableViewCell行为令我感到困惑。 我有一个非常简单的UITableViewCell子类。 它为基础视图添加了一些额外的元素（通过[self.contentView addSubview:...]并在元素上设置背景颜色，使其看起来像黑色和灰色矩形框。 
 
 因为整个表的背景具有这样一个具体的纹理图像，每个单元格的背景都需要是透明的，即使被选中，但在这种情况下它应该变暗一点。 我设置了一个自定义半透明选择的背景来实现这一效果： 
 
UIView *background = [[[UIView alloc] initWithFrame:self.bounds] autorelease];
background.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent:0.6];
background.opaque = NO;

[self setSelectedBackgroundView:background];
 
 虽然这样可以看出背景，但是当我选择单元格时，会发生奇怪的副作用; 所有其他背景都是以某种方式摆脱的 。 这是一个截图。 底部细胞看起来应该和没有被选中。 选择顶部单元格，但应显示黑色和灰色矩形区域，但它们已经消失！ 
 
 
 谁知道这里发生了什么，甚至更重要：我该如何纠正？ 

My current project's UITableViewCell behavior is baffling me. I have a fairly straightforward subclass of UITableViewCell. It adds a few extra elements to the base view (via [self.contentView addSubview:...] and sets background colors on the elements to have them look like black and grey rectangular boxes. 
 
Because the background of the entire table has this concrete-like texture image, each cell's background needs to be transparent, even when selected, but in that case it should darken a bit. I've set a custom semi-transparent selected background to achieve this effect:
 
UIView *background = [[[UIView alloc] initWithFrame:self.bounds] autorelease];
background.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent:0.6];
background.opaque = NO;

[self setSelectedBackgroundView:background];
 
And although that yields the right look for the background, a weird side effect happens when I select the cell; all other backgrounds are somehow turnt off. Here's a screenshot. The bottom cell looks like it should and is not selected. The top cell is selected, but it should display the black and grey rectangular areas, yet they are gone!
 
 
Who knows what's going on here and even more important: how can I correct this?

原文：https://stackoverflow.com/questions/7053340