ViewWithTag:仅第一次在 UITableViewCell 上返回 nil
问题说明
当 UITableViewCell 通过 dequeueReusableCellWithIdentifier: 从 Storyboard 第一次加载时: viewWithTag: 返回 nil 对象.但是在第二次和下一次重新加载时，它会返回正确的对象.
When UITableViewCell is loaded first time from Storyboard via dequeueReusableCellWithIdentifier: viewWithTag: returns nil object. But on second and next reloads it returns proper object.
我的tableView嵌入在带有原型单元格的 UIViewController(在 Storyboard 中)
My tableView is embedded in UIViewController(in Storyboard) with prototype cells
cellAttachment = [_tableView dequeueReusableCellWithIdentifier:@"cellAttachment"];
UIButton *btnAttachment = nil;
btnAttachment = (UIButton*)[cellAttachment viewWithTag:10];
当第一次加载 cellAttachment 时，btnAttachment 为零.在下次重新加载 btnAttachment 时正确返回.
When cellAttachment is loaded first time, btnAttachment is nil. On next reload btnAttachment is returned properly.
Cell View 层次结构第一次加载
(lldb) po [cellAttachment recursiveDescription]
<UITableViewCell: 0x7fd3e611cc20; frame = (0 0; 0 0); layer = <CALayer: 0x7fd3e611be00>>
| <UITableViewCellContentView: 0x7fd3e3fc9850; frame = (0 0; 0 0); clipsToBounds = YES; opaque = NO; gestureRecognizers = <NSArray: 0x7fd3e611b6a0>; layer = <CALayer: 0x7fd3e611bd00>>
| <_UITableViewCellSeparatorView: 0x7fd3e611cf20; frame = (0 -1; 15 1); layer = <CALayer: 0x7fd3e611c020>>
下次重新加载时的单元格视图层次结构
(lldb) po [cellAttachment recursiveDescription]
<UITableViewCell: 0x7fd3e611cc20; frame = (0 179; 320 42); hidden = YES; autoresize = W; layer = <CALayer: 0x7fd3e611be00>>
| <UITableViewCellContentView: 0x7fd3e3fc9850; frame = (0 0; 320 42); opaque = NO; gestureRecognizers = <NSArray: 0x7fd3e611b6a0>; layer = <CALayer: 0x7fd3e611bd00>>
| | <UIButton: 0x7fd3e611d0f0; frame = (286 6; 15 22); opaque = NO; autoresize = RM BM; tag = 10; layer = <CALayer: 0x7fd3e611c0b0>>
| | | <UIImageView: 0x7fd3e6015410; frame = (0.5 1; 14 20); clipsToBounds = YES; opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x7fd3e3ccd960>>
| <_UITableViewCellSeparatorView: 0x7fd3e611cf20; frame = (0 -1; 15 1); layer = <CALayer: 0x7fd3e611c020>>
| <UIView: 0x7fd3e3c4c140; frame = (15 41; 305 1); layer = <CALayer: 0x7fd3e3cecb40>>
正确答案
在遇到这个问题后，我将旧的工作文件与新的故事板文件进行了比较，以了解可能导致这种行为的原因.这样做之后，我能够通过以下方式之一解决我的问题.
After having the issue I compared my old working files with new storyboard files to know what may cause such a behavior. After doing that I was able to fix my problem in one of following ways.
1:在 UITableViewCell 的每个子视图上启用已安装"字段
或
2:在 .storyboard 文件中禁用使用尺寸类别"
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