如何设置表视图单元附件视图以保留以前初始化的UIImageView？ [英] How to set the table view cell accessory view to retain a previously initialized UIImageView?
问题描述
假设我的视图控制器中有一个属性，定义如下：
Let's say I have a property in my view controller, defined as follows:
@property (nonatomic, retain) UIImageView *checkmarkOffAccessoryView;
我 @synthesize 这在实施中， 发布它在 -dealloc 中并在 -viewDidLoad 中初始化它如下：
I @synthesize this in the implementation, release it in -dealloc and initialize it in -viewDidLoad as follows:
self.checkmarkOffAccessoryView = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"checkmarkOff.png"]] autorelease];
到目前为止还不错。
我在我的表视图委托中使用它作为多个单元格的附件视图，发生了两件事：
When I use it in my table view delegate as an accessory view for multiple cells, two things happen:
- 只有一个单元格的附件视图显示图像
- 应用程序UI冻结。
应用程序不会崩溃，因为我可以说，用户界面根本没有响应。这是在模拟器和设备上。
The app doesn't crash, as near as I can tell, the UI simply becomes unresponsive. This is both in the simulator and on the device.
以下是我在单元格中使用初始化属性的方法：
Here is how I use the initialized property with my cell:
- (UITableViewCell *) tableView:(UITableView *)tv cellForRowAtIndexPath:(NSIndexPath *)indexPath {
// initialize or dequeue cell...
if (condition)
cell.accessoryView = self.checkmarkOffAccessoryView;
else
cell.accessoryView = nil;
}
使用上述代码，只有一个单元显示附件视图，UI冻结。
With the aforementioned code, only one cell shows the accessory view and the UI freezes.
如果我直接在委托方法中初始化 UIImageView 实例，我会得到所有满足条件的单元格显示附件查看，我没有遇到UI冻结：
If I initialize the UIImageView instance directly in the delegate method I get all condition-satisfying cells showing the accessory view and I do not experience the UI freeze:
- (UITableViewCell *) tableView:(UITableView *)tv cellForRowAtIndexPath:(NSIndexPath *)indexPath {
// initialize or dequeue cell...
if (condition)
cell.accessoryView = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"checkmarkOff.png"]] autorelease];
else
cell.accessoryView = nil;
}
我的目标是初始化尽可能少的对象并重用一个的UIImageView 。我很好奇为什么第一块代码是有问题的，我可以做些什么来解决这个问题。
My goal is to initialize as few objects as possible and reuse one UIImageView. I'm curious why the first chunk of code is problematic and what I could do to fix this.
好像单元格的 accessoryView 属性应该只增加 retain 计数 self.checkmarkOffAccessoryView 但似乎我遗漏了一些细节。
It seems like the cell's accessoryView property should just increment the retain count of self.checkmarkOffAccessoryView but it appears I am missing some detail.
我忽略了什么？感谢您的建议。
What have I overlooked? Thanks for your advice.
编辑
我认为：
self.checkmarkOffAccessoryView = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"checkmarkOff.png"]] autorelease];
与以下内容相同：
UIImageView *uncheckedView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"checkmarkOff.png"]];
self.checkmarkOffAccessoryView = uncheckedView;
[uncheckedView release];
无论哪种方式，我都会遇到相同的冻结症状。
Either way, I experience the same freeze symptom.
推荐答案
您无法多次添加同一视图。 UI处理程序将疯狂。为了确保这一点，我试着按照你上面所说的做，我也遇到了同样的问题。 UI冻结，图像仅出现在其中一个单元格中。
You cannot add the same view multiple times. The UI handler will go bonkers. To make sure of this, I tried doing what you said above and I got the same issue. The UI freezes up, the image only appears for one of the cells.
你可以做的最好的事情是将你的图像存储为分配的UIImage，并有一个辅助函数，每个单元格返回一个新的UIImageView。
The best thing you can do is to store your image as a UIImage allocated, and to have a helper function which returns a new UIImageView per cell.
您可以使用当前的方法（没有存储的UIImage）：
Using your current method (without a stored UIImage) you might do:
-(UIImageView *) makeCheckmarkOffAccessoryView
{
return [[[UIImageView alloc] initWithImage:
[UIImage imageNamed:@"checkmarkOff.png"]] autorelease];
}
然后再做
cell.accessoryView = [self makeCheckmarkOffAccessoryView];
您可能知道，另一方面，UIImages可能会被使用多次。 UIImageView不占用大量空间，因此您可以轻松拥有一堆而不用担心。
As you may be aware, UIImages on the other hand may be used any number of times. a UIImageView doesn't take up a lot of space, so you can easily have a bunch of those without worrying.
要扩展一个地方的交易，想象一下你可以同时在两个地方添加一个UIView。
To expand on the one place only deal, imagine that you add a UIView to two places at the same time.
[ob removeFromSuperview]会为这个对象做什么？它会从两个地方删除视图吗？只从他们中的一个？请求[ob superview]时会返回哪个值？很明显，用户界面并不能满足您的要求。
What will [ob removeFromSuperview] do for this object? Will it remove the view from both places? From one of them only? Which value will be returned when you request [ob superview]? Clearly the UI is not made to handle what you're asking for.
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