更改 UIImageView 上的视图属性时出现内存问题
我在弹出窗口 (iPad) 中使用 UITableView 从文档目录中选择图像。然后该图像显示在 UIImageView 中。这是我用来将新图像放入 UIImageView 的代码：
- (void)changeImage:(NSString *)imageFilename {
NSLog(@"changeImage to: %@", imageFilename);
NSFileManager *fileMgr;
fileMgr = [NSFileManager defaultManager];
NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docsDir = [dirPaths objectAtIndex:0];
NSString *imagePath = [docsDir stringByAppendingPathComponent:imageFilename];
UIImage *newImage = [UIImage imageWithContentsOfFile:imagePath];
NSLog(@"Path for new image: %@", imagePath);
self.imageView.image = newImage;
[newImage release];
[fileMgr release];
}
第一次总是工作正常，但每当我尝试从弹出窗口再次更改显示的图像时，我都会收到以下错误： 程序收到信号：“EXC_BAD_ACCESS”。
我已将问题缩小到这一行：
self.imageView.image = newImage;
我尝试在该行之前添加以下内容：
self.imageView.image = nil;
这没有什么区别。我不明白为什么这第一次会起作用，但下次不会重复同样的行为。
非常感谢任何帮助。
I am using a UITableView inside a popover (iPad) to select an image from the Documents Directory. This image is then displayed in a UIImageView. Here is the code I am using to put the new image into the UIImageView:
- (void)changeImage:(NSString *)imageFilename {
NSLog(@"changeImage to: %@", imageFilename);
NSFileManager *fileMgr;
fileMgr = [NSFileManager defaultManager];
NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docsDir = [dirPaths objectAtIndex:0];
NSString *imagePath = [docsDir stringByAppendingPathComponent:imageFilename];
UIImage *newImage = [UIImage imageWithContentsOfFile:imagePath];
NSLog(@"Path for new image: %@", imagePath);
self.imageView.image = newImage;
[newImage release];
[fileMgr release];
}
This always works fine the first time around, but whenever I try to change the displayed image again from the popover, I get the following error:
Program received signal: “EXC_BAD_ACCESS”.
I've narrowed the problem down to this line:
self.imageView.image = newImage;
I tried adding the following before that line:
self.imageView.image = nil;
It made no difference. I can't figure out why this works the first time but won't repeat the same behaviour next time around.
Would greatly appreciate any help.
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顺便说一句，您也不应该释放 fileMgr，因为您不拥有它。文档说它始终是同一个实例（单例） - 它不会中断，因为通常会覆盖单例上的“release”而不执行任何操作。不过，它不一定是这样的，而且是错误的。
BTW you also shouldn't release fileMgr, because you don't own it. Docs say that it is always the same instance (a singleton) - it doesn't break since it is common to override "release" on singletons to do nothing. Still, it doesn't have to be this way and is wrong.
从代码中删除
[newImage release];就可以了！您没有分配/保留/新建 newImage，因此您不必释放它。
它第一次起作用是因为
UIImage *newImage = [UIImage imageWithContentsOfFile:imagePath];返回了一个对当前运行循环有效的自动释放对象，但是您过度释放了它，并且当run-loop 尝试再次使用它，因此会出现 EXC_BAD_ACCESS 信号。Remove
[newImage release];from your code and you should be fine!You didn't alloc/retain/new the newImage so you don't have to release it.
It works the first time because
UIImage *newImage = [UIImage imageWithContentsOfFile:imagePath];returned you an autorelease'd object that is valid for the current run-loop but you are over releasing it, and when the run-loop tries to use it again and hence the EXC_BAD_ACCESS signal.我对 Objective-C 没有深入的了解，但我认为你应该复制图片：
I doesn't have a deep understanding of Objective-C, but I think you should copy the image: