iphone - UIImage释放问题

Question

我一直在为这个问题烦恼，我已经阅读了所有关于释放问题的帖子，但无法理解为什么，因为我对 Objective-C 和 iphone 还很陌生，正如你所知道的:)

但我不明白的是下面的这段代码说我已经过度释放了 UIImage，现在我已经尝试了一切，但应用程序仍然崩溃

UIImage *imageSave      = [UIImage imageNamed:@"btn_save.png"];
UIButton *btnSave       = [UIButton buttonWithType:UIButtonTypeCustom];

[btnSave setBackgroundImage:imageSave forState:UIControlStateNormal];

btnSave.frame = CGRectMake(0, 0, imageSave.size.width, imageSave.size.height);

[btnSave addTarget:self action:@selector(save) forControlEvents:UIControlEventTouchUpInside];

UIBarButtonItem *barBtnSave = [[UIBarButtonItem alloc] initWithCustomView:btnSave];

self.navigationItem.rightBarButtonItem  = barBtnSave;

//[imageSave release];
//[btnSave release];
[barBtnSave release];


UIImage *imageCancel    = [UIImage imageNamed:@"btn_cancel.png"];
UIButton *btnCancel     = [UIButton buttonWithType:UIButtonTypeCustom];

[btnCancel setBackgroundImage:imageCancel forState:UIControlStateNormal];

btnCancel.frame = CGRectMake(0, 0, imageCancel.size.width, imageCancel.size.height);

[btnCancel addTarget:self action:@selector(cancel) forControlEvents:UIControlEventTouchUpInside];
UIBarButtonItem *barBtnCancel = [[UIBarButtonItem alloc] initWithCustomView:btnCancel];

self.navigationItem.leftBarButtonItem   = barBtnCancel;

//[imageCancel release];
//[btnCancel release];
[barBtnCancel release];

Answer 1

好的，让我们看一下这两行:

UIImage *imageCancel = [UIImage imageNamed:@"btn_cancel.png"];

[imageCancel release];

在第1行中，你创建了一个autorelease镜像，那么retainCount将为0。然后，你释放该镜像，这将使retainCount为-1​​，从而导致崩溃

您需要记住的是增加retainCount的列表:alloc、copy、retain ...如果您调用其中之一对于对象的这些方法，您必须执行以下任一操作:autorelease 或 release