UIAlertview exc_bad_access [英] UIAlertview exc_bad_access

问题描述

我添加了一个函数以在几秒钟后关闭UIAlertView.整个代码如下:

I add a function to dismiss the UIAlertView after several seconds.The whole code is like:

- (void)netWorkAlert
{
    UIAlertView *netWork = [[UIAlertView alloc] initWithTitle:@"error" message:@"network has problems" delegate:self cancelButtonTitle:nil otherButtonTitles: nil];
    [netWork show];
    [self performSelector:@selector(dismissAlert:) withObject:netWork afterDelay:2];
}
- (void)dismissAlert:(UIAlertView *)alert
{
    if(alert)
    {
        [alert dismissWithClickedButtonIndex:0 animated:YES];
        [alert release];
    }
}

netWorkAlert在网络不可用时被调用.

the netWorkAlert is invoked when the network is unavailable.

现在我遇到的问题是第二次调用netWorkAlert时，应用程序已损坏并且Xcode显示错误

Now the problem I met is when the netWorkAlert is invoked at the second time, the app is broken and the Xcode shows error in

int main(int argc, char *argv[])
{
    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([ZJAppDelegate class]));
//Thread 1 :EXC_BAD_ACCESS(code=1,address=xc0000004)
    }
}

我没有使用ARC，也不知道为什么它崩溃.即使我评论[alert release];，第二次它仍然有相同的问题.

I didn;t use ARC and I don't know why it crashes. Even I comment the [alert release];, it still has the same problem at the second time.

有人可以帮我检查一下吗? 谢谢！

Could anyone help me to check it? thanks!

推荐答案

在调用dismissAlert方法时，UIAlertView可能不在范围内(您检查alert是否为nil可以防止此代码崩溃但是，还有一种更好的方法可以实现alert永远不会超出范围.

The UIAlertView could be out of scope by the time the dismissAlert method is called (your checking for alert being nil will prevent this code crashing. There is, however, a better way of implementing this where alert will never be out of scope.

您定义networkAlert方法的类应实现<UIAlertViewDelegate>协议.下面的代码使您可以拦截用户单击取消"按钮并执行自定义操作.按取消的默认操作是关闭UIAlertView.

Your class that defines the networkAlert method should implement the <UIAlertViewDelegate> protocol. The code below allows you to intercept the user clicking the 'cancel' button and perform a custom action. The default action of pressing cancel is to close the UIAlertView.

@interface YourClassName : UIViewController <UIAlertViewDelegate> {}

@implementation YourClassName

-(void) networkAlert
{
    UIAlertView *netWork = [[UIAlertView alloc] initWithTitle:@"error" 
                                                      message:@"network has problems"
                                                     delegate:self 
                                            cancelButtonTitle:@"cancel" 
                                            otherButtonTitles:nil];
    [netWork show];
}

- (void) alertViewCancel:(UIAlertView*)alertView 
{
    what ever it is you want to do when the cancel button is pressed here
}

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