目标-C UIKit UIAlertViewDelegate未调用

Question

我开始学习目标-C uikit，我遇到了一个problem.UIAlertViewDelegate而不是called.Can，有人告诉我为什么？谢谢!

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
@interface AlertLearn : NSObject <UIAlertViewDelegate>
-(void) showAlertTest;
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex;
@end

#import "AlertLearn.h"
#import <UIKit/UIKit.h>

@implementation AlertLearn

-(void) showAlertTest{
    UIAlertView * alertView = [[UIAlertView alloc] initWithTitle:@"alert" message:@"alert test" delegate:self cancelButtonTitle:@"cancel" otherButtonTitles:@"ok", nil];
    [alertView show];

}
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{

    NSLog(@"clickedButtonAtIndex = %ld",buttonIndex );
    NSString *buttonTitle = [alertView buttonTitleAtIndex:buttonIndex];
    NSLog(@"clickedButtonAtIndex title = %@",buttonTitle);
}
@end

Answer 1

这是因为您要在比预期更严格的生命周期内分配警报视图，请尝试将警报设置为iVar或属性，然后再试一次。

@interface AlertLearn : NSObject <UIAlertViewDelegate>
{
UIAlertView * alertView;
}
-(void) showAlertTest;
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex;
@end
...
-(void) showAlertTest{
    alertView = [[UIAlertView alloc] initWithTitle:@"alert" message:@"alert test" delegate:self cancelButtonTitle:@"cancel" otherButtonTitles:@"ok", nil];
    [alertView show];

}

并从showAlertTest方法中删除定义。

P.S.：请注意，这种类型的显示警告视图在iOS 8中被取消，您应该使用UIAlertController，但是如果出于任何原因您需要支持iOS 7及以下，那么您应该为您的警告做一个强指针。