ios - 未调用 Objective-C UIKit UIAlertViewDelegate

Question

我开始学习 Objective-C uikit，我遇到了一个问题。没有调用 UIAlertViewDelegate。谁能告诉我为什么？谢谢你!

#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

这是因为您在比应有的更严格的生命周期内分配警报 View ，请尝试将您的警报设为 iVar 或属性，然后重试。

@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];

}

并从您的 showAlertTest 方法中删除定义。

P.S.:请注意，这种显示警报 View 的类型在 iOS 8 中已弃用，您应该改用 UIAlertController，但如果出于任何原因您需要支持iOS 7 及以下版本，嗯，你应该为你的警报做一个强指针。