在 iOS 8.1 之后，在所有设备上，当点击 alertview 取消按钮时，ScrollView 向上并且不滚动

Posted 2023-03-11

【中文标题】在 iOS 8.1 之后，在所有设备上，当点击 alertview 取消按钮时，ScrollView 向上并且不滚动

【英文标题】：After iOS 8.1, on all devices ScrollView goes upwards and not scrolling when tapping on alertview cancel button

【发布时间】：2015-08-18 22:10:33

【问题描述】：

我有一个登录屏幕，其中有两个用于用户名和密码的文本字段。当电子邮件不正确时，我向下移动键盘并向用户显示适当的警报。当我单击警报视图的取消按钮时，警报视图消失并且滚动视图向上。此问题仅出现在 ios 8.1 之后的设备上。在 iOS 8.1 及更早版本上，它运行良好。不明白具体原因是什么？下面是代码

-(BOOL)textFieldShouldReturn:(UITextField *)textField

    if (txtActiveField == txtUsername) 
        [txtPassword becomeFirstResponder];
    
    else if (txtActiveField == txtPassword) 
        [txtPassword resignFirstResponder];
        //[self loginViaEmail:self];
        [self performSelector:@selector(loginViaEmail:) withObject:btnLogin afterDelay:0.0];
    

    return YES;

-(IBAction)loginViaEmail:(id)sender

    //[txtActiveField resignFirstResponder];
    if ([[txtUsername.text stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@" "]] length] == 0)
    
        [AppDelegate showWithTitle:title message:@"Please enter Username/Email for your account"];
    
    else if ([txtPassword.text length] < 6)
    
        if([[txtPassword.text stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@" "]] length] == 0)
            [AppDelegate showWithTitle:title message:@"Please enter Password"];
        else
            [AppDelegate showWithTitle:title message:@"Password contain minimum 6 characters"];
    


#pragma mark Show alert with message
+(void)showWithTitle:(NSString *)title message:(NSString *)msg


    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title message:msg delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alert show];

【参考方案1】：

我认为这是警报视图的问题。从 iOS 8 开始，AlertViewController 代替了警报视图。尝试使用以下代码，它在 iOS 8.4 及以下版本上运行良好

if (IS_OS_8_OR_LATER) 
        UIAlertController *alertVC = [UIAlertController alertControllerWithTitle:title message:msg preferredStyle:UIAlertControllerStyleAlert];

        UIAlertAction *cancelAction = [UIAlertAction
                                     actionWithTitle:@"OK"
                                     style:UIAlertActionStyleCancel
                                     handler:^(UIAlertAction *action)
                                     

                                     ];
        [alertVC addAction:cancelAction];

        [[[[[UIApplication sharedApplication] windows] objectAtIndex:0] rootViewController] presentViewController:alertVC animated:YES completion:^

        ];
    
    else
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title message:msg delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil];
        [alert show];