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

【问题标题】：After iOS 8.1, on all devices ScrollView goes upwards and not scrolling when tapping on alertview cancel button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
【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];
}

【问题讨论】：

标签： ios objective-c iphone uiscrollview ios8.3

【解决方案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];
    }
}

【讨论】：