TextfieldShouldBeginediting Objective-c 中的 UIAlertcontroller

Question

我想在确定按钮单击文本字段后在文本字段中输入文本之前显示警报，但我正在显示警报但文本字段不可编辑。

if(textField == contractValueField)
{
    [self showAlertWithTitle:@"Information" textfield:contractValueField];
    return YES;
}

我搜索了很多网站，但使用 UIAlertView 没有得到正确答案，它正在工作，但我想使用 UIAlertController。我的项目中有 20 多个文本字段，每个文本字段都会在编辑开始前显示警报。

- (void)showAlertWithTitle:(NSString *)title textfield:(UITextField*)textfield
{
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:title message:@"Please enter Amount in Lakhs" preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction* ok = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action)
    {
        [alert dismissViewControllerAnimated:YES completion:nil];
        [textfield becomeFirstResponder];
    }];

    [alert addAction:ok];
    [self.navigationController presentViewController:alert animated:YES completion:nil];
}

Answer 1

原因是当你调用[textfield becomeFirstResponder]时，-(BOOL)textFieldShouldBeginEditing:(UITextField *)textField也被再次调用，这反过来显示你的alertView，当你从alert中选择ok按钮时，alert view再次显示，你卡在一个循环中。以下是修复它的快速方法：

-(BOOL)textFieldShouldBeginEditing:(UITextField *)textField{
    // check to see if the alert has already been shown, if it has the tag value will be 1
    if (textField == contractValueField && textField.tag != 1) {
        [self showAlertWithTitle:@"Information" textfield:textField];
        return false;
    }
    return true;
}

alertView 的代码如下：

- (void)showAlertWithTitle:(NSString *)title textfield:(UITextField*)textfield{
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:title message:@"Please enter Amount in Lakhs" preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction* ok = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action){
        textfield.tag = 1;
        [alert dismissViewControllerAnimated:YES completion:nil];
        [textfield becomeFirstResponder];
    }];

    [alert addAction:ok];
    [self presentViewController:alert animated:true completion:nil];
}

编辑完成后将textField的标签值恢复为0：

-(BOOL)textFieldShouldEndEditing:(UITextField *)textField{
    textField.tag = 0;
    return true;
}

Answer 2

声明一个 UITextField，它将引用最后选择的 textField：

@interface ViewController (){
    UITextField *lastSelectedTextField;
}

-(BOOL)textFieldShouldBeginEditing:(UITextField *)textField{
    // check to see if the textField is the last shown textField
    if (textField == lastSelectedTextField) {
        return true;
    }
    [self showAlertWithTitle:@"Information" textfield:textField];
    return false;
 }


- (void)showAlertWithTitle:(NSString *)title textfield:(UITextField*)textfield{
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:title message:@"Please enter Amount in Lakhs" preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction* ok = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action){
        lastSelectedTextField = textfield;;
        [alert dismissViewControllerAnimated:YES completion:nil];
        [textfield becomeFirstResponder];
    }];

    [alert addAction:ok];
    [self presentViewController:alert animated:true completion:nil];
}

这将是更好的选择，我没有意识到即使之前已经选择了 textField，您也希望每次都显示警报