ios - UIAlertView 中的 UITextField 无法设置光标

Question

这是我的代码:

    UIAlertView * alert = [[UIAlertView alloc] initWithTitle:@"Confirm Address" message:@"Please confirm your address:" delegate:self cancelButtonTitle:@"Confirm" otherButtonTitles:nil];
    alert.alertViewStyle = UIAlertViewStylePlainTextInput;
    UITextField * alertTextField = [alert textFieldAtIndex:0];
    alertTextField.text = @"1234 ABC Street";
    [alertTextField becomeFirstResponder];
    UITextPosition *beginning = [alertTextField beginningOfDocument];
    [alertTextField setSelectedTextRange: [alertTextField
                                   textRangeFromPosition:beginning
                                   toPosition:beginning]];

    [alert show];

光标未设置到文本字段的开头。我做错了什么？

Answer 1

实现UITextFieldDelegate在你的 Controller 上，移动你的 setSelectedTextRange textFieldDidBeginEditing 的代码委托(delegate)回调:

UIAlertView * alert = [[UIAlertView alloc] initWithTitle:@"Confirm Address" message:@"Please confirm your address:" delegate:self cancelButtonTitle:@"Confirm" otherButtonTitles:nil];
alert.alertViewStyle = UIAlertViewStylePlainTextInput;
UITextField * alertTextField = [alert textFieldAtIndex:0];
alertTextField.text = @"1234 ABC Street";
[alertTextField becomeFirstResponder];

// Your UITextFieldDelegate implementer here
[alertTextField setDelegate:self];

[alert show];

- (void)textFieldDidBeginEditing:(UITextField *)textField
{
    UITextPosition *beginning = [textField beginningOfDocument];
    [textField setSelectedTextRange:[textField textRangeFromPosition:beginning
                                                          toPosition:beginning]];
}

在头文件或实现的类扩展中指定很重要 <UITextFieldDelegate>并如上所示设置委托(delegate)。