如何逐步遍历多个 UITextField

Question

我有四个 UITextFields 我想在 UIAlertView 中使用，目前这就是它的样子

我希望能够将每个框限制为 4 个字符，一旦每个字段达到 4 个字符的限制，然后我希望下一个 UITextField 成为第一响应者。

我也希望能够反向执行此操作，因此如果在第二个字段中没有可用字符时删除字符，请转到第一个并开始删除等。

目前我的代码非常草率，因为我只是想让这样的东西正常工作..所以这就是到目前为止的样子。

//提示用户在此处输入注册 UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"请注册设备" message:@" " delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];

UITextField *myTextField = [[UITextField alloc] initWithFrame:CGRectMake(12, 45, 53, 30)];

UITextField *myTextField1 = [[UITextField alloc] initWithFrame:CGRectMake(77, 45, 53, 30)];
UITextField *myTextField2 = [[UITextField alloc] initWithFrame:CGRectMake(142, 45, 53, 30)];
UITextField *myTextField3 = [[UITextField alloc] initWithFrame:CGRectMake(207, 45, 53, 30)];

// need to do something with first reasponder once 4 digits has been entered per box etc.
[myTextField becomeFirstResponder];

myTextField.placeholder =@"AAAA";
myTextField.autocapitalizationType = UITextAutocapitalizationTypeAllCharacters;
myTextField.textAlignment = NSTextAlignmentCenter;
myTextField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;

myTextField1.placeholder =@"AAAA";
myTextField1.autocapitalizationType = UITextAutocapitalizationTypeAllCharacters;
myTextField1.textAlignment = NSTextAlignmentCenter;
myTextField1.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;

myTextField2.placeholder =@"AAAA";
myTextField2.autocapitalizationType = UITextAutocapitalizationTypeAllCharacters;
myTextField2.textAlignment = NSTextAlignmentCenter;
myTextField2.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;

myTextField3.placeholder =@"AAAA";
myTextField3.autocapitalizationType = UITextAutocapitalizationTypeAllCharacters;
myTextField3.textAlignment = NSTextAlignmentCenter;
myTextField3.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;

[myTextField setBackgroundColor:[UIColor whiteColor]];
[myTextField1 setBackgroundColor:[UIColor whiteColor]];
[myTextField2 setBackgroundColor:[UIColor whiteColor]];
[myTextField3 setBackgroundColor:[UIColor whiteColor]];

[alert addSubview:myTextField];
[alert addSubview:myTextField1];
[alert addSubview:myTextField2];
[alert addSubview:myTextField3];

[alert show];

任何帮助将不胜感激。

// 更新： 这就是我尝试使用委托方法的方式

//.h
<UITextFieldDelegate>

//.m
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
//..
    [self.myTextField setDelegate:self];
    [self.myTextField1 setDelegate:self];
    [self.myTextField2 setDelegate:self];
    [self.myTextField3 setDelegate:self];
//..
}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
     NSLog(@"yay");
    return NO;
}

Answer 1

更新

我尝试了下面的代码，并且确实有效，但出于某种原因，如果您更改 FirstResponder，文本将不会被写入。所以我修改了功能。你应该这样做：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    if(textField.text.length >= MAX_LENGTH)
        return NO;

    if((textField.text.length + string.length) >= MAX_LENGTH)
    {
        int currentTag = textField.tag;

        if(currentTag == 4)
            return YES;

        UITextField *newTextField = (UITextField *) [textField.superview viewWithTag:(currentTag+1)];
        [newTextField becomeFirstResponder];
        textField.text = [textField.text stringByAppendingString:string];
    }
    return YES; //you probably want to review this...
}

无论如何，当您不想删除内容时，这不起作用，但如果您更改代码以检查更改范围，这很容易解决。

我做了一个示例项目，你可以在这里获取：TextFieldTest

---

我就是这样做的，使用文本字段委托，您可以检查新插入的字符，如果达到最大值，则移动到下一个文本字段：

static int MAX_LENGTH = 4;
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
   if((textField.text.length + string.length) >= MAX_LENGTH)
   {
       //Get next TextField... A simple way to do this:
       UITextField *newTextField = [textField.superview viewWithTag:(textField.tag+1)];
       [newTextField becomeFirstResponder];
       //remember to set the tags in order
   }
   return YES; //you probably want to review this... 
}

（如果没有编译，抱歉我直接写到这里了）

祝你好运！

Answer 2

您可以为这些文本字段设置委托，并在委托方法中实现您的业务逻辑（将其中一个文本字段设置为新的第一响应者）。