iphone - 如何遍历多个 UITextField

Question

我有四个 UITextField，我想在 UIAlertView 中使用，目前它是这样的

一旦达到 4 个字符限制，我希望能够将每个框限制为 4 个字符，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后删除字符，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工作..所以这就是它到目前为止的样子。

//提示用户在此处输入注册 UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Please Register Device"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];

如有任何帮助，我们将不胜感激。

//更新: 这就是我尝试使用委托(delegate)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，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。所以我修改了函数。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，当你不想删除内容时这不起作用，但如果你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，你可以在这里得到它:TextFieldTest

---

这就是我的做法，使用文本字段委托(delegate)，您可以检查新插入的字符，如果达到最大值，则移至下一个文本字段:

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... 
}

(不好意思编译不了我直接写在这里)

祝你好运!