在文本字段中输入一个字符时返回键盘

Question

我正在开发一个 iPhone 应用程序，只要我在文本字段中只输入一个字符，我就必须返回键盘。如何实现这一目标，请提出一些解决方案。

谢谢。

Answer 1

步骤 1：创建一个实现 UITextFieldDelegate 协议的类

@interface TheDelegateClass : NSObject <UITextFieldDelegate>

步骤 2：在您的实现中，重写方法 - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    // newString is what the user is trying to input.
    NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string];
    if ([newString length] < 1) {
        // If newString is blank we will just ingore it.
        return YES;
    } else
    {
        // Otherwise we cut the length of newString to 1 (if needed) and set it to the textField.
        textField.text = [newString length] > 1 ? [newString substringToIndex:1] : newString;
        // And make the keyboard disappear.
        [textField resignFirstResponder];
        // Return NO to not change text again as we've already changed it.
        return NO;
    }
}

步骤 3：设置实例委托类的代理作为 UITextField 的委托。

TheDelegateClass *theDelegate = [[TheDelegateClass alloc] init];
[theTextField setDelegate:theDelegate];

Answer 2

您必须在 的 文本委托方法中编写代码

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
   if([textField.text length] == 1){
    [textField resignFirstResponder];
}

，然后在 textFieldDidBeginEditing 中检查字符串的长度

- (void)textFieldDidBeginEditing:(UITextField *)textField{

    if([textField.text length] == 1){
    [textField resignFirstResponder];
}

}

Answer 3

在文本字段中添加通知创建代码

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(changeText:) name:UITextFieldTextDidChangeNotification object:textField];

并实施

- (void) changeText: (id) sender;
{
    if ([textField.text length] == 1) 
    {
        [textField resignFirstResponder];
    }        
}

Answer 4

我想这就是你正在寻找的东西？

- (BOOL)textFieldShouldReturn:(UITextField *)textField 
{
   [textField resignFirstResponder];
   [add your method here];
    return YES;

}

或者，如果您希望它在开始编辑时立即退出，您可以将此代码放入 textFieldDidBeginEditing: delegate 方法中

[textField resignFirstResponder];

，检查此链接

https://developer.apple.com/library/ios/#documentation/uikit/reference/UITextFieldDelegate_Protocol/UITextFieldDelegate/UITextFieldDelegate.html

Answer 5

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
   if([textField.text length] == 1){
       [textField resignFirstResponder];
}

- (BOOL)textFieldShouldEndEditing:(UITextField *)textField
{
   if([textField.text length]==1)
   {
       // here perform the action you want to do
   }

}