- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range  replacementText:(NSString *)text
{
    if (range.length==0) {
        if ([text isEqualToString:@"\n"]) {
            [txtView resignFirstResponder];
            if(textView.returnKeyType== UIReturnKeyGo){

                [self PreviewLatter];
                return NO;
            }
            return NO;
        }
    }   return YES;
}

UITextView没有任何在用户点击返回键时被调用的方法。如果您希望用户只能添加一行文本，请使用UITextField。按回车键并隐藏UITextView的键盘不符合接口准则。

即使这样，如果你想这样做，实现textView:shouldChangeTextInRange:replacementText:方法的UITextViewDelegate，并在检查替换文本是否\n，隐藏键盘。

也许还有别的办法，但我不知道有什么办法。

//你可以使用这个…

步骤1。第一步是确保声明了对UITextViewDelegate协议的支持。这是在你的头文件中完成的，例如这里的头文件叫做

EditorController。h:

@interface EditorController : UIViewController  {
  UITextView *messageTextView;
}

@property (nonatomic, retain) UITextView *messageTextView;

@end

步骤2。接下来你需要将控制器注册为UITextView的委托。从上面的例子继续，这里是我如何用EditorController作为委托初始化UITextView…

- (id) init {
    if (self = [super init]) {
        // define the area and location for the UITextView
        CGRect tfFrame = CGRectMake(10, 10, 300, 100);
        messageTextView = [[UITextView alloc] initWithFrame:tfFrame];
        // make sure that it is editable
        messageTextView.editable = YES;

        // add the controller as the delegate
        messageTextView.delegate = self;
    }

步骤3。现在拼图的最后一块是采取行动响应shouldCahngeTextInRange消息如下:

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range 
  replacementText:(NSString *)text
{
    // Any new character added is passed in as the "text" parameter
    if ([text isEqualToString:@"\n"]) {
        // Be sure to test for equality using the "isEqualToString" message
        [textView resignFirstResponder];

        // Return FALSE so that the final '\n' character doesn't get added
        return FALSE;
    }
    // For any other character return TRUE so that the text gets added to the view
    return TRUE;
}

-(BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text {
    if([text isEqualToString:@"\n"])
        [textView resignFirstResponder];
    return YES;
}

yourtextView.delegate=self;

还要添加UITextViewDelegate

别忘了确认协议

如果你没有添加IF ([text isEqualToString:@"\n"])，你就不能编辑

试试这个:

 - (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{
    if ([text isEqualToString:@"\n"]) {
        [self.view endEditing:YES];
    }

    return YES;

}

类似于使用UITextViewDelegate的其他答案，但一个更新的swift接口isNewline将是:

func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
    if let character = text.first, character.isNewline {
        textView.resignFirstResponder()
        return false
    }
    return true
}