+ (void)addDoneButtonToControl:(id)txtFieldOrTextView
{
    if([txtFieldOrTextView isKindOfClass:[UITextField class]])
    {
        txtFieldOrTextView = (UITextField *)txtFieldOrTextView;
    }
    else if([txtFieldOrTextView isKindOfClass:[UITextView class]])
    {
        txtFieldOrTextView = (UITextView *)txtFieldOrTextView;
    }

    UIToolbar* numberToolbar = [[UIToolbar alloc]initWithFrame:CGRectMake(0,
                                                                          0,
                                                                          [Global returnDeviceWidth],
                                                                          50)];
    numberToolbar.barStyle = UIBarStyleDefault;


    UIBarButtonItem *btnDone = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"btn_return"]
                                                                style:UIBarButtonItemStyleBordered
                                                               target:txtFieldOrTextView
                                                               action:@selector(resignFirstResponder)];

    numberToolbar.items = [NSArray arrayWithObjects:btnDone,nil];
    [numberToolbar sizeToFit];

    if([txtFieldOrTextView isKindOfClass:[UITextField class]])
    {
         ((UITextField *)txtFieldOrTextView).inputAccessoryView = numberToolbar;
    }
    else if([txtFieldOrTextView isKindOfClass:[UITextView class]])
    {
         ((UITextView *)txtFieldOrTextView).inputAccessoryView = numberToolbar;
    }
}

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。

我想我应该把这个片段放在这里:

确保声明了对UITextViewDelegate协议的支持。

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text {

    if([text isEqualToString:@"\n"]) {
        [textView resignFirstResponder];
        return NO;
    }

    return YES;
}

Swift 4.0更新:

func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
    if text == "\n" {
        textView.resignFirstResponder()
        return false
    }
    return true
}

-(BOOL)textFieldShouldReturn:(UITextField *)textField; // called from textfield (keyboard)

-(BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text; // good tester function - thanks

试试这个:

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

    return YES;

}

函数hideQueboard。

- (void)HideQueyboard
{
    [[UIApplication sharedApplication] sendAction:@selector(resignFirstResponder)   to:nil from:nil forEvent:nil];
}