给键盘添加工具栏（按钮）

 UIToolbar *keyboardDoneButtonView = [[UIToolbar alloc] init];

    [keyboardDoneButtonView sizeToFit];

    UIBarButtonItem *doneButton = [[UIBarButtonItem alloc] initWithTitle:@"Done"

                                                                   style:UIBarButtonItemStylePlain target:self

                                                                  action:@selector(doneClicked:)];

    [keyboardDoneButtonView setItems:[NSArray arrayWithObjects:doneButton, nil]];

    self.textField.inputAccessoryView = keyboardDoneButtonView;