为键盘添加inputAccessoryView

    UIToolbar* numberToolbar = [[UIToolbar alloc]initWithFrame:CGRectMake(0, 0, 320, 50)];
    numberToolbar.barStyle = UIBarStyleBlackTranslucent;
    numberToolbar.items = [NSArray arrayWithObjects:
                           [[UIBarButtonItem alloc]initWithTitle:@"取消" style:UIBarButtonItemStyleBordered target:self action:@selector(cancelNumberPad)],
                           [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil],
                           [[UIBarButtonItem alloc]initWithTitle:@"确定" style:UIBarButtonItemStyleDone target:self action:@selector(doneWithNumberPad)],
                           nil];
    [numberToolbar sizeToFit];
    textField.inputAccessoryView = numberToolbar;