oc中在输入法上面增加自定义行，添加几个按钮

注意此方法要慎用，因为一旦在一处写过了，在其他所有界面弹出键盘时都会出现此处定义的悬浮窗，不过备忘嘛，此方法还是要贴出来

- (UIView *)inputAccessoryView {
    UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 50, 30)];
    [button setTitle:@"按钮" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];
    button.backgroundColor = [UIColor redColor];

    UIView *containerView = [UIView new];
    containerView.frame = CGRectMake(0, 0, 10, 60);
    containerView.backgroundColor = [UIColor greenColor];
    [containerView addSubview:button];

    return containerView;
}