-(void)tapBackground //在ViewDidLoad中调用
{
    UITapGestureRecognizer * tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapOnce)];//定义一个手势
    [tap setNumberOfTouchesRequired:1];//触击次数这里设为1
    [self.view addGestureRecognizer:tap];//添加手势到View中
}

-(void)tapOnce//手势方法
{
   [self.view endEditing:YES];
}

-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self.view endEditing:YES];
}