一，效果图。

二，代码。

RootViewController.m

//点击任何处出现sheet
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UIActionSheet * sheet = [[UIActionSheet alloc] initWithTitle:@"确定要清空图片缓存？" delegate:self cancelButtonTitle:@"取消" destructiveButtonTitle:@"确定" otherButtonTitles:nil, nil];
    [sheet showInView:self.view];
}