2.27 Displaying Popovers with UIPopoverController

弹出一个视图，而不是占用整个Screen, 只能用在iPad上
在iPad上的safari，当用户点击书签，就会弹出Popover

默认情况下，当弹出popover后，用户点击其他地方，popover就会消失掉。

在书上用了好多的篇幅详细讲解了popover的用法

我这里只想用我自己的一小段代码概括总结一下

//声明中加上
@property (nonatomic, strong)UIPopoverController * myPopoverController;

//下面是实现部分
#pragma mark 测试popover
-(void)performBtnClick:(id)sender
{
    if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad) {
        UIViewController * viewController = [[UIViewController alloc] init];
        viewController.contentSizeForViewInPopover = CGSizeMake(200, 125);
        UIImage * img = [UIImage imageNamed:@"QQ20131107-2.png"];
        UIImageView * imgView = [[UIImageView alloc] initWithImage:img];
        [viewController.view addSubview:imgView];
       
        _myPopoverController = [[UIPopoverController alloc] initWithContentViewController:viewController];
        [_myPopoverController presentPopoverFromRect:[sender frame] inView:self.view permittedArrowDirections:UIPopoverArrowDirectionUp animated:YES];
       
    }else{
        UIAlertView * alertView = [[UIAlertView alloc] initWithTitle:@"hahahah.." message:@"message" delegate:nil cancelButtonTitle:@"cancel" otherButtonTitles: nil];
        [alertView show];
    }
}

-(void)addPopButton
{
    UIButton * btn = [UIButton buttonWithType:UIButtonTypeContactAdd];
    CGRect mRect = CGRectMake(20, 20, 20, 20);
    [btn setFrame:mRect];
    [btn addTarget:self action:@selector(performBtnClick:) forControlEvents:UIControlEventTouchUpInside];
   
    [self.view addSubview:btn];
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self addPopButton];
}