UITapGestureRecognizer单击和双击事件响应

如果tap事件定义在同一个地方的通用方法是下面：

UITapGestureRecognizer *singleTap = [[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(doSingleTap)] autorelease];
singleTap.numberOfTapsRequired = 1; 
[self.view addGestureRecognizer:singleTap];
UITapGestureRecognizer *doubleTap = [[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(doDoubleTap)] autorelease];
doubleTap.numberOfTapsRequired = 2; 
[self.view addGestureRecognizer:doubleTap];
[singleTap requireGestureRecognizerToFail:doubleTap];

但是如果子类的tap事件定义在别处，上面方法就比较麻烦了。就可以使用代理来解决这个问题.UIGestureRecognizerDelegate。这边假设doubleTap定义在子类，singleTap定义在父类，则由于代理的效果先响应doubleTap

UITapGestureRecognizer *singleTap = [[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(doSingleTap)] autorelease];
singleTap.numberOfTapsRequired = 1; 
singleTap.delegate = self;
[self.view addGestureRecognizer:singleTap];

//该方法返回YES，则就可以实现先响应别的方法
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRequireFailureOfGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return YES;
}

UIViewController如何背景透明

通过设置modalPresentationStyle来实现，iOS8以前和iOS8以后方法不一样

if (IsGreaterIOS8) {
    _browser.modalPresentationStyle = UIModalPresentationOverCurrentContext;
}else{
    _browser.modalPresentationStyle = UIModalPresentationCurrentContext;
}

常用到的常量定义

#define ScreenWidth [UIScreen mainScreen].bounds.size.width
#define ScreenHeight [UIScreen mainScreen].bounds.size.height
#define SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(v)  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedAscending)
#define IsGreaterIOS8 SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"8.0")