iOS手势篇(三)-UIGestureRecognizer代理详解

3.代理

@protocol UIGestureRecognizerDelegate 
@optional
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer;
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer;
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRequireFailureOfGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch;
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceivePress:(UIPress *)press;
@end

1. - (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer;
   手势识别器是否能够开始识别手势.
   当手势识别器识别到手势,准备从UIGestureRecognizerStatePossible状态开始转换时.调用此代理,如果返回YES,那么就继续识别,如果返回NO,那么手势识别器将会将状态置为UIGestureRecognizerStateFailed.

2. - (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer;
   gestureRecognizer : 此对象发送的代理消息.
   返回YES允许gestureRecognizer与otherGestureRecognizer同时识别.
   如果返回NO,分两种情况.1.两个手势都返回NO,那么不会同时识别.如果一个NO,一个YES.可能会同时识别.

3. - (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRequireFailureOfGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);
   一般用来重写该方法.来定义什么时候手势识别失败.如果直接返回YES,那么gestureRecognizer与otherGestureRecognizer互斥的话gestureRecognizer识别失败. 可以用tap手势和longPress手势试试.

4. - (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);
   和3差不多,注意这个Be,所以是相反的,如果互斥,otherGestureRecognizer识别失败.

5. - (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch;
   返回手势识别器是否允许检查手势对象.
   UIKit将会在touchesBegan:withEvent:方法之前调用这个代理.

6. - (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceivePress:(UIPress *)press;
   返回手势识别器是否允许检查按压(UIPress对象).
   UIKit将会在touchesBegan:withEvent:方法之前调用这个代理.