UIGestureRecognizer的使用
用UIGestureRecognizer侦测使用者输入操作
????在3.2以前,我们要拿到UITouch跟使用者互动,大部分都是透过UIResponder的四种methods
?- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
?- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
?- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
?- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
????有些人会把UITouch重新wrap丢到自己的queue里面去处理，不然就是直接在这几个function里直接判断。其实都不会差太多。简单的说，就是麻烦
????3.2以后，透过UIGestureRecognizer及其它继承它的UIxxxGestureRecognizer，侦测使用者输入就变的简单许多。
?UILongPressGestureRecognizer
?UIPanGestureRecognizer
?UIPinchGestureRecognizer
?UIRotationGestureRecognizer
?UISwipeGestureRecognizer
?UITapGestureRecognizer
????照名字看大概就知道这是做什么用的，所以就不解释了，直接看用法：
????以UIPanGestureRecognizer为例，这是处理使用者用一只手指(或多只)在屏幕上滑来滑去的动作。要侦测这个动作，只要加下面这段code进viewDidLoad或任何你需要的地方
UIPanGestureRecognizer *panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePanFrom:)];
[self.view addGestureRecognizer:panRecognizer];
panRecognizer.maximumNumberOfTouches = 1;
panRecognizer.delegate = self;
[panRecognizer release];
????第一个很简单，就是确定要给这个recognizer handle的event，就会去call这个class底下的handlePanFrom: 然后把recognizer加进UIView(addGestureRecognizer)。因为同时间我只想知道一只手指的动作，所以我用maximumNumberOfTouches=1来限制。
????当然，你可以改变maximumNumberOfTouches跟minimumNumberOfTouches的值来当成filter，接着把 delegate设定成自己(记得header要加上UIGestureRecognizerDelegate)。
????不过这样还没有结束，我们要补上这个delegate method
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch {
????里面可以先filter event,决定要不要丢给一开始assign给panRecognizer的selector function，
譬如我只想要看某个subview的事件
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch{
????UIView *aview = [self.view viewWithTag:1000];
????if (touch.view != aview) {
??????return NO; // 不理event
????}
????return YES;
?}
????接下来就是
- (void)handlePanFrom:(UIPanGestureRecognizer *)recognizer {????????
?????????//拿到手指目前的位置
?????????CGPoint location = [recognizer locationInView:self.view];
?????????UIView *aview = [self.view viewWithTag:1000];
?????????// 如果UIGestureRecognizerStateEnded的...你是拿不到location的
?????????// 不判的,底下改framesubview消失,因origin的x和y就不了!!!
?????????if(recognizer.state != UIGestureRecognizerStateEnded)
?????????{
?????????????????aview.frame = CGRectMake(location.x, location.y, aview.frame.size.width, aview.frame.size.height);
?????????}
?}
????不同的UIGestureRecognizer subclass都会有不同特点。譬如说Pinch的scale、velocity和Swipe的direction，直接简化了处理UITouch的步骤。大家只要知道这些特点，处理使用者输入就会得心应手了。遇到问题记得先看看有没有判断UIGestureRecognizer的state。