[转]iPhone 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; // 不理這個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的話...你是拿不到location的
         // 不判斷的話,底下改frame會讓這個subview消失,因為origin的x和y就不見了!!!
         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。

 

原文链接:http://hi.baidu.com/cyltws/blog/item/e6cca42da685cb20359bf73e.html

by zxzhao