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。

One Response to 用UIGestureRecognizer侦测使用者输入操作
  1. i like it 用UIGestureRecognizer侦测使用者输入操作 « Sealyu's Blog it being so that im your rss reader


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