iOS 利用平移缩放旋转手势对view实现对应的平移缩放旋转效果（一）

     当你看见这个题目的时候，就应该知道平移缩放旋转手势和view对应的平移缩放旋转是两码事儿。也就是说如果我们想利用手势，对某个view进行某些操作，就必须明白两个问题，一是如何分辨和接收手势操作，二是如何根据接收到的手势对视图进行平移缩放旋转。

    一、先说说如何分辨和接收手势操作

    手机端的手势无非分为三种，就是题目中所提到的平移缩放旋转，ios有专门的类，来对应这三种手势。把这些手势绑定在那个view上，那一旦这个view触发了这个手势，我们该调哪个函数呢？这个问题问的好，在这些手势累初始化的时候，把其对应的view和触发后调用的的方法传进去，请看下边的示例代码：    

    UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc]//缩放手势
                                                       initWithTarget:self
                                                        action:@selector(handlePinch:)];//绑定方法
    [_scrollView addGestureRecognizer:pinchGestureRecognizer];   //绑定view

   
    //平移手势 
    UIPanGestureRecognizer  *moveGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self
                        
                                                               action:@selector(moveGesture:)];  
    moveGesture.delegate = self;
    
    [_scrollView addGestureRecognizer:moveGesture];
    
   

 
    //单指双击手势
    
    UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self
                       
                                                              action:@selector(singleTapGesture:)];
    
    tapGesture.numberOfTapsRequired = 2;
    
        self.tapGesture.delegate = self;
        [_scrollView addGestureRecognizer:tapGesture];

细心的同学，可能发现了这句话

 moveGesture.delegate = self;

手势的代理，如果我们把代理指向了自己，应该实现什么方法呢？具体先看看这个代理具体是什么样的吧？

@protocol UIGestureRecognizerDelegate <NSObject>
@optional
// called when a gesture recognizer attempts to transition out of UIGestureRecognizerStatePossible. returning NO causes it to transition to UIGestureRecognizerStateFailed
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer;

// called when the recognition of one of gestureRecognizer or otherGestureRecognizer would be blocked by the other
// return YES to allow both to recognize simultaneously. the default implementation returns NO (by default no two gestures can be recognized simultaneously)
//
// note: returning YES is guaranteed to allow simultaneous recognition. returning NO is not guaranteed to prevent simultaneous recognition, as the other gesture's delegate may return YES
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer;

// called once per attempt to recognize, so failure requirements can be determined lazily and may be set up between recognizers across view hierarchies
// return YES to set up a dynamic failure requirement between gestureRecognizer and otherGestureRecognizer
//
// note: returning YES is guaranteed to set up the failure requirement. returning NO does not guarantee that there will not be a failure requirement as the other gesture's counterpart delegate or subclass methods may return YES
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRequireFailureOfGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer NS_AVAILABLE_IOS(7_0);

// called before touchesBegan:withEvent: is called on the gesture recognizer for a new touch. return NO to prevent the gesture recognizer from seeing this touch
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch;

@end

上边是从UIKit中拷取的源码，很明显，手势不同的的状态会调用不同的方法，这个我们可以根据需要自己实现，反正是optional可选的。

那我能在某个视图上添加上手势了，然后也知道手势触发的方法了，之后要做的，就是从手势中提取相关的信息，然后对视图进行变换了，这个将在下篇文章中详述。