#iOS开发笔记#UIImageView实现拖动，放大/缩小，旋转

UIImageView是iOS上最基本的图片显示控件，但默认情况下是不支持拖动，放大缩小等功能的。后来在stackoverflow上查找到一种很简单的方法，加上本人自己的理解，步骤整理如下：

1.
开启userInteractionEnabled

首先看苹果官方对UIImageView相关内容地介绍：（UIImageView
Class Reference）

New image view objects are configured to disregard user events by default. If you want to handle events in a custom subclass of 

UIImageView

,
you must explicitly change the value of the

userInteractionEnabled

 property
to 

YES

 after
initializing the object.

所以首先第一步要set这个属性

[imageView setUserInteractionEnabled:YES];

2. 在当前controller中添加UIGestureRecognizerDelegate协议

@interface MyViewController : UIViewController <UIGestureRecognizerDelegate>

3.
重写gestureRecognizer方法

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
return YES;
}

4.
定义手势引发的操作方法。UIImageView对象主要应用三种手势操作：UIPinchGestureRecognizer，UIPanGestureRecognizer和UIRotationGestureRecognizer，分别对应（二指）放大缩小，拖动和（二指）旋转的手势操作。三个对应方法如下：

- (void)pinchGestureDetected:(UIPinchGestureRecognizer *)recognizer
{
UIGestureRecognizerState state = [recognizer state];

if (state == UIGestureRecognizerStateBegan || state == UIGestureRecognizerStateChanged)
{
CGFloat scale = [recognizer scale];
[recognizer.view setTransform:CGAffineTransformScale(recognizer.view.transform, scale, scale)];
[recognizer setScale:1.0];
}
}

- (void)panGestureDetected:(UIPanGestureRecognizer *)recognizer
{
UIGestureRecognizerState state = [recognizer state];

if (state == UIGestureRecognizerStateBegan || state == UIGestureRecognizerStateChanged)
{
CGPoint translation = [recognizer translationInView:recognizer.view];
[recognizer.view setTransform:CGAffineTransformTranslate(recognizer.view.transform, translation.x, translation.y)];
[recognizer setTranslation:CGPointZero inView:recognizer.view];
}
}

- (void)rotationGestureDetected:(UIRotationGestureRecognizer *)recognizer
{
UIGestureRecognizerState state = [recognizer state];

if (state == UIGestureRecognizerStateBegan || state == UIGestureRecognizerStateChanged)
{
CGFloat rotation = [recognizer rotation];
[recognizer.view setTransform:CGAffineTransformRotate(recognizer.view.transform, rotation)];
[recognizer setRotation:0];
}
}

5. 新建三种recognizer对象，分别调用上一步的三种方法，并绑定到UIImageView对象中

UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinchGestureDetected:)];
[pinchGestureRecognizer setDelegate:self];
[imageView addGestureRecognizer:pinchGestureRecognizer];

UIRotationGestureRecognizer *rotationGestureRecognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotationGestureDetected:)];
[rotationGestureRecognizer setDelegate:self];
[imageView addGestureRecognizer:rotationGestureRecognizer];

UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panGestureDetected:)];
[panGestureRecognizer setDelegate:self];
[imageView addGestureRecognizer:panGestureRecognizer];

Done. 经过上述五步，imageView已经能实现放大缩小，拖动和旋转的功能，全部参考代码如下：

MyViewController.h

@interface MyViewController : UIViewController <UIGestureRecognizerDelegate>
@property (weak, nonatomic) IBOutlet UIImageView *imageView;
...

@end

MyViewController.m

@implementation MyViewController

- (void)viewDidLoad {
[super viewDidLoad];

[self enableGestureOnView:self.imageView];

}

#pragma mark - View Gesture Process

- (void)enableGestureOnView:(UIView *)view{
[view setUserInteractionEnabled:YES];
// create and configure the pinch gesture
UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRe
4000
cognizer alloc] initWithTarget:self action:@selector(pinchGestureDetected:)];
[pinchGestureRecognizer setDelegate:self];
[view addGestureRecognizer:pinchGestureRecognizer];

// create and configure the rotation gesture
UIRotationGestureRecognizer *rotationGestureRecognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotationGestureDetected:)];
[rotationGestureRecognizer setDelegate:self];
[view addGestureRecognizer:rotationGestureRecognizer];

// creat and configure the pan gesture
UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panGestureDetected:)];
[panGestureRecognizer setDelegate:self];
[view addGestureRecognizer:panGestureRecognizer];

}

- (void)pinchGestureDetected:(UIPinchGestureRecognizer *)recognizer
{
UIGestureRecognizerState state = [recognizer state];

if (state == UIGestureRecognizerStateBegan || state == UIGestureRecognizerStateChanged)
{
CGFloat scale = [recognizer scale];
[recognizer.view setTransform:CGAffineTransformScale(recognizer.view.transform, scale, scale)];
[recognizer setScale:1.0];
}
}

- (void)rotationGestureDetected:(UIRotationGestureRecognizer *)recognizer
{
UIGestureRecognizerState state = [recognizer state];

if (state == UIGestureRecognizerStateBegan || state == UIGestureRecognizerStateChanged)
{
CGFloat rotation = [recognizer rotation];
[recognizer.view setTransform:CGAffineTransformRotate(recognizer.view.transform, rotation)];
[recognizer setRotation:0];
}
}

- (void)panGestureDetected:(UIPanGestureRecognizer *)recognizer
{
UIGestureRecognizerState state = [recognizer state];

if (state == UIGestureRecognizerStateBegan || state == UIGestureRecognizerStateChanged)
{
CGPoint translation = [recognizer translationInView:recognizer.view];
[recognizer.view setTransform:CGAffineTransformTranslate(recognizer.view.transform, translation.x, translation.y)];
[recognizer setTranslation:CGPointZero inView:recognizer.view];
}
}

-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer{
return YES;
}

参考资料：
http://stackoverflow.com/questions/3907397/uigesturerecognizer-on-uiimageview/18622373#18622373 https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIImageView_Class/index.html

另：iOS中如何限制UIImageView放大缩小的比例？