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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）
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 = [[UIPinchGestureRecognizer 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？
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