iOS开发——手势识别器（用手势实现图片旋转和缩小放大）

iOS开发中，除了有关触摸的这组方法来控制用户的手指触控外，还可以用UIGestureRecognize的衍生类来进行判断，方便了开发。
UIGestureRecognize的子类类别有以下几种：

• UITapGestureRecognizer //轻拍识别器
• UIPinchGestureRecognizer //捏合识别器
• UIRotationGestureRecognizer //旋转识别器
• UISwipeGestureRecognizer //扫动识别器
• UIPanGestureRecognizer //拖动识别器
• UILongPressGestureRecognizer //长按识别器

下面的例子我是用UIPinchGestureRecognizer和UIRotationGestureRecognizer通过手势实现图片旋转和缩小放大。

ViewController.m中的代码如下；

#import "ViewController.h"

@interface ViewController ()

@property(nonatomic,strong) UIImageView *imageView;
@property(nonatomic) CGFloat lastRotation;

-(void)changeImageSize:(UIPinchGestureRecognizer *)recognizer;
-(void)rotateImage:(UIRotationGestureRecognizer *)rotateRecognizer;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.view.backgroundColor = [UIColor whiteColor];

    //在view上添加一个ImageView
    UIImageView *image = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"Totoro"]];
    image.frame = CGRectMake(0, 0, 128, 128);
    self.imageView = image;
    self.imageView.center = CGPointMake(self.view.frame.size.width/2, self.view.frame.size.height/2);
    [self.view addSubview:self.imageView];

    //添加捏合手势识别器，changeImageSize:方法实现图片的放大与缩小
    UIPinchGestureRecognizer *pinchRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(changeImageSize:)];
    [self.view addGestureRecognizer:pinchRecognizer];

    //添加旋转手势识别器，rotateImage:方法实现图片的旋转
    UIRotationGestureRecognizer *rotateRecognizer = [[UIRotationGestureRecognizer alloc]initWithTarget:self action:@selector(rotateImage:)];
    [self.view addGestureRecognizer:rotateRecognizer];

}

-(void)changeImageSize:(UIPinchGestureRecognizer *)recognizer
{
    CGRect frame = self.imageView.frame;

    //监听两手指滑动的距离，改变imageView的frame
    frame.size.width = recognizer.scale*128;
    frame.size.height = recognizer.scale*128;
    self.imageView.frame = frame;

    //保证imageView中心不动
    self.imageView.center =CGPointMake(self.view.frame.size.width/2, self.view.frame.size.height/2);
}

-(void)rotateImage:(UIRotationGestureRecognizer *)rotateRecognizer
{
    //改变imageView的角度，使图片旋转
    if ([rotateRecognizer state]==UIGestureRecognizerStateEnded) {
        self.lastRotation = 0.0;
        return;
    }
    CGAffineTransform currentTransform = self.imageView.transform;
    CGFloat rotation = 0.0 - (self.lastRotation - rotateRecognizer.rotation);
    CGAffineTransform newTransform = CGAffineTransformRotate(currentTransform,rotation);
    self.imageView.transform = newTransform;
    self.lastRotation = rotateRecognizer.rotation;
}


@end

运行代码，实现效果如下：