2018-08-13 使用UIScrollView 进行图片缩放

1、创建UIScrollView，设置属性：

       scrollView.delegate=self;

        scrollView.contentSize=CGSizeMake(SCREEN_WIDTH,SCREEN_HEIGHT);

        scrollView.showsVerticalScrollIndicator = NO;

        scrollView.showsHorizontalScrollIndicator = NO;

        scrollView.pagingEnabled=NO;

        scrollView.bounces=NO;

        scrollView.minimumZoomScale=0.5;

        scrollView.maximumZoomScale=2;

2、指定要缩放的视图组件

- (UIView*)viewForZoomingInScrollView:(UIScrollView*)scrollView{

           return self.imageView;

}

3、确保图片在视图中间

- (void)scrollViewDidZoom:(UIScrollView*)scrollView {

    UIImageView *imgView =(UIImageView*)[self.imgViewList objectAtIndex:self.whichIndex];

    if(imgView.frame.size.width>=scrollView.size.width&& imgView.size.height>= scrollView.frame.size.height){

        imgView.frame=CGRectMake(0,0, imgView.size.width,imgView.size.height);

    }

    if(imgView.frame.size.width< scrollView.frame.size.width){

        imgView.frame=CGRectMake((scrollView.frame.size.width-imgView.size.width)/2, imgView.origin.y, imgView.size.width, imgView.size.height);

    }

    if(imgView.size.height< scrollView.size.height){

        imgView.frame = CGRectMake(imgView.frame.origin.x, (scrollView.frame.size.height-imgView.frame.size.height)/2, imgView.frame.size.width, imgView.frame.size.height);

    }

}

4、如果同时还有图片浏览功能的话，可以用UIScrollView嵌套UIScrollView，再嵌套UIImageView