README.md

SFScaleImageView

Example

To run the example project, clone the repo, and run pod install from the Example directory first.

Requirements

Installation

SFScaleImageView is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod 'SFScaleImageView'

总体效果：

步骤如下：

一、初始化各view，添加事件

- (void)viewDidLoad {
    [super viewDidLoad];
    
    /*首先，本文要实现的效果类似于微信个人中心中查看自己的头像，具体功能点如下：
     1.进入界面原始状态为image居中显示
     2.当scale==1时，双击放大图片到：高度等于屏幕高度，同时等比缩放宽度，放大后，竖直方向不可滚动，水平可以
     3.当scale>1时，双击复原
     4.捏合手势缩放后，zoomScale在min与max之间，这时保持imageView竖直居中
     */
    UIScrollView *scrollView = [[UIScrollView alloc] init];
    _scrollV = scrollView;
    
    scrollView.backgroundColor = UIColor.blackColor;
    scrollView.delegate = self;
    [self.view addSubview:scrollView];
    
    UITapGestureRecognizer *tapGes = [[UITapGestureRecognizer alloc] initWithTarget:self
                                                                             action:@selector(doubleTapScrollV:)];
    tapGes.numberOfTapsRequired = 2;
    [scrollView addGestureRecognizer:tapGes];
    
    //这里有个小tips，[[UIImageView alloc] initWithImage:]这个方法，
    //初始化出来的imageView.frame是等于(0, 0, image.size.width, image.size.height)的
    //之前一直以为是CGRectZero...
    _imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"soccer"]];
    [scrollView addSubview:self.imageView];
    
    //想要做到放大后刚好竖直方向撑满屏幕，那么maxScale就等于SCREEN_HEIGHT/SCREEN_WIDTH
    CGFloat maxScale = SCREEN_HEIGHT/SCREEN_WIDTH;
    scrollView.maximumZoomScale = maxScale;
    scrollView.minimumZoomScale = 1;
    //scrollView是全屏大小
    scrollView.frame = UIScreen.mainScreen.bounds;
    
    //imageView居中,与scrollView等宽
    _imageView.frame = CGRectMake(0, 0, scrollView.frame.size.width, scrollView.frame.size.width);
    _imageView.center = _scrollV.center;
}

二、返回需要缩放的子视图

//返回需要缩放的子视图
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView{
    return self.imageView;
}

三、scrollView进行了缩放

//scrollView进行了缩放
//通过方法zoomToRect来缩放时，这个方法只会调用一次，调用时间点在scrollViewWillBeginZooming之后，scrollViewDidEndZooming之前
//使用双指捏合手势缩放中，这个方法会一直调用,缩放中,scrollView的contentSize会变化,即放大缩小
//如果内容宽(高)小于scrollView宽(高),内容以scrollView宽(高)为准居中
//如果内容宽(高)大于scrollView宽(高),内容从x=0(y=0)开始
//如此便达到了,内容任一方向小于父容器时,居中该方向,
//大于父容器时,内容占满该方向
- (void)scrollViewDidZoom:(UIScrollView *)scrollView{
    UIView *targetView = [self viewForZoomingInScrollView:scrollView];
    BOOL widthIsSmall = targetView.width < scrollView.width;
    BOOL heightIsSmall = targetView.height < scrollView.height;
    
    if (widthIsSmall) {
        targetView.centerX = scrollView.centerX;
    } else {
        targetView.left = 0;
    }
    
    if (heightIsSmall) {
        targetView.centerY = scrollView.centerY;
    } else {
        targetView.top = 0;
    }
}

四、处理点击事件

- (void)doubleTapScrollV:(UITapGestureRecognizer*)tapGes{
    CGFloat currScale = self.scrollV.zoomScale;
    CGFloat minScale = self.scrollV.minimumZoomScale;
    CGFloat maxScale = self.scrollV.maximumZoomScale;
    CGFloat goalScale;
    
    if (currScale == minScale) {
        goalScale = maxScale;
    } else {
        goalScale = minScale;
    }
    
    if (currScale == goalScale) {
        return;
    }
    
    CGPoint touchPoint = [tapGes locationInView:[self viewForZoomingInScrollView:self.scrollV]];
    //缩放后的目标frame大小,当然是通过容器(scrollView)的size/scale来计算的,如下:
    CGFloat xsize = self.scrollV.frame.size.width/goalScale;
    CGFloat ysize = self.scrollV.frame.size.height/goalScale;
    //origin当然是点击点减去一半的宽高,
    //x,y可能小于0,但是没问题,因为内容不能从负值开始,如下
    CGFloat x = touchPoint.x-xsize/2;
    CGFloat y = touchPoint.y-ysize/2;
    
    [self.scrollV zoomToRect:CGRectMake(x, y, xsize, ysize) animated:YES];
}

Author

liuxuleidota, liu_xu_lei@163.com

License

SFScaleImageView is available under the MIT license. See the LICENSE file for more info.