前言

公司項(xiàng)目有很多地方要用到圖片上傳功能，還有上傳的歷史記錄，這方面就有需要預(yù)覽這個(gè)需求啦，之前做的都沒(méi)有這個(gè)功能，于是夏夏自己寫(xiě)了個(gè)簡(jiǎn)易的預(yù)覽。。。

照片預(yù)覽demo.gif

由于是模擬器，沒(méi)有辦法把放大，縮小等功能展示出來(lái)。

思路

1.只是簡(jiǎn)單的實(shí)現(xiàn)下預(yù)覽的功能，于是夏夏只是單純的寫(xiě)了個(gè)view用于展示，一般的預(yù)覽都是全屏展示的，而且長(zhǎng)按的時(shí)候要能保存圖片，也就是說(shuō)要present出sheet出來(lái)，于是夏夏就添加到NavigationController的View上了。當(dāng)然，為了美觀，夏夏也是加了個(gè)專場(chǎng)動(dòng)畫(huà)~ show code 思密達(dá)：

UIImageView *imageView = (UIImageView *)tap.view;
UIImage *image = imageView.image;
ReViewPhotoView *review = [[ReViewPhotoView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) Photo:image];

CATransition *transition = [CATransition animation];
transition.type = kCATransitionReveal;
transition.duration = 0.5;
[review.layer addAnimation:transition forKey:nil];
[self.navigationController.view addSubview:review];

2.先給一個(gè)整個(gè)window的背景View，再加個(gè)展現(xiàn)照片的imageView。一般圖片都是劇中顯示，每個(gè)圖片都是帶有size屬性，可以根據(jù)圖片原有的size和屏幕款高比，從而寫(xiě)出展示的imageView的frame。

CGFloat scale = photo.size.width / self.frame.size.width;
CGFloat height = photo.size.height / scale;
    
self.backgroundColor = [UIColor blackColor];
    
UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, (self.frame.size.height - height)/2, self.frame.size.width, height)];
imageView.image = photo;
imageView.userInteractionEnabled = YES;
[self addSubview:imageView];

3.接下來(lái)就是給imageView加手勢(shì)了，加上了各種手勢(shì)才能有各種交互的功能呀~

先加一個(gè)可以放大的功能思密達(dá)~~

UIPinchGestureRecognizer *pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinchChangeScale:)];
[imageView addGestureRecognizer:pinchGesture];

- (void)pinchChangeScale:(UIPinchGestureRecognizer *)pinch {
    UIImageView *imageView = (UIImageView *)pinch.view;
    if (pinch.state == UIGestureRecognizerStateBegan) {
            lastScare = 1.0;
  }
    CGFloat scare = 1 - (lastScare - pinch.scale);
    CGAffineTransform currentTransform = imageView.transform;
    CGAffineTransform newTransform = CGAffineTransformScale(currentTransform, scare, scare);
    [imageView setTransform:newTransform];
    lastScare = pinch.scale;
}

當(dāng)然咯，要是能放大肯定是要能拖動(dòng)查看的說(shuō)~

UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(move:)];
[imageView addGestureRecognizer:panGesture];

- (void)move:(UIPanGestureRecognizer *)pan {
    CGPoint transpoint = [pan translationInView:self];
    UIImageView *imageView = (UIImageView *)pan.view;
    if (pan.state == UIGestureRecognizerStateBegan) {
        firstX = imageView.center.x;
       firstY = imageView.center.y;
    }
    if (lastScare == 1.0f) {
        return;
    }
    transpoint = CGPointMake(firstX+transpoint.x, firstY+transpoint.y);
    [imageView setCenter:transpoint];
}

唔~還要有一個(gè)雙擊可以返回原來(lái)的狀態(tài)手勢(shì)！

UITapGestureRecognizer *doubleTapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapResolve:)];
    doubleTapGesture.numberOfTapsRequired = 2;
[imageView addGestureRecognizer:doubleTapGesture];

- (void)tapResolve:(UITapGestureRecognizer *)tap {
    UIImageView *imageView = (UIImageView *)tap.view;
    [imageView setTransform:transform];
    [imageView setFrame:imgFrame];
    lastScare = 1.0f;
}

但是還需要一個(gè)單擊返回的手勢(shì)，雙擊和單擊會(huì)沖突，這個(gè)時(shí)候可以使用這個(gè)函數(shù)requireGestureRecognizerToFail。

最后如果是網(wǎng)上的圖片預(yù)覽，可能需要長(zhǎng)按本地保存的功能，可以這樣寫(xiě)喲：

- (void)longPress:(UILongPressGestureRecognizer *)longPress {
    UIImageView *imageView = (UIImageView *)longPress.view;
    if (longPress.state == UIGestureRecognizerStateBegan) {
        if (self.longpressblock && imageView.image) {
            self.longpressblock(imageView.image);
        }
    }
}

本地保存圖片的方法是這個(gè)：UIImageWriteToSavedPhotosAlbum,之所以用block是因?yàn)檫@只是個(gè)view，沒(méi)辦法present出UIAlertController。

結(jié)束啦~

這就是一個(gè)簡(jiǎn)單的圖片預(yù)覽，demo的地址在這里：https://github.com/ioscick/-Demo
可以用于互相學(xué)習(xí)討論喲！