看了一些app的返回效果，自己忍不住抽時(shí)間研究了一下，demo：FullScreenReturn

動(dòng)畫效果：·········································································································

demo.gif

核心代碼

• 在NavViewController中重寫下面兩個(gè)方法，我們就可以自定義想要的返回效果

- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated {
    UIImage *image = [self currentScreenCaptureImage];
    if (image) {
        [self.screenCaptureList addObject:image];
    }
    [super pushViewController:viewController animated:animated];
    
    [self resetPanGestureEnableStatus];
}

- (UIViewController *)popViewControllerAnimated:(BOOL)animated {
    [self.screenCaptureList removeLastObject];
    UIViewController *VC = [super popViewControllerAnimated:animated];
    if ([VC isKindOfClass:[self.topViewController class]]) {
        [self.screenCaptureList removeAllObjects];
    }
    [self resetPanGestureEnableStatus];
    return VC;
}

• 創(chuàng)建并獲取當(dāng)前屏幕的視圖，也就是截屏

- (UIImage *)currentScreenCaptureImage {
    UIView *view = self.view.superview;
    if (self.tabBarController) {
        view = self.tabBarController.view;
    }
    if (!view || CGRectIsEmpty(view.frame)) {
        return nil;
    }
    
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, NO, [UIScreen mainScreen].scale);

    [view.subviews enumerateObjectsUsingBlock:^(__kindof UIView * _Nonnull subView, NSUInteger idx, BOOL * _Nonnull stop) {
        [subView drawViewHierarchyInRect:subView.frame afterScreenUpdates:NO];
    }];
    UIImage *screenCaptureImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return screenCaptureImage;
}

UIGraphicsBeginImageContextWithOptions(CGSize size, BOOL opaque, CGFloat scale);

創(chuàng)建一個(gè)基于位圖的上下文（context）,并將其設(shè)置為當(dāng)前上下文(context)。
size: 新創(chuàng)建的位圖上下文的大小。也是UIGraphicsGetImageFromCurrentImageContext()返回的image大小。
opaque: 透明開關(guān),一般設(shè)置為YES,如果圖形不用透明，設(shè)置為YES以優(yōu)化位圖的存儲(chǔ)，渲染效率更高。
scale 縮放比例, 一般設(shè)置為0，系統(tǒng)會(huì)自動(dòng)設(shè)置正確的比例。iPhone 4是2.0，其他是1.0。

• 添加拖動(dòng)手勢

- (void)addPanGestureRecognizer {
    self.panGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panGestureRecognizerAction:)];
    self.panGestureRecognizer.delegate = self;
    [self.view addGestureRecognizer:self.panGestureRecognizer];
}

• 自定義返回效果(行間有注釋)

- (void)panGestureRecognizerAction:(UIPanGestureRecognizer *)panGestureRecognizer {
    //觸點(diǎn)位置
    CGPoint touchPoint = [panGestureRecognizer locationInView:[[UIApplication sharedApplication] keyWindow]];
    
    switch (panGestureRecognizer.state) {
        case UIGestureRecognizerStateBegan: {
            //觸點(diǎn)開始位置
            self.startTouchPoint = touchPoint;
            
            //將上一個(gè)屏幕的截圖放在當(dāng)前view的下面
            self.screenCaptureImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, self.view.width, self.view.height)];
            UIImage *lastScreenCaptureImage = [self.screenCaptureList lastObject];
            [self.screenCaptureImageView setImage:lastScreenCaptureImage];
            
            self.blackMaskView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.view.width, self.view.height)];
            [self.backgroundView insertSubview:self.screenCaptureImageView belowSubview:self.blackMaskView];
            
            self.backgroundView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.view.width, self.view.height)];
            [self.view.superview insertSubview:self.backgroundView belowSubview:self.view];
            [self.backgroundView addSubview:self.blackMaskView];
        }
            break;
        case UIGestureRecognizerStateChanged: {
            //根據(jù)拖動(dòng)的距離實(shí)現(xiàn)動(dòng)畫效果
            CGFloat displacement = touchPoint.x - self.startTouchPoint.x;
            [self moveViewWithDisplacement:displacement > 0 ? displacement : 0];
        }
            break;
        case UIGestureRecognizerStateEnded: {
            //根據(jù)設(shè)定的距離判斷是否返回，并作出相應(yīng)處理
            CGFloat displacement = touchPoint.x - self.startTouchPoint.x;
            if (displacement > moveWidth) {
                [UIView animateWithDuration:animateDuration animations:^{
                    [self moveViewWithDisplacement:[UIScreen mainScreen].bounds.size.width];
                } completion:^(BOOL finished) {
                    [self popViewControllerAnimated:NO];
                    self.view.leftX = 0;
                    self.backgroundView.hidden = YES;
                }];
            } else {
                [UIView animateWithDuration:animateDuration animations:^{
                    [self moveViewWithDisplacement:0];
                } completion:^(BOOL finished) {
                    self.backgroundView.hidden = YES;
                }];
            }
        }
            break;
        //其他異常情況處理
        case UIGestureRecognizerStateCancelled:
        case UIGestureRecognizerStateFailed:
        case UIGestureRecognizerStatePossible:
        {
            [UIView animateWithDuration:animateDuration animations:^{
                 [self moveViewWithDisplacement:0];
             } completion:^(BOOL finished) {
                 self.backgroundView.hidden = YES;
             }];
        }
            break;
        default:
            break;
    }
}

• 根據(jù)拖動(dòng)的距離實(shí)現(xiàn)動(dòng)畫效果

- (void)moveViewWithDisplacement:(CGFloat)displacement {
    CGFloat width = self.view.width;
    displacement = displacement <= width ? displacement : 0;
    displacement = displacement > 0 ? displacement : 0;
    self.view.leftX = displacement;
    
    CGFloat scale = displacement / (width * 20) + 0.95f;
    CGFloat alpha = 0.4f - displacement / 800;
    
    self.screenCaptureImageView.transform = CGAffineTransformMakeScale(scale, scale);
    self.blackMaskView.alpha = alpha;
}

其他細(xì)節(jié)問題，可能要根據(jù)不同App的業(yè)務(wù)邏輯自行實(shí)現(xiàn)。其實(shí)很簡單。