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我使用 Quartz Core 和 CGPDF 在我的应用程序中显示可缩放的 PDF 已经有一段时间了，但是自从 Xcode 8 并试图使我的应用程序与 iOS 9 和 10 兼容后，PDF 代码似乎已经损坏。这是我一直在使用的代码：

- (void)loadPDF
{
    [self.scrollView removeFromSuperview];
    [self.aContentView removeFromSuperview];
    [self.tiledLayer removeFromSuperlayer];

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *cachePath = [paths objectAtIndex:0];
    NSURL *fileURL = [NSURL fileURLWithPath:[cachePath stringByAppendingPathComponent:@"Exmaple.pdf"]];

    self.aDocumentRef = CGPDFDocumentCreateWithURL((CFURLRef)CFBridgingRetain(fileURL));
    self.aPageRef = CGPDFDocumentGetPage(self.aDocumentRef, 1);

    CGRect rect = CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height);

    self.tiledLayer = [CATiledLayer layer];
    self.tiledLayer.delegate = nil;
    self.tiledLayer.tileSize = rect.size;
    self.tiledLayer.levelsOfDetail = 100;
    self.tiledLayer.levelsOfDetailBias = 100;
    self.tiledLayer.frame = rect;

    self.aContentView = [[UIView alloc] initWithFrame:rect];
    [self.aContentView.layer addSublayer:self.tiledLayer];

    self.scrollView = [[UIScrollView alloc] initWithFrame:rect];
    self.scrollView.delegate = self;
    self.scrollView.contentSize = rect.size;
    self.scrollView.maximumZoomScale = ZOOM_MAXIMUM;
    [self.scrollView addSubview:self.aContentView];

    [self.view addSubview:self.scrollView];

    [self.aContentView setTag:ZOOM_VIEW_TAG];

    UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleDoubleTap:)];
    UITapGestureRecognizer *twoFingerTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTwoFingerTap:)];

    [doubleTap setNumberOfTapsRequired:2];
    [twoFingerTap setNumberOfTouchesRequired:2];

    [self.aContentView addGestureRecognizer:doubleTap];
    [self.aContentView addGestureRecognizer:twoFingerTap];

    float minimumScale = [self.scrollView frame].size.width  / [self.aContentView frame].size.width;

    [self.scrollView setMinimumZoomScale:minimumScale];
    [self.scrollView setZoomScale:minimumScale];

    self.aContentView.translatesAutoresizingMaskIntoConstraints = YES;
    self.scrollView.translatesAutoresizingMaskIntoConstraints = YES;
}

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollViewLocal
{
    return [self.scrollView viewWithTag:ZOOM_VIEW_TAG];
}

- (void)handleDoubleTap:(UIGestureRecognizer *)gestureRecognizer
{
    float newScale = [self.scrollView zoomScale] * ZOOM_STEP;
    CGRect zoomRect = [self zoomRectForScale:newScale withCenter:[gestureRecognizer locationInView:gestureRecognizer.view]];
    [self.scrollView zoomToRect:zoomRect animated:YES];
}

- (void)handleTwoFingerTap:(UIGestureRecognizer *)gestureRecognizer
{
    float newScale = [self.scrollView zoomScale] / ZOOM_STEP;
    CGRect zoomRect = [self zoomRectForScale:newScale withCenter:[gestureRecognizer locationInView:gestureRecognizer.view]];
    [self.scrollView zoomToRect:zoomRect animated:YES];
}

- (CGRect)zoomRectForScale:(float)scale withCenter:(CGPoint)center
{
    CGRect zoomRect;
    zoomRect.size.height = [self.scrollView frame].size.height / scale;
    zoomRect.size.width  = [self.scrollView frame].size.width  / scale;
    zoomRect.origin.x    = center.x - (zoomRect.size.width  / 2.0);
    zoomRect.origin.y    = center.y - (zoomRect.size.height / 2.0);

    return zoomRect;
}

- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx
{
    CGContextSetRGBFillColor(ctx, 1.0, 1.0, 1.0, 1.0);
    CGContextFillRect(ctx, CGContextGetClipBoundingBox(ctx));
    CGContextTranslateCTM(ctx, 0.0, layer.bounds.size.height);
    CGContextScaleCTM(ctx, 1.0, -1.0);
    CGContextConcatCTM(ctx, CGPDFPageGetDrawingTransform(self.aPageRef, kCGPDFCropBox, layer.bounds, 0, true));
    CGContextDrawPDFPage(ctx, self.aPageRef);
}

滚动视图显示，但页面是空白的。PDF 是从正确的目录加载的。谁能给我一个提示我错过了什么？谢谢！

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