导致内存问题的CGPDFPage绘图(Swift 3)

Question

我正在开发一个应用程序,我想在UICollectionView上实现PDF阅读器.

我在每个单元格上使用自定义UIView,呈现相应的PDF页面:

weak var page: CGPDFPage! {

    didSet { setNeedsDisplay() }

}

override func draw(_ rect: CGRect) {

    if page == nil {
        print("page is nil")
        return }

    let context = UIGraphicsGetCurrentContext()

    context?.clear(bounds)

    context?.setFillColor(red: 1, green: 1, blue: 1, alpha: 1)
    context?.fill(bounds)

    context?.translateBy(x: 0.0, y: bounds.size.height);
    context?.scaleBy(x: 1.0, y: -1.0);

    var cropBox = page.getBoxRect(.cropBox)
    cropBox = CGRect(x: cropBox.origin.x, y: cropBox.origin.y, width: ceil(cropBox.width), height: ceil(cropBox.height))

    let scaleFactor = min(bounds.size.width/cropBox.size.width, bounds.size.height/cropBox.size.height)
    let scale = CGAffineTransform(scaleX: scaleFactor, y: scaleFactor)
    let scaledInnerRect = cropBox.applying(scale)
    let translate = CGAffineTransform(translationX: ((bounds.size.width - scaledInnerRect.size.width) / 2) - scaledInnerRect.origin.x, y: ((bounds.size.height - scaledInnerRect.size.height) / 2) - scaledInnerRect.origin.y)
    let concat = translate.scaledBy(x: scaleFactor, y: scaleFactor)

    context?.concatenate(concat)

    let clipRect = cropBox
    context?.addRect(clipRect)
    context?.clip()

    context?.drawPDFPage(page)

    UIGraphicsEndPDFContext()

}

到现在为止还挺好.它在单元格上呈现页面,但它会导致内存问题.

以某种方式,上下文保持对集合视图的单元格上呈现的所有页面的引用,并且它们不会被释放.CGPDFPageRelease不再可用.:(

另一方面,如果这个uiview子类在scrollview中缩放,我怎么能重绘pdf所以我不会失去质量？

任何帮助将受到高度赞赏.谢谢!

Answer 1

我有相同的代码和相同的问题,但一旦我改为这个新的解决方案,它帮助了我.现在,渲染PDF时我的内存没有任何问题.

autoreleasepool非常重要,因为它可以帮助您释放渲染的页面.这是我的代码.

迅速

class PDFPageRenderView: UIView {

    func render(page: CGPDFPage) {
        for subview in subviews { subview.removeFromSuperview() }
        let imageView = UIImageView(frame: bounds)
        imageView.contentMode = .scaleAspectFit
        imageView.clipsToBounds = true
        imageView.backgroundColor = UIColor.white
        autoreleasepool {
            let pageRect = page.getBoxRect(.mediaBox)
            let renderer = UIGraphicsImageRenderer(size: pageRect.size)
            let data =  renderer.jpegData(withCompressionQuality: kImageCompression, actions: { cnv in
                UIColor.white.set()
                cnv.fill(pageRect)
                cnv.cgContext.translateBy(x: 0.0, y: pageRect.size.height)
                cnv.cgContext.scaleBy(x: 1.0, y: -1.0)
                cnv.cgContext.drawPDFPage(page)
            })
            imageView.image = UIImage(data: data)
        }
        addSubview(imageView)
    }
}