Question

我设法在UIWebView中加载以下HTML字符串。文本和图像都正确呈现：

<b>Hello <i>World</i>!</b><img src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==\"/>

但是，如果我在UIWebView上调用loadHTMLString后立即尝试从此HTML字符串生成PDF，则Base64编码的图像不会显示在UIWebView中（也不会显示在PDF中）。

这是完整的代码：

@IBOutlet weak var webView: UIWebView!

override func viewDidLoad() {

    super.viewDidLoad()

    let htmlString = "<b>Hello <i>World!</i></b><img src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==\"/>"

    // load HTML string into the UIWebView
    // works correctly if the code after this line is commented
    webView.loadHTMLString(htmlString, baseURL: nil)

    /* Generate PDF and save it to file. */

    let fmt = UIMarkupTextPrintFormatter(markupText: htmlString)
    let render = UIPrintPageRenderer()
    render.addPrintFormatter(fmt, startingAtPageAtIndex: 0)

    let page = CGRect(x: 0, y: 0, width: 595.2, height: 841.8)
    render.setValue(NSValue(CGRect: page), forKey: "paperRect")

    let printable = CGRectInset(page, 0, 0)
    render.setValue(NSValue(CGRect: printable), forKey: "printableRect")

    let pdfData = NSMutableData()
    UIGraphicsBeginPDFContextToData(pdfData, CGRectZero, nil)

    for i in 1...render.numberOfPages() {
        UIGraphicsBeginPDFPage();
        let bounds = UIGraphicsGetPDFContextBounds()
        render.drawPageAtIndex(i - 1, inRect: bounds)
    }

    UIGraphicsEndPDFContext();

    let path = "\(NSTemporaryDirectory())file.pdf"
    pdfData.writeToFile(path, atomically: true)
    print("open \(path)")
}

没有警告或错误消息，所以发生了什么？

Answer 1

我在同样的问题上花费了很多时间。 似乎UIMarkupTextPrintFormatter无法正确解释base64图像，也无法正确解释从本地软件包加载的图像。 我能从HTML中正确呈现PDF的唯一方法是通过UIWebView：一旦UIWebView加载了你的HTML字符串，就必须使用它的UIViewPrinterFormatter作为绘制PDF的函数的printerFormatter。

这是我的UIWebView的一个例子：

override func viewDidLoad() {
    super.viewDidLoad()
    pdfRender = PdfRender()
    webView.loadHTMLString(pdfRender.renderPdfCard(wine: wine), baseURL: NSURL(string: pdfRender.pathTemplatePdf!)! as URL)
}

PdfRender是一个从带有占位符的HTML执行渲染的类（wine是我的模型对象）。方法 renderPdfCard 将完整的HTML作为字符串返回。

这里要实现UIWebViewDelegate：

func webViewDidFinishLoad(_ webView: UIWebView) {

    if !webView.isLoading{
        pdfRender.exportHTMLContentToPDF(wine: wine, printFormatter: webView.viewPrintFormatter())
    }
}

在这里，来自 PdfRender 类的一些方法：

func exportHTMLContentToPDF(wine: Wine, printFormatter: UIViewPrintFormatter) {
    let printPageRenderer = CustomPrintPageRenderer()
    printPageRenderer.addPrintFormatter(printFormatter, startingAtPageAt: 0)
    let pdfData = self.drawPDFUsingPrintPageRenderer(printPageRenderer: printPageRenderer)
    let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
    pdfFilename = "\(documentsPath)/test.pdf"
    pdfData?.write(toFile: pdfFilename, atomically: true)

    print(pdfFilename)
}

func drawPDFUsingPrintPageRenderer(printPageRenderer: UIPrintPageRenderer) -> NSData! {
    let data = NSMutableData()
    UIGraphicsBeginPDFContextToData(data, CGRect.zero, nil)
    UIGraphicsBeginPDFPage()
    printPageRenderer.drawPage(at: 0, in: UIGraphicsGetPDFContextBounds())
    UIGraphicsEndPDFContext()
    return data
}

代码更新为Swift 3。希望这可能有所帮助！

iOS：生成PDF时UIWebView和Base64编码图像的奇怪行为

1 个答案: