我在swift 3.0中用html内容创建一个pdf文件：
/**
*
*/
func exportHtmlContentToPDF(HTMLContent: String,filePath: String) {
// let webView = UIWebView(frame: CGRect(x: 0,y: 0,width: 694,height: 603));
// webView.loadHTMLString(HTMLContent,baseURL: nil);
let pdfPrinter = PDFPrinter();
let printFormatter = UIMarkupTextPrintFormatter(markupText: HTMLContent);
// let printFormatter = webView.viewPrintFormatter();
pdfPrinter.addPrintFormatter(printFormatter,startingAtPageAt: 0);
let pdfData = self.drawPDFUsingPrintPageRenderer(printPageRenderer: pdfPrinter);
pdfData?.write(toFile: filePath,atomically: true);
}
/**
*
*/
func drawPDFUsingPrintPageRenderer(printPageRenderer: UIPrintPageRenderer) -> NSData! {
let data = NSMutableData();
UIGraphicsBeginPDFContextToData(data,CGRect.zero,nil);
printPageRenderer.prepare(forDrawingPages: NSMakeRange(0,printPageRenderer.numberOfPages));
let bounds = UIGraphicsGetPDFContextBounds();
for i in 0...(printPageRenderer.numberOfPages - 1) {
UIGraphicsBeginPDFPage();
printPageRenderer.drawPage(at: i,in: bounds);
}
UIGraphicsEndPDFContext();
return data;
}
除了我的base64编码图像,一切都很好. Webview或内部safari或chrome浏览器中的HTML内容本身正确显示并正确显示所有图像.但图像永远不会呈现为PDF格式.
为什么图像没有渲染,我怎样才能渲染它们？
解决方法
发生这种情况是因为WebKit首先将HTML解析为DOM,并在多个事件循环周期中呈现内容.因此,您不仅要等待页面DOM准备好,还要等待资源加载完成.正如您所建议的那样,您需要重构代码,以便首先加载webview,然后才导出其内容.
要确定触发导出的正确时间,您可以在Web视图中观察DOM文档的状态.有多种方法可以做到这一点,但我找到的最可读的选项是a port of an answer to a related Objective-C question：在UIWebViewDelegate实现中,按照以下方式实现webViewDidFinishLoad以监控document.readyState：
func webViewDidFinishLoad(_ webView: UIWebView) {
guard let readyState = webView.stringByEvaluatingJavaScript(from: "document.readyState"),readyState == "complete" else
{
// document not yet parsed,or resources not yet loaded.
return
}
// This is the last webViewDidFinishLoad call --> export.
//
// There is a problem with this method if you have JS code loading more content:
// in that case -webViewDidFinishLoad can get called again still after document.readyState has already been in state 'complete' once or more.
self.exportHtmlContentToPDF(…)
}
