[Android Study Notes: Webview interact with Js] pages generated excel / pdf and other files stored webview download

[Function] needs webview page loaded, use the file jsPdf or jsExcel generated, downloaded to the phone to save through webview.

[Realize] thinking

① Can you use webView.setDownloadListener achieve?

  The answer is: NO, downloadListener required file download link, generated by the front end of the link file does not exist.

② acquiring data file generated corresponding files then generated java

  Is not realistic, it is too much trouble, trouble to want to give up.

③ Final Program: base64 encoded by js files and base64 decoding the generated java file!

Ideas: Web pages generated by jsPdf pdf file --js get file base64 code - by interacting with webview js, passed base64 encoding to use java webview-- decoding base64 and writes files to the phone

【Code】

①webview add js call permissions

webView=(WebView)findViewById(R.id.mWebView);
        webView.getSettings().setJavaScriptCanOpenWindowsAutomatically(true);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.setWebChromeClient(webChromeClient);
        // 设置可以支持缩放
        webView.getSettings().setSupportZoom(true);
        // 设置出现缩放工具
        webView.getSettings().setBuiltInZoomControls(true);
        //扩大比例的缩放
        webView.getSettings().setUseWideViewPort(true);
        //自适应屏幕
        webView.getSettings().setLayoutAlgorithm(WebSettings.LayoutAlgorithm.SINGLE_COLUMN);
        webView.getSettings().setLoadWithOverviewMode(true);

② Implementation and interaction code js

 class decodeInterface {
        @RequiresApi(api = Build.VERSION_CODES.O)
        @JavascriptInterface
        public void decoderBase64File(String base64Code) throws IOException {
            Log.e("tag", "decoderBase64File: 被调用"+base64Code );
            String savePath= Config.filePath+"pdfDoc.pdf";
            byte[] xml=base64Code.getBytes("UTF-8");
            byte[] buffer = android.util.Base64.decode(base64Code, Base64.NO_WRAP);
           // byte[] buffer= Base64.getDecoder().decode(base64Code);
            for (int i = 0; i <buffer.length ; i++) {
                if (buffer[i] < 0) {
                    buffer[i] += 256;
				}
            }
            FileOutputStream out = new FileOutputStream(savePath);
            out.write(buffer);
            out.close();
        }
    }


//绑定
webView.addJavascriptInterface(new decodeInterface(),"wv");

③ about how to obtain base64 encoded jsPdf

pdf.addHTML(document.getElementById("saveBox"),options,function() {
				   pdf.save('report.pdf');
				   var datauri = pdf.output('dataurlstring');
				   console.log(datauri);
				   var base64 = datauri.substring(28);
				   wv.decoderBase64File(base64);//调用webview方法

			 });

[Summary] This article only provides an idea using base64 encoded file to transfer files, webview with js interaction code as a bridge.