在开发中WebView不会主动去下载文件，但webView提供了下载文件的的接口

webView.setOnDownloadListener(new OnDownloadListener(){    

})；

第一种：实现Java代码下载

其中有一个回调方法返回要下载文件的url，我们可以使用该url在native中实现网络下载

class MyDownloadStart implements DownloadListener{            @Override          public void onDownloadStart(String url, String userAgent,                  String contentDisposition, String mimetype, long contentLength) {              // TODO Auto-generated method stub              //调用自己的下载方式  //          new HttpThread(url).start();                 }                }

第二种：使用系统下载器下载

class MyDownloadStart implements DownloadListener{            @Override          public void onDownloadStart(String url, String userAgent,                  String contentDisposition, String mimetype, long contentLength){          AppUtils.LogD(mimetype);        // download file        DownloadManager downloadManager = ((DownloadManager) activity                .getSystemService(Activity.DOWNLOAD_SERVICE));        Request request = new Request(Uri.parse(url));        // set request header, 如session等 www.2cto.com            request.addRequestHeader("Accept",                    "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");            request.addRequestHeader("Accept-Language", "en-us,en;q=0.5");            request.addRequestHeader("Accept-Encoding", "gzip, deflate");            request.addRequestHeader("Accept-Charset",                    "ISO-8859-1,utf-8;q=0.7,*;q=0.7");            request.addRequestHeader("Cache-Control", "max-age=0");            String host = "";            try {                host = new URL(url).getHost();            } catch (MalformedURLException e) {                e.printStackTrace();            }            String cookieStr = CookieManager.getInstance().getCookie(host);            if (!AppUtils.isEmpty(cookieStr)) {                request.addRequestHeader("Cookie", cookieStr + "; AcSe=0");            }            // generate filename dynamically            String fileName = contentDisposition.replaceFirst(                    "attachment; filename=", "");            request.setDestinationInExternalPublicDir(                    Environment.DIRECTORY_DOWNLOADS, fileName);        downloadManager.enqueue(request);});

第三种：使用默认浏览器下载

将获得到的url转为 uri，然后调用系统的浏览器去下载，这种方式可以看见文件下载进度条

class MyDownloadStart implements DownloadListener{            @Override          public void onDownloadStart(String url, String userAgent,                  String contentDisposition, String mimetype, long contentLength) {              // TODO Auto-generated method stub              //调用系统浏览器下载              Uri uri = Uri.parse(url);                Intent intent = new Intent(Intent.ACTION_VIEW, uri);                startActivity(intent);                }                }