WebView控制调用相应的WEB页面进行展示。当碰到页面有下载链接的时候，点击上去是一点反应都没有的。原来是因为WebView默认没有开启文件下载的功能，如果要实现文件下载的功能，需要设置WebView的DownloadListener，通过实现自己的DownloadListener来实现文件的下载。具体操作如下：

1、设置WebView的DownloadListener：
    webView.setDownloadListener(new MyWebViewDownLoadListener());

2、实现MyWebViewDownLoadListener这个类，具体可以如下这样：

private class MyWebViewDownLoadListener implements DownloadListener{@Overridepublic void onDownloadStart(String url, String userAgent, String contentDisposition, String mimetype,long contentLength) {           Log.i("tag", "url="+url);           Log.i("tag", "userAgent="+userAgent);Log.i("tag", "contentDisposition="+contentDisposition);         Log.i("tag", "mimetype="+mimetype);Log.i("tag", "contentLength="+contentLength);Uri uri = Uri.parse(url);Intent intent = new Intent(Intent.ACTION_VIEW, uri);startActivity(intent);           }}

这只是调用系统中已经内置的浏览器进行下载，还没有WebView本身进行的文件下载，不过，这也基本上满足我们的应用场景了。

我在项目中的运用
项目要求这样：
1，需要使用WebView加载一个网页；
2，网页中有文件下载的链接，点击后需要下载文件到SDcard；
3，然后自动打开文件；
下面是具体解决办法
第一步，对WebView进行一系列设置。

WebView webview=(WebView)layout.findViewById(R.id.webview);webview.getSettings().setJavaScriptEnabled(true);webview.setWebChromeClient(new MyWebChromeClient());webview.requestFocus();
//              webview.loadUrl("file:///android_asset/risktest.html");webview.loadUrl(jcrs_sub.get(position).addr);// 设置web视图客户端webview.setWebViewClient(new MyWebViewClient());webview.setDownloadListener(new MyWebViewDownLoadListener());//内部类
public class MyWebViewClient extends WebViewClient {// 如果页面中链接，如果希望点击链接继续在当前browser中响应，// 而不是新开Android的系统browser中响应该链接，必须覆盖 webview的WebViewClient对象。public boolean shouldOverviewUrlLoading(WebView view, String url) {L.i("shouldOverviewUrlLoading");view.loadUrl(url);return true;}public void onPageStarted(WebView view, String url, Bitmap favicon) {L.i("onPageStarted");showProgress();}public void onPageFinished(WebView view, String url) {L.i("onPageFinished");closeProgress();}public void onReceivedError(WebView view, int errorCode,String description, String failingUrl) {L.i("onReceivedError");closeProgress();}}// 如果不做任何处理，浏览网页，点击系统“Back”键，整个Browser会调用finish()而结束自身，// 如果希望浏览的网 页回退而不是推出浏览器，需要在当前Activity中处理并消费掉该Back事件。public boolean onKeyDown(int keyCode, KeyEvent event) {// if((keyCode==KeyEvent.KEYCODE_BACK)&&webview.canGoBack()){// webview.goBack();// return true;// }return false;}

第二步，起线程开始下载文件。

//内部类
private class MyWebViewDownLoadListener implements DownloadListener {@Overridepublic void onDownloadStart(String url, String userAgent, String contentDisposition, String mimetype,long contentLength) {if(!Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){Toast t=Toast.makeText(mContext, "需要SD卡。", Toast.LENGTH_LONG);t.setGravity(Gravity.CENTER, 0, 0);t.show();return;}DownloaderTask task=new DownloaderTask();task.execute(url);}}//内部类private class DownloaderTask extends AsyncTask<String, Void, String> { public DownloaderTask() { }@Overrideprotected String doInBackground(String... params) {// TODO Auto-generated method stubString url=params[0];
//          Log.i("tag", "url="+url);String fileName=url.substring(url.lastIndexOf("/")+1);fileName=URLDecoder.decode(fileName);Log.i("tag", "fileName="+fileName);File directory=Environment.getExternalStorageDirectory();File file=new File(directory,fileName);if(file.exists()){Log.i("tag", "The file has already exists.");return fileName;}try {  HttpClient client = new DefaultHttpClient();
//                client.getParams().setIntParameter("http.socket.timeout",3000);//设置超时HttpGet get = new HttpGet(url);  HttpResponse response = client.execute(get);if(HttpStatus.SC_OK==response.getStatusLine().getStatusCode()){HttpEntity entity = response.getEntity();InputStream input = entity.getContent();writeToSDCard(fileName,input);input.close();
//                  entity.consumeContent();return fileName;  }else{return null;}} catch (Exception e) {  e.printStackTrace();return null;}}@Overrideprotected void onCancelled() {// TODO Auto-generated method stubsuper.onCancelled();}@Overrideprotected void onPostExecute(String result) {// TODO Auto-generated method stubsuper.onPostExecute(result);closeProgressDialog();if(result==null){Toast t=Toast.makeText(mContext, "连接错误！请稍后再试！", Toast.LENGTH_LONG);t.setGravity(Gravity.CENTER, 0, 0);t.show();return;}Toast t=Toast.makeText(mContext, "已保存到SD卡。", Toast.LENGTH_LONG);t.setGravity(Gravity.CENTER, 0, 0);t.show();File directory=Environment.getExternalStorageDirectory();File file=new File(directory,result);Log.i("tag", "Path="+file.getAbsolutePath());Intent intent = getFileIntent(file);startActivity(intent);}@Overrideprotected void onPreExecute() {// TODO Auto-generated method stubsuper.onPreExecute();showProgressDialog();}@Overrideprotected void onProgressUpdate(Void... values) {// TODO Auto-generated method stubsuper.onProgressUpdate(values);} }

第三步，实现一些工具方法。