Android WebView实现文件下载和查看

本文系转载，原文地址：http://gundumw100.iteye.com/blog/1338645

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{        @Override        public 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 {        @Override        public 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() {         }        @Override        protected String doInBackground(String... params) {            // TODO Auto-generated method stub            String 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;            }        }        @Override        protected void onCancelled() {            // TODO Auto-generated method stub            super.onCancelled();        }        @Override        protected void onPostExecute(String result) {            // TODO Auto-generated method stub            super.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);        }        @Override        protected void onPreExecute() {            // TODO Auto-generated method stub            super.onPreExecute();            showProgressDialog();        }        @Override        protected void onProgressUpdate(Void... values) {            // TODO Auto-generated method stub            super.onProgressUpdate(values);        }     } 

第三步，实现一些工具方法。

private ProgressDialog mDialog;    private void showProgressDialog(){        if(mDialog==null){            mDialog = new ProgressDialog(mContext);              mDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);//设置风格为圆形进度条              mDialog.setMessage("正在加载 ，请等待...");              mDialog.setIndeterminate(false);//设置进度条是否为不明确              mDialog.setCancelable(true);//设置进度条是否可以按退回键取消              mDialog.setCanceledOnTouchOutside(false);            mDialog.setOnDismissListener(new OnDismissListener() {                @Override                public void onDismiss(DialogInterface dialog) {                    // TODO Auto-generated method stub                    mDialog=null;                }            });            mDialog.show();        }    }    private void closeProgressDialog(){        if(mDialog!=null){            mDialog.dismiss();            mDialog=null;        }    }     public Intent getFileIntent(File file){//       Uri uri = Uri.parse("http://m.ql18.com.cn/hpf10/1.pdf");        Uri uri = Uri.fromFile(file);        String type = getMIMEType(file);        Log.i("tag", "type="+type);        Intent intent = new Intent("android.intent.action.VIEW");        intent.addCategory("android.intent.category.DEFAULT");        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);        intent.setDataAndType(uri, type);        return intent;      }    public void writeToSDCard(String fileName,InputStream input){        if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){            File directory=Environment.getExternalStorageDirectory();            File file=new File(directory,fileName);//          if(file.exists()){//              Log.i("tag", "The file has already exists.");//              return;//          }            try {                FileOutputStream fos = new FileOutputStream(file);                byte[] b = new byte[2048];                int j = 0;                while ((j = input.read(b)) != -1) {                    fos.write(b, 0, j);                }                fos.flush();                fos.close();            } catch (FileNotFoundException e) {                // TODO Auto-generated catch block                e.printStackTrace();            } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }else{            Log.i("tag", "NO SDCard.");        }    }    private String getMIMEType(File f){         String type="";        String fName=f.getName();        /* 取得扩展名 */        String end=fName.substring(fName.lastIndexOf(".")+1,fName.length()).toLowerCase();      /* 依扩展名的类型决定MimeType */      if(end.equals("pdf")){          type = "application/pdf";//      }      else if(end.equals("m4a")||end.equals("mp3")||end.equals("mid")||        end.equals("xmf")||end.equals("ogg")||end.equals("wav")){          type = "audio/*";         }        else if(end.equals("3gp")||end.equals("mp4")){          type = "video/*";        }        else if(end.equals("jpg")||end.equals("gif")||end.equals("png")||        end.equals("jpeg")||end.equals("bmp")){          type = "image/*";        }        else if(end.equals("apk")){           /* android.permission.INSTALL_PACKAGES */           type = "application/vnd.android.package-archive";       }//      else if(end.equals("pptx")||end.equals("ppt")){//        type = "application/vnd.ms-powerpoint"; //      }else if(end.equals("docx")||end.equals("doc")){//        type = "application/vnd.ms-word";//      }else if(end.equals("xlsx")||end.equals("xls")){//        type = "application/vnd.ms-excel";//      }      else{//        /*如果无法直接打开，就跳出软件列表给用户选择 */          type="*/*";      }      return type;    }   

over.