WebView實現文件下載功能

WebView控制調用相應的WEB頁面進行展現。當碰到頁面有下載連接的時候，點擊上去是一點反應都沒有的。原來是由於WebView默認沒有開啓文件下載的功能，若是要實現文件下載的功能，須要設置WebView的DownloadListener，經過實現本身的DownloadListener來實現文件的下載。具體操做以下： 

一、設置WebView的DownloadListener： 
    webView.setDownloadListener(new MyWebViewDownLoadListener()); 

二、實現MyWebViewDownLoadListener這個類，具體能夠以下這樣：  

Java代碼  

1. private class MyWebViewDownLoadListener implements DownloadListener{  

2.   

3.         @Override  

4.         public void onDownloadStart(String url, String userAgent, String contentDisposition, String mimetype,  

5.                                     long contentLength) {             

6.             Log.i("tag", "url="+url);             

7.             Log.i("tag", "userAgent="+userAgent);  

8.             Log.i("tag", "contentDisposition="+contentDisposition);           

9.             Log.i("tag", "mimetype="+mimetype);  

10.             Log.i("tag", "contentLength="+contentLength);  

11.             Uri uri = Uri.parse(url);  

12.             Intent intent = new Intent(Intent.ACTION_VIEW, uri);  

13.             startActivity(intent);             

14.         }  

15.     }  

  這只是調用系統中已經內置的瀏覽器進行下載，尚未WebView自己進行的文件下載，不過，這也基本上知足咱們的應用場景了。 

我在項目中的運用 
項目要求這樣： 
1，須要使用WebView加載一個網頁； 
2，網頁中有文件下載的連接，點擊後須要下載文件到SDcard； 
3，而後自動打開文件； 
下面是具體解決辦法 
第一步，對WebView進行一系列設置。 

Java代碼  

1. WebView webview=(WebView)layout.findViewById(R.id.webview);  

2.                 webview.getSettings().setJavaScriptEnabled(true);  

3.                 webview.setWebChromeClient(new MyWebChromeClient());  

4.                 webview.requestFocus();  

5. //              webview.loadUrl("file:///android_asset/risktest.html");  

6.                 webview.loadUrl(jcrs_sub.get(position).addr);  

7.                 // 設置web視圖客戶端  

8.                 webview.setWebViewClient(new MyWebViewClient());  

9.                 webview.setDownloadListener(new MyWebViewDownLoadListener());  

10.   

11. //內部類  

12. public class MyWebViewClient extends WebViewClient {  

13.         // 若是頁面中連接，若是但願點擊連接繼續在當前browser中響應，  

14.         // 而不是新開Android的系統browser中響應該連接，必須覆蓋 webview的WebViewClient對象。  

15.         public boolean shouldOverviewUrlLoading(WebView view, String url) {  

16.             L.i("shouldOverviewUrlLoading");  

17.             view.loadUrl(url);  

18.             return true;  

19.         }  

20.   

21.         public void onPageStarted(WebView view, String url, Bitmap favicon) {  

22.             L.i("onPageStarted");  

23.             showProgress();  

24.         }  

25.   

26.         public void onPageFinished(WebView view, String url) {  

27.             L.i("onPageFinished");  

28.             closeProgress();  

29.         }  

30.   

31.         public void onReceivedError(WebView view, int errorCode,  

32.                 String description, String failingUrl) {  

33.             L.i("onReceivedError");  

34.             closeProgress();  

35.         }  

36.     }  

37.   

38. // 若是不作任何處理，瀏覽網頁，點擊系統「Back」鍵，整個Browser會調用finish()而結束自身，  

39.     // 若是但願瀏覽的網 頁回退而不是推出瀏覽器，須要在當前Activity中處理並消費掉該Back事件。  

40.     public boolean onKeyDown(int keyCode, KeyEvent event) {  

41.         // if((keyCode==KeyEvent.KEYCODE_BACK)&&webview.canGoBack()){  

42.         // webview.goBack();  

43.         // return true;  

44.         // }  

45.         return false;  

46.     }  

第二步，起線程開始下載文件。 

Java代碼  

1. //內部類  

2. private class MyWebViewDownLoadListener implements DownloadListener {  

3.   

4.         @Override  

5.         public void onDownloadStart(String url, String userAgent, String contentDisposition, String mimetype,  

6.                                     long contentLength) {  

7.             if(!Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){  

8.                 Toast t=Toast.makeText(mContext, "須要SD卡。", Toast.LENGTH_LONG);  

9.                 t.setGravity(Gravity.CENTER, 0, 0);  

10.                 t.show();  

11.                 return;  

12.             }  

13.             DownloaderTask task=new DownloaderTask();  

14.             task.execute(url);  

15.         }  

16.   

17.     }  

18.     //內部類  

19.     private class DownloaderTask extends AsyncTask<String, Void, String> {   

20.   

21.         public DownloaderTask() {   

22.         }  

23.   

24.         @Override  

25.         protected String doInBackground(String... params) {  

26.             // TODO Auto-generated method stub  

27.             String url=params[0];  

28. //          Log.i("tag", "url="+url);  

29.             String fileName=url.substring(url.lastIndexOf("/")+1);  

30.             fileName=URLDecoder.decode(fileName);  

31.             Log.i("tag", "fileName="+fileName);  

32.               

33.             File directory=Environment.getExternalStorageDirectory();  

34.             File file=new File(directory,fileName);  

35.             if(file.exists()){  

36.                 Log.i("tag", "The file has already exists.");  

37.                 return fileName;  

38.             }  

39.             try {    

40.                 HttpClient client = new DefaultHttpClient();    

41. //                client.getParams().setIntParameter("http.socket.timeout",3000);//設置超時  

42.                 HttpGet get = new HttpGet(url);    

43.                 HttpResponse response = client.execute(get);  

44.                 if(HttpStatus.SC_OK==response.getStatusLine().getStatusCode()){  

45.                     HttpEntity entity = response.getEntity();  

46.                     InputStream input = entity.getContent();  

47.                       

48.                     writeToSDCard(fileName,input);  

49.                       

50.                     input.close();  

51. //                  entity.consumeContent();  

52.                     return fileName;    

53.                 }else{  

54.                     return null;  

55.                 }  

56.             } catch (Exception e) {    

57.                 e.printStackTrace();  

58.                 return null;  

59.             }  

60.         }  

61.   

62.         @Override  

63.         protected void onCancelled() {  

64.             // TODO Auto-generated method stub  

65.             super.onCancelled();  

66.         }  

67.   

68.         @Override  

69.         protected void onPostExecute(String result) {  

70.             // TODO Auto-generated method stub  

71.             super.onPostExecute(result);  

72.             closeProgressDialog();  

73.             if(result==null){  

74.                 Toast t=Toast.makeText(mContext, "鏈接錯誤！請稍後再試！", Toast.LENGTH_LONG);  

75.                 t.setGravity(Gravity.CENTER, 0, 0);  

76.                 t.show();  

77.                 return;  

78.             }  

79.               

80.             Toast t=Toast.makeText(mContext, "已保存到SD卡。", Toast.LENGTH_LONG);  

81.             t.setGravity(Gravity.CENTER, 0, 0);  

82.             t.show();  

83.             File directory=Environment.getExternalStorageDirectory();  

84.             File file=new File(directory,result);  

85.             Log.i("tag", "Path="+file.getAbsolutePath());  

86.               

87.             Intent intent = getFileIntent(file);  

88.               

89.             startActivity(intent);  

90.                   

91.         }  

92.   

93.         @Override  

94.         protected void onPreExecute() {  

95.             // TODO Auto-generated method stub  

96.             super.onPreExecute();  

97.             showProgressDialog();  

98.         }  

99.   

100.         @Override  

101.         protected void onProgressUpdate(Void... values) {  

102.             // TODO Auto-generated method stub  

103.             super.onProgressUpdate(values);  

104.         }   

105.   

106.           

107.     }   

第三步，實現一些工具方法。 

Java代碼  

1. private ProgressDialog mDialog;  

2.     private void showProgressDialog(){  

3.         if(mDialog==null){  

4.             mDialog = new ProgressDialog(mContext);    

5.             mDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);//設置風格爲圓形進度條    

6.             mDialog.setMessage("正在加載 ，請等待...");    

7.             mDialog.setIndeterminate(false);//設置進度條是否爲不明確    

8.             mDialog.setCancelable(true);//設置進度條是否能夠按退回鍵取消    

9.             mDialog.setCanceledOnTouchOutside(false);  

10.             mDialog.setOnDismissListener(new OnDismissListener() {  

11.                   

12.                 @Override  

13.                 public void onDismiss(DialogInterface dialog) {  

14.                     // TODO Auto-generated method stub  

15.                     mDialog=null;  

16.                 }  

17.             });  

18.             mDialog.show();  

19.               

20.         }  

21.     }  

22.     private void closeProgressDialog(){  

23.         if(mDialog!=null){  

24.             mDialog.dismiss();  

25.             mDialog=null;  

26.         }  

27.     }  

28.      public Intent getFileIntent(File file){  

29. //       Uri uri = Uri.parse("http://m.ql18.com.cn/hpf10/1.pdf");  

30.         Uri uri = Uri.fromFile(file);  

31.         String type = getMIMEType(file);  

32.         Log.i("tag", "type="+type);  

33.         Intent intent = new Intent("android.intent.action.VIEW");  

34.         intent.addCategory("android.intent.category.DEFAULT");  

35.         intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);  

36.         intent.setDataAndType(uri, type);  

37.         return intent;  

38.       }  

39.        

40.     public void writeToSDCard(String fileName,InputStream input){  

41.           

42.         if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){  

43.             File directory=Environment.getExternalStorageDirectory();  

44.             File file=new File(directory,fileName);  

45. //          if(file.exists()){  

46. //              Log.i("tag", "The file has already exists.");  

47. //              return;  

48. //          }  

49.             try {  

50.                 FileOutputStream fos = new FileOutputStream(file);  

51.                 byte[] b = new byte[2048];  

52.                 int j = 0;  

53.                 while ((j = input.read(b)) != -1) {  

54.                     fos.write(b, 0, j);  

55.                 }  

56.                 fos.flush();  

57.                 fos.close();  

58.             } catch (FileNotFoundException e) {  

59.                 // TODO Auto-generated catch block  

60.                 e.printStackTrace();  

61.             } catch (IOException e) {  

62.                 // TODO Auto-generated catch block  

63.                 e.printStackTrace();  

64.             }  

65.         }else{  

66.             Log.i("tag", "NO SDCard.");  

67.         }  

68.     }  

69.       

70.     private String getMIMEType(File f){     

71.       String type="";    

72.       String fName=f.getName();    

73.       /* 取得擴展名 */    

74.       String end=fName.substring(fName.lastIndexOf(".")+1,fName.length()).toLowerCase();  

75.         

76.       /* 依擴展名的類型決定MimeType */  

77.       if(end.equals("pdf")){  

78.           type = "application/pdf";//  

79.       }  

80.       else if(end.equals("m4a")||end.equals("mp3")||end.equals("mid")||    

81.       end.equals("xmf")||end.equals("ogg")||end.equals("wav")){    

82.         type = "audio/*";     

83.       }    

84.       else if(end.equals("3gp")||end.equals("mp4")){    

85.         type = "video/*";    

86.       }    

87.       else if(end.equals("jpg")||end.equals("gif")||end.equals("png")||    

88.       end.equals("jpeg")||end.equals("bmp")){    

89.         type = "image/*";    

90.       }    

91.       else if(end.equals("apk")){     

92.         /* android.permission.INSTALL_PACKAGES */     

93.         type = "application/vnd.android.package-archive";   

94.       }  

95. //      else if(end.equals("pptx")||end.equals("ppt")){  

96. //        type = "application/vnd.ms-powerpoint";   

97. //      }else if(end.equals("docx")||end.equals("doc")){  

98. //        type = "application/vnd.ms-word";  

99. //      }else if(end.equals("xlsx")||end.equals("xls")){  

100. //        type = "application/vnd.ms-excel";  

101. //      }  

102.       else{  

103. //        /*若是沒法直接打開，就跳出軟件列表給用戶選擇 */    

104.         type="*/*";  

105.       }  

106.       return type;  

107.     }