WebView实现文件下载功能

转自：http://www.myexception.cn/web/445840.html

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;
    }   

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