Android WebView实现文件下载功能

发布时间：2020-10-11 22:30:06 来源：脚本之家阅读：397 作者：摄氏三十七度栏目：移动开发

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; 
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持亿速云。

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