Android WebView实现文件下载功能

2020-11-05 10:49:46 浏览数 (1)

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：

代码语言：javascript复制
 webView.setDownloadListener(new MyWebViewDownLoadListener());

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

代码语言：javascript复制
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。

代码语言：javascript复制
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。

代码语言：javascript复制
//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。

代码语言：javascript复制
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。

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