无法以编程方式下载.apk文件

Question

I am trying to download an android apk file by clicking on update button. I have used Async Task to carry out the process in background.

A new file ec.apk is created in phone's Sdcard/Download but file is not downloaded. File size = 0 bytes. I also used fos.flush() method to make buffer empty.

if(v==btUpdate){
  UpdateApp atualizaApp=new UpdateApp();
  atualizaApp.setContext(getApplicationContext());
  atualizaApp.execute("http://mobileapp.abc.org/e-mobapps/ec.apk");
}


public class UpdateApp extends AsyncTask<String,Void,Void>{
  private Context context;
  public void setContext(Context contextf){
    context = contextf;
  }

  @Override
  protected Void doInBackground(String... arg0) {
    try {
      URL url = new URL(arg0[0]);
      HttpURLConnection c = (HttpURLConnection) url.openConnection();
      c.setRequestMethod("GET");
      c.setDoOutput(true);
      c.connect();


      File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/download/");
      file.mkdirs();
      File outputFile = new File(file, "ec.apk");
      if(outputFile.exists()){
        outputFile.delete();
      }
      FileOutputStream fos = new FileOutputStream(outputFile);

      InputStream is = c.getInputStream();

      byte[] buffer = new byte[1024];
      int len1 = 0;
      while ((len1 = is.read(buffer)) != -1) {
        fos.write(buffer, 0, len1);
      }
      fos.close();
      is.close();

      Intent intent = new Intent(Intent.ACTION_VIEW);
      intent.setDataAndType(Uri.fromFile(new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/download/" + "ec.apk")), "application/vnd.android.package-archive");
      intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); // without this flag android returned a intent error!
      context.startActivity(intent);


    } catch (Exception e) {
      Log.e("UpdateAPP", "Update error! " + e.getMessage());
    }
    return null;
  }

Answer 1

I also used fos.flush() method to make buffer empty.

That is insufficient if you are trying to use the file immediately, as you appear to be doing here. You also need to call getFD().sync() on the FileOutputStream before close() , so the OS buffers get flushed to disk. See this Android Developers Blog post for more.

Beyond that, you might wish to use the three-parameter e() method, so you get the full stack trace, then double-check LogCat to see if you are encountering any problems.