Unable to install .apk from app

I have an app hosted on SourceForge (https://sourceforge.net/projects/pokedroid/). I decided to add a button to download the newest version of the app straight from the CVS server. The .apk downloads fine, but when I try to install it, the package installer gives a "cannot parse package" error. The code I'm using:

    private class DownloadAndInstall extends AsyncTask<String, Integer, Boolean>
{
    protected Boolean doInBackground(String... derp)
    {
        String ur=derp[0];
        String fileName=derp[1];
        ByteArrayBuffer baf = new ByteArrayBuffer(50);

        try
        {
            URL url = new URL(ur);
            URLConnection ucon = null;
            ucon = url.openConnection();

            InputStream is = ucon.getInputStream();
            BufferedInputStream bis = new BufferedInputStream(is);

            int current = 0;
            int updateCount=0;
            while ((current = bis.read()) != -1)
            {
                if(updateCount==256)
                {
                    publishProgress(baf.length());
                    updateCount=0;
                }
                baf.append((byte) current);
                updateCount++;
            }

            FileOutputStream fos = PokeDroid.openFileOutput(fileName, Context.MODE_WORLD_READABLE);
            fos.write(baf.toByteArray());
            fos.close();

        } catch (Exception e) {
            Log.e("pokedroid", e.toString());
        }

        MessageDigest digest = null;
        try {
            digest = java.security.MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            Log.e("pokedroid", e.toString());
        }
        digest.update(baf.toByteArray());
        byte[] h = digest.digest();

        if(baf.length()==0)
            return null;
        String[] fileList=fileList();
        boolean exists=false;
        for(String i:fileList)
            if(i.equals("updatehash.md5"))
                exists=true;

        String newHash=new String(h);
        Log.e("pokedroid", "new="+newHash);

        if(exists)
        {
            try
            {
                String oldHash=l开发者_如何学运维oadObject("updatehash.md5");
                Log.e("pokedroid", "old="+oldHash);
                if(oldHash.equals(newHash))
                    return false;
                else
                    saveObject(newHash, "updatehash.md5");
            }
            catch (Exception e)
            {
                Log.e("pokedroid",e.toString());
            }
        }
        else
        {
            try {
                saveObject(newHash, "updatehash.md5");
            } catch (IOException e) {
                Log.e("pokedroid",e.toString());
            }
        }
        return true;
    }

    protected void onProgressUpdate(Integer...integers)
    {
        p.setMessage("Downloading update...\n"+integers[0]/1000+"kb downloaded so far.");
    }

    protected void onPostExecute(Boolean b)
    {
        if(b==null)
        {
            noConnection.show();
            deleteFile("PokeDroid.apk");
            p.dismiss();
            return;
        }
        if(!b)
            noNewUpdate.show();
        else
        {
            Intent intent=new Intent();
            intent.setAction(android.content.Intent.ACTION_VIEW);
            intent.setDataAndType(Uri.parse("file:///data/data/com.games.pokedroid/files/PokeDroid.apk"), "application/vnd.android.package-archive");
            startActivity(intent);
            deleteFile("PokeDroid.apk");
        }
        p.dismiss();
    }

    public void saveObject(String obj, String filename) throws IOException
    {
        FileOutputStream fos = openFileOutput(filename,Context.MODE_PRIVATE);
        ObjectOutputStream out = new ObjectOutputStream(fos);
        out.writeObject(obj);
        out.close();
        fos.close();
    }

    public String loadObject(String filename) throws StreamCorruptedException, IOException, ClassNotFoundException
    {
        FileInputStream fis=openFileInput(filename);
        ObjectInputStream in=new ObjectInputStream(fis);
        String out=(String) in.readObject();
        in.close();
        fis.close();
        return out;
    }
}

This is a subclass in my Activity, of course. What am I doing wrong?

I can see one issue in your code:

 startActivity(intent);
 deleteFile("PokeDroid.apk");

This code sends intent and then deletes the file. Note that startActivity is asynchronous function. I.e. it sends the request, but does not wait for completion of that request. So when the intent is actually received by Application Installer Activity (let's call it that way ) your .apk file has already been deleted by you.

How to fix:

You need to replace those two lines of code with:

startActivityForResult(intent);

And then in onActivityResult function:

deleteFile("PokeDroid.apk");

have you checked that your mobile is configured to accept 3rd party apps?

is the apk signed?