Android background download on WiFi only

Question

My app requires to download files in the evening if there is Wi-Fi. Is Service the best way to implement it?

If user closes my app, does that mean I cannot download in any way? That means my user has to keep my app in the background?

Answer 1

You could just use DownloadManager and restrict the allowed network types to Wi-Fi only.

For example:

DownloadManager manager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
Uri uri = Uri.parse("http://something.xyz/somefile.asd");

DownloadManager.Request request = new DownloadManager.Request(uri);
// allowing Wi-Fi only
request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI);

long id = manager.enqueue(request);

To get notified when your download completes, you could define a receiver for the ACTION_DOWNLOAD_COMPLETE broadcast:

private final BroadcastReceiver downloadReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {

        // the ID of the finished download
        long downloadedId = intent.getLongExtra(
            DownloadManager.EXTRA_DOWNLOAD_ID, -1);

        // do whatever you'd like here
    }
};

And register/unregister it:

@Override
protected void onResume() {
    super.onResume();
    registerReceiver(downloadReceiver,
        new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
}

@Override
protected void onPause() {
    unregisterReceiver(downloadReceiver);
    super.onPause();
}

Don't forget to add the appropriate permissions to your Manifest:

<!-- required -->
<uses-permission android:name="android.permission.INTERNET" />

<!-- optional -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />