Scan Android SD card for new files

You could also call media scanner explicitly by sending broadcast.

sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED, Uri
                    .parse("file://"
                            + Environment.getExternalStorageDirectory())));

Edit

This was an old post. Updating it to new versions

Android is taking steps to prevent apps from spoofing more system broadcasts like this.

If you want to tell Android to index a file you put on external storage, either use MediaScannerConnection or ACTION_MEDIA_SCANNER_SCAN_FILE

Reference: This post

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
    final Intent scanIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
    final Uri contentUri = Uri.fromFile(outputFile); 
    scanIntent.setData(contentUri);
    sendBroadcast(scanIntent);
} else {
    final Intent intent = new Intent(Intent.ACTION_MEDIA_MOUNTED, Uri.parse("file://" + Environment.getExternalStorageDirectory()));
    sendBroadcast(intent);
}

If the above piece of code is not working you can try the following:

MediaScannerConnection.scanFile(this, new String[] {
    file.getAbsolutePath()
}, null, new MediaScannerConnection.OnScanCompletedListener() {

    @Override
    public void onScanCompleted(String path, Uri uri) {


    }
});

I've tried plenty of different methods to trigger the MediaScanner, and these are my results.

SendBroadcast

The most simple and naive solution. It consists in executing the following instruction from your code:

sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED,
              Uri.parse("file://"+ Environment.getExternalStorageDirectory())));

However, this no longer works in KitKat devices, due to a lack of required permissions.

---

MediaScannerWrapper

As posted here (per @Brian's answer), it consists in wrapping a MediaScannerConnection instance in order to trigger the scan() method over a specific directory. This method has proven to be working fine for 4.3 and below, but still no luck with KitKat (4.4+).

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FileWalker

One of the many Play Store apps that tries to overcome the MediaStore's lack of commitment to update its database is ReScan SD. It sends a lot of different broadcasts:

  sendBroadcast(new Intent("android.intent.action.MEDIA_MOUNTED", Uri.parse("file://" + Environment.getExternalStorageDirectory())));
  sendBroadcast(new Intent("android.intent.action.MEDIA_MOUNTED", Uri.parse("file:///Removable")));
  sendBroadcast(new Intent("android.intent.action.MEDIA_MOUNTED", Uri.parse("file:///Removable/SD")));
  sendBroadcast(new Intent("android.intent.action.MEDIA_MOUNTED", Uri.parse("file:///Removable/MicroSD")));
  sendBroadcast(new Intent("android.intent.action.MEDIA_MOUNTED", Uri.parse("file:///mnt/Removable/MicroSD")));
  sendBroadcast(new Intent("android.intent.action.MEDIA_MOUNTED", Uri.parse("file:///mnt")));
  sendBroadcast(new Intent("android.intent.action.MEDIA_MOUNTED", Uri.parse("file:///storage")));
  sendBroadcast(new Intent("android.intent.action.MEDIA_MOUNTED", Uri.parse("file:///Removable")));

and tries to support KitKat by manually triggering the scan() method over each file of the base directory. Unfortunately, this is both very CPU-intensive and time-consuming, so it is not very recommended.

---

"The shell way"

The only thing that seem to work with KitKat in some cases is sending the broadcast via adb shell. So, this snippet allows you to do just that programmatically:

Runtime.getRuntime().exec("am broadcast -a android.intent.action.MEDIA_MOUNTED -d file://" + Environment.getExternalStorageDirectory());

It is more of an hack-ish way of doing it, but at the moment is the best I could come up with.

---

Bottom line

Each of the above solutions actually works for everything that is not KitKat. That's because, thanks to Justin, a bug has been found and issued to the official Tracker. This means that, until the bug is ironed out, we are left with no true KitKat support.

Which one to use? Among those, I would use the MediaScannerWrapper solution, together with the shell-ish approach (the last one).

Use MediaScannerConnection:

http://developer.android.com/reference/android/media/MediaScannerConnection.html

It can be a little bit of a pain because of the multiple levels of asynchronous calls, so as of API 8 (Froyo) there is a helper function:

http://developer.android.com/reference/android/media/MediaScannerConnection.html#scanFile(android.content.Context, java.lang.String[], java.lang.String[], android.media.MediaScannerConnection.OnScanCompletedListener)

Since the last answer I posted apparently wasn't an appropriate method, I found another method here. You basically create a wrapper class, initialize it, and then call the scan() method. Very helpful post. Let me know if this isn't appropriate either.