How to launch an Activity without a UI?

Android also provides a theme specifically for this:

android:theme="@android:style/Theme.NoDisplay"

Just in case you are using Android 6.0+ or Target SDK is 23+, having a theme android:theme = "@android:style/Theme.NoDisplay" will lead to a crash with error did not call finish() prior to onResume() completing. This in fact is a bug recognised by Google developers here.

So it is recommended to use an activity with following theme as a workaround.

android:theme = "@android:style/Theme.Translucent.NoTitleBar"

In your manifest, when you declare the activity, use theme "@android:style/Theme.Translucent.NoTitleBar"

Ex:

<activity android:name="yourActivityName" android:label="@string/app_name" android:theme="@android:style/Theme.Translucent.NoTitleBar">

You need to add the Intent flag,

intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

Or

call "finish();" after firing the intent.