Android (at least API level 11). Update UI from not UI thread via Activity.runOnUiThread method.

UpdateUiFromAnotherThreadViaRunOnUiThreadMethod.java

//----- inside an Activity class ----------

// ... Create task in separate thread:

Runnable heavyTask = new Runnable() {
    @Override
    public void run() {
      // do heavy work...
      
      runOnUiThread(new Runnable() {
          @Override
          public void run() {
              // Update UI...
          }
      });
    }
}

new Thread(heavyTask).start();