handle.java

public class handle{
  private boolean done = false;
  
  public void onClick(View v){
    final Handler handler = new Handler();
    final Random random = new Random();
    Runnable toast = new Runnable(){
      @Override
      public void run(){
        if(done){
          Toast.makeText(getBaseContext(), "Done", LENGTH_SHORT).show();
        }else{
          Toast.makeText(getBaseContext(), "Please wait", LENGTH_SHORT).show();
          handler.postDelayed(this, 1000);
        }
      }
    };
    Runnable yourFunc = new Runnable(){
      private int count = 0;
      @Override
      public void run(){
        count++;
        runYourFunc();
        if(count >= 20){
          done = true;
        }else{
          handler.postDelayed(this, random.nextInt(5000));
        }
      }
    }
    runnable.run();
    handler.postDelayed(yourFunc, random.nextInt(5000));
  }
  private void runYourFunc(){
    // your function here
  }
}