Wafi, auto cycle iterate through colors at set interval using handler

MainActivity.java

import android.graphics.Color;
import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.LinearLayout;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private final String[] COLORS = {
            "#F44336",  //red
            "#E91E63",  //pink
            "#9C27B0",  //purple
            "#2196F3",  //blue
            "#4CAF50",  //green - black
            "#FFEB3B",  //yellow - black
            "#FF9800",  //orange - black
            "#795548",  //brown
            "#9E9E9E",  //grey - black
    };

    private Handler handler;
    private Runnable runnable;

    private LinearLayout rootLayout;
    private Button btnStart;

    private int counter = 0;
    final int DURATION = 1500;
    boolean inAutoMode = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        rootLayout = (LinearLayout)findViewById(R.id.root_layout);
        btnStart = (Button)findViewById(R.id.button_start);

        rootLayout.setOnClickListener(this);
        btnStart.setOnClickListener(this);

        handler = new Handler();

        runnable = new Runnable() {
            @Override
            public void run() {
                rootLayout.setBackgroundColor(Color.parseColor(COLORS[counter]));
                counter++;
                if (counter == COLORS.length) counter = 0;
                handler.postDelayed(this, DURATION);
            }
        };
    }

    @Override
    public void onClick(View v) {

        if (v == btnStart){
            btnStart.setVisibility(View.GONE);
            inAutoMode = true;
            handler.post(runnable);
        }

        if ((v == rootLayout) && inAutoMode){
            handler.removeCallbacks(runnable);
            counter = 0;
            rootLayout.setBackgroundColor(Color.WHITE);
            btnStart.setVisibility(View.VISIBLE);
        }
    }
}