Main Activity of the Reflex Game for the tutorial on the SSaurel's Channel

MainActivity.java

package com.ssaurel.myreflexgame;

import android.graphics.Color;
import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.WindowManager;
import android.widget.TextView;

import butterknife.BindView;
import butterknife.ButterKnife;
import butterknife.OnTouch;

public class MainActivity extends AppCompatActivity {

    public static final int BG_COLOR = Color.parseColor("#E8EAF6");
    public static final long MIN_DELAY = 1000; // 1 sec
    public static final long MAX_DELAY = 5000; // 5 sec
    public static final int NB_TRIES = 5; // 5 tries during our Reflex Game
    public int currentTry = 1;
    @BindView(R.id.root)
    View root;
    @BindView (R.id.touchArea)
    View touchArea;
    @BindView(R.id.targetIv)
    View targetIv;
    @BindView(R.id.msgTv)
    TextView msgTv;
    private boolean gameStarted, displayed;
    // we will store total time for NB_TRIES, best time and average time
    private long totalTime, startTime, bestTime, averageTime;
    private static Handler HANDLER;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_play);
        // Keep screen on during the game
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        // bind views
        ButterKnife.bind(this);
        HANDLER = new Handler();
    }

    @Override
    protected void onPause() {
        super.onPause();

        if (HANDLER != null) {
            // cancel all callbacks in on pause state
            HANDLER.removeCallbacksAndMessages(null);
        }
    }

    @OnTouch(R.id.root)
    public boolean manageGame() {
        if (gameStarted) {
            // game started, we need to manage touch on the screen
            if (displayed) {
                // bg in red ==> we need to manage time
                // delay before user touched the screen
                long delay = System.currentTimeMillis() - startTime;

                if (delay < bestTime) {
                    // new best time
                    bestTime = delay;
                }

                totalTime += delay; // we add to total time
                msgTv.setText(getString(R.string.ok_in).replace("#delay#", delay + ""));
                root.setBackgroundColor(BG_COLOR); // set classical bg color
                touchArea.setVisibility(View.GONE);
                targetIv.setVisibility(View.GONE);
                currentTry++;

                if (currentTry > NB_TRIES) {
                    // game ended
                    averageTime = totalTime / NB_TRIES; // we calculate average time
                    gameStarted = false;
                    msgTv.setText(getString(R.string.game_ended).
                            replace("#averageTime#", averageTime + "").
                            replace("#bestTime#", bestTime + ""));

                } else {
                    // we plan next display randomly for red backgound
                    displayed = false;
                    HANDLER.postDelayed(bgColorTask, randomLongBetween(MIN_DELAY, MAX_DELAY));
                }

            } else {
                // bg is not in red ==> You lose
                HANDLER.removeCallbacks(bgColorTask);
                gameStarted = false;
                msgTv.setText(R.string.you_lose);
            }

        } else {
            // game not started, we need to start the game
            // we init variables
            gameStarted = true;
            displayed = false;
            bestTime = Long.MAX_VALUE;
            totalTime = 0;
            currentTry = 1;
            msgTv.setText(R.string.be_ready);
            // we will change the background color in a random time between MIN_DELAY and MAX_DELAY
            HANDLER.postDelayed(bgColorTask, randomLongBetween(MIN_DELAY, MAX_DELAY));
        }

        return false;
    }

    // we need to create a bg color task runnable instance to change the bg color before user touch the screen as fast as possible
    private Runnable bgColorTask = new Runnable() {
        @Override
        public void run() {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    msgTv.setText("");
                    root.setBackgroundColor(Color.RED); // bg in RED ==> Touch the screen as fast as you can
                    touchArea.setVisibility(View.VISIBLE);
                    targetIv.setVisibility(View.VISIBLE);
                    displayed = true; // bg in RED is displayed
                    startTime = System.currentTimeMillis();
                }
            });
        }
    };

    public static long randomLongBetween(long origin, long bound) {
        return origin + (long) (Math.random() * (bound - origin));
    }
}

This is deprecated. Use FusedLocation API