apps-android-commons/app/src/main/java/fr/free/nrw/commons/WelcomeActivity.java

package fr.free.nrw.commons;

import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.view.ViewPager;

import com.viewpagerindicator.CirclePageIndicator;

import butterknife.BindView;
import butterknife.ButterKnife;
import fr.free.nrw.commons.quiz.QuizActivity;
import fr.free.nrw.commons.theme.BaseActivity;

public class WelcomeActivity extends BaseActivity {

    @BindView(R.id.welcomePager) ViewPager pager;
    @BindView(R.id.welcomePagerIndicator) CirclePageIndicator indicator;

    private WelcomePagerAdapter adapter = new WelcomePagerAdapter();
    private boolean isQuiz;

    /**
     * Initialises exiting fields and dependencies
     *
     * @param savedInstanceState WelcomeActivity bundled data
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_welcome);

        if(getIntent() != null) {
            Bundle bundle = getIntent().getExtras();
            if (bundle != null) {
                isQuiz = bundle.getBoolean("isQuiz");
            }
        } else{
            isQuiz = false;
        }

        ButterKnife.bind(this);

        pager.setAdapter(adapter);
        indicator.setViewPager(pager);
        adapter.setCallback(this::finish);
    }

    /**
     * References WelcomePageAdapter to null before the activity is destroyed
     */
    @Override
    public void onDestroy() {
        if(isQuiz){
            Intent i = new Intent(WelcomeActivity.this, QuizActivity.class);
            startActivity(i);
        }
        adapter.setCallback(null);
        super.onDestroy();
    }

    /**
     * Creates a way to change current activity to WelcomeActivity
     *
     * @param context Activity context
     */
    public static void startYourself(Context context) {
        Intent welcomeIntent = new Intent(context, WelcomeActivity.class);
        context.startActivity(welcomeIntent);
    }
}