QuizActivity.java

/*
* Copyright (C) 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*  	http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package com.example.android.classicalmusicquiz;

import android.content.Intent;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.graphics.PorterDuff;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.google.android.exoplayer2.DefaultLoadControl;
import com.google.android.exoplayer2.ExoPlaybackException;
import com.google.android.exoplayer2.ExoPlayer;
import com.google.android.exoplayer2.ExoPlayerFactory;
import com.google.android.exoplayer2.LoadControl;
import com.google.android.exoplayer2.SimpleExoPlayer;
import com.google.android.exoplayer2.Timeline;
import com.google.android.exoplayer2.extractor.DefaultExtractorsFactory;
import com.google.android.exoplayer2.source.ExtractorMediaSource;
import com.google.android.exoplayer2.source.MediaSource;
import com.google.android.exoplayer2.source.TrackGroupArray;
import com.google.android.exoplayer2.trackselection.DefaultTrackSelector;
import com.google.android.exoplayer2.trackselection.TrackSelectionArray;
import com.google.android.exoplayer2.trackselection.TrackSelector;
import com.google.android.exoplayer2.ui.SimpleExoPlayerView;
import com.google.android.exoplayer2.upstream.DefaultDataSourceFactory;
import com.google.android.exoplayer2.util.Util;

import java.util.ArrayList;

public class QuizActivity extends AppCompatActivity implements View.OnClickListener, ExoPlayer.EventListener {

    private static final int CORRECT_ANSWER_DELAY_MILLIS = 1000;
    private static final String REMAINING_SONGS_KEY = "remaining_songs";
    private static final String TAG = QuizActivity.class.getSimpleName();
    private int[] mButtonIDs = {R.id.buttonA, R.id.buttonB, R.id.buttonC, R.id.buttonD};
    private ArrayList<Integer> mRemainingSampleIDs;
    private ArrayList<Integer> mQuestionSampleIDs;
    private int mAnswerSampleID;
    private int mCurrentScore;
    private int mHighScore;
    private Button[] mButtons;
    private SimpleExoPlayer mExoPlayer;
    private SimpleExoPlayerView mPlayerView;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_quiz);


        // Initialize the player view.
        mPlayerView = (SimpleExoPlayerView) findViewById(R.id.playerView);


        boolean isNewGame = !getIntent().hasExtra(REMAINING_SONGS_KEY);

        // If it's a new game, set the current score to 0 and load all samples.
        if (isNewGame) {
            QuizUtils.setCurrentScore(this, 0);
            mRemainingSampleIDs = Sample.getAllSampleIDs(this);
            // Otherwise, get the remaining songs from the Intent.
        } else {
            mRemainingSampleIDs = getIntent().getIntegerArrayListExtra(REMAINING_SONGS_KEY);
        }

        // Get current and high scores.
        mCurrentScore = QuizUtils.getCurrentScore(this);
        mHighScore = QuizUtils.getHighScore(this);

        // Generate a question and get the correct answer.
        mQuestionSampleIDs = QuizUtils.generateQuestion(mRemainingSampleIDs);
        mAnswerSampleID = QuizUtils.getCorrectAnswerID(mQuestionSampleIDs);

        // Load the question mark as the background image until the user answers the question.
        mPlayerView.setDefaultArtwork(BitmapFactory.decodeResource
                (getResources(), R.drawable.question_mark));

        // If there is only one answer left, end the game.
        if (mQuestionSampleIDs.size() < 2) {
            QuizUtils.endGame(this);
            finish();
        }

        // Initialize the buttons with the composers names.
        mButtons = initializeButtons(mQuestionSampleIDs);
        
        Sample answerSample = Sample.getSampleByID(this, mAnswerSampleID);

        if (answerSample == null) {
            Toast.makeText(this, getString(R.string.sample_not_found_error),
                    Toast.LENGTH_SHORT).show();
            return;
        }

        // Initialize the player.
        initializePlayer(Uri.parse(answerSample.getUri()));
    }


    /**
     * Initializes the button to the correct views, and sets the text to the composers names,
     * and set's the OnClick listener to the buttons.
     *
     * @param answerSampleIDs The IDs of the possible answers to the question.
     * @return The Array of initialized buttons.
     */
    private Button[] initializeButtons(ArrayList<Integer> answerSampleIDs) {
        Button[] buttons = new Button[mButtonIDs.length];
        for (int i = 0; i < answerSampleIDs.size(); i++) {
            Button currentButton = (Button) findViewById(mButtonIDs[i]);
            Sample currentSample = Sample.getSampleByID(this, answerSampleIDs.get(i));
            buttons[i] = currentButton;
            currentButton.setOnClickListener(this);
            if (currentSample != null) {
                currentButton.setText(currentSample.getComposer());
            }
        }
        return buttons;
    }


    /**
     * Initialize ExoPlayer.
     * @param mediaUri The URI of the sample to play.
     */
    private void initializePlayer(Uri mediaUri) {
        if (mExoPlayer == null) {
            // Create an instance of the ExoPlayer.
            TrackSelector trackSelector = new DefaultTrackSelector();
            LoadControl loadControl = new DefaultLoadControl();
            mExoPlayer = ExoPlayerFactory.newSimpleInstance(this, trackSelector, loadControl);
            mPlayerView.setPlayer(mExoPlayer);

            // Set the ExoPlayer.EventListener to this activity.
            mExoPlayer.addListener(this);
            
            // Prepare the MediaSource.
            String userAgent = Util.getUserAgent(this, "ClassicalMusicQuiz");
            MediaSource mediaSource = new ExtractorMediaSource(mediaUri, new DefaultDataSourceFactory(
                    this, userAgent), new DefaultExtractorsFactory(), null, null);
            mExoPlayer.prepare(mediaSource);
            mExoPlayer.setPlayWhenReady(true);
        }
    }


    /**
     * Release ExoPlayer.
     */
    private void releasePlayer() {
        mExoPlayer.stop();
        mExoPlayer.release();
        mExoPlayer = null;
    }


    /**
     * The OnClick method for all of the answer buttons. The method uses the index of the button
     * in button array to to get the ID of the sample from the array of question IDs. It also
     * toggles the UI to show the correct answer.
     *
     * @param v The button that was clicked.
     */
    @Override
    public void onClick(View v) {

        // Show the correct answer.
        showCorrectAnswer();

        // Get the button that was pressed.
        Button pressedButton = (Button) v;

        // Get the index of the pressed button
        int userAnswerIndex = -1;
        for (int i = 0; i < mButtons.length; i++) {
            if (pressedButton.getId() == mButtonIDs[i]) {
                userAnswerIndex = i;
            }
        }

        // Get the ID of the sample that the user selected.
        int userAnswerSampleID = mQuestionSampleIDs.get(userAnswerIndex);

        // If the user is correct, increase there score and update high score.
        if (QuizUtils.userCorrect(mAnswerSampleID, userAnswerSampleID)) {
            mCurrentScore++;
            QuizUtils.setCurrentScore(this, mCurrentScore);
            if (mCurrentScore > mHighScore) {
                mHighScore = mCurrentScore;
                QuizUtils.setHighScore(this, mHighScore);
            }
        }

        // Remove the answer sample from the list of all samples, so it doesn't get asked again.
        mRemainingSampleIDs.remove(Integer.valueOf(mAnswerSampleID));

        // Wait some time so the user can see the correct answer, then go to the next question.
        final Handler handler = new Handler();
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                mExoPlayer.stop();
                Intent nextQuestionIntent = new Intent(QuizActivity.this, QuizActivity.class);
                nextQuestionIntent.putExtra(REMAINING_SONGS_KEY, mRemainingSampleIDs);
                finish();
                startActivity(nextQuestionIntent);
            }
        }, CORRECT_ANSWER_DELAY_MILLIS);
    }

    /**
     * Disables the buttons and changes the background colors and player art to
     * show the correct answer.
     */
    private void showCorrectAnswer() {
        mPlayerView.setDefaultArtwork(Sample.getComposerArtBySampleID(this, mAnswerSampleID));
        for (int i = 0; i < mQuestionSampleIDs.size(); i++) {
            int buttonSampleID = mQuestionSampleIDs.get(i);

            mButtons[i].setEnabled(false);

            if (buttonSampleID == mAnswerSampleID) {
                mButtons[i].getBackground().setColorFilter(ContextCompat.getColor
                                (this, android.R.color.holo_green_light),
                        PorterDuff.Mode.MULTIPLY);
                mButtons[i].setTextColor(Color.WHITE);
            } else {
                mButtons[i].getBackground().setColorFilter(ContextCompat.getColor
                                (this, android.R.color.holo_red_light),
                        PorterDuff.Mode.MULTIPLY);
                mButtons[i].setTextColor(Color.WHITE);
            }
        }
    }


    /**
     * Release the player when the activity is destroyed.
     */
    @Override
    protected void onDestroy() {
        super.onDestroy();
        releasePlayer();
    }

    
    // ExoPlayer Event Listeners

    @Override
    public void onTimelineChanged(Timeline timeline, Object manifest) {
    }

    @Override
    public void onTracksChanged(TrackGroupArray trackGroups, TrackSelectionArray trackSelections) {
    }

    @Override
    public void onLoadingChanged(boolean isLoading) {
    }

    @Override
    public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
        if((playbackState == ExoPlayer.STATE_READY) && playWhenReady){
            Log.d(TAG, "onPlayerStateChanged: PLAYING");
        } else if((playbackState == ExoPlayer.STATE_READY)){
            Log.d(TAG, "onPlayerStateChanged: PAUSED");
        }
    }

    @Override
    public void onPlayerError(ExoPlaybackException error) {
    }

    @Override
    public void onPositionDiscontinuity() {
    }
}