Android IllegalAccessError java.util.concurrent.TimeUnit.toMinutes

Question

I am currently working on my very first, complete Android app. I am developing a Maths Brain Trainer Game so I am in need of a countdown timer. Hence, I am using Android's CountDownTimer to build it.

The following is the Java code of my GameActivity.java class which I am using to control my game play.

package lk.iit.mobiletechnology.mathematicsbraintrainer;

import java.util.concurrent.TimeUnit;

import lk.iit.mobiletechnology.mathematicsbraintrainer.entity.Challenge;
import lk.iit.mobiletechnology.mathematicsbraintrainer.entity.Game;
import android.annotation.SuppressLint;
import android.annotation.TargetApi;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.os.Bundle;
import android.os.CountDownTimer;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;

@TargetApi(Build.VERSION_CODES.LOLLIPOP)
@SuppressLint("NewApi")
public class GameActivity extends ActionBarActivity {

    private Game game;
    private Challenge currentChallenge;
    private int questionCount;
    private TextView timeView;
    private TextView question;
    private EditText inputField;

    private static final String TAG = "Brain Trainer" ;
    private static final int MAXIMUM_QUESTIONS = 10;
    public static final String KEY_DIFFICULTY = "lk.iit.mobiletechnology.mathematicsbraintrainer.difficulty";
    public static final int DIFFICULTY_NOVICE = 0;
    public static final int DIFFICULTY_EASY = 1;
    public static final int DIFFICULTY_MEDIUM = 2;
    public static final int DIFFICULTY_GURU = 3;

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

        int difficultyLevel = this.getIntent().getIntExtra(KEY_DIFFICULTY, GameActivity.DIFFICULTY_NOVICE);
        this.game = new Game(GameActivity.MAXIMUM_QUESTIONS, difficultyLevel);
        this.questionCount = 0;

        this.question = (TextView)(this.findViewById(R.id.question_text));
        currentChallenge = this.game.getChallenges().get(questionCount);
        question.setText(currentChallenge.toString());
        this.timeView = (TextView)(this.findViewById(R.id.time_text));
        timeView.setText("00:10");

        final CountDownMachine timer = new CountDownMachine(10000, 1000);
        timer.start();

        this.setButtonClickListener();
    }

    private void setButtonClickListener() {
        Button testButton = (Button)(findViewById(R.id.test_button));
        inputField = (EditText)(findViewById(R.id.question_input));
        testButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {               
                double inputValue = Double.parseDouble(inputField.getText().toString());
                ImageView imageView = (ImageView)(findViewById(R.id.answer_feedback));
                Drawable drawable;
                if(questionCount < 10) {

                    if(currentChallenge.correctAnswer(inputValue)) {
                        drawable = getResources().getDrawable(R.drawable.fixed_correct_image);
                        imageView.setImageDrawable(drawable);
                    }
                    else {
                        drawable = getResources().getDrawable(R.drawable.fixed_wrong_image);
                        imageView.setImageDrawable(drawable);
                    }

                    questionCount++;
                    if(questionCount == 5) {
                        //Intent intent = new Intent(, UserEntryActivity.class);
                        finish();

                    }

                    currentChallenge = game.getChallenges().get(questionCount);
                    question.setText(currentChallenge.toString());
                    inputField.setText(" ?");
                }
            }
        });
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    @SuppressLint("NewApi")
    public class CountDownMachine extends CountDownTimer {

        public CountDownMachine(long millisInFuture, long countDownInterval) {
            super(millisInFuture, countDownInterval);
        }

        @TargetApi(Build.VERSION_CODES.LOLLIPOP)
        @SuppressLint("NewApi")
        @Override
        public void onTick(long millisUntilFinished) {
            long timeRemaining = millisUntilFinished;
            String text = String.format("%02d:%02d", (TimeUnit.MILLISECONDS.toMinutes(timeRemaining) - TimeUnit.HOURS.toMinutes(TimeUnit.MILLISECONDS.toHours(timeRemaining))), (TimeUnit.MILLISECONDS.toSeconds(timeRemaining) - (TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(timeRemaining)))));
            timeView.setText(text);
        }

        @Override
        public void onFinish() {
            ImageView imageView = (ImageView)(findViewById(R.id.answer_feedback));
            Drawable drawable;
            if(!(inputField.getText().toString().equals(""))) {
                double inputValue = Double.parseDouble(inputField.getText().toString());
                if(questionCount < 10) {
                    if(currentChallenge.correctAnswer(inputValue)) {
                        drawable = getResources().getDrawable(R.drawable.fixed_correct_image);
                        imageView.setImageDrawable(drawable);
                    }
                    else {
                        drawable = getResources().getDrawable(R.drawable.fixed_wrong_image);
                        imageView.setImageDrawable(drawable);
                    }
                }
            }
            else {
                drawable = getResources().getDrawable(R.drawable.fixed_wrong_image);
                imageView.setImageDrawable(drawable);
            }
            questionCount++;
            if(questionCount == 5) {
                finish();
            }
            currentChallenge = game.getChallenges().get(questionCount);
            question.setText(currentChallenge.toString());
            inputField.setText(" ?");
            timeView.setText("00:10");
        }

    }

}

The associated activity_game.xml which defines the layout is as follows:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:background="@color/background"
    tools:context="lk.iit.mobiletechnology.mathematicsbraintrainer.GameActivity" >

    <TextView 
        android:id="@+id/time_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:textSize="15sp"
        android:textStyle="bold"
        android:textColor="#000"
        />

    <TextView 
        android:id="@+id/question_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:textSize="15sp"
        android:textStyle="bold"
        android:textColor="#000"
        android:layout_below="@+id/time_text"
        />

    <EditText 
        android:id="@+id/question_input"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:inputType="numberDecimal|numberSigned"
        android:text=" ?"
        android:layout_below="@+id/question_text"
        android:background="#fff"
        />

    <ImageView 
        android:id="@+id/answer_feedback"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingTop="@dimen/image_text_gap"
        android:layout_below="@+id/question_input"
        android:layout_centerHorizontal="true"
        />

    <Button 
        android:id="@+id/test_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Test"
        android:layout_below="@+id/answer_feedback"
        android:layout_centerHorizontal="true"
        />

</RelativeLayout>

Note that this java class still does not cover the entire requirements but it is capable of firing 10 questions during each game play. I have introduced the timer but since the call to timer.start() method I am constantly getting the following exception:

Android IllegalAccessError java.util.concurrent.TimeUnit.toMinutes

Since I am new to this field of development and it is quite rare to find a proper solution to this I would be grateful if somebody can help me by explaining why I am getting this and what kind of solution(s) exist.

This is the logcat content of the exception I am getting:

03-06 01:52:59.328: D/AndroidRuntime(278): Shutting down VM
03-06 01:52:59.328: W/dalvikvm(278): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
03-06 01:52:59.348: E/AndroidRuntime(278): FATAL EXCEPTION: main
03-06 01:52:59.348: E/AndroidRuntime(278): java.lang.IllegalAccessError: tried to access method java.util.concurrent.TimeUnit.toMinutes:(J)V from class lk.iit.mobiletechnology.mathematicsbraintrainer.GameActivity$CountDownMachine
03-06 01:52:59.348: E/AndroidRuntime(278):  at lk.iit.mobiletechnology.mathematicsbraintrainer.GameActivity$CountDownMachine.onTick(GameActivity.java:108)
03-06 01:52:59.348: E/AndroidRuntime(278):  at android.os.CountDownTimer$1.handleMessage(CountDownTimer.java:124)
03-06 01:52:59.348: E/AndroidRuntime(278):  at android.os.Handler.dispatchMessage(Handler.java:99)
03-06 01:52:59.348: E/AndroidRuntime(278):  at android.os.Looper.loop(Looper.java:123)
03-06 01:52:59.348: E/AndroidRuntime(278):  at android.app.ActivityThread.main(ActivityThread.java:4627)
03-06 01:52:59.348: E/AndroidRuntime(278):  at java.lang.reflect.Method.invokeNative(Native Method)
03-06 01:52:59.348: E/AndroidRuntime(278):  at java.lang.reflect.Method.invoke(Method.java:521)
03-06 01:52:59.348: E/AndroidRuntime(278):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
03-06 01:52:59.348: E/AndroidRuntime(278):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
03-06 01:52:59.348: E/AndroidRuntime(278):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

Don't use TimeUnit to convert millis into seconds, minutes and so on, just do it yourself.

int seconds = (millis / 1000) % 60;
int minutes = millis / (1000 * 60);

Apparently you get this error when TimeUnit is not available in your runtime, see here:

Android IllegalAccessError java.util.concurrent.TimeUnit.toHours