TrafficSim/app/src/main/java/de/hems/trafficsim/MainActivity.java

package de.hems.trafficsim;

import androidx.appcompat.app.AppCompatActivity;
import androidx.constraintlayout.widget.ConstraintLayout;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.util.Observable;
import java.util.Observer;

public class MainActivity extends AppCompatActivity implements Observer {

    protected Track track;
    protected TrackView trackView;
    protected Worker worker;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        this.track = new Track(25, 100);
        this.trackView = new TrackView(this, this.track);
        this.track.addObserver(this);
        ConstraintLayout layout = (ConstraintLayout) findViewById(R.id.constr_layout);
        layout.addView(this.trackView);
    }

    @Override
    public void update(Observable observable, Object o) {
        final Track trackRef = this.track;
        final TrackView viewRef = this.trackView;
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                String s = "";
                for (Vehicle v: trackRef.getVehicles()){
                    s+= "Vehicle " + v.id + "   |   "
                            + "Pos = " + v.getPosition() + "   |   "
                            + "Vel = " + v.getCurVelocity()+ "   |   "
                            + "\n";
                    ;
                }
                TextView view = (TextView) findViewById(R.id.debugTextView);
                view.setText(s);
                view.invalidate();
                viewRef.invalidate();
            }
        });

    }

    public void onStepButtonClick(View view) {
        //for (int j = 0; j < 3000; j++) {
            this.track.timeElapse(50);
        //}
    }

    public void onPlayButtonClick(View view) {
        Button playButton = (Button) findViewById(R.id.playButton);
        playButton.setEnabled(false);
        Button stepButton = (Button) findViewById(R.id.stepButton);
        stepButton.setEnabled(false);
        Button stopButton = (Button) findViewById(R.id.stopButton);
        stopButton.setEnabled(true);

        this.worker = new Worker(track);
        this.worker.start();
    }

    public void onStopButtonClick(View view) {
        Button playButton = (Button) findViewById(R.id.playButton);
        playButton.setEnabled(true);
        Button stepButton = (Button) findViewById(R.id.stepButton);
        stepButton.setEnabled(true);
        Button stopButton = (Button) findViewById(R.id.stopButton);
        stopButton.setEnabled(false);

        this.worker.setStop(true);
        try {
            this.worker.join();
        } catch (InterruptedException ex) {

        }
    }
}