App crashes after just one iteration. It didn't run at all without a runnable. And now it crashes after the first iteration

Question

 package com.example.chirag.example;

 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.view.View;
 import android.widget.Button;
 import android.widget.TextView;

 import java.util.Random;


 public class MainActivity extends AppCompatActivity {
TextView TV;
Button upbutton;
Button downbutton;
TextView score;
String n1;
int bool=0;
int a;
int b;
int sc=0;

@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    TextView TV = (TextView)findViewById(R.id.TV);
    TextView score = (TextView)findViewById(R.id.score);
    Button upbutton = (Button) findViewById(R.id.upbutton);
    Button downbutton = (Button) findViewById(R.id.downbutton);
    Button start = (Button) findViewById(R.id.start);
    n1 = generate();
    TV.setText(n1);
    start.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            start();
        }
    });
}
String generate()
{
    TextView TV = (TextView)findViewById(R.id.TV);
    int n = new Random().nextInt(20);
    String s = String.valueOf(n);
    return s;
}
void start() {
    Runnable  myRunnable = new Runnable() {
        @Override
        public void run()
        {while (bool == 0) {
            final TextView TV = (TextView) findViewById(R.id.TV);
            final TextView score = (TextView) findViewById(R.id.score);
            Button upbutton = (Button) findViewById(R.id.upbutton);
            Button downbutton = (Button) findViewById(R.id.downbutton);
            Button start = (Button) findViewById(R.id.start);
            String n2 = generate();
            TV.setText(n2);

            a = Integer.valueOf(n1.toString());
            b = Integer.valueOf(n2.toString());
            if (a > b) {
                downbutton.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        String n3 = generate();
                        TV.setText(n3);
                        a = b;
                        b = Integer.valueOf(n3.toString());
                        score.setText("Score" + (sc + 1));
                    }
                });
                upbutton.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        TV.setText("Game Over");
                        bool = 1;
                    }
                });
            } else {
                upbutton.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        String n3 = generate();
                        TV.setText(n3);
                        a = b;
                        b = Integer.valueOf(n3.toString());
                        score.setText("Score" + (sc + 1));
                    }
                });
                downbutton.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        TV.setText("Game Over");
                        bool = 1;
                    }
                });
            }
        }

        }
    };


    Thread myThread = new Thread(myRunnable);
    myThread.start();

}

}

I have put the code in a runnable. The logic seems correct but it doesn't work. the generate method creates a new number and displays it in 'TV'. when start is clicked, a new number is generated and the second number is compared with the first. if the correct button( up or down) is pressed, the score is increased and the process is continued. "Game Over" if the wrong button is clicked

Please post logact and show us where the application crash at. — Gilad Eshkoli, Jul 24 '16 at 06:17
Hey. Could i have your email id please? i would love to clarify some doubts! — Chirag, Jul 24 '16 at 08:27

score 1 · Accepted Answer · answered Jul 24 '16 at 06:38

1

You can't touch the UI from another Thread. All the UI tasks in Android should be performed in the main thread also called UI Thread. This line (for example) tries to affect the ui from inside the run() command of non-main thread:

 TV.setText(n2);

For information about how to communicate with UI Thread refer to this tutorial

answered Jul 24 '16 at 06:38

Evgeniy Mishustin

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Hey. A loop needs a runnable to execute properly. And UI tasks cannot be updated in a thread. What if my program requires me to update my tasks in a loop? – Chirag Jul 24 '16 at 13:06
you need to get an Instance of main looper and update your UI via that instance or to use runOnUiThread method. Look here http://stackoverflow.com/a/13974916/2031068 – Evgeniy Mishustin Jul 24 '16 at 13:09
I replaced every task in the thread in the runnable with a handler. now, every time i click start, it crashes! :( – Chirag Jul 24 '16 at 13:50

App crashes after just one iteration. It didn't run at all without a runnable. And now it crashes after the first iteration

1 Answers1