Java why hangs while loop in background thread?

Question

Java

Good afternoon, I just started learning Java + android studio and immediately ran into a problem: I am writing a simple application - I want the button to start / stop the counter (1,2,3,4 ......)
I can’t understand why the application freezes and stops answer if in the background thread I do the counter in the while loop.
here is the code:

public class MainActivity extends AppCompatActivity {
private Button my_button;
private boolean  start_stop = false;
private int counter = 0;
private TextView my_text;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    my_button = findViewById(R.id.My_Button);
    my_text = findViewById(R.id.my_text);
}
public void onClick_button(View view) {
    if(start_stop != true) {
        my_button.setText("STOP");
        start_stop = true;

       runOnUiThread(new Runnable() {
            @Override
            public void run() {
                while (start_stop) {
                    my_text.setText(Integer.toString(counter));
                    counter++;
                    try {
                        Thread.sleep(1000);     // sleep 1 sec
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        });

    }else {
        my_button.setText("START");
        start_stop = false;
    }
}
@Override
protected void onDestroy() {
    super.onDestroy();
    start_stop = false;
}

Answer 1

as usual, the solution was found on Stackoverflow

package com.example.switch_pictures;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private Button my_button;
    private boolean  start_stop = false;
    private int counter = 0;
    private TextView my_text;


        @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        my_button = findViewById(R.id.My_Button);
        my_text = findViewById(R.id.my_text);


        }
    public void onClick_button(View view) {
        if(start_stop != true) {
            my_button.setText("STOP");
            start_stop = true;

            new Thread(new Runnable() {
                @Override
                public void run() {
                    while (start_stop) {
                        runOnUiThread(new Runnable() {
                            @Override
                            public void run() {
                                my_text.setText(Integer.toString(counter));
                            }
                        });
                        counter++;
                        try {
                            Thread.sleep(100);     // sleep 1 sec
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }).start();


        }else {
            my_button.setText("START");
            start_stop = false;
        }
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        start_stop = false;
    }


}

Answer 2

runOnUiThread runs on the main thread, which is why the application hangs