Counter

activity_main.xml


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
 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"
 tools:context=".MainActivity"
 tools:ignore="Deprecated">
 <TextView
 android:id="@+id/idDisplay"
 android:layout_width="181dp"
 android:layout_height="40dp"
 android:layout_x="16dp"
 android:layout_y="16dp"
 android:gravity="center"
 android:hint="press start to begin"/>
 <Button
 android:id="@+id/idStart"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_x="16dp"
 android:layout_y="61dp"
 android:text="start"/>
 <Button
 android:id="@+id/idStop"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_x="110dp"
 android:layout_y="61dp"
 android:text="stop"/>
</LinearLayout>

MainActivity.java


package com.example.program5;
import android.os.Bundle;
import android.view.View;
import android.os.Handler;
import android.os.Message;
import android.widget.Button;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity implements View.OnClickListener, Runnable {
 Thread th;
 int count = 0;
 TextView display;
 Button start, stop;
 Boolean isRunning = false;
 @Override
 protected void onCreate(Bundle b) {
 super.onCreate(b);
 setContentView(R.layout.activity_main);
 display = findViewById(R.id.idDisplay);
 start = findViewById(R.id.idStart);
 stop = findViewById(R.id.idStop);
 start.setOnClickListener(this);
 stop.setOnClickListener(this);
 }
 @Override
 public void onClick(View v) {
 if(v.equals(start)){
 isRunning = true;
 th = new Thread(this);
 th.start();
 }
 else if(v.equals(stop)){
 isRunning = false;
 }
 }
 Handler h = new Handler(){
 @Override
 public void handleMessage(Message msg) {
 display.setText(""+msg.what);
 }
 };
 public void run(){
 while(isRunning){
 try {
 Thread.sleep(1000);
 } catch (InterruptedException e) {
 e.printStackTrace();
 }
 count++;
 h.sendEmptyMessage(count);
 }
 }
}