How to Build a StopWatch Application in Android Studio.

Steps:

1. First of all, create a new project and name it.

2. After doing so, we will see two files opened in front of us, So in the file activity_main.xml, we will write the following code:

<?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"
   android:orientation="vertical"
   android:background="#C0E7EC"
   android:padding="16dp"
   tools:context="com.ProjectGurukul.stopwatch.MainActivity">

<TextView
   android:id="@+id/time_view"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_gravity="center_horizontal"
   android:layout_marginTop="100dp"
   android:background="@drawable/border"
   android:textAppearance="@android:style/TextAppearance.Large"
   android:textSize="50dp" />

   <Button
   android:id="@+id/start_button"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_gravity="center_horizontal"
   android:layout_marginTop="50dp"
   android:onClick="onClickStart"
   android:text="@string/start" />

   <Button
   android:id="@+id/stop_button"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_gravity="center_horizontal"
   android:layout_marginTop="50dp"
   android:onClick="onClickStop"
   android:text="@string/stop" />

   <Button
   android:id="@+id/reset_button"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_marginTop="50dp"
   android:layout_gravity="center_horizontal"
   android:onClick="onClickReset"
   android:text="@string/reset" />
</LinearLayout>

In the above code, we have added the UI components for our application like buttons and textview.

3. After writing the code for activity_main.xml we’ll write the following code in MainActivity.java file:

package com.Example.stopwatch;

import android.os.Bundle;
import android.app.Activity;
import android.os.Handler;
import android.view.View;
import java.util.Locale;
import android.widget.TextView;

public class MainActivity extends Activity {
   private int sec = 0;
   private boolean is_running;
   private boolean was_running;

   @Override
   protected void onCreate(Bundle savedInstanceState)
   {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
       if (savedInstanceState != null) {
           sec = savedInstanceState.getInt("seconds");
           is_running = savedInstanceState.getBoolean("running");
           was_running = savedInstanceState .getBoolean("wasRunning");
       }
       running_Timer();
   }

   @Override
   public void onSaveInstanceState(
           Bundle savedInstanceState)
   {
       savedInstanceState.putInt("seconds", sec);
       savedInstanceState.putBoolean("running", is_running);
       savedInstanceState.putBoolean("wasRunning", was_running);
   }

   @Override
   protected void onPause()
   {
       super.onPause();
       was_running = is_running;
       is_running = false;
   }

   @Override
   protected void onResume()
   {
       super.onResume();
       if (was_running) {
           is_running = true;
       }
   }

   public void onClickStart(View view)
   {
       is_running = true;
   }

   public void onClickStop(View view)
   {
       is_running = false;
   }

   public void onClickReset(View view)
   {
       is_running = false;
       sec = 0;
   }

   private void running_Timer()
   {

       final TextView t_View = (TextView)findViewById(R.id.time_view);
       final Handler handle = new Handler();

       handle.post(new Runnable() {
           @Override

           public void run()
           {
               int hrs = sec / 3600;
               int mins = (sec % 3600) / 60;
               int secs = sec % 60;

               String time_t = String .format(Locale.getDefault(), "    %d:%02d:%02d   ", hrs,mins, secs);

               t_View.setText(time_t);

               if (is_running) {
                   sec++;
               }

               handle.postDelayed(this, 1000);
           }
       });
   }
}

4. After writing this, we’ll add the following in the string.xml file present in the resource folder

<resources>
   <string name="app_name">ProjectGurukul Stopwatch</string>
   <string name="start"> Start </string>
   <string name="reset"> Reset </string>
   <string name="stop"> Stop </string>
</resources>

5. Now, we’ll create a folder in the res drawable file and name it as Border.xml. In this file, we will make a border for the Textview for the time, so it looks better. After creating the file write the following code in it:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:shape="rectangle">
   <stroke
       android:width="2dp"
       android:color="#932424"
   />
</shape>