Last Updated : 12 Jul, 2025
In this article, an Android app is created to display a basic Stopwatch. The layout for Stopwatch includes:
<activity android:name=".StopwatchActivity"></activity>Step 3: Using Resource Files
Add String resources We are going to use three String values in our stopwatch layout, one for the text value of each button. These values are String resources, so they need to be added to strings.xml.
Add the String values below to your version of strings.xml:
Strings.xml
<resources>
<string name="app_name">GFG|Stopwatch</string>
<string name="start">Start</string>
<string name="stop">Stop</string>
<string name="reset">Reset</string>
</resources>
Update the Stopwatch layout code Here is the XML for the layout. It describes a single text view that's used to display the timer, and three buttons to control the stopwatch. Replace the XML currently in activity_stopwatch.xml with the XML shown here: activity_main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="16dp">
<TextView
android:id="@+id/tvMainTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Welcome to MainActivity"
android:textSize="18sp"
android:layout_gravity="center_horizontal"
android:paddingBottom="20dp"/>
<Button
android:id="@+id/btnGoToStopwatch"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Go to Stopwatch"
android:layout_gravity="center_horizontal"/>
</LinearLayout>
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="#0F9D58"
android:padding="16dp"
tools:context=".MainActivity">
<TextView
android:id="@+id/time_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:textAppearance="@android:style/TextAppearance.Large"
android:textSize="56sp" />
<Button
android:id="@+id/start_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginTop="20dp"
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="8dp"
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_gravity="center_horizontal"
android:layout_marginTop="8dp"
android:onClick="onClickReset"
android:text="@string/reset" />
</LinearLayout>
Step 4: How the activity code will work
The layout defines three buttons that we will use to control the stopwatch. Each button uses its onClick attribute to specify which method in the activity should run when the button is clicked. When the Start button is clicked, the onClickStart() method gets called, when the Stop button is clicked the onClickStop() method gets called, and when the Reset button is clicked the onClickReset() method gets called. We will use these methods to start, stop and reset the stopwatch.
We will update the stopwatch using a method we will create called runTimer(). The runTimer() method will run code every second to check whether the stopwatch is running, and, if it is, increment the number of seconds and display the number of seconds in the text view.
To help us with this, we will use two private variables to record the state of the stopwatch. We will use an int called seconds to track how many seconds have passed since the stopwatch started running, and a boolean called running to record whether the stopwatch is currently running.
We will start by writing the code for the buttons, and then we will look at the runTimer() method.
Below is the following code to StopwatchActivity.java:
MainActivity.java
package com.gfg.stopwatch_app_java;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button btnGoToStopwatch = findViewById(R.id.btnGoToStopwatch);
btnGoToStopwatch.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// Create an Intent to start StopwatchActivity
Intent intent = new Intent(MainActivity.this, StopwatchActivity.class);
startActivity(intent);
}
});
}
}StopwatchActivity.javapackage com.gfg.stopwatch_app_java;
import android.app.Activity;
import android.os.Handler;
import android.view.View;
import android.os.Bundle;
import java.util.Locale;
import android.widget.TextView;
public class StopwatchActivity extends Activity {
// Use seconds, running and wasRunning respectively
// to record the number of seconds passed,
// whether the stopwatch is running and
// whether the stopwatch was running
// before the activity was paused.
// Number of seconds displayed
// on the stopwatch.
private int seconds = 0;
// Is the stopwatch running?
private boolean running;
private boolean wasRunning;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_stopwatch);
if (savedInstanceState != null) {
// Get the previous state of the stopwatch
// if the activity has been
// destroyed and recreated.
seconds
= savedInstanceState
.getInt("seconds");
running
= savedInstanceState
.getBoolean("running");
wasRunning
= savedInstanceState
.getBoolean("wasRunning");
}
runTimer();
}
// Save the state of the stopwatch
// if it's about to be destroyed.
@Override
public void onSaveInstanceState(
Bundle savedInstanceState)
{
savedInstanceState
.putInt("seconds", seconds);
savedInstanceState
.putBoolean("running", running);
savedInstanceState
.putBoolean("wasRunning", wasRunning);
}
// If the activity is paused,
// stop the stopwatch.
@Override
protected void onPause()
{
super.onPause();
wasRunning = running;
running = false;
}
// If the activity is resumed,
// start the stopwatch
// again if it was running previously.
@Override
protected void onResume()
{
super.onResume();
if (wasRunning) {
running = true;
}
}
// Start the stopwatch running
// when the Start button is clicked.
// Below method gets called
// when the Start button is clicked.
public void onClickStart(View view)
{
running = true;
}
// Stop the stopwatch running
// when the Stop button is clicked.
// Below method gets called
// when the Stop button is clicked.
public void onClickStop(View view)
{
running = false;
}
// Reset the stopwatch when
// the Reset button is clicked.
// Below method gets called
// when the Reset button is clicked.
public void onClickReset(View view)
{
running = false;
seconds = 0;
}
// Sets the NUmber of seconds on the timer.
// The runTimer() method uses a Handler
// to increment the seconds and
// update the text view.
private void runTimer()
{
// Get the text view.
final TextView timeView
= (TextView)findViewById(
R.id.time_view);
// Creates a new Handler
final Handler handler
= new Handler();
// Call the post() method,
// passing in a new Runnable.
// The post() method processes
// code without a delay,
// so the code in the Runnable
// will run almost immediately.
handler.post(new Runnable() {
@Override
public void run()
{
int hours = seconds / 3600;
int minutes = (seconds % 3600) / 60;
int secs = seconds % 60;
// Format the seconds into hours, minutes,
// and seconds.
String time
= String
.format(Locale.getDefault(),
"%d:%02d:%02d", hours,
minutes, secs);
// Set the text view text.
timeView.setText(time);
// If running is true, increment the
// seconds variable.
if (running) {
seconds++;
}
// Post the code again
// with a delay of 1 second.
handler.postDelayed(this, 1000);
}
});
}
}
Output:
Output of Stopwatch App.RetroSearch is an open source project built by @garambo | Open a GitHub Issue
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HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4