Android App to Create a Digital Stopwatch Clock Using Java & XML Using Android Studio for Beginners

Android App to Create a Digital Stopwatch Clock Using Java & XML Using Android Studio for Beginners

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>

XML Code

activity_main.xml

 

 

<?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"

    <!-- Add some background color -->
    android:background="#0F9D58"
    android:padding="16dp"
    tools:context="org.geeksforgeeks.stopwatch.StopwatchActivity">

    <TextView

        <!-- We will use text view "time_view" -->
        <!-- to display the number of seconds. -->
        android:id="@+id/time_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"

        <!-- These below attributes make the stopwatch -->
        <!-- timer nice and big. -->
        android:textAppearance="@android:style/TextAppearance.Large"
        android:textSize="56sp" />

    <Button
        <!-- This code is for the Start 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"

        <!-- When it gets clicked, the Start button -->
        <!-- calls the onClickStart() method. -->
        android:onClick="onClickStart"
        android:text="@string/start" />
    <Button

        <!-- This code is for the Stop 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"

        <!-- When it gets clicked, the Stop button -->
        <!-- calls the onClickStop() method. -->
        android:onClick="onClickStop"
        android:text="@string/stop" />
    <Button

        <!-- This code is for Reset 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"

        <!-- When it gets clicked, the Reset button -->
        <!-- calls the onClickReset() method. -->
        android:onClick="onClickReset"
        android:text="@string/reset" />
</LinearLayout>

Java Code

activity_main.xml

 

 

package org.geeksforgeeks.stopwatch;

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);
            }
        });
    }
}