Chronometer in Kotlin

Android ChronoMeter is user interface control which shows timer in the view. We can easily start up or down counter with base time using the chronometer widget. By default, start() method can assume base time and starts the counter.
Generally, we can create use ChronoMeter widget in XML layout but we can do it programmatically also.

First we create a new project by following the below steps: 

1. Click on File, then New => New Project.
2. After that include the Kotlin support and click on next.
3. Select the minimum SDK as per convenience and click next button.
4. Then select the Empty activity => next => finish.

Different attributes for ChronoMeter widget

XML attributes	Description
android:id	Used to specify the id of the view.
android:textAlignment	Used to the text alignment in the dropdown list.
android:background	Used to set the background of the view.
android:padding	Used to set the padding of the view.
android:visibility	Used to set the visibility of the view.
android:gravity	Used to specify the gravity of the view like center, top, bottom, etc
android:format	Used to define the format of the string to be displayed.
android:countDown	Used to define whether the chronometer will count up or count down.

Modify activity_main.xml file

In this file, we use the ChronoMeter widget along with a button to start or stop the meter and also set attributes for both of them.

XML

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:id="@+id/constraint_layout">


    <Chronometer
        android:id="@+id/c_meter"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="20dp"
        android:layout_marginStart="68dp"
        android:layout_marginTop="256dp"
        android:layout_marginEnd="68dp"
        android:layout_marginBottom="28dp"
        android:textAppearance="@style/TextAppearance.AppCompat.Large"
        android:textColor="#092FEC"
        android:textSize="36sp"
        app:layout_constraintBottom_toTopOf="@+id/btn"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="163dp"
        android:layout_marginTop="20dp"
        android:layout_marginEnd="163dp"
        android:text="@string/start"
        app:layout_constraintEnd_toEndOf="@id/c_meter"
        app:layout_constraintHorizontal_bias="0.485"
        app:layout_constraintStart_toEndOf="@+id/c_meter"
        app:layout_constraintStart_toStartOf="@id/c_meter"
        app:layout_constraintTop_toBottomOf="@+id/c_meter" />

</androidx.constraintlayout.widget.ConstraintLayout>

Update strings.xml file

Here, we update the name of the application using the string tag. We also other strings which can be used in MainActivity.kt file. 

XML

<resources>
    <string name="app_name">ChronometerInKotlin</string>
    <string name="stop">Stop Timer</string>
    <string name="start">Start Timer</string>
    <string name="working">Started</string>
    <string name="stopped">Stopped</string>
</resources>

Access ChronoMeter in MainActivity.kt file

First, we declare a variable meter to access the Chronometer from the XML layout file. 

val meter = findViewById<Chronometer>(R.id.c_meter)

then, we access the button from the xml file and set setOnClickListener to start and stop the timer. 

val btn = findViewById<Button>(R.id.btn)
        btn?.setOnClickListener(object : View.OnClickListener {...}

Kotlin

package com.geeksforgeeks.myfirstkotlinapp

import androidx.appcompat.app.AppCompatActivity

import android.os.Bundle
import android.widget.Button
import android.view.View
import android.widget.Chronometer
import android.widget.Toast

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // access the chronometer from XML file
        val meter = findViewById<Chronometer>(R.id.c_meter)

        //access the button using id
        val btn = findViewById<Button>(R.id.btn)
        btn?.setOnClickListener(object : View.OnClickListener {

            var isWorking = false

            override fun onClick(v: View) {
                if (!isWorking) {
                    meter.start()
                    isWorking = true
                } else {
                    meter.stop()
                    isWorking = false
                }

                btn.setText(if (isWorking) R.string.start else R.string.stop)

                Toast.makeText(this@MainActivity, getString(
                    if (isWorking)
                        R.string.working
                    else
                        R.string.stopped),
                    Toast.LENGTH_SHORT).show()
            }
        })
    }
}

AndroidManifest.xml file

XML

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.geeksforgeeks.myfirstkotlinapp">

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

</manifest>

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