In this android example tutorial, we will learn how to create background task with alarm manager in android studio using kotlin language.
AlarmManager: AlarmManager acts as a link between the application and the Android system alarm service. It can send a broadcast to your app (which the user can entirely discontinue) at a certain time, and your app can then conduct any task as a result. The system can postpone any alarm in order to improve device performance.
Task scheduling is occasionally necessary. For example, your apps may be required to perform a specific task on a daily basis at a time specified by the user. Then we may use Android's AlarmManager to do it. So let's get started.
Implementation:
Step 1. Create a new Project in android studio.
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Go to File > New > New Project > Google Maps Activity > Next > Enter Name > Select Language Kotlin > Finish.
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After creating the new project, Android Studio starts Gradle and builds your project, which may take a few seconds.
Step2. The following UI will be created within activity_main.xml file. We only have a TimePicker and a Button in this case.
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<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:gravity="center"
android:padding="10dp"
android:orientation="vertical"
tools:context=".MainActivity">
<TimePicker
android:id="@+id/timePicker"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="@+id/buttonAlarm"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Set Alarm" />
</LinearLayout>
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TimePicker: The Android TimePicker is a user interface control that allows you to select the time in 24-hour format or AM/PM mode. It is utilised in our application to verify that users select the correct time for the day.
Above xml code will give you output like this.
Step 3. Create a new kotlin file in project name AlarmReceiver.
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app > java > com.example.alarmmanager > right-click > new > Kotlin Class/File > Enter Name (AlarmReceiver) > Enter.
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Step 4. Open AlarmReceiver.kt file and add the following code
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class AlarmReciever : BroadcastReceiver() {
override fun onReceive(p0: Context?, p1: Intent?) {
//you can check the log that it is fired
//Here we are actually not doing anything
//but you can do any task here that you want to be done at a specific time everyday
Log.d("MyAlarm", "Alarm is just fired");
}
}
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Broadcast Receivers merely reply to broadcast messages sent by other apps or the system. These signals are sometimes referred to as happenings or intentions. A broadcast receiver is implemented as a subclass of BroadcastReceiver class and overriding the onReceive() method where each message is received as a Intent object parameter.
Step 5. Registering BroadcastReceiver
This BroadcastReceiver must also be registered in the Manifest file. So, in the AndroidManifest.xml file, immediately before the tag.
<receiver
android:name=".AlarmReciever"
android:enabled="true"
android:exported="true" /> |
Step 6. Go to MainActivity.kt file and add the following code
Instantiate the views by its unique id of TimePicker and Button.
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val timePicker = findViewById(R.id.timePicker)
val setAlarm = findViewById(R.id.buttonAlarm)
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Attach onClick event on button
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setAlarm.setOnClickListener(object : View.OnClickListener {
override fun onClick(view: View?) {
//We need a calendar object to get the specified time in millis
//as the alarm manager method takes time in millis to setup the alarm
val calendar: Calendar = Calendar.getInstance()
if (Build.VERSION.SDK_INT >= 23) {
calendar.set(
calendar.get(Calendar.YEAR),
calendar.get(Calendar.MONTH),
calendar.get(Calendar.DAY_OF_MONTH),
timePicker.hour,
timePicker.minute,
0
)
} else {
calendar.set(
//Calculating the current year i.e. 2022
calendar.get(Calendar.YEAR),
// Calculating the current month i.e. Jan (01)
calendar.get(Calendar.MONTH),
// Day of month i.e. Thursday
calendar.get(Calendar.DAY_OF_MONTH),
// Current hour i.e. 10
timePicker.currentHour,
// Current minute i.e. 10:20
timePicker.currentMinute,
0
)
}
setAlarm(calendar.getTimeInMillis())
}
})
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Build.VERSION>SDK_INT >= 23 (Check if we're running on Android 6.0 or higher)
Create a function setAlarm for setting up the alarm
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private fun setAlarm(time: Long) {
//getting the alarm manager
val am = getSystemService(ALARM_SERVICE) as AlarmManager
//creating a new intent specifying the broadcast receiver
val i = Intent(this, AlarmReciever::class.java)
//creating a pending intent using the intent
val pi = PendingIntent.getBroadcast(this, 0, i, 0)
//setting the repeating alarm that will be fired every day
am.setRepeating(AlarmManager.RTC, time, AlarmManager.INTERVAL_DAY, pi)
Toast.makeText(this, "Alarm is set", Toast.LENGTH_SHORT).show()
}
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Step 7. Now run the app in your emulator or real device, you will get the following output:
OUTPUT:
Even if you close your application after setting the alarm. The method will be called at the time indicated. And as a scheduled task, you can perform whatever you want. Right now, it will do nothing and will output a message to the log, as shown below.
Complete Source Code of Alarm Manager Example:
activity_main.xml file
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<?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:gravity="center"
android:padding="10dp"
android:orientation="vertical"
tools:context=".MainActivity">
<TimePicker
android:id="@+id/timePicker"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="@+id/buttonAlarm"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Set Alarm" />
</LinearLayout>
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MainActivity.kt file
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import android.app.AlarmManager
import android.app.PendingIntent
import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Toast
import android.os.Build
import android.view.View
import android.widget.Button
import android.widget.TimePicker
import java.util.*
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
//Instantiate the views TimePicker and Button
val timePicker = findViewById(R.id.timePicker)
val setAlarm = findViewById(R.id.buttonAlarm)
//attaching clicklistener on setAlarm button
setAlarm.setOnClickListener(object : View.OnClickListener {
override fun onClick(view: View?) {
//We need a calendar object to get the specified time in millis
//as the alarm manager method takes time in millis to setup the alarm
val calendar: Calendar = Calendar.getInstance()
if (Build.VERSION.SDK_INT >= 23) {
calendar.set(
calendar.get(Calendar.YEAR),
calendar.get(Calendar.MONTH),
calendar.get(Calendar.DAY_OF_MONTH),
timePicker.hour,
timePicker.minute,
0
)
} else {
calendar.set(
calendar.get(Calendar.YEAR),
calendar.get(Calendar.MONTH),
calendar.get(Calendar.DAY_OF_MONTH),
timePicker.currentHour,
timePicker.currentMinute,
0
)
}
setAlarm(calendar.getTimeInMillis())
}
})
}
private fun setAlarm(time: Long) {
//getting the alarm manager
val am = getSystemService(ALARM_SERVICE) as AlarmManager
//creating a new intent specifying the broadcast receiver
val i = Intent(this, AlarmReciever::class.java)
//creating a pending intent using the intent
val pi = PendingIntent.getBroadcast(this, 0, i, 0)
//setting the repeating alarm that will be fired every day
am.setRepeating(AlarmManager.RTC, time, AlarmManager.INTERVAL_DAY, pi)
Toast.makeText(this, "Alarm is set", Toast.LENGTH_SHORT).show()
}
}
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AlarmReceiver.kt file
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import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.util.Log
class AlarmReciever : BroadcastReceiver() {
override fun onReceive(p0: Context?, p1: Intent?) {
//you can check the log that it is fired
//Here we are actually not doing anything
//but you can do any task here that you want to be done at a specific time everyday
Log.d("MyAlarm", "Alarm is just fired");
}
}
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AndroidManifest.xml file
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<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.alarmmanagerandroid">
<uses-permission android:name="android.permission.SET_ALARM"></uses-permission>
<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/Theme.AlarmManagerAndroid">
<activity
android:name=".MainActivity"
android:exported="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<receiver
android:name=".AlarmReciever"
android:enabled="true"
android:exported="true" />
</application>
</manifest>
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Conclusion: In this article we have covered how to create Background task with alarm manager in Android apps using Kotlin language.
