AlarmManager Android

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To access the system alarm in Android, the Android AlarmManager is used. It is used to schedule an application to run at a specific time in the future, that works whether the phone is running or not. To guarantee not to sleep the phone until the broadcast is handled, a CPU wake lock is held by the Android AlarmManager.

Android AlarmManager Example:

In the below example, we are demonstrating the usage of the AlarmManager to run the alarm after a specific time provided by the user.

activity_main.xml:

In the activity_main.xml file, we will drag an EditText and a button.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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"
    tools:context="MainActivity">
    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Alarm"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="103dp" />
    <EditText
        android:id="@+id/time"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="22dp"
        android:ems="10" />
</RelativeLayout>

Activity class:(File: MainActivity.java)

In the MainActivity.java file, we will write the code to start the alarm service when the user clicks on the button.

package com.example.radioapp;
 
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
    Button start;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        start = findViewById(R.id.button);
        start.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                startAlert();
            }
        });
    }
    public void startAlert() {
        EditText text = findViewById(R.id.time);
        int i = Integer.parseInt(text.getText().toString());
        Intent intent = new Intent(this, MyBroadcastReceiver.class);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(this.getApplicationContext(), 234324243, intent, 0);
        AlarmManager alarmManager = (AlarmManager)getSystemService(ALARM_SERVICE);
        alarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + (i * 1000), pendingIntent);
        Toast.makeText(this, "Alarm set:: " + i + " seconds", Toast.LENGTH_LONG).show();
    }
}

BroadcastReceiver class:(File: MyBroadcastReceiver.java)

In the MyBroadcastReceiver class, we will write the code to start the alarm.:

package com.example.radioapp;
 
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.media.MediaPlayer;
import android.widget.Toast;
class MyBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        MediaPlayer mp=MediaPlayer.create(context, R.raw.alarm);
        mp.start();
        Toast.makeText(context, "Alarm....", Toast.LENGTH_LONG).show();
    }
}

Manifest file:(File: AndroidManifest.xml)

In the AndroidManifest.xml file, we will provide a receiver entry.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.radioapp">
    <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>
 
        <receiver android:name=".MyBroadcastReceiver" ></receiver>
    </application>
</manifest>

Output 1:

Output 2: