Android AlarmManager exmaple

Output:

1/ Modify your AndroidManifest.xml

<uses-permission android:name="android.permission.POST_NOTIFICATIONS"/>
<uses-permission android:name="com.android.alarm.permission.SET_ALARM" />
<uses-permission android:name="android.permission.SCHEDULE_EXACT_ALARM" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<uses-permission android:name="android.permission.USE_EXACT_ALARM" />
<uses-permission android:name= "android.permission.VIBRATE" />

2/Modify your 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:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    android:orientation="vertical">

    <TimePicker
        android:id="@+id/time"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:timePickerMode="clock"/>




    <Button
        android:id="@+id/set_alarm"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Set Alarm"
        android:layout_gravity="center_horizontal">
    </Button>




    <Button
        android:id="@+id/EXIT"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="EXIT"
        android:layout_gravity="center_horizontal">
    </Button>


</LinearLayout>

package com.tutorialb.alarmmanager;

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TimePicker;
import android.widget.Toast;
import androidx.activity.EdgeToEdge;
import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
import java.util.Calendar;
import java.util.Random;
import android.os.Bundle;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private TimePicker tp;
    private Button setTime;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        tp = findViewById(R.id.time);
        setTime = findViewById(R.id.set_alarm);
        setTime.setOnClickListener(this);
        Button EXIT = (Button)findViewById(R.id.EXIT);
        EXIT.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                finish();
                System.exit(0);
            }
        });

    }

    @RequiresApi(api = Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
    @Override
    public void onClick(View v) {


        Calendar calendar = Calendar.getInstance();
        calendar.set(calendar.get(Calendar.YEAR),
                calendar.get(Calendar.MONTH),
                calendar.get(Calendar.DAY_OF_MONTH),
                tp.getHour(),
                tp.getMinute(),0);


        setExactAlarm(calendar.getTimeInMillis(), 1);


    }




    @RequiresApi(api = Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
    public void setExactAlarm(long triggerAtMillis, int requestCode) {


        AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
        Intent intent = new Intent(MainActivity.this, Alarm.class);


        PendingIntent pendingIntent = PendingIntent.getBroadcast(MainActivity.this, requestCode, intent,
                PendingIntent.FLAG_UPDATE_CURRENT | PendingIntent.FLAG_IMMUTABLE);


        if (alarmManager != null) {
            alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP,triggerAtMillis, pendingIntent);
        }
        else{
            alarmManager.cancelAll();
            alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP,triggerAtMillis, pendingIntent);
        }
        Toast.makeText(this, "Set Alarm", Toast.LENGTH_SHORT).show();
    }



}

4/ Create a Alarm Class and Modify

package com.tutorialb.alarmmanager;


import android.Manifest;
import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.media.Ringtone;
import android.media.RingtoneManager;
import android.net.Uri;
import android.os.Build;
import android.os.Handler;
import android.widget.Toast;

import androidx.annotation.RequiresApi;
import androidx.core.app.ActivityCompat;
import androidx.core.app.NotificationCompat;
import androidx.core.app.NotificationManagerCompat;







public class Alarm extends BroadcastReceiver {

    public static final String CHANNEL_ID = "alarm_channel";
    public static final int NOTIFICATION_ID = 1;
    private Ringtone ringtone;


    @RequiresApi(api = Build.VERSION_CODES.P)
    @Override
    public void onReceive(Context context, Intent intent) {


        playAlarmSound(context);


        Toast.makeText(context, "Ringing", Toast.LENGTH_SHORT).show();
        NotificationChannel channel = new NotificationChannel(
                CHANNEL_ID, "Alarm Channel", NotificationManager.IMPORTANCE_HIGH);
        channel.setLockscreenVisibility(Notification.VISIBILITY_PUBLIC);
        NotificationManager notificationManager = context.getSystemService(NotificationManager.class);
        notificationManager.createNotificationChannel(channel);


        NotificationCompat.Builder builder = new NotificationCompat.Builder(context, CHANNEL_ID)
                .setSmallIcon(R.drawable.baseline_notifications_active_24)
                .setContentTitle("Your Alarm")
                .setContentText("Wake up Alarm is ringing")
                .setPriority(NotificationCompat.PRIORITY_HIGH)
                .setCategory(NotificationCompat.CATEGORY_ALARM)
                .setAutoCancel(true)
                .setOngoing(true);


        NotificationManagerCompat notificationManagerCompact = NotificationManagerCompat.from(context);
        if (ActivityCompat.checkSelfPermission(context, Manifest.permission.POST_NOTIFICATIONS) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        }
        notificationManagerCompact.notify(NOTIFICATION_ID, builder.build());


    }


    public void playAlarmSound(Context context) {
        Uri alarmUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_ALARM);
        if (alarmUri == null)
            alarmUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
        ringtone = RingtoneManager.getRingtone(context, alarmUri);
        if (ringtone != null) {
            ringtone.play();
        }
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                stopAlarmSound();
            }
        }, 5000);
    }


    public void stopAlarmSound() {
        if (ringtone != null && ringtone.isPlaying()) {
            ringtone.stop();
        }

    }
}