Alarm Manager

Uma opção para efetuar operações baseadas em tempo.

Para mais detalhes: GOOGLE DEVELOPERS. Disponível em: https://developer.android.com/training/scheduling/alarms?hl=pt-br#java. Acesso em: 27 ago. 2025.

Exemplo 01:

No arquivo AndroidManifest.xml acrescente <receiver android:name=".MyBroadcastReceiver"/>

activity_main.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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
    <TextView
        android:id="@+id/textViewMensagem"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.java

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 androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import java.util.Calendar;
public class MainActivity extends AppCompatActivity {
    private AlarmManager alarmManager;
    private PendingIntent pendingIntent;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    @Override
    protected void onStart() {
        super.onStart();
        disparar();
    }
    private void disparar() {
        alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
        Intent intent = new Intent(this, MyBroadcastReceiver.class);
        int flags = PendingIntent.FLAG_UPDATE_CURRENT;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
            flags |= PendingIntent.FLAG_IMMUTABLE;
        }
        pendingIntent = PendingIntent.getBroadcast(this, 0,
                intent, flags);
        Calendar calendar = Calendar.getInstance();
        calendar.setTimeInMillis(System.currentTimeMillis());
        calendar.set(Calendar.HOUR_OF_DAY, 20);
        calendar.set(Calendar.MINUTE, 38);
        alarmManager.set(AlarmManager.RTC_WAKEUP,
                calendar.getTimeInMillis() + 2000, pendingIntent);
    }
}

MyBroadcastReceiver.java

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
import android.widget.Toast;
public class MyBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Log.d("TAG", "hora de estudar!!");
    }
}

Exemplo 02:

No arquivo AndroidManifest.xml acrescente a tag <receiver android:name=".MyBroadcastReceiver"/>

MyBroadcastReceiver.java

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
import android.widget.Toast;
public class MyBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        int num = intent.getIntExtra("numeroGerado", 0);
        Log.d("TAG","Número gerado: " + num);
    }
}

activity_main.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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
    <TextView
        android:id="@+id/textViewHello"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:onClick="disparar"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.os.SystemClock;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;
import java.util.Random;
public class MainActivity extends AppCompatActivity {
    private AlarmManager alarmManager;
    private PendingIntent pendingIntent;
    private Integer numeroGerado;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TextView textViewHello = findViewById(R.id.textViewHello);
        numeroGerado = gerarNumero();
        Log.d("TAG",numeroGerado.toString());
        Toast.makeText(this, "Número sorteado: " + numeroGerado, Toast.LENGTH_SHORT).show();
    }
    private int gerarNumero() {
        Random random = new Random();
        return random.nextInt(10);
    }
    public void disparar(View view) {
        if (view.getId() == R.id.textViewHello) {
            Toast.makeText(this, "Clicado!", Toast.LENGTH_SHORT).show();
            alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
            Intent i = new Intent(this, MyBroadcastReceiver.class);
            i.putExtra("numeroGerado", numeroGerado);
            int flags = PendingIntent.FLAG_UPDATE_CURRENT;
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
                flags |= PendingIntent.FLAG_IMMUTABLE;
            }
            pendingIntent = PendingIntent.getBroadcast(this, 0, i, flags);
            alarmManager.set(
                    AlarmManager.ELAPSED_REALTIME_WAKEUP,
                    SystemClock.elapsedRealtime() + 60 * 1000,
                    pendingIntent
            );
        }
    }
}