Crear notificaciones en Android

En el Manifest:

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

package="com.lvsistemas.mynotificacion">

<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=".EstrellasActivity"

android:parentActivityName=".MainActivity" >

<meta-data

android:name="android.support.PARENT_ACTIVITY"

android:value=".MainActivity"/>

</activity>

<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>

En el MainActivity:

package com.lvsistemas.mynotificacion;

import androidx.appcompat.app.AppCompatActivity;

import androidx.core.app.NotificationCompat;

import androidx.core.app.NotificationManagerCompat;

import android.app.Notification;

import android.app.NotificationChannel;

import android.app.NotificationManager;

import android.app.PendingIntent;

import android.app.TaskStackBuilder;

import android.content.Intent;

import android.graphics.Color;

import android.os.Build;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

public class MainActivity extends AppCompatActivity {

private PendingIntent pendingIntent;

private final static String CHANNEL_ID="NOTIFICACION";

public final static int NOTIFICACION_ID=0;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

Button notificacion = (Button) findViewById(R.id.buttonNotificacion);

notificacion.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

irActivity();

crearCanalNotificacion();

crearNotificacion();

}});

}

private void irActivity() {

Intent intent = new Intent(this,EstrellasActivity.class);

TaskStackBuilder stackBuilder=TaskStackBuilder.create(this);

stackBuilder.addParentStack(EstrellasActivity.class);

stackBuilder.addNextIntent(intent);

pendingIntent=stackBuilder.getPendingIntent(1,PendingIntent.FLAG_UPDATE_CURRENT);

}

private void crearCanalNotificacion() {

if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.O){

CharSequence name="Notificacion";

NotificationChannel notificationChannel=new NotificationChannel(CHANNEL_ID,name, NotificationManager.IMPORTANCE_DEFAULT);

NotificationManager notificationManager=(NotificationManager) getSystemService(NOTIFICATION_SERVICE);

notificationManager.createNotificationChannel(notificationChannel);}

}

private void crearNotificacion() {

NotificationCompat.Builder builder=new NotificationCompat.Builder(getApplicationContext(),CHANNEL_ID);

builder.setSmallIcon(R.drawable.ic_star_black_24dp);

builder.setContentTitle("Goduria Food");

builder.setContentText("Has recibido nuevas estrellas!");

builder.setColor(Color.BLUE);

builder.setPriority(NotificationCompat.PRIORITY_DEFAULT);

builder.setLights(Color.MAGENTA,1000,1000);

builder.setVibrate(new long[]{1000,1000,1000,1000,1000});

builder.setDefaults(Notification.DEFAULT_SOUND);

builder.setContentIntent(pendingIntent);

NotificationManagerCompat notificationManagerCompat=NotificationManagerCompat.from(getApplicationContext());

notificationManagerCompat.notify(NOTIFICACION_ID,builder.build());

}

}

Xml del MainActivity

<?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:layout_width="match_parent"

android:layout_height="match_parent"

tools:context=".MainActivity">

<Button

android:id="@+id/buttonNotificacion"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="@string/notificacion" />

</LinearLayout>

Codigo del Activity donde abrira la notificacion (en mi caso se llama EstrellasActivity)

package com.lvsistemas.mynotificacion;

import androidx.appcompat.app.AppCompatActivity;

import androidx.core.app.NotificationManagerCompat;

import static com.lvsistemas.mynotificacion.MainActivity.NOTIFICACION_ID;

import android.os.Bundle;

public class EstrellasActivity extends AppCompatActivity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_estrellas);

//borrar la notificacion

NotificationManagerCompat notificationManagerCompat=NotificationManagerCompat.from(getApplicationContext());

notificationManagerCompat.cancel(NOTIFICACION_ID);

}

}

Xml de EstrellaActivity

<?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:layout_width="match_parent"

android:layout_height="match_parent"

tools:context=".EstrellasActivity">

<TextView

android:id="@+id/textView"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="@string/notificacion" />

</LinearLayout>