title: The notification is not displayed and I think the code is correct
body: <p>i'm amateur in android and i want show notification with my app.</p>
  <p>this is my code: but does not show notification.</p>
  <p>please help me.   thanks</p>
  <pre><code>public class MainActivity extends AppCompatActivity {
  
      Button btn_ok;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
          btn_ok = findViewById(R.id.btn_ok);
  
          btn_ok.setOnClickListener(new View.OnClickListener() {
              @Override
              public void onClick(View v) {
  
                  NotificationCompat.Builder mbuilder = (NotificationCompat.Builder)
                          new NotificationCompat.Builder(getApplicationContext())
                                  .setSmallIcon(R.drawable.ic_launcher_background, 10)
                                  .setContentTitle(&quot;Notification&quot;)
                                  .setContentText(&quot;This is a notification for you&quot;);
  
                  NotificationManager notificationManager = (NotificationManager)
                          getSystemService(NOTIFICATION_SERVICE);
                  notificationManager.notify(0, mbuilder.build());
  
  
              }
  
  
          });
  
  
      }
  }
  </code></pre>