Android8未満最小構成ローカル通知

MainActivity.java

import android.os.Handler;
import android.support.v4.app.NotificationCompat;
import android.support.v4.app.NotificationManagerCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity
{
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button buttonNoti = this.findViewById(R.id.button_noti);
        // ボタンをクリックしたら3秒後に通知
        buttonNoti.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                new Handler().postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        NotificationCompat.Builder builder = new NotificationCompat.Builder(getApplicationContext());
                        builder.setSmallIcon(R.drawable.ic_launcher_foreground);
                        NotificationManagerCompat manager = NotificationManagerCompat.from(getApplicationContext());
                        manager.notify(0, builder.build());
                    }
                }, 3000);
            }
        });
    }
}