Button

<Button
   android:id="@+id/btn"
   android:text="发送通知"
   android:backgroundTint="@color/red"
   android:layout_width="100dp"
   android:layout_height="60dp"
   tools:ignore="MissingConstraints" />

绑定按钮

Button btn =  findViewById(R.id.btn);

声明变量

private NotificationManager manager;
private Notification notification1;

创建通知

manager = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.O){
            NotificationChannel channel = new NotificationChannel("web","通知",NotificationManager.IMPORTANCE_HIGH);
            manager.createNotificationChannel(channel);
        }
notification1 = new NotificationCompat.Builder(this,"web")
           .setContentTitle("点击通知")
           .setContentText("你点击了按钮")
           .setSmallIcon(R.drawable.ic_launcher_background)
           .build();

按钮点击事件

btn.setOnClickListener(new View.OnClickListener() {
      @Override
       public void onClick(View view) {
           manager.notify(1,notification1);
       }
});