通知在实际开发中还是比较常见的，例如新闻，音乐播放器，等。
1，基本通知
//初始化通知管理器
NotificationManager notificationManager = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
Notification.Builder builder = new Notification.Builder(this);
Intent mIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("https://www.jianshu.com/p/890acf8e5080"));
PendingIntent pendingIntent = PendingIntent.getActivity(this,0,mIntent,0);
builder.setContentIntent(pendingIntent);
builder.setSmallIcon(R.drawable.ic_launcher_background);
builder.setContentTitle("标题");
builder.setAutoCancel(true);
builder.setContentText("通知消息");
Notification notification = builder.build();
notificationManager.notify(0, notification);
Screenshot_1531046655.png
2，基础扩展通知自定义布局
xml >> item_notification
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@mipmap/ic_launcher"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="this is my View ，https://www.jianshu.com/u/6bbde9df8181https://www.jianshu.com/u/6bbde9df8181https://www.jianshu.com/u/6bbde9df8181https://www.jianshu.com/u/6bbde9df8181https://www.jianshu.com/u/6bbde9df8181https://www.jianshu.com/u/6bbde9df8181"
/>
</LinearLayout>
JAVA类
首先要创建一个RemoteViews自定义视图 详情https://blog.csdn.net/baidu_26352053/article/details/54943759
RemoteViews remoteViews = new RemoteViews(getPackageName(),R.layout.item_notification);
Notification notification1 = builder.build();
notification1.bigContentView= remoteViews;
notificationManager.notify(1, notification1);
注意，这里是在第一个通知的基础上写的，和第一个的区别就是可展开的自定义视图，
notification1.bigContentView= remoteViews;表示设置为普通视图，但是可以展开，如果需要默认展开，则设置notification1.contentView= remoteViews; 效果图如下
Screenshot_1531046886.png
可以看到在第二个通知中存在可以展开的符号，也就是,layout >> item_notification这个布局。
3，基础再扩展，悬浮通知，都是基于第一个例子
Intent flutterIntent =new Intent();
flutterIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
flutterIntent.setClass(NotificationActivity.this,RecycleViewActivity.class);
PendingIntent flutterPendingIntent = PendingIntent.getActivity(NotificationActivity.this,0,flutterIntent,PendingIntent.FLAG_CANCEL_CURRENT);
builder.setFullScreenIntent(flutterPendingIntent,true);
Notification notification2 = builder.build();
notificationManager.notify(2,notification2);
值得注意的是这种方式弹窗不会自动消失
Screenshot_1531046892.png
除了上述的用法，通知在5.0之后添加了通知等级，分别有
builder.setVisibility(Notification.VISIBILITY_PUBLIC); 任何情况都都通知
builder.setVisibility(Notification.VISIBILITY_PRIVATE); 只有在没有锁屏情况下通知
builder.setVisibility(Notification.VISIBILITY_SECRET); 在pin，password等安全锁和没有锁屏的情况下才能通知。
