这部分主要涉及的知识点：
（1）RemoteView
（2）PendingIntent
（3）Notification

任玉刚的《Android开发艺术探索》里有第5章“理解RemoteViews”讲的比较详细。

RemoteView

应用场景：主要是用在通知栏Notification、桌面小部件AppWidgetProvider场景

内部机制：跨进程显示并更新View

支持的View的类型有限：
Layout – FrameLayout, LinearLayout, RelativeLayout, GridLayout
View – AnalogClock, Button, Chronometer, ImageButton, ImageView, ProgressBar, TextView, ViewFlipper, ListView, GridView, StackView, AdapterViewFlipper, ViewStub

public class RemoteViews implements Parcelable    
private abstract static class Action implements Parcelable    

RemoteViews维护了一个List，使用了反射机制，每一个set方法实际上就是一个对View的操作的Action。

PendingIntent

PendingIntent.getActivity(Context context, int requestCode, Intent intent, int flags)

PendingIntent.getService(Context context, int requestCode, Intent intent, int flags)

PendingIntent.getBroadcast(Context context, int requestCode, Intent intent, int flags)

flags参数：

FLAG_ONE_SHOT
FLAG_NO_CREATE
FLAG_CANCEL_CURRENT
FLAG_UPDATE_CURRENT

Notification

示例代码：

RemoteViews notificationView = new RemoteViews(context.getPackageName(), R.layout.xxx);
notificationView.setTextViewText(R.id.title, title);
notificationView.setTextViewText(R.id.content, content);
notificationView.setImageViewResource(R.id.icon, icon);
  
PendingIntent contentIntent = PendingIntent.getActivity(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);

Notification notification = new NotificationCompat.Builder(context)
  .setCustomContentView(notificationView)
  .setContentIntent(contentIntent)
  ....
  .build();

NotificationManager nm = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
nm.notify(id, notification);

target 26开始，通知栏部分涉及到NotificationChannel概念，即Notification的显示需要先创建NotificationChannel，通过NotificationChannel来控制Notification的显示逻辑。

官方文档：
https://developer.android.com/reference/android/app/PendingIntent
https://developer.android.com/reference/android/widget/RemoteViews
https://developer.android.com/reference/android/app/Notification
https://developer.android.com/reference/android/app/NotificationChannel