Android 9.0 native SystemUI drop-down notification bar, each notification is expanded by default

1 Introduction

In the native development of the 9.0 system rom, when the product customizes the SystemUI drop-down notification bar, when the status bar is pulled down, the last
notification in the notification bar defaults to shrinking. Clicking the button will expand the native system systemui. It is more beautiful, so the last notification is required to be expanded by default, which looks more beautiful.
The final rendering:

2. The default expanded core class for each notification in the native SystemUI pull-down notification bar

frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/NotificationViewHierarchyManager.java
frameworks\base\packages\SystemUI\res\values\config.xml

 3. The core function analysis and implementation of the default expansion of each notification in the native SystemUI pull-down notification bar

In systemui, regarding the management of the drop-down notification bar, it is preferred that each notification of these drop-down notification bars is managed by the NotificationViewHierarchyManager. Let’s first look
at the NotificationViewHierarchyManager notification management class

public class NotificationViewHierarchyManager implements DynamicPrivacyController.Listener {
    private static final String TAG = "NotificationViewHierarchyManager";

   public Notifica