1 /*
2  * Copyright (C) 2021 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.systemui.statusbar.notification.collection
18 
19 import androidx.lifecycle.Observer
20 
21 /**
22  * An object which provides pieces of information about the notification shade.
23  *
24  * Note that individual fields of this object are updated together before synchronous observers are
25  * notified, so synchronous observers of two fields can be assured that they will see consistent
26  * results: e.g. if [hasActiveNotifs] is false then [activeNotifList] will be empty, and vice versa.
27  *
28  * This interface is read-only.
29  */
30 interface NotifLiveDataStore {
31     val hasActiveNotifs: NotifLiveData<Boolean>
32     val activeNotifCount: NotifLiveData<Int>
33     val activeNotifList: NotifLiveData<List<NotificationEntry>>
34 }
35 
36 /**
37  * An individual value which can be accessed directly, or observed for changes either synchronously
38  * or asynchronously.
39  *
40  * This interface is read-only.
41  */
42 interface NotifLiveData<T> {
43     /** Access the current value */
44     val value: T
45     /** Add an observer which will be invoked synchronously when the value is changed. */
addSyncObservernull46     fun addSyncObserver(observer: Observer<T>)
47     /** Add an observer which will be invoked asynchronously after the value has changed */
48     fun addAsyncObserver(observer: Observer<T>)
49     /** Remove an observer previously added with [addSyncObserver] or [addAsyncObserver]. */
50     fun removeObserver(observer: Observer<T>)
51 }
52