| /* |
| * Copyright (C) 2022 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package com.android.systemui.util.service; |
| |
| /** |
| * The {@link Observer} interface specifies an entity which listeners |
| * can be informed of changes to the source, which will require updating. Note that this deals |
| * with changes to the source itself, not content which will be updated through the interface. |
| */ |
| public interface Observer { |
| /** |
| * Callback for receiving updates from the {@link Observer}. |
| */ |
| interface Callback { |
| /** |
| * Invoked when the source has changed. |
| */ |
| void onSourceChanged(); |
| } |
| |
| /** |
| * Adds a callback to receive future updates from the {@link Observer}. |
| */ |
| void addCallback(Callback callback); |
| |
| /** |
| * Removes a callback from receiving further updates. |
| * @param callback |
| */ |
| void removeCallback(Callback callback); |
| } |