| /* |
| * Copyright (C) 2020 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.server.utils; |
| |
| import android.annotation.NonNull; |
| import android.annotation.Nullable; |
| import android.os.Build; |
| import android.util.Log; |
| |
| import java.lang.reflect.Field; |
| |
| /** |
| * Notify registered {@link Watcher}s when the content changes. |
| */ |
| public interface Watchable { |
| |
| /** |
| * Ensures an observer is in the list, exactly once. The observer cannot be null. The |
| * function quietly returns if the observer is already in the list. |
| * |
| * @param observer The {@link Watcher} to be notified when the {@link Watchable} changes. |
| */ |
| public void registerObserver(@NonNull Watcher observer); |
| |
| /** |
| * Ensures an observer is not in the list. The observer must not be null. The function |
| * quietly returns if the objserver is not in the list. |
| * |
| * @param observer The {@link Watcher} that should not be in the notification list. |
| */ |
| public void unregisterObserver(@NonNull Watcher observer); |
| |
| /** |
| * Return true if the {@link Watcher) is a registered observer. |
| * @param observer A {@link Watcher} that might be registered |
| * @return true if the observer is registered with this {@link Watchable}. |
| */ |
| public boolean isRegisteredObserver(@NonNull Watcher observer); |
| |
| /** |
| * Invokes {@link Watcher#onChange} on each registered observer. The method can be called |
| * with the {@link Watchable} that generated the event. In a tree of {@link Watchable}s, this |
| * is generally the first (deepest) {@link Watchable} to detect a change. |
| * |
| * @param what The {@link Watchable} that generated the event. |
| */ |
| public void dispatchChange(@Nullable Watchable what); |
| |
| /** |
| * Verify that all @Watched {@link Watchable} attributes are being watched by this |
| * class. This requires reflection and only runs in engineering or user debug |
| * builds. |
| * @param base The object that contains watched attributes. |
| * @param observer The {@link Watcher} that should be watching these attributes. |
| * @param logOnly If true then log errors; if false then throw an RuntimeExecption on error. |
| */ |
| static void verifyWatchedAttributes(Object base, Watcher observer, boolean logOnly) { |
| if (!(Build.IS_ENG || Build.IS_USERDEBUG)) { |
| return; |
| } |
| for (Field f : base.getClass().getDeclaredFields()) { |
| final Watched annotation = f.getAnnotation(Watched.class); |
| if (annotation != null) { |
| final String fn = base.getClass().getName() + "." + f.getName(); |
| try { |
| f.setAccessible(true); |
| final Object o = f.get(base); |
| if (o instanceof Watchable) { |
| Watchable attr = (Watchable) (o); |
| if (attr != null && !attr.isRegisteredObserver(observer)) { |
| handleVerifyError("Watchable " + fn + " missing an observer", logOnly); |
| } |
| } else if (!annotation.manual()) { |
| handleVerifyError("@Watched annotated field " + fn + " is not a watchable" |
| + " type and is not flagged for manual watching.", logOnly); |
| } |
| } catch (IllegalAccessException e) { |
| // The field is protected; ignore it. Other exceptions that may be thrown by |
| // Field.get() are allowed to roll up. |
| handleVerifyError("Watchable " + fn + " not visible", logOnly); |
| } |
| } |
| } |
| } |
| |
| static void handleVerifyError(String errorMessage, boolean logOnly) { |
| if (logOnly) { |
| Log.e("Watchable", errorMessage); |
| } else { |
| throw new RuntimeException(errorMessage); |
| } |
| } |
| |
| /** |
| * Verify that all @Watched {@link Watchable} attributes are being watched by this |
| * class. This calls verifyWatchedAttributes() with logOnly set to false. |
| * @param base The object that contains watched attributes. |
| * @param observer The {@link Watcher} that should be watching these attributes. |
| */ |
| static void verifyWatchedAttributes(Object base, Watcher observer) { |
| verifyWatchedAttributes(base, observer, false); |
| } |
| } |