Slice background worker with Wi-Fi Slice

Test: manual

Change-Id: Ic4fdc5713f511ff80f03728c99c68fda3d0cab02

src/com/android/settings/slices/SliceBackgroundWorker.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2018 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.settings.slices;
+
+import android.content.ContentResolver;
+import android.net.Uri;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * The Slice background worker is used to make Settings Slices be able to work with data that is
+ * changing continuously, e.g. available Wi-Fi networks.
+ *
+ * The background worker will be started at {@link SettingsSliceProvider#onSlicePinned(Uri)}, and be
+ * stopped at {@link SettingsSliceProvider#onSliceUnpinned(Uri)}.
+ *
+ * {@link SliceBackgroundWorker} caches the results, uses the cache to compare if there is any data
+ * changed, and then notifies the Slice {@link Uri} to update.
+ */
+public abstract class SliceBackgroundWorker<E> {
+
+    private final ContentResolver mContentResolver;
+    private final Uri mUri;
+
+    private List<E> mCachedResults;
+
+    protected SliceBackgroundWorker(ContentResolver cr, Uri uri) {
+        mContentResolver = cr;
+        mUri = uri;
+    }
+
+    /**
+     * Called when the Slice is pinned. This is the place to register callbacks or initialize scan
+     * tasks.
+     */
+    protected abstract void onSlicePinned();
+
+    /**
+     * Called when the Slice is unpinned. This is the place to unregister callbacks or perform any
+     * final cleanup.
+     */
+    protected abstract void onSliceUnpinned();
+
+    /**
+     * @return a {@link List} of cached results
+     */
+    public final List<E> getResults() {
+        return mCachedResults == null ? null : new ArrayList<>(mCachedResults);
+    }
+
+    /**
+     * Update the results when data changes
+     */
+    protected final void updateResults(List<E> results) {
+        boolean needNotify = false;
+
+        if (results == null) {
+            if (mCachedResults != null) {
+                needNotify = true;
+            }
+        } else {
+            needNotify = !results.equals(mCachedResults);
+        }
+
+        if (needNotify) {
+            mCachedResults = results;
+            mContentResolver.notifyChange(mUri, null);
+        }
+    }
+}