Rewrite dream settings.

The available dreams will now be shown in a grid, with a preview button
at the bottom.

Screenshot (white placeholder image used):
http://screen/6pe6EoACPoQN8TZ.png
http://screen/4nR6Wg5pN7pL6Wb.png

Phone (single column layout):
http://screen/4WFqzZR8Yf9H3VZ.png

Colors and margins will be finalized once final mocks are done.

Bug: 207681076
Bug: 214250590
Test: locally on device
Change-Id: Ie68bdc60e74e72dc3c3cee3f1ffd40f5613109b9

src/com/android/settings/dream/DreamPickerController.java

@@ -0,0 +1,138 @@
+/*
+ * 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.settings.dream;
+
+import android.content.Context;
+import android.widget.Button;
+
+import androidx.annotation.Nullable;
+import androidx.preference.Preference;
+import androidx.recyclerview.widget.GridLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
+
+import com.android.settings.R;
+import com.android.settings.core.BasePreferenceController;
+import com.android.settings.dream.DreamPickerAdapter.OnItemClickListener;
+import com.android.settingslib.dream.DreamBackend;
+import com.android.settingslib.widget.LayoutPreference;
+
+import java.util.List;
+
+/**
+ * Controller for the dream picker where the user can select a screensaver.
+ */
+public class DreamPickerController extends BasePreferenceController {
+    public static final String KEY = "dream_picker";
+
+    private final DreamBackend mBackend;
+    private final List<DreamBackend.DreamInfo> mDreamInfos;
+    private Button mPreviewButton;
+    @Nullable
+    private DreamBackend.DreamInfo mActiveDream;
+
+    private final OnItemClickListener mItemClickListener =
+            new OnItemClickListener() {
+                @Override
+                public void onItemClicked(DreamBackend.DreamInfo dreamInfo) {
+                    mActiveDream = dreamInfo;
+                    mBackend.setActiveDream(
+                            mActiveDream == null ? null : mActiveDream.componentName);
+                    updatePreviewButtonState();
+                }
+            };
+
+    private final OnItemClickListener mCustomizeListener = new OnItemClickListener() {
+        @Override
+        public void onItemClicked(DreamBackend.DreamInfo dreamInfo) {
+            mBackend.launchSettings(mContext, dreamInfo);
+        }
+    };
+
+    public DreamPickerController(Context context, String preferenceKey) {
+        this(context, preferenceKey, DreamBackend.getInstance(context));
+    }
+
+    public DreamPickerController(Context context, String preferenceKey, DreamBackend backend) {
+        super(context, preferenceKey);
+        mBackend = backend;
+        mDreamInfos = mBackend.getDreamInfos();
+    }
+
+    @Override
+    public String getPreferenceKey() {
+        return KEY;
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return mDreamInfos.size() > 0 ? AVAILABLE : CONDITIONALLY_UNAVAILABLE;
+    }
+
+    @Override
+    public void updateState(Preference preference) {
+        super.updateState(preference);
+
+        mActiveDream = getActiveDreamInfo();
+
+        final DreamPickerAdapter adapter =
+                new DreamPickerAdapter(mDreamInfos, mItemClickListener, mCustomizeListener);
+
+        final RecyclerView recyclerView =
+                ((LayoutPreference) preference).findViewById(R.id.dream_list);
+        recyclerView.setLayoutManager(new AutoFitGridLayoutManager(mContext));
+        recyclerView.setAdapter(adapter);
+
+        mPreviewButton = ((LayoutPreference) preference).findViewById(R.id.preview_button);
+        mPreviewButton.setOnClickListener(v -> mBackend.preview(mActiveDream));
+        updatePreviewButtonState();
+    }
+
+    private void updatePreviewButtonState() {
+        final boolean hasDream = mActiveDream != null;
+        mPreviewButton.setClickable(hasDream);
+        mPreviewButton.setEnabled(hasDream);
+    }
+
+    @Nullable
+    private DreamBackend.DreamInfo getActiveDreamInfo() {
+        return mDreamInfos
+                .stream()
+                .filter(d -> d.isActive)
+                .findFirst()
+                .orElse(null);
+    }
+
+    /** Grid layout manager that calculates the number of columns for the screen size. */
+    private static final class AutoFitGridLayoutManager extends GridLayoutManager {
+        private final float mColumnWidth;
+
+        AutoFitGridLayoutManager(Context context) {
+            super(context, /* spanCount= */ 1);
+            this.mColumnWidth = context
+                    .getResources()
+                    .getDimensionPixelSize(R.dimen.dream_item_min_column_width);
+        }
+
+        @Override
+        public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
+            final int totalSpace = getWidth() - getPaddingRight() - getPaddingLeft();
+            final int spanCount = Math.max(1, (int) (totalSpace / mColumnWidth));
+            setSpanCount(spanCount);
+            super.onLayoutChildren(recycler, state);
+        }
+    }
+}