Implement CarUiListItem specific layout manager.
Bug: 143234489
Test: Manual test
Change-Id: I06d4899ba00a2e3533f94c968609c59634716bba
diff --git a/car-ui-lib/src/com/android/car/ui/recyclerview/CarUiListItemLayoutManager.java b/car-ui-lib/src/com/android/car/ui/recyclerview/CarUiListItemLayoutManager.java
new file mode 100644
index 0000000..c825052
--- /dev/null
+++ b/car-ui-lib/src/com/android/car/ui/recyclerview/CarUiListItemLayoutManager.java
@@ -0,0 +1,170 @@
+/*
+ * Copyright 2019 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.car.ui.recyclerview;
+
+import android.content.Context;
+import android.view.View;
+
+import androidx.annotation.NonNull;
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
+
+import com.android.car.ui.R;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * A {@link LinearLayoutManager} implementation which provides a fixed scrollbar when used with
+ * viewholders that vary in height. This layout manager is only compatible with {@link
+ * CarUiListItemAdapter}.
+ */
+public class CarUiListItemLayoutManager extends LinearLayoutManager {
+
+ private final int mContentItemSize;
+ private final int mHeaderItemSize;
+
+ private List<Integer> mListItemHeights;
+ private CarUiListItemAdapter mAdapter;
+
+ public CarUiListItemLayoutManager(@NonNull Context context) {
+ super(context);
+ mContentItemSize = (int) context.getResources().getDimension(
+ R.dimen.car_ui_list_item_height);
+ mHeaderItemSize = (int) context.getResources().getDimension(
+ R.dimen.car_ui_header_list_item_height);
+
+ setSmoothScrollbarEnabled(false);
+ }
+
+ @Override
+ public void onAttachedToWindow(RecyclerView recyclerView) {
+ super.onAttachedToWindow(recyclerView);
+ populateHeightMap(recyclerView.getAdapter());
+ }
+
+ @Override
+ public void onAdapterChanged(RecyclerView.Adapter oldAdapter, RecyclerView.Adapter newAdapter) {
+ super.onAdapterChanged(oldAdapter, newAdapter);
+ populateHeightMap(newAdapter);
+ }
+
+ @Override
+ public void onItemsAdded(@NonNull RecyclerView recyclerView, int positionStart, int itemCount) {
+ super.onItemsAdded(recyclerView, positionStart, itemCount);
+ populateHeightMap(recyclerView.getAdapter());
+ }
+
+ @Override
+ public void onItemsRemoved(@NonNull RecyclerView recyclerView, int positionStart,
+ int itemCount) {
+ super.onItemsRemoved(recyclerView, positionStart, itemCount);
+ populateHeightMap(recyclerView.getAdapter());
+ }
+
+ @Override
+ public void onItemsUpdated(@NonNull RecyclerView recyclerView, int positionStart,
+ int itemCount) {
+ super.onItemsUpdated(recyclerView, positionStart, itemCount);
+ populateHeightMap(recyclerView.getAdapter());
+ }
+
+ @Override
+ public void onItemsChanged(@NonNull RecyclerView recyclerView) {
+ super.onItemsChanged(recyclerView);
+ populateHeightMap(recyclerView.getAdapter());
+ }
+
+ @Override
+ public int computeVerticalScrollExtent(RecyclerView.State state) {
+ final int count = getChildCount();
+ return count > 0 ? mContentItemSize * 3 : 0;
+ }
+
+ @Override
+ public int computeVerticalScrollRange(RecyclerView.State state) {
+ return Math.max(mListItemHeights.get(mListItemHeights.size() - 1), 0);
+ }
+
+ @Override
+ public int computeVerticalScrollOffset(RecyclerView.State state) {
+ if (getChildCount() <= 0) {
+ return 0;
+ }
+
+ int firstPos = findFirstVisibleItemPosition();
+ if (firstPos == RecyclerView.NO_POSITION) {
+ return 0;
+ }
+
+ View view = findViewByPosition(firstPos);
+ if (view == null) {
+ return 0;
+ }
+
+ final int top = getDecoratedTop(view);
+ final int height = getDecoratedMeasuredHeight(view);
+
+ int heightOfScreen;
+ if (height <= 0) {
+ heightOfScreen = 0;
+ } else {
+ CarUiListItem item = mAdapter.getItems().get(firstPos);
+ if (item instanceof CarUiContentListItem) {
+ heightOfScreen = Math.abs(mContentItemSize * top / height);
+ } else if (item instanceof CarUiHeaderListItem) {
+ heightOfScreen = Math.abs(mHeaderItemSize * top / height);
+ } else {
+ throw new IllegalStateException("Unknown list item type.");
+ }
+ }
+
+ return (mListItemHeights.get(firstPos)) + heightOfScreen;
+ }
+
+ /**
+ * Populates an internal list of cumulative heights at each position for the list to be laid out
+ * for the adapter parameter.
+ *
+ * @param adapter the action type for the item.
+ */
+ private void populateHeightMap(RecyclerView.Adapter adapter) {
+ if (!(adapter instanceof CarUiListItemAdapter)) {
+ throw new IllegalStateException(
+ "Cannot use CarUiListItemLayoutManager with an adapter that is not of type "
+ + "CarUiListItemAdapter");
+ }
+
+ mAdapter = (CarUiListItemAdapter) adapter;
+ List<CarUiListItem> itemList = mAdapter.getItems();
+ mListItemHeights = new ArrayList<>();
+
+ int cumulativeHeight = 0;
+ mListItemHeights.add(cumulativeHeight);
+ for (CarUiListItem item : itemList) {
+ if (item instanceof CarUiContentListItem) {
+ cumulativeHeight += mContentItemSize;
+ mListItemHeights.add(cumulativeHeight);
+ } else if (item instanceof CarUiHeaderListItem) {
+ cumulativeHeight += mHeaderItemSize;
+ mListItemHeights.add(cumulativeHeight);
+ } else {
+ throw new IllegalStateException("Unknown CarUiListItem type");
+ }
+ }
+ }
+}
diff --git a/car-ui-lib/tests/paintbooth/src/com/android/car/ui/paintbooth/caruirecyclerview/CarUiListItemActivity.java b/car-ui-lib/tests/paintbooth/src/com/android/car/ui/paintbooth/caruirecyclerview/CarUiListItemActivity.java
index 636b0ba..3b5cf7a 100644
--- a/car-ui-lib/tests/paintbooth/src/com/android/car/ui/paintbooth/caruirecyclerview/CarUiListItemActivity.java
+++ b/car-ui-lib/tests/paintbooth/src/com/android/car/ui/paintbooth/caruirecyclerview/CarUiListItemActivity.java
@@ -26,6 +26,7 @@
import com.android.car.ui.recyclerview.CarUiHeaderListItem;
import com.android.car.ui.recyclerview.CarUiListItem;
import com.android.car.ui.recyclerview.CarUiListItemAdapter;
+import com.android.car.ui.recyclerview.CarUiListItemLayoutManager;
import com.android.car.ui.recyclerview.CarUiRecyclerView;
import java.util.ArrayList;
@@ -45,6 +46,7 @@
CarUiListItemAdapter adapter = new CarUiListItemAdapter(generateDummyData());
recyclerView.setAdapter(adapter);
+ recyclerView.setLayoutManager(new CarUiListItemLayoutManager(this));
}
private ArrayList<CarUiListItem> generateDummyData() {
