src/com/android/car/media/drawer/MediaItemsFetcher.java

/*
 * Copyright (C) 2017 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.media.drawer;

import android.content.Context;
import android.graphics.Bitmap;
import android.media.MediaDescription;
import android.text.TextUtils;
import android.view.View;

import androidx.car.drawer.CarDrawerAdapter;
import androidx.car.drawer.DrawerItemViewHolder;

import com.android.car.apps.common.BitmapDownloader;
import com.android.car.apps.common.BitmapWorkerOptions;
import com.android.car.apps.common.UriUtils;
import com.android.car.media.R;

/**
 * Component that handles fetching of items for {@link MediaDrawerAdapter}.
 * <p>
 * It also handles ViewHolder population and item clicks.
 */
interface MediaItemsFetcher {
    int DONT_SCROLL = -1;

    /**
     * Used to inform owning {@link MediaDrawerAdapter} that items have changed.
     */
    interface ItemsUpdatedCallback {
        void onItemsUpdated();
    }

    /**
     * Kick-off fetching/monitoring of items.
     *
     * @param callback Callback that is invoked when items are first loaded ar if they change
     *                 subsequently.
     */
    void start(ItemsUpdatedCallback callback);

    /**
     * @return Number of items currently fetched.
     */
    int getItemCount();

    /**
     * Used to indicate the kind of layout (small or normal) to use for the views that will display
     * this item in a {@link CarDrawerAdapter}. See {@link CarDrawerAdapter#usesSmallLayout}
     *
     * @param position Adapter position of item
     * @return Whether to use small (true) or normal layout (false).
     */
    boolean usesSmallLayout(int position);

    /**
     * Used by owning {@link MediaDrawerAdapter} to populate views.
     *
     * @param holder View-holder to populate.
     * @param position Item position.
     */
    void populateViewHolder(DrawerItemViewHolder holder, int position);

    /**
     * Used by owning {@link MediaDrawerAdapter} to handle clicks.
     *
     * @param position Item position.
     */
    void onItemClick(int position);

    /**
     * Used when this instance is going to be released. Subclasses should release resources.
     */
    void cleanup();


    /**
     * Get the position to scroll to if any.
     * @return An integer greater than or equal to 0 if there is a position to scroll to, the
     *         constant {@link DONT_SCROLL} otherwise.
     */
    int getScrollPosition();

    /**
     * Utility method to determine if description can be displayed in a small layout.
     */
    static boolean usesSmallLayout(MediaDescription description) {
        // Small layout is sufficient if there's no sub-title to display for the item.
        return TextUtils.isEmpty(description.getSubtitle());
    }

    /**
     * Utility method to populate {@code holder} with details from {@code description}. It populates
     * title, text and icon at most.
     */
    static void populateViewHolderFrom(DrawerItemViewHolder holder, MediaDescription description) {
        Context context = holder.itemView.getContext();
        holder.getTitle().setText(description.getTitle());
        // If normal layout, populate subtitle.
        if (!usesSmallLayout(description)) {
            holder.getText().setText(description.getSubtitle());
        }
        Bitmap iconBitmap = description.getIconBitmap();
        holder.getIcon().setImageBitmap(iconBitmap);    // Ok to set null here for clearing.
        if (iconBitmap == null) {
            if (description.getIconUri() != null) {
                holder.getIcon().setVisibility(View.VISIBLE);
                int bitmapSize =
                        context.getResources().getDimensionPixelSize(R.dimen.car_primary_icon_size);
                // We don't want to cache android resources as they are needed to be refreshed after
                // configuration changes.
                int cacheFlag = UriUtils.isAndroidResourceUri(description.getIconUri())
                        ? (BitmapWorkerOptions.CACHE_FLAG_DISK_DISABLED
                        | BitmapWorkerOptions.CACHE_FLAG_MEM_DISABLED)
                        : 0;
                BitmapWorkerOptions options = new BitmapWorkerOptions.Builder(context)
                        .resource(description.getIconUri())
                        .height(bitmapSize)
                        .width(bitmapSize)
                        .cacheFlag(cacheFlag)
                        .build();
                BitmapDownloader.getInstance(context).loadBitmap(options, holder.getIcon());
            } else {
                holder.getIcon().setVisibility(View.GONE);
            }
        }
    }
}