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      1 /*
      2  * Copyright (C) 2017 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 package com.android.car.media.drawer;
     17 
     18 import android.content.Context;
     19 import android.support.annotation.Nullable;
     20 import com.android.car.app.CarDrawerActivity;
     21 import com.android.car.app.CarDrawerAdapter;
     22 import com.android.car.app.DrawerItemViewHolder;
     23 
     24 /**
     25  * Subclass of CarDrawerAdapter used by the Media app.
     26  * <p>
     27  * This adapter delegates actual fetching of items (and other operations) to a
     28  * {@link MediaItemsFetcher}. The current fetcher being used can be updated at runtime.
     29  */
     30 class MediaDrawerAdapter extends CarDrawerAdapter {
     31     private final CarDrawerActivity mActivity;
     32     private MediaItemsFetcher mCurrentFetcher;
     33     private MediaFetchCallback mFetchCallback;
     34     private int mCurrentScrollPosition;
     35 
     36     /**
     37      * Interface for a callback object that will be notified of changes to the fetch status of
     38      * items in a media drawer.
     39      */
     40     interface MediaFetchCallback {
     41         /**
     42          * Called when a fetch for items starts.
     43          */
     44         void onFetchStart();
     45 
     46         /**
     47          * Called when a fetch for items ends.
     48          */
     49         void onFetchEnd();
     50     }
     51 
     52     MediaDrawerAdapter(CarDrawerActivity activity) {
     53         super(activity, true /* showDisabledListOnEmpty */);
     54         mActivity = activity;
     55     }
     56 
     57     /**
     58      * Sets the object to be notified of changes to the fetching of items in the media drawer.
     59      */
     60     void setFetchCallback(@Nullable MediaFetchCallback callback) {
     61         mFetchCallback = callback;
     62     }
     63 
     64     /**
     65      * Switch the {@link MediaItemsFetcher} being used to fetch items. The new fetcher is kicked-off
     66      * and the drawer's content's will be updated to show newly loaded items. Any old fetcher is
     67      * cleaned up and released.
     68      *
     69      * @param fetcher New {@link MediaItemsFetcher} to use for display Drawer items.
     70      */
     71     void setFetcher(MediaItemsFetcher fetcher) {
     72         if (mCurrentFetcher != null) {
     73             mCurrentFetcher.cleanup();
     74         }
     75         mCurrentFetcher = fetcher;
     76         mCurrentFetcher.start(() -> {
     77             if (mFetchCallback != null) {
     78                 mFetchCallback.onFetchEnd();
     79             }
     80             notifyDataSetChanged();
     81         });
     82 
     83         if (mFetchCallback != null) {
     84             mFetchCallback.onFetchStart();
     85         }
     86     }
     87 
     88     @Override
     89     protected int getActualItemCount() {
     90         return mCurrentFetcher != null ? mCurrentFetcher.getItemCount() : 0;
     91     }
     92 
     93     @Override
     94     protected boolean usesSmallLayout(int position) {
     95         return mCurrentFetcher.usesSmallLayout(position);
     96     }
     97 
     98     @Override
     99     protected void populateViewHolder(DrawerItemViewHolder holder, int position) {
    100         if (mCurrentFetcher == null) {
    101             return;
    102         }
    103 
    104         mCurrentFetcher.populateViewHolder(holder, position);
    105         scrollToCurrent();
    106     }
    107 
    108     @Override
    109     public void onItemClick(int position) {
    110         if (mCurrentFetcher != null) {
    111             mCurrentFetcher.onItemClick(position);
    112         }
    113     }
    114 
    115     @Override
    116     public void cleanup() {
    117         super.cleanup();
    118         if (mCurrentFetcher != null) {
    119             mCurrentFetcher.cleanup();
    120             mCurrentFetcher = null;
    121         }
    122         mFetchCallback = null;
    123     }
    124 
    125     public void scrollToCurrent() {
    126         if (mCurrentFetcher == null) {
    127             return;
    128         }
    129         int scrollPosition = mCurrentFetcher.getScrollPosition();
    130         if (scrollPosition != MediaItemsFetcher.DONT_SCROLL
    131                 && mCurrentScrollPosition != scrollPosition) {
    132             mActivity.scrollToPosition(scrollPosition);
    133             mCurrentScrollPosition = scrollPosition;
    134         }
    135     }
    136 }
    137