content: /*
   * 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.setupwizardlib.template;
  
  import androidx.annotation.NonNull;
  import androidx.annotation.Nullable;
  import android.util.Log;
  import android.widget.AbsListView;
  import android.widget.ListAdapter;
  import android.widget.ListView;
  import com.android.setupwizardlib.template.RequireScrollMixin.ScrollHandlingDelegate;
  
  /**
   * {@link ScrollHandlingDelegate} which analyzes scroll events from {@link ListView} and notifies
   * {@link RequireScrollMixin} about scrollability changes.
   */
  public class ListViewScrollHandlingDelegate
      implements ScrollHandlingDelegate, AbsListView.OnScrollListener {
  
    private static final String TAG = "ListViewDelegate";
  
    private static final int SCROLL_DURATION = 500;
  
    @NonNull private final RequireScrollMixin requireScrollMixin;
  
    @Nullable private final ListView listView;
  
    public ListViewScrollHandlingDelegate(
        @NonNull RequireScrollMixin requireScrollMixin, @Nullable ListView listView) {
      this.requireScrollMixin = requireScrollMixin;
      this.listView = listView;
    }
  
    @Override
    public void startListening() {
      if (listView != null) {
        listView.setOnScrollListener(this);
  
        final ListAdapter adapter = listView.getAdapter();
        if (listView.getLastVisiblePosition() < adapter.getCount()) {
          requireScrollMixin.notifyScrollabilityChange(true);
        }
      } else {
        Log.w(TAG, "Cannot require scroll. List view is null");
      }
    }
  
    @Override
    public void pageScrollDown() {
      if (listView != null) {
        final int height = listView.getHeight();
        listView.smoothScrollBy(height, SCROLL_DURATION);
      }
    }
  
    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {}
  
    @Override
    public void onScroll(
        AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
      if (firstVisibleItem + visibleItemCount >= totalItemCount) {
        requireScrollMixin.notifyScrollabilityChange(false);
      } else {
        requireScrollMixin.notifyScrollabilityChange(true);
      }
    }
  }
  