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 androidx.recyclerview.widget.RecyclerView;
  import android.util.Log;
  import com.android.setupwizardlib.template.RequireScrollMixin.ScrollHandlingDelegate;
  
  /**
   * {@link ScrollHandlingDelegate} which analyzes scroll events from {@link RecyclerView} and
   * notifies {@link RequireScrollMixin} about scrollability changes.
   */
  public class RecyclerViewScrollHandlingDelegate implements ScrollHandlingDelegate {
  
    private static final String TAG = "RVRequireScrollMixin";
  
    @Nullable private final RecyclerView recyclerView;
  
    @NonNull private final RequireScrollMixin requireScrollMixin;
  
    public RecyclerViewScrollHandlingDelegate(
        @NonNull RequireScrollMixin requireScrollMixin, @Nullable RecyclerView recyclerView) {
      this.requireScrollMixin = requireScrollMixin;
      this.recyclerView = recyclerView;
    }
  
    private boolean canScrollDown() {
      if (recyclerView != null) {
        // Compatibility implementation of View#canScrollVertically
        final int offset = recyclerView.computeVerticalScrollOffset();
        final int range =
            recyclerView.computeVerticalScrollRange() - recyclerView.computeVerticalScrollExtent();
        return range != 0 && offset < range - 1;
      }
      return false;
    }
  
    @Override
    public void startListening() {
      if (this.recyclerView != null) {
        this.recyclerView.addOnScrollListener(
            new RecyclerView.OnScrollListener() {
              @Override
              public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                requireScrollMixin.notifyScrollabilityChange(canScrollDown());
              }
            });
  
        if (canScrollDown()) {
          requireScrollMixin.notifyScrollabilityChange(true);
        }
      } else {
        Log.w(TAG, "Cannot require scroll. Recycler view is null.");
      }
    }
  
    @Override
    public void pageScrollDown() {
      if (recyclerView != null) {
        final int height = recyclerView.getHeight();
        recyclerView.smoothScrollBy(0, height);
      }
    }
  }
  