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      1 /*
      2  * Copyright (C) 2016 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 
     17 package com.android.setupwizardlib.util;
     18 
     19 import android.support.v7.widget.RecyclerView;
     20 
     21 import com.android.setupwizardlib.view.NavigationBar;
     22 
     23 /**
     24  * Add this helper to require the recycler view to be scrolled to the bottom, making sure that the
     25  * user sees all content on the screen. This will change the navigation bar to show the more button
     26  * instead of the next button when there is more content to be seen. When the more button is
     27  * clicked, the scroll view will be scrolled one page down.
     28  */
     29 public class RecyclerViewRequireScrollHelper extends AbstractRequireScrollHelper {
     30 
     31     public static void requireScroll(NavigationBar navigationBar, RecyclerView recyclerView) {
     32         new RecyclerViewRequireScrollHelper(navigationBar, recyclerView).requireScroll();
     33     }
     34 
     35     private final RecyclerView mRecyclerView;
     36 
     37     private RecyclerViewRequireScrollHelper(NavigationBar navigationBar,
     38             RecyclerView recyclerView) {
     39         super(navigationBar);
     40         mRecyclerView = recyclerView;
     41     }
     42 
     43     protected void requireScroll() {
     44         super.requireScroll();
     45         mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
     46             @Override
     47             public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
     48                 if (!canScrollDown()) {
     49                     notifyScrolledToBottom();
     50                 } else {
     51                     notifyRequiresScroll();
     52                 }
     53             }
     54         });
     55 
     56         if (canScrollDown()) {
     57             notifyRequiresScroll();
     58         }
     59     }
     60 
     61     private boolean canScrollDown() {
     62         // Compatibility implementation of View#canScrollVertically
     63         final int offset = mRecyclerView.computeVerticalScrollOffset();
     64         final int range = mRecyclerView.computeVerticalScrollRange()
     65                 - mRecyclerView.computeVerticalScrollExtent();
     66         return range != 0 && offset < range - 1;
     67     }
     68 
     69     @Override
     70     protected void pageScrollDown() {
     71         final int height = mRecyclerView.getHeight();
     72         mRecyclerView.smoothScrollBy(0, height);
     73     }
     74 }
     75