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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 
requireScroll(NavigationBar navigationBar, RecyclerView recyclerView)31     public static void requireScroll(NavigationBar navigationBar, RecyclerView recyclerView) {
32         new RecyclerViewRequireScrollHelper(navigationBar, recyclerView).requireScroll();
33     }
34 
35     private final RecyclerView mRecyclerView;
36 
RecyclerViewRequireScrollHelper(NavigationBar navigationBar, RecyclerView recyclerView)37     private RecyclerViewRequireScrollHelper(NavigationBar navigationBar,
38             RecyclerView recyclerView) {
39         super(navigationBar);
40         mRecyclerView = recyclerView;
41     }
42 
requireScroll()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 
canScrollDown()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
pageScrollDown()70     protected void pageScrollDown() {
71         final int height = mRecyclerView.getHeight();
72         mRecyclerView.smoothScrollBy(0, height);
73     }
74 }
75