[go: nahoru, domu]
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
17package com.android.setupwizardlib.util;
18
19import android.support.v7.widget.RecyclerView;
20
21import 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 */
29public 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