1/*
2 * Copyright (C) 2017 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.template;
18
19import android.support.annotation.NonNull;
20import android.support.annotation.Nullable;
21import android.support.v7.widget.RecyclerView;
22import android.util.Log;
23
24import com.android.setupwizardlib.template.RequireScrollMixin.ScrollHandlingDelegate;
25
26/**
27 * {@link ScrollHandlingDelegate} which analyzes scroll events from {@link RecyclerView} and
28 * notifies {@link RequireScrollMixin} about scrollability changes.
29 */
30public class RecyclerViewScrollHandlingDelegate implements ScrollHandlingDelegate {
31
32    private static final String TAG = "RVRequireScrollMixin";
33
34    @Nullable
35    private final RecyclerView mRecyclerView;
36
37    @NonNull
38    private final RequireScrollMixin mRequireScrollMixin;
39
40    public RecyclerViewScrollHandlingDelegate(
41            @NonNull RequireScrollMixin requireScrollMixin,
42            @Nullable RecyclerView recyclerView) {
43        mRequireScrollMixin = requireScrollMixin;
44        mRecyclerView = recyclerView;
45    }
46
47    private boolean canScrollDown() {
48        if (mRecyclerView != null) {
49            // Compatibility implementation of View#canScrollVertically
50            final int offset = mRecyclerView.computeVerticalScrollOffset();
51            final int range = mRecyclerView.computeVerticalScrollRange()
52                    - mRecyclerView.computeVerticalScrollExtent();
53            return range != 0 && offset < range - 1;
54        }
55        return false;
56    }
57
58    @Override
59    public void startListening() {
60        if (mRecyclerView != null) {
61            mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
62                @Override
63                public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
64                    mRequireScrollMixin.notifyScrollabilityChange(canScrollDown());
65                }
66            });
67
68            if (canScrollDown()) {
69                mRequireScrollMixin.notifyScrollabilityChange(true);
70            }
71        } else {
72            Log.w(TAG, "Cannot require scroll. Recycler view is null.");
73        }
74    }
75
76    @Override
77    public void pageScrollDown() {
78        if (mRecyclerView != null) {
79            final int height = mRecyclerView.getHeight();
80            mRecyclerView.smoothScrollBy(0, height);
81        }
82    }
83}
84