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.util.Log;
22import android.widget.AbsListView;
23import android.widget.ListAdapter;
24import android.widget.ListView;
25
26import com.android.setupwizardlib.template.RequireScrollMixin.ScrollHandlingDelegate;
27
28/**
29 * {@link ScrollHandlingDelegate} which analyzes scroll events from {@link ListView} and
30 * notifies {@link RequireScrollMixin} about scrollability changes.
31 */
32public class ListViewScrollHandlingDelegate implements ScrollHandlingDelegate,
33        AbsListView.OnScrollListener {
34
35    private static final String TAG = "ListViewDelegate";
36
37    private static final int SCROLL_DURATION = 500;
38
39    @NonNull
40    private final RequireScrollMixin mRequireScrollMixin;
41
42    @Nullable
43    private final ListView mListView;
44
45    public ListViewScrollHandlingDelegate(
46            @NonNull RequireScrollMixin requireScrollMixin,
47            @Nullable ListView listView) {
48        mRequireScrollMixin = requireScrollMixin;
49        mListView = listView;
50    }
51
52    @Override
53    public void startListening() {
54        if (mListView != null) {
55            mListView.setOnScrollListener(this);
56
57            final ListAdapter adapter = mListView.getAdapter();
58            if (mListView.getLastVisiblePosition() < adapter.getCount()) {
59                mRequireScrollMixin.notifyScrollabilityChange(true);
60            }
61        } else {
62            Log.w(TAG, "Cannot require scroll. List view is null");
63        }
64    }
65
66    @Override
67    public void pageScrollDown() {
68        if (mListView != null) {
69            final int height = mListView.getHeight();
70            mListView.smoothScrollBy(height, SCROLL_DURATION);
71        }
72    }
73
74    @Override
75    public void onScrollStateChanged(AbsListView view, int scrollState) {
76    }
77
78    @Override
79    public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount,
80            int totalItemCount) {
81        if (firstVisibleItem + visibleItemCount >= totalItemCount) {
82            mRequireScrollMixin.notifyScrollabilityChange(false);
83        } else {
84            mRequireScrollMixin.notifyScrollabilityChange(true);
85        }
86    }
87}
88