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 17 package com.android.setupwizardlib.template; 18 19 import android.support.annotation.NonNull; 20 import android.support.annotation.Nullable; 21 import android.util.Log; 22 import android.widget.AbsListView; 23 import android.widget.ListAdapter; 24 import android.widget.ListView; 25 26 import 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 */ 32 public 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