1 /* 2 * Copyright (C) 2020 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.deskclock 18 19 import android.animation.ValueAnimator 20 import android.view.View 21 import android.widget.AbsListView 22 import android.widget.ListView 23 import androidx.recyclerview.widget.RecyclerView 24 25 import com.android.deskclock.data.DataModel 26 import com.android.deskclock.uidata.TabScrollListener 27 import com.android.deskclock.uidata.UiDataModel 28 29 /** 30 * This controller encapsulates the logic that watches a model for changes to scroll state and 31 * updates the display state of an associated drop shadow. The observable model may take many forms 32 * including ListViews, RecyclerViews and this application's UiDataModel. Each of these models can 33 * indicate when content is scrolled to its top. When the content is scrolled to the top the drop 34 * shadow is hidden and the content appears flush with the app bar. When the content is scrolled 35 * up the drop shadow is displayed making the content appear to scroll below the app bar. 36 */ 37 class DropShadowController private constructor( 38 /** The component that displays a drop shadow. */ 39 private val mDropShadowView: View 40 ) { 41 /** Updates [.mDropShadowView] in response to changes in the backing scroll model. */ 42 private val mScrollChangeWatcher = ScrollChangeWatcher() 43 44 /** Fades the [@mDropShadowView] in/out as scroll state changes. */ 45 private val mDropShadowAnimator: ValueAnimator = 46 AnimatorUtils.getAlphaAnimator(mDropShadowView, 0f, 1f) 47 .setDuration(UiDataModel.uiDataModel.shortAnimationDuration) 48 49 /** Tab bar's hairline, which is hidden whenever the drop shadow is displayed. */ 50 private var mHairlineView: View? = null 51 52 // Supported sources of scroll position include: ListView, RecyclerView and UiDataModel. 53 private var mRecyclerView: RecyclerView? = null 54 private var mUiDataModel: UiDataModel? = null 55 private var mListView: ListView? = null 56 57 /** 58 * @param dropShadowView to be hidden/shown as `uiDataModel` reports scrolling changes 59 * @param uiDataModel models the vertical scrolling state of the application's selected tab 60 * @param hairlineView at the bottom of the tab bar to be hidden or shown when the drop shadow 61 * is displayed or hidden, respectively. 62 */ 63 constructor( 64 dropShadowView: View, 65 uiDataModel: UiDataModel, 66 hairlineView: View 67 ) : this(dropShadowView) { 68 mUiDataModel = uiDataModel 69 mUiDataModel?.addTabScrollListener(mScrollChangeWatcher) 70 mHairlineView = hairlineView 71 updateDropShadow(!uiDataModel.isSelectedTabScrolledToTop) 72 } 73 74 /** 75 * @param dropShadowView to be hidden/shown as `listView` reports scrolling changes 76 * @param listView a scrollable view that dictates the visibility of `dropShadowView` 77 */ 78 constructor(dropShadowView: View, listView: ListView) : this(dropShadowView) { 79 mListView = listView 80 mListView?.setOnScrollListener(mScrollChangeWatcher) 81 updateDropShadow(!Utils.isScrolledToTop(listView)) 82 } 83 84 /** 85 * @param dropShadowView to be hidden/shown as `recyclerView` reports scrolling changes 86 * @param recyclerView a scrollable view that dictates the visibility of `dropShadowView` 87 */ 88 constructor(dropShadowView: View, recyclerView: RecyclerView) : this(dropShadowView) { 89 mRecyclerView = recyclerView 90 mRecyclerView?.addOnScrollListener(mScrollChangeWatcher) 91 updateDropShadow(!Utils.isScrolledToTop(recyclerView)) 92 } 93 94 /** 95 * Stop updating the drop shadow in response to scrolling changes. Stop listening to the backing 96 * scrollable entity for changes. This is important to avoid memory leaks. 97 */ stopnull98 fun stop() { 99 when { 100 mRecyclerView != null -> mRecyclerView?.removeOnScrollListener(mScrollChangeWatcher) 101 mListView != null -> mListView?.setOnScrollListener(null) 102 mUiDataModel != null -> mUiDataModel?.removeTabScrollListener(mScrollChangeWatcher) 103 } 104 } 105 106 /** 107 * @param shouldShowDropShadow `true` indicates the drop shadow should be displayed; 108 * `false` indicates the drop shadow should be hidden 109 */ updateDropShadownull110 private fun updateDropShadow(shouldShowDropShadow: Boolean) { 111 if (!shouldShowDropShadow && mDropShadowView.alpha != 0f) { 112 if (DataModel.dataModel.isApplicationInForeground) { 113 mDropShadowAnimator.reverse() 114 } else { 115 mDropShadowView.alpha = 0f 116 } 117 mHairlineView?.visibility = View.VISIBLE 118 } 119 if (shouldShowDropShadow && mDropShadowView.alpha != 1f) { 120 if (DataModel.dataModel.isApplicationInForeground) { 121 mDropShadowAnimator.start() 122 } else { 123 mDropShadowView.alpha = 1f 124 } 125 mHairlineView?.visibility = View.INVISIBLE 126 } 127 } 128 129 /** 130 * Update the drop shadow as the scrollable entity is scrolled. 131 */ 132 private inner class ScrollChangeWatcher 133 : RecyclerView.OnScrollListener(), TabScrollListener, AbsListView.OnScrollListener { 134 // RecyclerView scrolled. onScrollednull135 override fun onScrolled(view: RecyclerView, dx: Int, dy: Int) { 136 updateDropShadow(!Utils.isScrolledToTop(view)) 137 } 138 139 // ListView scrolled. onScrollStateChangednull140 override fun onScrollStateChanged(view: AbsListView, scrollState: Int) { 141 } 142 onScrollnull143 override fun onScroll( 144 view: AbsListView, 145 firstVisibleItem: Int, 146 visibleItemCount: Int, 147 totalItemCount: Int 148 ) { 149 updateDropShadow(!Utils.isScrolledToTop(view)) 150 } 151 152 // UiDataModel reports scroll change. selectedTabScrollToTopChangednull153 override fun selectedTabScrollToTopChanged( 154 selectedTab: UiDataModel.Tab, 155 scrolledToTop: Boolean 156 ) { 157 updateDropShadow(!scrolledToTop) 158 } 159 } 160 }