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1 /*
2  * Copyright (C) 2015 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 package com.android.launcher3.allapps;
17 
18 import androidx.recyclerview.widget.LinearSmoothScroller;
19 import androidx.recyclerview.widget.RecyclerView.ViewHolder;
20 
21 import com.android.launcher3.allapps.AlphabeticalAppsList.FastScrollSectionInfo;
22 
23 public class AllAppsFastScrollHelper {
24 
25     private static final int NO_POSITION = -1;
26 
27     private int mTargetFastScrollPosition = NO_POSITION;
28 
29     private AllAppsRecyclerView mRv;
30     private ViewHolder mLastSelectedViewHolder;
31 
AllAppsFastScrollHelper(AllAppsRecyclerView rv)32     public AllAppsFastScrollHelper(AllAppsRecyclerView rv) {
33         mRv = rv;
34     }
35 
36     /**
37      * Smooth scrolls the recycler view to the given section.
38      */
smoothScrollToSection(FastScrollSectionInfo info)39     public void smoothScrollToSection(FastScrollSectionInfo info) {
40         if (mTargetFastScrollPosition == info.fastScrollToItem.position) {
41             return;
42         }
43         mTargetFastScrollPosition = info.fastScrollToItem.position;
44         mRv.getLayoutManager().startSmoothScroll(new MyScroller(mTargetFastScrollPosition));
45     }
46 
onFastScrollCompleted()47     public void onFastScrollCompleted() {
48         mTargetFastScrollPosition = NO_POSITION;
49         setLastHolderSelected(false);
50         mLastSelectedViewHolder = null;
51     }
52 
53 
setLastHolderSelected(boolean isSelected)54     private void setLastHolderSelected(boolean isSelected) {
55         if (mLastSelectedViewHolder != null) {
56             mLastSelectedViewHolder.itemView.setActivated(isSelected);
57             mLastSelectedViewHolder.setIsRecyclable(!isSelected);
58         }
59     }
60 
61     private class MyScroller extends LinearSmoothScroller {
62 
63         private final int mTargetPosition;
64 
MyScroller(int targetPosition)65         public MyScroller(int targetPosition) {
66             super(mRv.getContext());
67 
68             mTargetPosition = targetPosition;
69             setTargetPosition(targetPosition);
70         }
71 
72         @Override
getVerticalSnapPreference()73         protected int getVerticalSnapPreference() {
74             return SNAP_TO_START;
75         }
76 
77         @Override
onStop()78         protected void onStop() {
79             super.onStop();
80             if (mTargetPosition != mTargetFastScrollPosition) {
81                 // Target changed, before the last scroll can finish
82                 return;
83             }
84 
85             ViewHolder currentHolder = mRv.findViewHolderForAdapterPosition(mTargetPosition);
86             if (currentHolder == mLastSelectedViewHolder) {
87                 return;
88             }
89 
90             setLastHolderSelected(false);
91             mLastSelectedViewHolder = currentHolder;
92             setLastHolderSelected(true);
93         }
94 
95         @Override
onStart()96         protected void onStart() {
97             super.onStart();
98             if (mTargetPosition != mTargetFastScrollPosition) {
99                 setLastHolderSelected(false);
100                 mLastSelectedViewHolder = null;
101             }
102         }
103     }
104 }
105