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 
17 package com.android.setupwizardlib.view;
18 
19 import android.annotation.TargetApi;
20 import android.content.Context;
21 import android.os.Build;
22 import android.util.AttributeSet;
23 import android.view.View;
24 import android.view.WindowInsets;
25 
26 /**
27  * This class provides sticky header functionality in a scroll view, to use with
28  * SetupWizardIllustration. To use this, add a subview tagged with "sticky", or a subview tagged
29  * with "stickyContainer" and one of its child tagged as "sticky". The sticky container will be
30  * drawn when the sticky element hits the top of the view.
31  *
32  * <p>There are a few things to note:
33  * <ol>
34  *   <li>The two supported scenarios are StickyHeaderScrollView -> subview (stickyContainer) ->
35  *   sticky, and StickyHeaderScrollView -> container -> subview (sticky).
36  *   The arrow (->) represents parent/child relationship and must be immediate child.
37  *   <li>If fitsSystemWindows is true, then this will offset the sticking position by the height of
38  *   the system decorations at the top of the screen.
39  *   <li>For versions before Honeycomb, this will behave like a regular ScrollView.
40  * </ol>
41  *
42  * @see StickyHeaderListView
43  */
44 public class StickyHeaderScrollView extends BottomScrollView {
45 
46     private View mSticky;
47     private View mStickyContainer;
48     private int mStatusBarInset = 0;
49 
StickyHeaderScrollView(Context context)50     public StickyHeaderScrollView(Context context) {
51         super(context);
52     }
53 
StickyHeaderScrollView(Context context, AttributeSet attrs)54     public StickyHeaderScrollView(Context context, AttributeSet attrs) {
55         super(context, attrs);
56     }
57 
StickyHeaderScrollView(Context context, AttributeSet attrs, int defStyleAttr)58     public StickyHeaderScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
59         super(context, attrs, defStyleAttr);
60     }
61 
62     @Override
onLayout(boolean changed, int l, int t, int r, int b)63     protected void onLayout(boolean changed, int l, int t, int r, int b) {
64         super.onLayout(changed, l, t, r, b);
65         if (mSticky == null) {
66             updateStickyView();
67         }
68         updateStickyHeaderPosition();
69     }
70 
updateStickyView()71     public void updateStickyView() {
72         mSticky = findViewWithTag("sticky");
73         mStickyContainer = findViewWithTag("stickyContainer");
74     }
75 
updateStickyHeaderPosition()76     private void updateStickyHeaderPosition() {
77         // Note: for pre-Honeycomb the header will not be moved, so this ScrollView essentially
78         // behaves like a normal BottomScrollView.
79         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
80             if (mSticky != null) {
81                 // The view to draw when sticking to the top
82                 final View drawTarget = mStickyContainer != null ? mStickyContainer : mSticky;
83                 // The offset to draw the view at when sticky
84                 final int drawOffset = mStickyContainer != null ? mSticky.getTop() : 0;
85                 // Position of the draw target, relative to the outside of the scrollView
86                 final int drawTop = drawTarget.getTop() - getScrollY();
87                 if (drawTop + drawOffset < mStatusBarInset || !drawTarget.isShown()) {
88                     // ScrollView translates the whole canvas so we have to compensate for that
89                     drawTarget.setTranslationY(getScrollY() - drawOffset);
90                 } else {
91                     drawTarget.setTranslationY(0);
92                 }
93             }
94         }
95     }
96 
97     @Override
onScrollChanged(int l, int t, int oldl, int oldt)98     protected void onScrollChanged(int l, int t, int oldl, int oldt) {
99         super.onScrollChanged(l, t, oldl, oldt);
100         updateStickyHeaderPosition();
101     }
102 
103     @Override
104     @TargetApi(Build.VERSION_CODES.LOLLIPOP)
onApplyWindowInsets(WindowInsets insets)105     public WindowInsets onApplyWindowInsets(WindowInsets insets) {
106         if (getFitsSystemWindows()) {
107             mStatusBarInset = insets.getSystemWindowInsetTop();
108             insets = insets.replaceSystemWindowInsets(
109                     insets.getSystemWindowInsetLeft(),
110                     0, /* top */
111                     insets.getSystemWindowInsetRight(),
112                     insets.getSystemWindowInsetBottom()
113             );
114         }
115         return insets;
116     }
117 }
118