1 /*
2  * Copyright (C) 2016 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.graphics.Canvas;
22 import android.graphics.RectF;
23 import android.os.Build;
24 import android.util.AttributeSet;
25 import android.view.MotionEvent;
26 import android.view.View;
27 import android.view.WindowInsets;
28 
29 /**
30  * This class provides sticky header functionality in a recycler view, to use with
31  * SetupWizardIllustration. To use this, add a header tagged with "sticky". The header will continue
32  * to be drawn when the sticky element hits the top of the view.
33  *
34  * <p>There are a few things to note:
35  * <ol>
36  *   <li>The view does not work well with padding. b/16190933
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  * </ol>
40  */
41 public class StickyHeaderRecyclerView extends HeaderRecyclerView {
42 
43     private View mSticky;
44     private int mStatusBarInset = 0;
45     private RectF mStickyRect = new RectF();
46 
StickyHeaderRecyclerView(Context context)47     public StickyHeaderRecyclerView(Context context) {
48         super(context);
49     }
50 
StickyHeaderRecyclerView(Context context, AttributeSet attrs)51     public StickyHeaderRecyclerView(Context context, AttributeSet attrs) {
52         super(context, attrs);
53     }
54 
StickyHeaderRecyclerView(Context context, AttributeSet attrs, int defStyleAttr)55     public StickyHeaderRecyclerView(Context context, AttributeSet attrs, int defStyleAttr) {
56         super(context, attrs, defStyleAttr);
57     }
58 
59     @Override
onLayout(boolean changed, int l, int t, int r, int b)60     protected void onLayout(boolean changed, int l, int t, int r, int b) {
61         super.onLayout(changed, l, t, r, b);
62         if (mSticky == null) {
63             updateStickyView();
64         }
65         if (mSticky != null) {
66             final View headerView = getHeader();
67             if (headerView != null && headerView.getHeight() == 0) {
68                 headerView.layout(0, -headerView.getMeasuredHeight(),
69                         headerView.getMeasuredWidth(), 0);
70             }
71         }
72     }
73 
74     @Override
onMeasure(int widthSpec, int heightSpec)75     protected void onMeasure(int widthSpec, int heightSpec) {
76         super.onMeasure(widthSpec, heightSpec);
77         if (mSticky != null) {
78             measureChild(getHeader(), widthSpec, heightSpec);
79         }
80     }
81 
updateStickyView()82     public void updateStickyView() {
83         final View header = getHeader();
84         if (header != null) {
85             mSticky = header.findViewWithTag("sticky");
86         }
87     }
88 
89     @Override
draw(Canvas canvas)90     public void draw(Canvas canvas) {
91         super.draw(canvas);
92         if (mSticky != null) {
93             final View headerView = getHeader();
94             final int saveCount = canvas.save();
95             // The view to draw when sticking to the top
96             final View drawTarget = headerView != null ? headerView : mSticky;
97             // The offset to draw the view at when sticky
98             final int drawOffset = headerView != null ? mSticky.getTop() : 0;
99             // Position of the draw target, relative to the outside of the scrollView
100             final int drawTop = drawTarget.getTop();
101             if (drawTop + drawOffset < mStatusBarInset || !drawTarget.isShown()) {
102                 // RecyclerView does not translate the canvas, so we can simply draw at the top
103                 mStickyRect.set(0, -drawOffset + mStatusBarInset, drawTarget.getWidth(),
104                         drawTarget.getHeight() - drawOffset + mStatusBarInset);
105                 canvas.translate(0, mStickyRect.top);
106                 canvas.clipRect(0, 0, drawTarget.getWidth(), drawTarget.getHeight());
107                 drawTarget.draw(canvas);
108             } else {
109                 mStickyRect.setEmpty();
110             }
111             canvas.restoreToCount(saveCount);
112         }
113     }
114 
115     @Override
116     @TargetApi(Build.VERSION_CODES.LOLLIPOP)
onApplyWindowInsets(WindowInsets insets)117     public WindowInsets onApplyWindowInsets(WindowInsets insets) {
118         if (getFitsSystemWindows()) {
119             mStatusBarInset = insets.getSystemWindowInsetTop();
120             insets.replaceSystemWindowInsets(
121                     insets.getSystemWindowInsetLeft(),
122                     0, /* top */
123                     insets.getSystemWindowInsetRight(),
124                     insets.getSystemWindowInsetBottom()
125             );
126         }
127         return insets;
128     }
129 
130     @Override
dispatchTouchEvent(MotionEvent ev)131     public boolean dispatchTouchEvent(MotionEvent ev) {
132         if (mStickyRect.contains(ev.getX(), ev.getY())) {
133             ev.offsetLocation(-mStickyRect.left, -mStickyRect.top);
134             return getHeader().dispatchTouchEvent(ev);
135         } else {
136             return super.dispatchTouchEvent(ev);
137         }
138     }
139 }
140