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 
82     /**
83      * Call this method when the "sticky" view has changed, so this view can update its internal
84      * states as well.
85      */
updateStickyView()86     public void updateStickyView() {
87         final View header = getHeader();
88         if (header != null) {
89             mSticky = header.findViewWithTag("sticky");
90         }
91     }
92 
93     @Override
draw(Canvas canvas)94     public void draw(Canvas canvas) {
95         super.draw(canvas);
96         if (mSticky != null) {
97             final View headerView = getHeader();
98             final int saveCount = canvas.save();
99             // The view to draw when sticking to the top
100             final View drawTarget = headerView != null ? headerView : mSticky;
101             // The offset to draw the view at when sticky
102             final int drawOffset = headerView != null ? mSticky.getTop() : 0;
103             // Position of the draw target, relative to the outside of the scrollView
104             final int drawTop = drawTarget.getTop();
105             if (drawTop + drawOffset < mStatusBarInset || !drawTarget.isShown()) {
106                 // RecyclerView does not translate the canvas, so we can simply draw at the top
107                 mStickyRect.set(0, -drawOffset + mStatusBarInset, drawTarget.getWidth(),
108                         drawTarget.getHeight() - drawOffset + mStatusBarInset);
109                 canvas.translate(0, mStickyRect.top);
110                 canvas.clipRect(0, 0, drawTarget.getWidth(), drawTarget.getHeight());
111                 drawTarget.draw(canvas);
112             } else {
113                 mStickyRect.setEmpty();
114             }
115             canvas.restoreToCount(saveCount);
116         }
117     }
118 
119     @Override
120     @TargetApi(Build.VERSION_CODES.LOLLIPOP)
onApplyWindowInsets(WindowInsets insets)121     public WindowInsets onApplyWindowInsets(WindowInsets insets) {
122         if (getFitsSystemWindows()) {
123             mStatusBarInset = insets.getSystemWindowInsetTop();
124             insets.replaceSystemWindowInsets(
125                     insets.getSystemWindowInsetLeft(),
126                     0, /* top */
127                     insets.getSystemWindowInsetRight(),
128                     insets.getSystemWindowInsetBottom()
129             );
130         }
131         return insets;
132     }
133 
134     @Override
dispatchTouchEvent(MotionEvent ev)135     public boolean dispatchTouchEvent(MotionEvent ev) {
136         if (mStickyRect.contains(ev.getX(), ev.getY())) {
137             ev.offsetLocation(-mStickyRect.left, -mStickyRect.top);
138             return getHeader().dispatchTouchEvent(ev);
139         } else {
140             return super.dispatchTouchEvent(ev);
141         }
142     }
143 }
144