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 17package com.android.setupwizardlib.view; 18 19import android.annotation.TargetApi; 20import android.content.Context; 21import android.graphics.Canvas; 22import android.graphics.RectF; 23import android.os.Build; 24import android.util.AttributeSet; 25import android.view.MotionEvent; 26import android.view.View; 27import 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 */ 41public class StickyHeaderRecyclerView extends HeaderRecyclerView { 42 43 private View mSticky; 44 private int mStatusBarInset = 0; 45 private RectF mStickyRect = new RectF(); 46 47 public StickyHeaderRecyclerView(Context context) { 48 super(context); 49 } 50 51 public StickyHeaderRecyclerView(Context context, AttributeSet attrs) { 52 super(context, attrs); 53 } 54 55 public StickyHeaderRecyclerView(Context context, AttributeSet attrs, int defStyleAttr) { 56 super(context, attrs, defStyleAttr); 57 } 58 59 @Override 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 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 public void updateStickyView() { 83 final View header = getHeader(); 84 if (header != null) { 85 mSticky = header.findViewWithTag("sticky"); 86 } 87 } 88 89 @Override 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) 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 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