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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 
     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 
     50     public StickyHeaderScrollView(Context context) {
     51         super(context);
     52     }
     53 
     54     public StickyHeaderScrollView(Context context, AttributeSet attrs) {
     55         super(context, attrs);
     56     }
     57 
     58     public StickyHeaderScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
     59         super(context, attrs, defStyleAttr);
     60     }
     61 
     62     @Override
     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 
     71     public void updateStickyView() {
     72         mSticky = findViewWithTag("sticky");
     73         mStickyContainer = findViewWithTag("stickyContainer");
     74     }
     75 
     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
     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)
    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