content: /*
   * Copyright (C) 2015 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.android.setupwizardlib.view;
  
  import android.annotation.TargetApi;
  import android.content.Context;
  import android.os.Build;
  import android.util.AttributeSet;
  import android.view.View;
  import android.view.WindowInsets;
  
  /**
   * This class provides sticky header functionality in a scroll view, to use with
   * SetupWizardIllustration. To use this, add a subview tagged with "sticky", or a subview tagged
   * with "stickyContainer" and one of its child tagged as "sticky". The sticky container will be
   * drawn when the sticky element hits the top of the view.
   *
   * <p>There are a few things to note:
   *
   * <ol>
   *   <li>The two supported scenarios are StickyHeaderScrollView -> subview (stickyContainer) ->
   *       sticky, and StickyHeaderScrollView -> container -> subview (sticky). The arrow (->)
   *       represents parent/child relationship and must be immediate child.
   *   <li>If fitsSystemWindows is true, then this will offset the sticking position by the height of
   *       the system decorations at the top of the screen.
   *   <li>For versions before Honeycomb, this will behave like a regular ScrollView.
   * </ol>
   *
   * @see StickyHeaderListView
   */
  public class StickyHeaderScrollView extends BottomScrollView {
  
    private View sticky;
    private View stickyContainer;
    private int statusBarInset = 0;
  
    public StickyHeaderScrollView(Context context) {
      super(context);
    }
  
    public StickyHeaderScrollView(Context context, AttributeSet attrs) {
      super(context, attrs);
    }
  
    public StickyHeaderScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
      super(context, attrs, defStyleAttr);
    }
  
    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
      super.onLayout(changed, l, t, r, b);
      if (sticky == null) {
        updateStickyView();
      }
      updateStickyHeaderPosition();
    }
  
    public void updateStickyView() {
      sticky = findViewWithTag("sticky");
      stickyContainer = findViewWithTag("stickyContainer");
    }
  
    private void updateStickyHeaderPosition() {
      // Note: for pre-Honeycomb the header will not be moved, so this ScrollView essentially
      // behaves like a normal BottomScrollView.
      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
        if (sticky != null) {
          // The view to draw when sticking to the top
          final View drawTarget = stickyContainer != null ? stickyContainer : sticky;
          // The offset to draw the view at when sticky
          final int drawOffset = stickyContainer != null ? sticky.getTop() : 0;
          // Position of the draw target, relative to the outside of the scrollView
          final int drawTop = drawTarget.getTop() - getScrollY();
          if (drawTop + drawOffset < statusBarInset || !drawTarget.isShown()) {
            // ScrollView translates the whole canvas so we have to compensate for that
            drawTarget.setTranslationY(getScrollY() - drawOffset);
          } else {
            drawTarget.setTranslationY(0);
          }
        }
      }
    }
  
    @Override
    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
      super.onScrollChanged(l, t, oldl, oldt);
      updateStickyHeaderPosition();
    }
  
    @Override
    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    public WindowInsets onApplyWindowInsets(WindowInsets insets) {
      if (getFitsSystemWindows()) {
        statusBarInset = insets.getSystemWindowInsetTop();
        insets =
            insets.replaceSystemWindowInsets(
                insets.getSystemWindowInsetLeft(),
                0, /* top */
                insets.getSystemWindowInsetRight(),
                insets.getSystemWindowInsetBottom());
      }
      return insets;
    }
  }
  