content: /*
   * Copyright (C) 2016 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.graphics.Canvas;
  import android.graphics.RectF;
  import android.os.Build;
  import android.util.AttributeSet;
  import android.view.MotionEvent;
  import android.view.View;
  import android.view.WindowInsets;
  
  /**
   * This class provides sticky header functionality in a recycler view, to use with
   * SetupWizardIllustration. To use this, add a header tagged with "sticky". The header will continue
   * to be drawn when the sticky element hits the top of the view.
   *
   * <p>There are a few things to note:
   *
   * <ol>
   *   <li>The view does not work well with padding. b/16190933
   *   <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.
   * </ol>
   */
  public class StickyHeaderRecyclerView extends HeaderRecyclerView {
  
    private View sticky;
    private int statusBarInset = 0;
    private final RectF stickyRect = new RectF();
  
    public StickyHeaderRecyclerView(Context context) {
      super(context);
    }
  
    public StickyHeaderRecyclerView(Context context, AttributeSet attrs) {
      super(context, attrs);
    }
  
    public StickyHeaderRecyclerView(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();
      }
      if (sticky != null) {
        final View headerView = getHeader();
        if (headerView != null && headerView.getHeight() == 0) {
          headerView.layout(0, -headerView.getMeasuredHeight(), headerView.getMeasuredWidth(), 0);
        }
      }
    }
  
    @Override
    protected void onMeasure(int widthSpec, int heightSpec) {
      super.onMeasure(widthSpec, heightSpec);
      if (sticky != null) {
        measureChild(getHeader(), widthSpec, heightSpec);
      }
    }
  
    /**
     * Call this method when the "sticky" view has changed, so this view can update its internal
     * states as well.
     */
    public void updateStickyView() {
      final View header = getHeader();
      if (header != null) {
        sticky = header.findViewWithTag("sticky");
      }
    }
  
    @Override
    public void draw(Canvas canvas) {
      super.draw(canvas);
      if (sticky != null) {
        final View headerView = getHeader();
        final int saveCount = canvas.save();
        // The view to draw when sticking to the top
        final View drawTarget = headerView != null ? headerView : sticky;
        // The offset to draw the view at when sticky
        final int drawOffset = headerView != null ? sticky.getTop() : 0;
        // Position of the draw target, relative to the outside of the scrollView
        final int drawTop = drawTarget.getTop();
        if (drawTop + drawOffset < statusBarInset || !drawTarget.isShown()) {
          // RecyclerView does not translate the canvas, so we can simply draw at the top
          stickyRect.set(
              0,
              -drawOffset + statusBarInset,
              drawTarget.getWidth(),
              drawTarget.getHeight() - drawOffset + statusBarInset);
          canvas.translate(0, stickyRect.top);
          canvas.clipRect(0, 0, drawTarget.getWidth(), drawTarget.getHeight());
          drawTarget.draw(canvas);
        } else {
          stickyRect.setEmpty();
        }
        canvas.restoreToCount(saveCount);
      }
    }
  
    @Override
    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    public WindowInsets onApplyWindowInsets(WindowInsets insets) {
      if (getFitsSystemWindows()) {
        statusBarInset = insets.getSystemWindowInsetTop();
        insets.replaceSystemWindowInsets(
            insets.getSystemWindowInsetLeft(),
            0, /* top */
            insets.getSystemWindowInsetRight(),
            insets.getSystemWindowInsetBottom());
      }
      return insets;
    }
  
    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
      if (stickyRect.contains(ev.getX(), ev.getY())) {
        ev.offsetLocation(-stickyRect.left, -stickyRect.top);
        return getHeader().dispatchTouchEvent(ev);
      } else {
        return super.dispatchTouchEvent(ev);
      }
    }
  }
  