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.launcher3;
  
  import android.content.Context;
  import android.graphics.Canvas;
  import android.support.v7.widget.RecyclerView;
  import android.util.AttributeSet;
  import android.view.MotionEvent;
  import android.view.ViewGroup;
  import android.widget.TextView;
  
  import com.android.launcher3.views.RecyclerViewFastScroller;
  
  
  /**
   * A base {@link RecyclerView}, which does the following:
   * <ul>
   *   <li> NOT intercept a touch unless the scrolling velocity is below a predefined threshold.
   *   <li> Enable fast scroller.
   * </ul>
   */
  public abstract class BaseRecyclerView extends RecyclerView
          implements RecyclerView.OnItemTouchListener {
  
      protected RecyclerViewFastScroller mScrollbar;
  
      public BaseRecyclerView(Context context) {
          this(context, null);
      }
  
      public BaseRecyclerView(Context context, AttributeSet attrs) {
          this(context, attrs, 0);
      }
  
      public BaseRecyclerView(Context context, AttributeSet attrs, int defStyleAttr) {
          super(context, attrs, defStyleAttr);
      }
  
      @Override
      protected void onFinishInflate() {
          super.onFinishInflate();
          addOnItemTouchListener(this);
      }
  
      @Override
      protected void onAttachedToWindow() {
          super.onAttachedToWindow();
          ViewGroup parent = (ViewGroup) getParent();
          mScrollbar = parent.findViewById(R.id.fast_scroller);
          mScrollbar.setRecyclerView(this, (TextView) parent.findViewById(R.id.fast_scroller_popup));
      }
  
      /**
       * We intercept the touch handling only to support fast scrolling when initiated from the
       * scroll bar.  Otherwise, we fall back to the default RecyclerView touch handling.
       */
      @Override
      public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent ev) {
          return handleTouchEvent(ev);
      }
  
      @Override
      public void onTouchEvent(RecyclerView rv, MotionEvent ev) {
          handleTouchEvent(ev);
      }
  
      /**
       * Handles the touch event and determines whether to show the fast scroller (or updates it if
       * it is already showing).
       */
      private boolean handleTouchEvent(MotionEvent ev) {
          // Move to mScrollbar's coordinate system.
          int left = getLeft() - mScrollbar.getLeft();
          int top = getTop() - mScrollbar.getTop();
          ev.offsetLocation(left, top);
          try {
              return mScrollbar.handleTouchEvent(ev);
          } finally {
              ev.offsetLocation(-left, -top);
          }
      }
  
      public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
          // DO NOT REMOVE, NEEDED IMPLEMENTATION FOR M BUILDS
      }
  
      /**
       * Returns the height of the fast scroll bar
       */
      public int getScrollbarTrackHeight() {
          return getHeight() - getPaddingTop() - getPaddingBottom();
      }
  
      /**
       * Returns the available scroll height:
       *   AvailableScrollHeight = Total height of the all items - last page height
       */
      protected abstract int getAvailableScrollHeight();
  
      /**
       * Returns the available scroll bar height:
       *   AvailableScrollBarHeight = Total height of the visible view - thumb height
       */
      protected int getAvailableScrollBarHeight() {
          int availableScrollBarHeight = getScrollbarTrackHeight() - mScrollbar.getThumbHeight();
          return availableScrollBarHeight;
      }
  
      /**
       * Returns the scrollbar for this recycler view.
       */
      public RecyclerViewFastScroller getScrollBar() {
          return mScrollbar;
      }
  
      @Override
      protected void dispatchDraw(Canvas canvas) {
          onUpdateScrollbar(0);
          super.dispatchDraw(canvas);
      }
  
      /**
       * Updates the scrollbar thumb offset to match the visible scroll of the recycler view.  It does
       * this by mapping the available scroll area of the recycler view to the available space for the
       * scroll bar.
       *
       * @param scrollY the current scroll y
       */
      protected void synchronizeScrollBarThumbOffsetToViewScroll(int scrollY,
              int availableScrollHeight) {
          // Only show the scrollbar if there is height to be scrolled
          if (availableScrollHeight <= 0) {
              mScrollbar.setThumbOffsetY(-1);
              return;
          }
  
          // Calculate the current scroll position, the scrollY of the recycler view accounts for the
          // view padding, while the scrollBarY is drawn right up to the background padding (ignoring
          // padding)
          int scrollBarY =
                  (int) (((float) scrollY / availableScrollHeight) * getAvailableScrollBarHeight());
  
          // Calculate the position and size of the scroll bar
          mScrollbar.setThumbOffsetY(scrollBarY);
      }
  
      /**
       * @return whether fast scrolling is supported in the current state.
       */
      public boolean supportsFastScrolling() {
          return true;
      }
  
      /**
       * Maps the touch (from 0..1) to the adapter position that should be visible.
       * <p>Override in each subclass of this base class.
       *
       * @return the scroll top of this recycler view.
       */
      public abstract int getCurrentScrollY();
  
      /**
       * Maps the touch (from 0..1) to the adapter position that should be visible.
       * <p>Override in each subclass of this base class.
       */
      public abstract String scrollToPositionAtProgress(float touchFraction);
  
      /**
       * Updates the bounds for the scrollbar.
       * <p>Override in each subclass of this base class.
       */
      public abstract void onUpdateScrollbar(int dy);
  
      /**
       * <p>Override in each subclass of this base class.
       */
      public void onFastScrollCompleted() {}
  }