src/com/android/launcher3/BaseRecyclerView.java - LeafOS-Project/android_packages_apps_Launcher3 - Gitiles

 /*
  * 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 com.android.launcher3.util.Thunk;


 /**
  * 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 {

     private static final int SCROLL_DELTA_THRESHOLD_DP = 4;

     /** Keeps the last known scrolling delta/velocity along y-axis. */
     @Thunk int mDy = 0;
     private float mDeltaThreshold;

     protected final BaseRecyclerViewFastScrollBar mScrollbar;

     private int mDownX;
     private int mDownY;
     private int mLastY;

     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);
         mDeltaThreshold = getResources().getDisplayMetrics().density * SCROLL_DELTA_THRESHOLD_DP;
         mScrollbar = new BaseRecyclerViewFastScrollBar(this, getResources());

         ScrollListener listener = new ScrollListener();
         setOnScrollListener(listener);
     }

     private class ScrollListener extends OnScrollListener {
         public ScrollListener() {
             // Do nothing
         }

         @Override
         public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
             mDy = dy;

             // TODO(winsonc): If we want to animate the section heads while scrolling, we can
             //                initiate that here if the recycler view scroll state is not
             //                RecyclerView.SCROLL_STATE_IDLE.

             onUpdateScrollbar(dy);
         }
     }

     public void reset() {
         mScrollbar.reattachThumbToScroll();
     }

     @Override
     protected void onFinishInflate() {
         super.onFinishInflate();
         addOnItemTouchListener(this);
     }

     @Override
     protected void onAttachedToWindow() {
         super.onAttachedToWindow();
         mScrollbar.setPopupView(((ViewGroup) getParent()).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) {
         int action = ev.getAction();
         int x = (int) ev.getX();
         int y = (int) ev.getY();
         switch (action) {
             case MotionEvent.ACTION_DOWN:
                 // Keep track of the down positions
                 mDownX = x;
                 mDownY = mLastY = y;
                 if (shouldStopScroll(ev)) {
                     stopScroll();
                 }
                 mScrollbar.handleTouchEvent(ev, mDownX, mDownY, mLastY);
                 break;
             case MotionEvent.ACTION_MOVE:
                 mLastY = y;
                 mScrollbar.handleTouchEvent(ev, mDownX, mDownY, mLastY);
                 break;
             case MotionEvent.ACTION_UP:
             case MotionEvent.ACTION_CANCEL:
                 onFastScrollCompleted();
                 mScrollbar.handleTouchEvent(ev, mDownX, mDownY, mLastY);
                 break;
         }
         return mScrollbar.isDraggingThumb();
     }

     public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
         // DO NOT REMOVE, NEEDED IMPLEMENTATION FOR M BUILDS
     }

     /**
      * Returns whether this {@link MotionEvent} should trigger the scroll to be stopped.
      */
     protected boolean shouldStopScroll(MotionEvent ev) {
         if (ev.getAction() == MotionEvent.ACTION_DOWN) {
             if ((Math.abs(mDy) < mDeltaThreshold &&
                     getScrollState() != RecyclerView.SCROLL_STATE_IDLE)) {
                 // now the touch events are being passed to the {@link WidgetCell} until the
                 // touch sequence goes over the touch slop.
                 return true;
             }
         }
         return false;
     }

     /**
      * Returns the height of the fast scroll bar
      */
     protected int getScrollbarTrackHeight() {
         return getHeight();
     }

     /**
      * 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 track color (ignoring alpha), can be overridden by each subclass.
      */
     public int getFastScrollerTrackColor(int defaultTrackColor) {
         return defaultTrackColor;
     }

     /**
      * Returns the scrollbar for this recycler view.
      */
     public BaseRecyclerViewFastScrollBar getScrollBar() {
         return mScrollbar;
     }

     @Override
     protected void dispatchDraw(Canvas canvas) {
         super.dispatchDraw(canvas);
         onUpdateScrollbar(0);
         mScrollbar.draw(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.
      */
     protected 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.
      */
     protected abstract String scrollToPositionAtProgress(float touchFraction);

     /**
      * Updates the bounds for the scrollbar.
      * <p>Override in each subclass of this base class.
      */
     protected abstract void onUpdateScrollbar(int dy);

     /**
      * <p>Override in each subclass of this base class.
      */
     protected void onFastScrollCompleted() {}
 }
	/*
	* 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 com.android.launcher3.util.Thunk;


	/**
	* 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 {

	private static final int SCROLL_DELTA_THRESHOLD_DP = 4;

	/** Keeps the last known scrolling delta/velocity along y-axis. */
	@Thunk int mDy = 0;
	private float mDeltaThreshold;

	protected final BaseRecyclerViewFastScrollBar mScrollbar;

	private int mDownX;
	private int mDownY;
	private int mLastY;

	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);
	mDeltaThreshold = getResources().getDisplayMetrics().density * SCROLL_DELTA_THRESHOLD_DP;
	mScrollbar = new BaseRecyclerViewFastScrollBar(this, getResources());

	ScrollListener listener = new ScrollListener();
	setOnScrollListener(listener);
	}

	private class ScrollListener extends OnScrollListener {
	public ScrollListener() {
	// Do nothing
	}

	@Override
	public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
	mDy = dy;

	// TODO(winsonc): If we want to animate the section heads while scrolling, we can
	// initiate that here if the recycler view scroll state is not
	// RecyclerView.SCROLL_STATE_IDLE.

	onUpdateScrollbar(dy);
	}
	}

	public void reset() {
	mScrollbar.reattachThumbToScroll();
	}

	@Override
	protected void onFinishInflate() {
	super.onFinishInflate();
	addOnItemTouchListener(this);
	}

	@Override
	protected void onAttachedToWindow() {
	super.onAttachedToWindow();
	mScrollbar.setPopupView(((ViewGroup) getParent()).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) {
	int action = ev.getAction();
	int x = (int) ev.getX();
	int y = (int) ev.getY();
	switch (action) {
	case MotionEvent.ACTION_DOWN:
	// Keep track of the down positions
	mDownX = x;
	mDownY = mLastY = y;
	if (shouldStopScroll(ev)) {
	stopScroll();
	}
	mScrollbar.handleTouchEvent(ev, mDownX, mDownY, mLastY);
	break;
	case MotionEvent.ACTION_MOVE:
	mLastY = y;
	mScrollbar.handleTouchEvent(ev, mDownX, mDownY, mLastY);
	break;
	case MotionEvent.ACTION_UP:
	case MotionEvent.ACTION_CANCEL:
	onFastScrollCompleted();
	mScrollbar.handleTouchEvent(ev, mDownX, mDownY, mLastY);
	break;
	}
	return mScrollbar.isDraggingThumb();
	}

	public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
	// DO NOT REMOVE, NEEDED IMPLEMENTATION FOR M BUILDS
	}

	/**
	* Returns whether this {@link MotionEvent} should trigger the scroll to be stopped.
	*/
	protected boolean shouldStopScroll(MotionEvent ev) {
	if (ev.getAction() == MotionEvent.ACTION_DOWN) {
	if ((Math.abs(mDy) < mDeltaThreshold &&
	getScrollState() != RecyclerView.SCROLL_STATE_IDLE)) {
	// now the touch events are being passed to the {@link WidgetCell} until the
	// touch sequence goes over the touch slop.
	return true;
	}
	}
	return false;
	}

	/**
	* Returns the height of the fast scroll bar
	*/
	protected int getScrollbarTrackHeight() {
	return getHeight();
	}

	/**
	* 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 track color (ignoring alpha), can be overridden by each subclass.
	*/
	public int getFastScrollerTrackColor(int defaultTrackColor) {
	return defaultTrackColor;
	}

	/**
	* Returns the scrollbar for this recycler view.
	*/
	public BaseRecyclerViewFastScrollBar getScrollBar() {
	return mScrollbar;
	}

	@Override
	protected void dispatchDraw(Canvas canvas) {
	super.dispatchDraw(canvas);
	onUpdateScrollbar(0);
	mScrollbar.draw(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.
	*/
	protected 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.
	*/
	protected abstract String scrollToPositionAtProgress(float touchFraction);

	/**
	* Updates the bounds for the scrollbar.
	* <p>Override in each subclass of this base class.
	*/
	protected abstract void onUpdateScrollbar(int dy);

	/**
	* <p>Override in each subclass of this base class.
	*/
	protected void onFastScrollCompleted() {}
	}