/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.launcher3;
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import android.content.Context;
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import android.util.AttributeSet;
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import android.view.MotionEvent;
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import android.view.View;
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import android.view.ViewGroup;
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import com.android.launcher3.views.RecyclerViewFastScroller;
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import androidx.recyclerview.widget.RecyclerView;
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/**
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* A base {@link RecyclerView}, which does the following:
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* <ul>
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* <li> NOT intercept a touch unless the scrolling velocity is below a predefined threshold.
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* <li> Enable fast scroller.
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* </ul>
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*/
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public abstract class BaseRecyclerView extends RecyclerView {
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protected RecyclerViewFastScroller mScrollbar;
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public BaseRecyclerView(Context context) {
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this(context, null);
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}
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public BaseRecyclerView(Context context, AttributeSet attrs) {
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this(context, attrs, 0);
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}
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public BaseRecyclerView(Context context, AttributeSet attrs, int defStyleAttr) {
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super(context, attrs, defStyleAttr);
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}
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@Override
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protected void onAttachedToWindow() {
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super.onAttachedToWindow();
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bindFastScrollbar();
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}
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public void bindFastScrollbar() {
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ViewGroup parent = (ViewGroup) getParent().getParent();
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mScrollbar = parent.findViewById(R.id.fast_scroller);
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mScrollbar.setRecyclerView(this, parent.findViewById(R.id.fast_scroller_popup));
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onUpdateScrollbar(0);
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}
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public RecyclerViewFastScroller getScrollbar() {
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return mScrollbar;
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}
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public int getScrollBarTop() {
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return getPaddingTop();
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}
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/**
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* Returns the height of the fast scroll bar
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*/
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public int getScrollbarTrackHeight() {
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return mScrollbar.getHeight() - getScrollBarTop() - getPaddingBottom();
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}
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/**
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* Returns the available scroll height:
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* AvailableScrollHeight = Total height of the all items - last page height
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*/
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protected abstract int getAvailableScrollHeight();
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/**
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* Returns the available scroll bar height:
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* AvailableScrollBarHeight = Total height of the visible view - thumb height
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*/
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protected int getAvailableScrollBarHeight() {
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int availableScrollBarHeight = getScrollbarTrackHeight() - mScrollbar.getThumbHeight();
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return availableScrollBarHeight;
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}
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/**
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* Updates the scrollbar thumb offset to match the visible scroll of the recycler view. It does
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* this by mapping the available scroll area of the recycler view to the available space for the
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* scroll bar.
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*
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* @param scrollY the current scroll y
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*/
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protected void synchronizeScrollBarThumbOffsetToViewScroll(int scrollY,
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int availableScrollHeight) {
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// Only show the scrollbar if there is height to be scrolled
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if (availableScrollHeight <= 0) {
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mScrollbar.setThumbOffsetY(-1);
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return;
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}
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// Calculate the current scroll position, the scrollY of the recycler view accounts for the
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// view padding, while the scrollBarY is drawn right up to the background padding (ignoring
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// padding)
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int scrollBarY =
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(int) (((float) scrollY / availableScrollHeight) * getAvailableScrollBarHeight());
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// Calculate the position and size of the scroll bar
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mScrollbar.setThumbOffsetY(scrollBarY);
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}
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/**
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* Returns whether the view itself will handle the touch event or not.
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* @param ev MotionEvent in {@param eventSource}
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*/
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public boolean shouldContainerScroll(MotionEvent ev, View eventSource) {
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float[] point = new float[2];
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point[0] = ev.getX();
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point[1] = ev.getY();
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Utilities.mapCoordInSelfToDescendant(mScrollbar, eventSource, point);
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// IF the MotionEvent is inside the thumb, container should not be pulled down.
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if (mScrollbar.shouldBlockIntercept((int) point[0], (int) point[1])) {
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return false;
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}
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// IF scroller is at the very top OR there is no scroll bar because there is probably not
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// enough items to scroll, THEN it's okay for the container to be pulled down.
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if (getCurrentScrollY() == 0) {
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return true;
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}
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return false;
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}
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/**
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* @return whether fast scrolling is supported in the current state.
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*/
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public boolean supportsFastScrolling() {
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return true;
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}
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/**
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* Maps the touch (from 0..1) to the adapter position that should be visible.
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* <p>Override in each subclass of this base class.
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*
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* @return the scroll top of this recycler view.
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*/
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public abstract int getCurrentScrollY();
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/**
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* Maps the touch (from 0..1) to the adapter position that should be visible.
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* <p>Override in each subclass of this base class.
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*/
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public abstract String scrollToPositionAtProgress(float touchFraction);
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/**
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* Updates the bounds for the scrollbar.
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* <p>Override in each subclass of this base class.
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*/
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public abstract void onUpdateScrollbar(int dy);
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/**
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* <p>Override in each subclass of this base class.
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*/
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public void onFastScrollCompleted() {}
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}
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