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/*
* 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() {}
}
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