385 lines
15 KiB
Java
385 lines
15 KiB
Java
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/*
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* Copyright 2014 Soichiro Kashima
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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.github.ksoichiro.android.observablescrollview;
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import android.content.Context;
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import android.os.Build;
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import android.os.Parcel;
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import android.os.Parcelable;
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import android.util.AttributeSet;
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import android.util.SparseIntArray;
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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 android.widget.AbsListView;
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import android.widget.GridView;
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/**
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* GridView that its scroll position can be observed.
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*/
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public class ObservableGridView extends GridView implements Scrollable {
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// Fields that should be saved onSaveInstanceState
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private int mPrevFirstVisiblePosition;
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private int mPrevFirstVisibleChildHeight = -1;
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private int mPrevScrolledChildrenHeight;
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private int mPrevScrollY;
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private int mScrollY;
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private SparseIntArray mChildrenHeights;
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// Fields that don't need to be saved onSaveInstanceState
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private ObservableScrollViewCallbacks mCallbacks;
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private ScrollState mScrollState;
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private boolean mFirstScroll;
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private boolean mDragging;
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private boolean mIntercepted;
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private MotionEvent mPrevMoveEvent;
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private ViewGroup mTouchInterceptionViewGroup;
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private OnScrollListener mOriginalScrollListener;
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private OnScrollListener mScrollListener = new OnScrollListener() {
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@Override
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public void onScrollStateChanged(AbsListView view, int scrollState) {
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if (mOriginalScrollListener != null) {
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mOriginalScrollListener.onScrollStateChanged(view, scrollState);
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}
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}
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@Override
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public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
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if (mOriginalScrollListener != null) {
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mOriginalScrollListener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount);
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}
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// AbsListView#invokeOnItemScrollListener calls onScrollChanged(0, 0, 0, 0)
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// on Android 4.0+, but Android 2.3 is not. (Android 3.0 is unknown)
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// So call it with onScrollListener.
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onScrollChanged();
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}
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};
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public ObservableGridView(Context context) {
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super(context);
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init();
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}
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public ObservableGridView(Context context, AttributeSet attrs) {
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super(context, attrs);
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init();
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}
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public ObservableGridView(Context context, AttributeSet attrs, int defStyle) {
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super(context, attrs, defStyle);
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init();
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}
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@Override
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public void onRestoreInstanceState(Parcelable state) {
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SavedState ss = (SavedState) state;
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mPrevFirstVisiblePosition = ss.prevFirstVisiblePosition;
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mPrevFirstVisibleChildHeight = ss.prevFirstVisibleChildHeight;
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mPrevScrolledChildrenHeight = ss.prevScrolledChildrenHeight;
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mPrevScrollY = ss.prevScrollY;
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mScrollY = ss.scrollY;
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mChildrenHeights = ss.childrenHeights;
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super.onRestoreInstanceState(ss.getSuperState());
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}
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@Override
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public Parcelable onSaveInstanceState() {
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Parcelable superState = super.onSaveInstanceState();
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SavedState ss = new SavedState(superState);
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ss.prevFirstVisiblePosition = mPrevFirstVisiblePosition;
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ss.prevFirstVisibleChildHeight = mPrevFirstVisibleChildHeight;
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ss.prevScrolledChildrenHeight = mPrevScrolledChildrenHeight;
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ss.prevScrollY = mPrevScrollY;
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ss.scrollY = mScrollY;
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ss.childrenHeights = mChildrenHeights;
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return ss;
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}
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@Override
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public boolean onInterceptTouchEvent(MotionEvent ev) {
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if (mCallbacks != null) {
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switch (ev.getActionMasked()) {
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case MotionEvent.ACTION_DOWN:
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// Whether or not motion events are consumed by children,
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// flag initializations which are related to ACTION_DOWN events should be executed.
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// Because if the ACTION_DOWN is consumed by children and only ACTION_MOVEs are
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// passed to parent (this view), the flags will be invalid.
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// Also, applications might implement initialization codes to onDownMotionEvent,
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// so call it here.
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mFirstScroll = mDragging = true;
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mCallbacks.onDownMotionEvent();
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break;
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}
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}
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return super.onInterceptTouchEvent(ev);
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}
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@Override
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public boolean onTouchEvent(MotionEvent ev) {
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if (mCallbacks != null) {
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switch (ev.getActionMasked()) {
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case MotionEvent.ACTION_UP:
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case MotionEvent.ACTION_CANCEL:
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mIntercepted = false;
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mDragging = false;
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mCallbacks.onUpOrCancelMotionEvent(mScrollState);
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break;
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case MotionEvent.ACTION_MOVE:
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if (mPrevMoveEvent == null) {
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mPrevMoveEvent = ev;
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}
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float diffY = ev.getY() - mPrevMoveEvent.getY();
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mPrevMoveEvent = MotionEvent.obtainNoHistory(ev);
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if (getCurrentScrollY() - diffY <= 0) {
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// Can't scroll anymore.
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if (mIntercepted) {
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// Already dispatched ACTION_DOWN event to parents, so stop here.
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return false;
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}
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// Apps can set the interception target other than the direct parent.
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final ViewGroup parent;
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if (mTouchInterceptionViewGroup == null) {
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parent = (ViewGroup) getParent();
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} else {
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parent = mTouchInterceptionViewGroup;
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}
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// Get offset to parents. If the parent is not the direct parent,
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// we should aggregate offsets from all of the parents.
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float offsetX = 0;
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float offsetY = 0;
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for (View v = this; v != null && v != parent; v = (View) v.getParent()) {
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offsetX += v.getLeft() - v.getScrollX();
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offsetY += v.getTop() - v.getScrollY();
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}
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final MotionEvent event = MotionEvent.obtainNoHistory(ev);
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event.offsetLocation(offsetX, offsetY);
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if (parent.onInterceptTouchEvent(event)) {
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mIntercepted = true;
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// If the parent wants to intercept ACTION_MOVE events,
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// we pass ACTION_DOWN event to the parent
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// as if these touch events just have began now.
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event.setAction(MotionEvent.ACTION_DOWN);
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// Return this onTouchEvent() first and set ACTION_DOWN event for parent
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// to the queue, to keep events sequence.
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post(new Runnable() {
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@Override
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public void run() {
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parent.dispatchTouchEvent(event);
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}
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});
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return false;
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}
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// Even when this can't be scrolled anymore,
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// simply returning false here may cause subView's click,
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// so delegate it to super.
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return super.onTouchEvent(ev);
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}
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break;
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}
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}
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return super.onTouchEvent(ev);
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}
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@Override
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public void setOnScrollListener(OnScrollListener l) {
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// Don't set l to super.setOnScrollListener().
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// l receives all events through mScrollListener.
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mOriginalScrollListener = l;
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}
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@Override
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public void setScrollViewCallbacks(ObservableScrollViewCallbacks listener) {
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mCallbacks = listener;
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}
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@Override
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public void setTouchInterceptionViewGroup(ViewGroup viewGroup) {
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mTouchInterceptionViewGroup = viewGroup;
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}
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@Override
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public void scrollVerticallyTo(int y) {
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scrollTo(0, y);
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}
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@Override
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public int getCurrentScrollY() {
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return mScrollY;
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}
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private void init() {
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mChildrenHeights = new SparseIntArray();
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super.setOnScrollListener(mScrollListener);
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}
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private int getNumColumnsCompat() {
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if (Build.VERSION.SDK_INT >= 11) {
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return getNumColumns();
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} else {
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int columns = 0;
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if (getChildCount() > 0) {
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int width = getChildAt(0).getMeasuredWidth();
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if (width > 0) {
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columns = getWidth() / width;
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}
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}
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return columns > 0 ? columns : AUTO_FIT;
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}
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}
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private void onScrollChanged() {
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if (mCallbacks != null) {
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if (getChildCount() > 0) {
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int firstVisiblePosition = getFirstVisiblePosition();
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for (int i = getFirstVisiblePosition(), j = 0; i <= getLastVisiblePosition(); i++, j++) {
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if (mChildrenHeights.indexOfKey(i) < 0 || getChildAt(j).getHeight() != mChildrenHeights.get(i)) {
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if (i % getNumColumnsCompat() == 0) {
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mChildrenHeights.put(i, getChildAt(j).getHeight());
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}
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}
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}
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View firstVisibleChild = getChildAt(0);
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if (firstVisibleChild != null) {
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if (mPrevFirstVisiblePosition < firstVisiblePosition) {
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// scroll down
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int skippedChildrenHeight = 0;
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if (firstVisiblePosition - mPrevFirstVisiblePosition != 1) {
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for (int i = firstVisiblePosition - 1; i > mPrevFirstVisiblePosition; i--) {
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if (0 < mChildrenHeights.indexOfKey(i)) {
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skippedChildrenHeight += mChildrenHeights.get(i);
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}
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}
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}
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mPrevScrolledChildrenHeight += mPrevFirstVisibleChildHeight + skippedChildrenHeight;
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mPrevFirstVisibleChildHeight = firstVisibleChild.getHeight();
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} else if (firstVisiblePosition < mPrevFirstVisiblePosition) {
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// scroll up
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int skippedChildrenHeight = 0;
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if (mPrevFirstVisiblePosition - firstVisiblePosition != 1) {
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for (int i = mPrevFirstVisiblePosition - 1; i > firstVisiblePosition; i--) {
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if (0 < mChildrenHeights.indexOfKey(i)) {
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skippedChildrenHeight += mChildrenHeights.get(i);
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}
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}
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}
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mPrevScrolledChildrenHeight -= firstVisibleChild.getHeight() + skippedChildrenHeight;
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mPrevFirstVisibleChildHeight = firstVisibleChild.getHeight();
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} else if (firstVisiblePosition == 0) {
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mPrevFirstVisibleChildHeight = firstVisibleChild.getHeight();
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}
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if (mPrevFirstVisibleChildHeight < 0) {
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mPrevFirstVisibleChildHeight = 0;
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}
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mScrollY = mPrevScrolledChildrenHeight - firstVisibleChild.getTop();
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mPrevFirstVisiblePosition = firstVisiblePosition;
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mCallbacks.onScrollChanged(mScrollY, mFirstScroll, mDragging);
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if (mFirstScroll) {
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mFirstScroll = false;
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}
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if (mPrevScrollY < mScrollY) {
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mScrollState = ScrollState.UP;
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} else if (mScrollY < mPrevScrollY) {
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mScrollState = ScrollState.DOWN;
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} else {
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mScrollState = ScrollState.STOP;
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}
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mPrevScrollY = mScrollY;
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}
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}
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}
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}
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static class SavedState extends BaseSavedState {
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int prevFirstVisiblePosition;
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int prevFirstVisibleChildHeight = -1;
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int prevScrolledChildrenHeight;
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int prevScrollY;
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int scrollY;
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SparseIntArray childrenHeights;
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/**
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* Called by onSaveInstanceState.
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*/
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SavedState(Parcelable superState) {
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super(superState);
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}
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/**
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* Called by CREATOR.
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*/
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private SavedState(Parcel in) {
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super(in);
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prevFirstVisiblePosition = in.readInt();
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prevFirstVisibleChildHeight = in.readInt();
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prevScrolledChildrenHeight = in.readInt();
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prevScrollY = in.readInt();
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scrollY = in.readInt();
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childrenHeights = new SparseIntArray();
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final int numOfChildren = in.readInt();
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if (0 < numOfChildren) {
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for (int i = 0; i < numOfChildren; i++) {
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final int key = in.readInt();
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final int value = in.readInt();
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childrenHeights.put(key, value);
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}
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}
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}
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@Override
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public void writeToParcel(Parcel out, int flags) {
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super.writeToParcel(out, flags);
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out.writeInt(prevFirstVisiblePosition);
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out.writeInt(prevFirstVisibleChildHeight);
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out.writeInt(prevScrolledChildrenHeight);
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out.writeInt(prevScrollY);
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out.writeInt(scrollY);
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final int numOfChildren = childrenHeights == null ? 0 : childrenHeights.size();
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out.writeInt(numOfChildren);
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if (0 < numOfChildren) {
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for (int i = 0; i < numOfChildren; i++) {
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out.writeInt(childrenHeights.keyAt(i));
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out.writeInt(childrenHeights.valueAt(i));
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}
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}
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}
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public static final Parcelable.Creator<SavedState> CREATOR
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= new Parcelable.Creator<SavedState>() {
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@Override
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public SavedState createFromParcel(Parcel in) {
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return new SavedState(in);
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}
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@Override
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public SavedState[] newArray(int size) {
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return new SavedState[size];
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}
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};
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}
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}
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