253 lines
9 KiB
Java
253 lines
9 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.Parcel;
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import android.os.Parcelable;
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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 android.widget.ScrollView;
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/**
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* ScrollView that its scroll position can be observed.
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*/
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public class ObservableScrollView extends ScrollView implements Scrollable {
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// Fields that should be saved onSaveInstanceState
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private int mPrevScrollY;
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private int mScrollY;
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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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public ObservableScrollView(Context context) {
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super(context);
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}
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public ObservableScrollView(Context context, AttributeSet attrs) {
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super(context, attrs);
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}
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public ObservableScrollView(Context context, AttributeSet attrs, int defStyle) {
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super(context, attrs, defStyle);
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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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mPrevScrollY = ss.prevScrollY;
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mScrollY = ss.scrollY;
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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.prevScrollY = mPrevScrollY;
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ss.scrollY = mScrollY;
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return ss;
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}
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@Override
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protected void onScrollChanged(int l, int t, int oldl, int oldt) {
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super.onScrollChanged(l, t, oldl, oldt);
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if (mCallbacks != null) {
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mScrollY = t;
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mCallbacks.onScrollChanged(t, mFirstScroll, mDragging);
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if (mFirstScroll) {
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mFirstScroll = false;
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}
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if (mPrevScrollY < t) {
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mScrollState = ScrollState.UP;
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} else if (t < mPrevScrollY) {
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mScrollState = ScrollState.DOWN;
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//} else {
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// Keep previous state while dragging.
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// Never makes it STOP even if scrollY not changed.
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// Before Android 4.4, onTouchEvent calls onScrollChanged directly for ACTION_MOVE,
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// which makes mScrollState always STOP when onUpOrCancelMotionEvent is called.
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// STOP state is now meaningless for ScrollView.
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}
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mPrevScrollY = t;
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}
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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 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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static class SavedState extends BaseSavedState {
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int prevScrollY;
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int scrollY;
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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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prevScrollY = in.readInt();
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scrollY = in.readInt();
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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(prevScrollY);
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out.writeInt(scrollY);
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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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