/*
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* Copyright (C) 2016 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.settings.widget;
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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.text.TextUtils;
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import android.util.AttributeSet;
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import android.view.View;
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import androidx.viewpager.widget.ViewPager;
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import java.util.Locale;
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/**
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* A {@link ViewPager} that's aware of RTL changes when used with FragmentPagerAdapter.
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*/
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public final class RtlCompatibleViewPager extends ViewPager {
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/**
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* Callback interface for responding to changing state of the selected page.
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* Positions supplied will always be the logical position in the adapter -
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* that is, the 0 index corresponds to the left-most page in LTR and the
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* right-most page in RTL.
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*/
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public RtlCompatibleViewPager(Context context) {
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this(context, null /* attrs */);
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}
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public RtlCompatibleViewPager(Context context, AttributeSet attrs) {
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super(context, attrs);
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}
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@Override
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public int getCurrentItem() {
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return getRtlAwareIndex(super.getCurrentItem());
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}
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@Override
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public void setCurrentItem(int item) {
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super.setCurrentItem(getRtlAwareIndex(item));
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}
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@Override
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public Parcelable onSaveInstanceState() {
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Parcelable parcelable = super.onSaveInstanceState();
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RtlSavedState rtlSavedState = new RtlSavedState(parcelable);
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rtlSavedState.position = getCurrentItem();
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return rtlSavedState;
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}
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@Override
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public void onRestoreInstanceState(Parcelable state) {
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RtlSavedState rtlSavedState = (RtlSavedState) state;
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super.onRestoreInstanceState(rtlSavedState.getSuperState());
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setCurrentItem(rtlSavedState.position);
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}
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/**
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* Get a "RTL friendly" index. If the locale is LTR, the index is returned as is.
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* Otherwise it's transformed so view pager can render views using the new index for RTL. For
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* example, the second view will be rendered to the left of first view.
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*
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* @param index The logical index.
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*/
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public int getRtlAwareIndex(int index) {
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// Using TextUtils rather than View.getLayoutDirection() because LayoutDirection is not
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// defined until onMeasure, and this is called before then.
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if (TextUtils.getLayoutDirectionFromLocale(Locale.getDefault())
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== View.LAYOUT_DIRECTION_RTL) {
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return getAdapter().getCount() - index - 1;
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}
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return index;
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}
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static class RtlSavedState extends BaseSavedState {
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int position;
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public RtlSavedState(Parcelable superState) {
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super(superState);
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}
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private RtlSavedState(Parcel in, ClassLoader loader) {
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super(in, loader);
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position = 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(position);
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}
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public static final Parcelable.ClassLoaderCreator<RtlSavedState> CREATOR
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= new Parcelable.ClassLoaderCreator<RtlSavedState>() {
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@Override
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public RtlSavedState createFromParcel(Parcel source,
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ClassLoader loader) {
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return new RtlSavedState(source, loader);
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}
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@Override
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public RtlSavedState createFromParcel(Parcel in) {
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return new RtlSavedState(in, null);
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}
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@Override
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public RtlSavedState[] newArray(int size) {
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return new RtlSavedState[size];
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}
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};
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}
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}
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