1 /* 2 * Copyright (C) 2019 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.car.developeroptions.widget; 18 19 import android.content.Context; 20 import android.os.Parcel; 21 import android.os.Parcelable; 22 import android.text.TextUtils; 23 import android.util.AttributeSet; 24 import android.view.View; 25 26 import androidx.viewpager.widget.ViewPager; 27 28 import java.util.Locale; 29 30 /** 31 * A {@link ViewPager} that's aware of RTL changes when used with FragmentPagerAdapter. 32 */ 33 public final class RtlCompatibleViewPager extends ViewPager { 34 35 /** 36 * Callback interface for responding to changing state of the selected page. 37 * Positions supplied will always be the logical position in the adapter - 38 * that is, the 0 index corresponds to the left-most page in LTR and the 39 * right-most page in RTL. 40 */ 41 RtlCompatibleViewPager(Context context)42 public RtlCompatibleViewPager(Context context) { 43 this(context, null /* attrs */); 44 } 45 RtlCompatibleViewPager(Context context, AttributeSet attrs)46 public RtlCompatibleViewPager(Context context, AttributeSet attrs) { 47 super(context, attrs); 48 } 49 50 @Override getCurrentItem()51 public int getCurrentItem() { 52 return getRtlAwareIndex(super.getCurrentItem()); 53 } 54 55 @Override setCurrentItem(int item)56 public void setCurrentItem(int item) { 57 super.setCurrentItem(getRtlAwareIndex(item)); 58 } 59 60 @Override onSaveInstanceState()61 public Parcelable onSaveInstanceState() { 62 Parcelable parcelable = super.onSaveInstanceState(); 63 64 RtlSavedState rtlSavedState = new RtlSavedState(parcelable); 65 rtlSavedState.position = getCurrentItem(); 66 return rtlSavedState; 67 } 68 69 @Override onRestoreInstanceState(Parcelable state)70 public void onRestoreInstanceState(Parcelable state) { 71 RtlSavedState rtlSavedState = (RtlSavedState) state; 72 super.onRestoreInstanceState(rtlSavedState.getSuperState()); 73 74 setCurrentItem(rtlSavedState.position); 75 } 76 77 /** 78 * Get a "RTL friendly" index. If the locale is LTR, the index is returned as is. 79 * Otherwise it's transformed so view pager can render views using the new index for RTL. For 80 * example, the second view will be rendered to the left of first view. 81 * 82 * @param index The logical index. 83 */ getRtlAwareIndex(int index)84 public int getRtlAwareIndex(int index) { 85 // Using TextUtils rather than View.getLayoutDirection() because LayoutDirection is not 86 // defined until onMeasure, and this is called before then. 87 if (TextUtils.getLayoutDirectionFromLocale(Locale.getDefault()) 88 == View.LAYOUT_DIRECTION_RTL) { 89 return getAdapter().getCount() - index - 1; 90 } 91 return index; 92 } 93 94 static class RtlSavedState extends BaseSavedState { 95 int position; 96 RtlSavedState(Parcelable superState)97 public RtlSavedState(Parcelable superState) { 98 super(superState); 99 } 100 RtlSavedState(Parcel in, ClassLoader loader)101 private RtlSavedState(Parcel in, ClassLoader loader) { 102 super(in, loader); 103 position = in.readInt(); 104 } 105 106 @Override writeToParcel(Parcel out, int flags)107 public void writeToParcel(Parcel out, int flags) { 108 super.writeToParcel(out, flags); 109 out.writeInt(position); 110 } 111 112 public static final Parcelable.ClassLoaderCreator<RtlSavedState> CREATOR 113 = new Parcelable.ClassLoaderCreator<RtlSavedState>() { 114 @Override 115 public RtlSavedState createFromParcel(Parcel source, 116 ClassLoader loader) { 117 return new RtlSavedState(source, loader); 118 } 119 120 @Override 121 public RtlSavedState createFromParcel(Parcel in) { 122 return new RtlSavedState(in, null); 123 } 124 125 @Override 126 public RtlSavedState[] newArray(int size) { 127 return new RtlSavedState[size]; 128 } 129 }; 130 131 } 132 133 } 134