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/*
* Copyright (C) 2014 Google Inc.
* Licensed to 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.mail.ui;
import android.support.v4.view.ViewPager;
import com.android.mail.utils.ViewUtils;
/**
* Helper class for adding RTL support to a ViewPager. Note that this also requires a PagerAdapter
* that returns the pages in reversed order in the RTL case.
*/
public class BidiViewPagerHelper {
private ViewPager mViewPager;
public BidiViewPagerHelper(ViewPager viewPager) {
mViewPager = viewPager;
}
public int getFirstPage() {
return getIndexFromBidiIndex(0);
}
public int getLastPage() {
return getIndexFromBidiIndex(mViewPager.getAdapter().getCount() - 1);
}
public int getPreviousPage() {
return clampToBounds(getIndexFromBidiIndex(getBidiIndex(mViewPager.getCurrentItem()) - 1));
}
public int getNextPage() {
return clampToBounds(getIndexFromBidiIndex(getBidiIndex(mViewPager.getCurrentItem()) + 1));
}
private int clampToBounds(int position) {
return Math.max(0, Math.min(mViewPager.getAdapter().getCount() - 1, position));
}
private int getBidiIndex(int position) {
if (ViewUtils.isViewRtl(mViewPager)) {
return mViewPager.getAdapter().getCount() - 1 - position;
} else {
return position;
}
}
/** Inverse of {@link #getBidiIndex} function. */
private int getIndexFromBidiIndex(int position) {
// getBidiIndex is equal to its inverse function so we are just calling getBidiIndex.
return getBidiIndex(position);
}
}
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