原理：把viewpager的最后一个view加到第一个位置，在最后一个位置再加一个第一个元素。
代码：https://github.com/wds609/loopviewpager/blob/master/app/src/main/java/com/wds/loopviewpager/LoopViewPager.java
package com.wds.loopviewpager;
import android.content.Context;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.View;
import java.util.ArrayList;
public class LoopViewPager extends ViewPager {
public LoopViewPager(Context context) {
super(context);
}
public LoopViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public void setAdapter(PagerAdapter adapter) {
super.setAdapter(adapter);
addOnPageChangeListener(new LoopOnPageChangeListener(this));
setCurrentItem(1);
setOffscreenPageLimit(adapter.getCount());
}
public static class LoopOnPageChangeListener implements OnPageChangeListener {
private LoopViewPager mLoopViewPager;
private int mFinalPosition;
public LoopOnPageChangeListener(LoopViewPager loopViewPager) {
this.mLoopViewPager = loopViewPager;
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
mFinalPosition = position;
}
@Override
public void onPageSelected(int position) {
}
@Override
public void onPageScrollStateChanged(int state) {
if (state == ViewPager.SCROLL_STATE_IDLE) {
PagerAdapter adapter = mLoopViewPager.getAdapter();
if (mFinalPosition == 0) {
mLoopViewPager.setCurrentItem(adapter.getCount() - 2, false);
}
if (mFinalPosition == adapter.getCount() - 1) {
mLoopViewPager.setCurrentItem(1, false);
}
}
}
}
public static abstract class LoopViewPagerAdapter extends PagerAdapter {
protected ArrayList mDatas = new ArrayList<>();
public LoopViewPagerAdapter(ArrayList datas) {
if (datas != null && datas.size() != 0) {
mDatas.add(datas.get(datas.size() - 1));
mDatas.addAll(datas);
mDatas.add(datas.get(0));
}
}
@Override
public final int getCount() {
return mDatas.size();
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
}
}
