ViewPager真正实现无限轮播(偷梁换柱法,切换无回滚)

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.itheima.activity.MainActivity">

<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</RelativeLayout>

package com.example.activity;

import android.os.Bundle;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import com.itheima.activity.R;

public class MainActivity
extends AppCompatActivity
{

private ViewPager mViewPager;
//图片资源
private int[] mPic = {R.mipmap.home01,
R.mipmap.home02,
R.mipmap.home03,
R.mipmap.home04,
R.mipmap.home05};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//查找viewpager
mViewPager = (ViewPager) findViewById(R.id.viewpager);
//设置adapter
mViewPager.setAdapter(new MyPagerAdapter());
//初始化显示下标一位置
mViewPager.setCurrentItem(1);
//设置page改变监听
initListener();

}

class MyPagerAdapter
extends PagerAdapter
{
@Override
public int getCount() {
//左右各加两张图片,图片总数加二
return mPic.length + 2;
}

@Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}

@Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((View) object);
}

@Override
public Object instantiateItem(ViewGroup container, int position) {
//0下标与最大下标分别加入图一与图5,正常图片顺序从1下标开始.所以需要改变position

//如果下标是0,
if (position == 0) {
//将下标指向图五
position = mPic.length - 1;
//如果是最后一个下标
} else if (position == getCount() - 1) {
//将下标指向图一
position = 0;
} else {
//上面两步将左右两边的下标指向了图一和图五
//我们正常的图片从下标一开始,所以需要-1
position -= 1;
}
//设置图片
ImageView iv = new ImageView(MainActivity.this);
iv.setImageResource(mPic[position]);
container.addView(iv);
return iv;
}
}
//监听page位置改变
private void initListener() {
mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels)
{

}

@Override
public void onPageSelected(int position) {
Log.e("MainActivi", "当前下标:"+position);
}

@Override
public void onPageScrollStateChanged(int state) {
//如果当前状态是静止的状态(等待动画走完,静默切换界面)
if (state == ViewPager.SCROLL_STATE_IDLE) {
//如果当前page指向0下标的图5
if (mViewPager.getCurrentItem() == 0) {
//跳转到正常的图五
mViewPager.setCurrentItem(mPic.length, false);//false取消跳转动画(静默跳转)
//如果当前page指向最大下标的图一
} else if (mViewPager.getCurrentItem() == mPic.length + 1) {
//跳转到正常的图一
mViewPager.setCurrentItem(1, false);//false取消跳转动画(静默跳转)
}
}
}
});
}
}