ViewPager的IllegalStateException运

开发场景：
1.在activity执行oncreate()生命周期时，初始化viewpager控件、viewpager的适配器adapter，adapter的填充数组list；

2. 当用户刷新数据的时候，先清空listview，并将新数据填充到list中，调用adapter的notifyDataSetChanged()方法，此时产生运行错误。

错误类型： Caused by: java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.

代码如下：

package com.example.androidtest;
 
import java.util.ArrayList;
import java.util.List;
 
import android.app.Activity;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ImageView;
 
 
public class MainActivity extends Activity {
    private ViewPager vp ;
    private VPAdapter vpAdapter;
    private List<View> views;
 
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
        vp = (ViewPager)findViewById(R.id.vp);
        views = new ArrayList<View>();
        vpAdapter = new VPAdapter(views);
        vp.setAdapter(vpAdapter);
    }
 
    public void doClick(View v){
        switch (v.getId()) {
        case R.id.add:
            views.clear();
            for (int i = 0; i < 3; i++) {
                ImageView iv = (ImageView)((View)LayoutInflater.from(this).inflate(R.layout.imageview, null)).findViewById(R.id.iv);
                iv.setImageResource(R.drawable.ic_launcher);
                views.add(iv);
            }
            vpAdapter.notifyDataSetChanged();
            break;
        case R.id.del:
            break;
        }
    }
} 

package com.example.androidtest;
 
import java.util.ArrayList;
import java.util.List;
 
import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;
 
public class VPAdapter extends PagerAdapter {
    private List<View> viewList;
 
    public VPAdapter(List<View> viewList){
        if(viewList!=null){
            this.viewList = viewList;
        }else{
            this.viewList = new ArrayList<View>();
        }
    }
    
    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return viewList.size();
    }
 
    @Override
    public boolean isViewFromObject(View arg0, Object arg1) {
        // TODO Auto-generated method stub
        return arg0==arg1;
    }
 
    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        container.removeView(viewList.get(position));
    }
 
    @Override
    public Object instantiateItem(ViewGroup container, int position){
        //这里的判断是关键代码，首先我们要判断这个view的父容器是否为null；
        //如果为null，证明是第一次加入，直接添加即可，
        //如果不为null。此时需要先remove掉父容器，再将这个view添加到container中，否则就会产生IllegalStateException异常
        if(viewList.get(position).getParent()==null){
            container.addView(viewList.get(position), 0);
        }else{
            ((ViewGroup)viewList.get(position).getParent()).removeView(viewList.get(position));
            container.addView(viewList.get(position));
        }
        return viewList.get(position);
    }
    
    
}