ViewPager复用

import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class MainActivity extends AppCompatActivity { 
   

    private PagerAdapter mPagerAdapter;
    private List<String> mDataList = new ArrayList<>();
    private Button mUpdate, mDelete, mAdd, mClean;
    private LinkedList<View> mViewCache = new LinkedList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mDataList.add("1");
        mDataList.add("2");
        mDataList.add("3");
        mDataList.add("4");
        mDataList.add("5");

        ViewPager viewPager = findViewById(R.id.viewPager);
        viewPager.setAdapter(mPagerAdapter = new PagerAdapter() {
            @Override
            public int getCount() {
                return mDataList.size();
            }

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


            @Override
            public Object instantiateItem(ViewGroup container, int position) {
                View view = mViewCache.size() > 0 ? mViewCache.removeFirst() : null;
                String str = "";
                if (view == null) {
                    view = View.inflate(MainActivity.this, R.layout.item_pager, null);
                    str = "";
                } else{
                    str = "复用了position为= " + view.getTag() + " 的Item";
                }
                TextView textView = view.findViewById(R.id.pager_tv);
                textView.setText(str + "\n" +mDataList.get(position));
                view.setTag(position);
                container.addView(view);
                return view;
            }

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

        });

    }

}