Android : save listview item even after exit

hello friends i have listview that contain all install app and a checkbox.my problem is that when i check item using checkbox it is not remain permanently ie if i check some item using checkbox and exit app and then run app it should show all previous checked item.

here my package ApkListActivity.java

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

import android.app.Activity;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
import android.widget.Toast;

import com.ibc.android.demo.appslist.adapter.ApkAdapter;
import com.ibc.android.demo.appslist.app.AppData;

public class ApkListActivity extends Activity {

    PackageManager packageManager;
    ListView apkList;

    @Override
    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    packageManager = getPackageManager();
    List<PackageInfo> packageList = packageManager
        .getInstalledPackages(PackageManager.GET_PERMISSIONS);

    List<PackageInfo> packageList1 = new ArrayList<PackageInfo>();

    /* To filter out System apps */
    for (PackageInfo pi : packageList) {
        boolean b = isSystemPackage(pi);
        if (!b) {
        packageList1.add(pi);
        }
    }

    Collections.sort(packageList1, new Comparator<PackageInfo>() {
        public int compare(PackageInfo o1, PackageInfo o2) {
        return o1.applicationInfo
            .loadLabel(getPackageManager())
            .toString()
            .compareTo(
                o2.applicationInfo.loadLabel(
                    getPackageManager()).toString());
        }
    });
    apkList = (ListView) findViewById(R.id.applist);
    apkList.setAdapter(new ApkAdapter(this, packageList1, packageManager));
    apkList.setOnItemClickListener(new OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view,
            int position, long row) {
        PackageInfo packageInfo = (PackageInfo) parent
            .getItemAtPosition(position);
        AppData appData = (AppData) getApplicationContext();
        appData.setPackageInfo(packageInfo);

        // Intent appInfo = new Intent(getApplicationContext(),
        // ApkInfo.class);
        // startActivity(appInfo);
        PackageInfo country = (PackageInfo) parent
            .getItemAtPosition(position);
        Toast.makeText(
            getApplicationContext(),
            "Clicked on Row: "
                + country.applicationInfo.loadLabel(
                    getPackageManager()).toString(),
            Toast.LENGTH_LONG).show();

        }
    });

    }

    private boolean isSystemPackage(PackageInfo pkgInfo) {
    return ((pkgInfo.applicationInfo.flags & ApplicationInfo.FLAG_SYSTEM) != 0) ? true
        : false;
    }

}

and this is my ApkAdapter.java

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

import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.graphics.drawable.Drawable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.ImageView;
import android.widget.TextView;

import com.ibc.android.demo.appslist.activity.R;

public class ApkAdapter extends BaseAdapter {

    List<PackageInfo> packageList = null;
    Activity context;
    Context context2;
    PackageManager packageManager;
    private ArrayList<Boolean> checkList = new ArrayList<Boolean>();

    boolean selected = false;

    // List<ApplicationInfo> packageList = new ArrayList<ApplicationInfo>();

    public ApkAdapter(Activity context, List<PackageInfo> packageList,
        PackageManager packageManager) {
    super();
    this.context = context;
    this.packageList = packageList;
    this.packageManager = packageManager;

    for (int i = 0; i < packageList.size(); i++) {

        checkList.add(selected);

    }

    }

    public int getCount() {
    return ((null != packageList) ? packageList.size() : 0);
    // return packageList.size();
    }

    public PackageInfo getItem(int position) {
    return ((null != packageList) ? packageList.get(position) : null);
    }

    public long getItemId(int position) {
    return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
    View view = convertView;

    if (null == view) {
        LayoutInflater inflater = context.getLayoutInflater();
        view = inflater.inflate(R.layout.apklist_item, null);
        // holder = new ViewHolder();

    }
    PackageInfo data = packageList.get(position);
    if (null != data) {

        TextView apkName = (TextView) view.findViewById(R.id.appname);

        ImageView apkicon = (ImageView) view.findViewById(R.id.icon_image);
        TextView packageName = (TextView) view
            .findViewById(R.id.packagename);
        CheckBox checkBox = (CheckBox) view.findViewById(R.id.checkbox);
        checkBox.setTag(Integer.valueOf(position)); // set the tag so we can
                            // identify the correct
                            // row in the listener
        checkBox.setChecked(checkList.get(position)); // set the status
        // as
        // we stored it
        checkBox.setOnCheckedChangeListener(mListener); // set the listener
        PackageInfo packageInfo = (PackageInfo) getItem(position);

        Drawable appIcon = packageManager
            .getApplicationIcon(packageInfo.applicationInfo);
        String appName = packageManager.getApplicationLabel(
            packageInfo.applicationInfo).toString();
        ;
        apkicon.setImageDrawable(appIcon);
        apkName.setText(appName);
        packageName.setText(packageInfo.packageName);

    }

    return view;

    }

    OnCheckedChangeListener mListener = new OnCheckedChangeListener() {

    public void onCheckedChanged(CompoundButton buttonView,
        boolean isChecked) {
        checkList.set((Integer) buttonView.getTag(), isChecked);
    }
    };

}