android带图片的AlertDialog和文件管理器（代码）

AlertDialog.java

package com.leadtone.filelists;

import java.util.ArrayList;
import java.util.HashMap;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.ActivityNotFoundException;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.SimpleAdapter;
import android.widget.Toast;
public class AlertDialogs extends Activity {
 private Button button;
 private Intent intent;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
   button = (Button) findViewById(R.id.button);
   button.setOnClickListener(openDialog);
 }
 
   @Override
 protected void onResume() {
    openAlertDialog();
  super.onResume();
 }

 private OnClickListener openDialog=new OnClickListener(){
   @Override
   public void onClick(View v) {
    openAlertDialog();//点击执行弹出登录对话框
   }
   };
   public ListAdapter getAdapter(){
    ArrayList<HashMap<String, Object>> listItem = new ArrayList<HashMap<String, Object>>();
  
    HashMap<String, Object> map = new HashMap<String, Object>();
    map.put("ImageManager", R.drawable.donkey);
    map.put("ItemManager", "ES文件管理器");
    listItem.add(map);
    HashMap<String, Object> map1 = new HashMap<String, Object>();
    map1.put("ImageManager", R.drawable.icon);
    map1.put("ItemManager",  "图片");
    listItem.add(map1);
    HashMap<String, Object> map2 = new HashMap<String, Object>();
    map2.put("ImageManager", R.drawable.icon);
    map2.put("ItemManager", "音频");
    listItem.add(map2);
    HashMap<String, Object> map3 = new HashMap<String, Object>();
    map3.put("ImageManager", R.drawable.icon);
    map3.put("ItemManager", "文档");
    listItem.add(map3);
   
   SimpleAdapter listItemAdapter= new SimpleAdapter(this,listItem,R.layout.list_items,
     new String[]{"ImageManager","ItemManager"},
     new int[]{R.id.ImageManager,R.id.ItemManager});
   return listItemAdapter;
   }
  
   public void openAlertDialog(){
    AlertDialog  ad = new AlertDialog.Builder(AlertDialogs.this).setTitle("添加附件").setAdapter(getAdapter(), new DialogInterface.OnClickListener() {
   
    @Override
    public void onClick(DialogInterface dialog, int position) {
     onCreateAttachment(position);
    }

    private void onCreateAttachment(int position) {
     switch (position) {
     case 0:
      intent = new Intent(AlertDialogs.this, Filelist.class);
      break;

     default:
      Toast.makeText(AlertDialogs.this,"未设", 1).show();
      break;
     }
   &n