如何实现带照片缩略图的Listview

 ackage com.demo;

 import java.util.ArrayList;

 import android.app.Activity;
 import android.content.Context;
 import android.database.Cursor;
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
 import android.os.Bundle;
 import android.provider.MediaStore;
 import android.provider.MediaStore.Images;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.BaseAdapter;
 import android.widget.ImageView;
 import android.widget.ListView;
 import android.widget.TextView;

 public class PictureActivity extends Activity{
     private ListView picturefiles = null;
     private Cursor cursor;
     private ArrayList<PictureInfo> pictureList = new ArrayList<PictureActivity.PictureInfo>();

     private static final String[] STORE_IMAGES = {
         MediaStore.Images.Media.DATA,
         MediaStore.Images.Media.MIME_TYPE,
         MediaStore.Images.Media.DISPLAY_NAME,
         MediaStore.Images.Media._ID
     };

     /** Called when the activity is first created. */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.picture);
         showimage();
         // 单击显示图片
         //picturefiles.setOnItemClickListener(new ShowItemImageOnClickListener());
     }

     public void showimage(){
         picturefiles = (ListView)findViewById(R.id.picture_list);
         cursor = this.managedQuery(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, STORE_IMAGES, null, null, null);
         while(cursor.moveToNext()){
             PictureInfo info = new PictureInfo();

             info.filePath = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA));
             info.mimeType = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Media.MIME_TYPE));
             info.title = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DISPLAY_NAME));

             //获取当前Picture对应的Id，然后根据该ID获取其Thumb
             int id = cursor.getInt(cursor.getColumnIndexOrThrow(MediaStore.Images.Media._ID));
             /*if(info.bitmap!=null&&!info.bitmap.isRecycled())
             {
                 info.bitmap.recycle();
             }*/
             BitmapFactory.Options options=new BitmapFactory.Options();
             options.inDither=false;
             options.inPreferredConfig=Bitmap.Config.RGB_565;
             info.bitmap=MediaStore.Images.Thumbnails.getThumbnail(getContentResolver(), id,  Images.Thumbnails.MICRO_KIND, options);
             //然后将其加入到pictureList
             pictureList.add(info);
         }
         System.out.println(pictureList.size());
         //然后需要设置ListView的Adapter了，使用我们自定义的Adatper
         PictureAdapter adapter = new PictureAdapter(this);
         picturefiles=(ListView)findViewById(R.id.picture_list);
         picturefiles.setAdapter(adapter);
     }

     class PictureInfo{
         String filePath;
         String mimeType;
         Bitmap bitmap;
         String title;
     }

     class ViewHolder{
         ImageView thumbImage;
         TextView titleText;
     }

     /**
      * 定义一个Adapter来显示缩略图和视频title信息
      * @author Administrator
      *
      */
     private class PictureAdapter extends BaseAdapter{

         private Context mContext;
         private LayoutInflater inflater;

         public PictureAdapter(Context context){
             this.mContext = context;
             this.inflater = LayoutInflater.from(context);
             this.inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
         }
         @Override
         public int getCount() {
             // TODO Auto-generated method stub
             return pictureList.size();
         }
         @Override
         public Object getItem(int p) {
             // TODO Auto-generated method stub
             return pictureList.get(p);
         }
         @Override
         public long getItemId(int p) {
             // TODO Auto-generated method stub
             return p;
         }
         @Override
         public View getView(int position, View convertView, ViewGroup parent) {
             ViewHolder holder ;
             if(convertView == null){
                 holder = new ViewHolder();
                 convertView = inflater.inflate(R.layout.line, null);
                 holder.thumbImage = (ImageView)convertView.findViewById(R.id.icon);
                 holder.titleText = (TextView)convertView.findViewById(R.id.file_name);
                 convertView.setTag(holder);
             }else{
                 holder = (ViewHolder)convertView.getTag();
             }

             //显示信息
             holder.titleText.setText(pictureList.get(position).title);
             if(pictureList.get(position).bitmap != null){
                 holder.thumbImage.setImageBitmap(pictureList.get(position).bitmap);
             }
             return convertView;
         }
     }
 }