Implement AdapterView.OnItemClickListener for Gallery

     package com.AndroidGallery;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import android.R.color;
import android.app.Activity;
import android.app.Dialog;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.media.ExifInterface;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.view.Gravity;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.webkit.MimeTypeMap;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class AndroidGalleryActivity extends Activity {

 Gallery photoBar;

 Button buttonOpenDialog;
 Button buttonUp, buttonSelectFolder;
 TextView jpgList;

 String KEY_TEXTPSS = "TEXTPSS";
 static final int CUSTOM_DIALOG_ID = 0;

 ListView dialog_ListView;

 File root;
 File curFolder;

 private List fileList = new ArrayList();

 class PhotoItem{

  ExifInterface exifInterface = null;
  boolean exifHasThumbnail = false;

  String bitmapImageSrc;
  Bitmap bitmapImage = null;

  final static int itemWidth = 150;
  final static int itemHeight = 150;

  Handler handler;

  public PhotoItem(String src){
   bitmapImageSrc = src;
   StratBackgroundProcess();

   bitmapImage = BitmapFactory.decodeResource(getResources(), android.R.drawable.ic_menu_gallery);
  }

  public Bitmap getImage(){
   return bitmapImage; 
  }

  private void runResize(){
   BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
   bmpFactoryOptions.inJustDecodeBounds = true;

   Bitmap bitmap = BitmapFactory.decodeFile(bitmapImageSrc, bmpFactoryOptions);

   int heightRatio = (int)Math.ceil(bmpFactoryOptions.outHeight/(float)itemHeight);
   int widthRatio = (int)Math.ceil(bmpFactoryOptions.outWidth/(float)itemWidth);

   if (heightRatio > 1 || widthRatio > 1)
   {
    if (heightRatio > widthRatio){
     bmpFactoryOptions.inSampleSize = heightRatio; 
    } else {
     bmpFactoryOptions.inSampleSize = widthRatio;  
    }  
   }

   bmpFactoryOptions.inJustDecodeBounds = false;

   bitmapImage = BitmapFactory.decodeFile(bitmapImageSrc, bmpFactoryOptions);

  }

  private void getExif(){

   try {
    exifInterface = new ExifInterface(bitmapImageSrc);
    if(exifInterface.hasThumbnail()){
     byte[] thumbnail =  exifInterface.getThumbnail();
     bitmapImage = BitmapFactory.decodeByteArray(thumbnail, 0, thumbnail.length);
     exifHasThumbnail = true;
    }
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }

  }

  private void StratBackgroundProcess(){
   Runnable runnable = new Runnable(){

    @Override
    public void run() {

     getExif();
     if(!exifHasThumbnail){
      runResize();
     }

     handler.post(new Runnable(){

      @Override
      public void run() {
       myPhotoBarAdapter.notifyDataSetChanged();
      }});

    }

   };

   handler = new Handler();
   new Thread(runnable).start();
  }

 }

 PhotoBarAdapter myPhotoBarAdapter;

 public class PhotoBarAdapter extends BaseAdapter {

  Context context;
  ArrayList arrayPhotoItem;

  PhotoBarAdapter(Context c){
      context = c;
      arrayPhotoItem = new ArrayList();    
  }

  public void clear(){
   arrayPhotoItem.clear();
  }

  public void addPhotoItem(PhotoItem item){
   arrayPhotoItem.add(item);    
  }

  @Override
  public int getCount() {
   return arrayPhotoItem.size();
  }

  @Override
  public Object getItem(int position) {
   return arrayPhotoItem.get(position);
  }

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

  @Override
  public View getView(int position, View convertView, ViewGroup parent) {

   LinearLayout viewLayout = new LinearLayout(context);
   viewLayout.setLayoutParams(new Gallery.LayoutParams(200, 200));
   viewLayout.setGravity(Gravity.CENTER);
   viewLayout.setBackgroundColor(color.background_light);

   ImageView imageView;
   imageView = new ImageView(context);
   imageView.setLayoutParams(new Gallery.LayoutParams(150, 150));
   imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
   imageView.setImageBitmap(arrayPhotoItem.get(position).getImage());
   //return imageView;

   viewLayout.addView(imageView);
   return viewLayout;
  }

 }

 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);

  photoBar = (Gallery)findViewById(R.id.photobar);
  myPhotoBarAdapter = new PhotoBarAdapter(this);
  photoBar.setAdapter(myPhotoBarAdapter);

  jpgList = (TextView)findViewById(R.id.jpglist);

  buttonOpenDialog = (Button)findViewById(R.id.opendialog);
  buttonOpenDialog.setOnClickListener(new Button.OnClickListener(){
   @Override
   public void onClick(View arg0) {
    showDialog(CUSTOM_DIALOG_ID); 
   }});

  root = new File(Environment
    .getExternalStorageDirectory()
    .getAbsolutePath());

  curFolder = root;
  //ListJpgInFolder(curFolder);
  preparePhotoBarInFolder(curFolder);

  //Gallery onClickListener
  photoBar.setOnItemClickListener(photoBarOnItemClickListener);

 }

 OnItemClickListener photoBarOnItemClickListener
 = new OnItemClickListener(){

  @Override
  public void onItemClick(AdapterView parent, View view, int position,
    long id) {

   String itemInfo = ((PhotoItem)(parent.getItemAtPosition(position))).bitmapImageSrc;

   Toast.makeText(AndroidGalleryActivity.this, 
     "Clicked item:\n" + itemInfo, 
     Toast.LENGTH_LONG).show();

  }

 };


 @Override
 protected Dialog onCreateDialog(int id) {

  Dialog dialog = null;

  switch(id) {
  case CUSTOM_DIALOG_ID:
   dialog = new Dialog(AndroidGalleryActivity.this);
   dialog.setContentView(R.layout.dialoglayout);
   dialog.setTitle("Select JPG");

   dialog.setCancelable(true);
   dialog.setCanceledOnTouchOutside(true);

   buttonUp = (Button)dialog.findViewById(R.id.up);
   buttonUp.setOnClickListener(new OnClickListener(){

    @Override
    public void onClick(View v) {

     ListDir(curFolder.getParentFile()); 
    }});

   buttonSelectFolder = (Button)dialog.findViewById(R.id.selectfolder);
   buttonSelectFolder.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View v) {

    Toast.makeText(AndroidGalleryActivity.this,
      curFolder + " selected",
      Toast.LENGTH_LONG).show();
    dismissDialog(CUSTOM_DIALOG_ID);

    //ListJpgInFolder(curFolder);
    preparePhotoBarInFolder(curFolder);

   }});


   //Prepare ListView in dialog
   dialog_ListView = (ListView)dialog.findViewById(R.id.dialoglist);

   dialog_ListView.setOnItemClickListener(new OnItemClickListener(){

    @Override
    public void onItemClick(AdapterView parent, View view,
      int position, long id) {
     File selected = new File(fileList.get(position));
     if(selected.isDirectory()){
      ListDir(selected);  
     } 
    }});

   break;
  }
  return dialog; 
 }

 @Override
 protected void onPrepareDialog(int id, Dialog dialog, Bundle bundle) {

  super.onPrepareDialog(id, dialog, bundle);

  switch(id) {
  case CUSTOM_DIALOG_ID:
   ListDir(curFolder);

   break; 
  } 
 }

 void ListDir(File f){

  if(f.equals(root)){
   buttonUp.setEnabled(false); 
  }else{
   buttonUp.setEnabled(true); 
  }

  curFolder = f;
  buttonSelectFolder.setText("Select Folder " + curFolder);

  File[] files = f.listFiles();
  fileList.clear();
  for (File file : files){
   if(file.isDirectory()){
    fileList.add(file.getPath()); 
   }else{
    Uri selectedUri = Uri.fromFile(file);
    String fileExtension
     = MimeTypeMap.getFileExtensionFromUrl(selectedUri.toString());
    if(fileExtension.equalsIgnoreCase("jpg")){
     fileList.add(file.getName()); 
    } 
   } 
  }

  ArrayAdapter directoryList
   = new ArrayAdapter(this,
     android.R.layout.simple_list_item_1, fileList);
  dialog_ListView.setAdapter(directoryList); 
 }

 private void preparePhotoBarInFolder(File folder){

  String jpgs = "JPG fiels in folder " + folder.getAbsolutePath() + "\n\n";

  File[] files = folder.listFiles();

  myPhotoBarAdapter.clear();

  for (File file : files){
   if(!file.isDirectory()){
    Uri selectedUri = Uri.fromFile(file);
    String fileExtension
     = MimeTypeMap.getFileExtensionFromUrl(selectedUri.toString());
    if(fileExtension.equalsIgnoreCase("jpg")){
     jpgs += file.getAbsolutePath() + "\n";

     PhotoItem pItem = new PhotoItem(file.getAbsolutePath());
     myPhotoBarAdapter.addPhotoItem(pItem);

     //Forcer myPhotoBarAdapter update when each photos added.
     myPhotoBarAdapter.notifyDataSetChanged();
    }  
   }  
  }

  //Forcer myPhotoBarAdapter update again even without photo.
  myPhotoBarAdapter.notifyDataSetChanged();

  jpgList.setText(jpgs); 
 }

}