Update Gallery photos in background thread

Last article "Display photos from SD in android.widget.Gallery" load Gallery photos in UI thread. As I mentioned in some previous posts, it's not a good practice to perform long time operation in UI thread, specially when you load many large size photos.

Update Gallery photos in background thread


The main code, AndroidGalleryActivity.java, is further modified to perform the re-size job in background thread. Before the photos re-sized, the Gallery show items as a default bitmap (android.R.drawable.ic_menu_gallery). After re-size, myPhotoBarAdapter.notifyDataSetChanged() is called (in UI thread) to update Gallery.

Because every photo have its own background thread to re-size, and independent to each others. So the update sequence is not in order.

package com.AndroidGallery;

import java.io.File;
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.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<String> fileList = new ArrayList<String>();

class PhotoItem{

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

@Override
public void run() {

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<PhotoItem> arrayPhotoItem;

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

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);

}

@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<String> directoryList
= new ArrayAdapter<String>(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);

myPhotoBarAdapter.notifyDataSetChanged();
}
}
}
jpgList.setText(jpgs);
}

}


Next:
- Get Exif of jpg using ExifInterface, and thumbnail inside the JPEG.


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