Develop Reference

Android listview image button

First of all I'd like to thank all of you for helping me on numerous occasions before. SO have alwasy been my go-to place when faced with problems with programming.
This time however, I've been unable to find a solution to my problem...
I'm currently developing an android app that uses two activities (one main activity and a search activity).
Both of which hold a listview - the main activity has an already populated and fully functional listview and, the search activity has a populated one which seems to lack functionallity.
The listview is created in a custom adapter and contains an image button (toggling with a selector) and four textviews.
My problem is that when I toggle the image button in my search activity and then press back to get back to the main activity and finally go back to the search results, the image button is "unchecked".
Since the image button is a CRUCIAL point in both the design and the following functionallity, I'd really appriciate any kind of help.
package com.example.geostocks;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutionException;
import org.json.JSONArray;
import org.json.JSONException;
import com.example.geostocks.R;
import android.app.Activity;
import android.app.SearchManager;
import android.content.Context;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.ListView;
import android.widget.SearchView;
/* MainActivity.
* Made by: Joakim Bajoul Kakaei (881129-0298)
* Description: Creates and sets up the MainActivity programmatically.
* It is mainly associated with activity_main.xml, but uses the
* listview_layout.xml in connection to it.
*
* The idea was to keep the class as "clean" as possible and use
* multiple classes to help making coding and efficiency more easier.
*/
public class MainActivity extends Activity {
public Menu m; // Variable to store a menu-item as a public variable.
// This helps with data allocation; instead of declaring the
// searchview and searchmanager in the creation of the
// application,
// it will wait to do it once the user decides to start the
// search.
// an array to store all jsonobjects in.
private JSONArray companies;
// an arraylist to store multiple companyobjects created later.
private List<companiesBuilder> allCompanies = new ArrayList<companiesBuilder>();
/*
* (non-Javadoc)
*
* #see android.app.Activity#onCreate(android.os.Bundle)
*/
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
try {
/*
* executes the AsyncTask (top10). When the task is executed, it
* then gets the JSONArray which is bouncing around.
*/
companies = new top10().execute("DO IT!").get();
} catch (InterruptedException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (ExecutionException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
/*
* The following snippet mainly creates the adapterobject and associates
* it with it's elements, context and layout.
*/
final ListView companyList = (ListView) findViewById(R.id.listView);
final companiesAdapter compAdp = new companiesAdapter(this,
R.layout.listview_layout);
System.out.println("after"); // debugging
/*
* a loop to create companyBuilder-objects from the JSONArray and then
* add those objects to an ArrayList (allCompanies).
*/
for (int i = 0; companies.length() > i; i++) {
System.out.println("companies-looper"); // debugging
System.out.println(companies.length()); // debugging
try {
System.out.println(companies.getJSONObject(i)); // debugging
allCompanies.add(new companiesBuilder(companies
.getJSONObject(i)));
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/*
* this loop goes through every company that has been built and adds it
* to the custom listview adapter.
*/
for (companiesBuilder built : allCompanies) {
compAdp.add(built);
}
companyList.setAdapter(compAdp);
}
/*
* (non-Javadoc)
*
* #see android.app.Activity#onCreateOptionsMenu(android.view.Menu)
*/
#Override
public boolean onCreateOptionsMenu(Menu menu) {
m = menu; // adds a reference to the variable m (menu).
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.main, menu);
return (super.onCreateOptionsMenu(menu)); // returns the super for
// efficiency.
}
/*
* (non-Javadoc)
*
* #see android.app.Activity#onOptionsItemSelected(android.view.MenuItem)
*/
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.search:
openSearch(); // when searchbutton is clicked, it will start the
// opensearch method.
return true;
case R.id.action_settings:
// openSettings();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
/*
* Written by: Joakim Bajoul Kakaei Description: Invoked when user presses
* search icon. Opens up the searchview in the menu.
*/
public void openSearch() {
/*
* snippet taken from
* http://developer.android.com/training/search/setup.html with some
* changes to it.
*/
SearchManager sm = (SearchManager) getSystemService(Context.SEARCH_SERVICE);
SearchView sv = (SearchView) m.findItem(R.id.search).getActionView();
sv.setSearchableInfo(sm.getSearchableInfo(getComponentName()));
}
/*
* top10 (AsyncTask) Name: Joakim Bajoul Kakaei (881129-0298) Description:
* This class handles the connection between the JSONparser and the
* mainActivity using a different thread. It's mainly used to help with
* memory allocation as well as making sure the main-thread isn't too
* overloaded with too many assignments.
*/
private class top10 extends AsyncTask<String, String, JSONArray> {
#Override
protected JSONArray doInBackground(String... params) {
JSONparser jparser = new JSONparser();
companies = jparser.topCompanies();
System.out.println("background"); // debugging
return companies;
}
#Override
protected void onPostExecute(JSONArray jarr) {
System.out.println("onpost");
}
}
}
package com.example.geostocks;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutionException;
import org.json.JSONArray;
import org.json.JSONException;
import android.app.Activity;
import android.app.SearchManager;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.ListView;
public class SearchActivity extends Activity {
JSONArray companies;
String query;
private List<companiesBuilder> allCompanies = new ArrayList<companiesBuilder>();
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search);
handleIntent(getIntent());
try {
/*
* executes the AsyncTask (top10). When the task is executed, it
* then gets the JSONArray which is bouncing around.
*/
companies = new searchList().execute("DO IT!").get();
} catch (InterruptedException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (ExecutionException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
/*
* The following snippet mainly creates the adapterobject and associates
* it with it's elements, context and layout.
*/
final ListView companyList = (ListView) findViewById(R.id.listView_search);
final companiesAdapter compAdp = new companiesAdapter(this,
R.layout.listview_layout);
System.out.println("after"); // debugging
/*
* a loop to create companyBuilder-objects from the JSONArray and then
* add those objects to an ArrayList (allCompanies).
*/
for (int i = 0; companies.length() > i; i++) {
System.out.println("companies-looper"); // debugging
System.out.println(companies.length()); // debugging
try {
System.out.println(companies.getJSONObject(i)); // debugging
allCompanies.add(new companiesBuilder(companies
.getJSONObject(i)));
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/*
* this loop goes through every company that has been built and adds it
* to the custom listview adapter.
*/
for (companiesBuilder built : allCompanies) {
compAdp.add(built);
}
companyList.setAdapter(compAdp);
}
#Override
public void onBackPressed() {
super.onBackPressed();
}
#Override
protected void onNewIntent(Intent intent) {
handleIntent(intent);
}
private void handleIntent(Intent intent) {
if (Intent.ACTION_SEARCH.equals(intent.getAction())) {
query = intent.getStringExtra(SearchManager.QUERY);
System.out.println(query);
// use the query to search your data somehow
}
}
private class searchList extends AsyncTask<String, String, JSONArray> {
#Override
protected JSONArray doInBackground(String... params) {
JSONparser jparser = new JSONparser();
companies = jparser.search(query);
System.out.println("background"); // debugging
return companies;
}
#Override
protected void onPostExecute(JSONArray jarr) {
System.out.println("onpost");
}
}
}
Custom listviewAdapter:
package com.example.geostocks;
import java.util.ArrayList;
import android.app.AlertDialog;
import android.content.Context;
import android.graphics.Color;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageButton;
import android.widget.TextView;
/* companiesAdapter.
* Made by: Joakim Bajoul Kakaei (881129-0298)
* Description: Since the listview we have decided to use has multiple objects on each row,
* the listview's adapter needs to be customized to meet those requirements.
* This class may be revised later on (to add or remove objects from the rowItemObjects).
*/
public class companiesAdapter extends ArrayAdapter<companiesBuilder> implements
OnClickListener {
private final int companiesBuilderResource;
private ArrayList<companiesBuilder> companies;
public companiesAdapter(final Context context,
final int companiesBuilderResource) {
super(context, 0);
this.companiesBuilderResource = companiesBuilderResource;
companies = new ArrayList<companiesBuilder>();
}
public void add(companiesBuilder row) {
companies.add(row);
notifyDataSetChanged();
}
#Override
public int getCount() {
return companies.size();
}
#Override
public companiesBuilder getItem(int i) {
return companies.get(i);
}
#Override
public long getItemId(int i) {
return i;
}
#Override
public View getView(final int position, final View convertView,
final ViewGroup parent) {
// We need to get the best view (re-used if possible) and then
// retrieve its corresponding rowItem, to optimize lookup efficiency.
final View view = getourView(convertView);
final rowItem rowItem = getrowItem(view);
// final companiesBuilder company = getItem(position);
final companiesBuilder row = companies.get(position);
// Setting up both the titleobject's with their corresponding variables
// (from the row-object).
rowItem.titleView_left.setText(row.getName());
rowItem.titleView_right.setText(row.getPrice());
// Setting up the subtitle's items will be a little bit tougher, since
// it requires
// some manipulating of the xml-data.
rowItem.subTitleView_left.setText(row.getSymbol());
/*
* If-clauses to change the right subtitle's color palette to make it
* easier for the user to distinguish increase and decrease.
*/
if (Double.parseDouble(row.getChange()) < 0) {
rowItem.subTitleView_right
.setTextColor(Color.parseColor("#E51400"));
rowItem.subTitleView_right.setText(row.getPercent() + "%" + " "
+ "( " + row.getChange() + ")");
} else if (Double.parseDouble(row.getChange()) > 0) {
rowItem.subTitleView_right
.setTextColor(Color.parseColor("#339933"));
rowItem.subTitleView_right.setText(row.getPercent() + "%" + " "
+ "( +" + row.getChange() + ")");
} else {
rowItem.subTitleView_right.setText(row.getPercent() + "%" + " "
+ "(" + row.getChange() + ")");
}
// Setting image view is simple enough...
rowItem.imageButton.setSelected(row.getSelected());
view.setOnClickListener(new OnClickListener() {
/*
* Add an onClickListener that is associated with view (view being
* every row).
*/
#Override
public void onClick(View v) {
new AlertDialog.Builder(getContext()).setTitle(row.getName())
.show();
}
});
rowItem.imageButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View button) {
if (button.isSelected()) {
button.setSelected(false);
} else {
button.setSelected(true);
}
row.setSelect(view.isSelected());
}
});
return view;
}
private View getourView(final View convertView) {
// The ourView will be recycling / reusing the convertview if
// possible.
// Guess why? Exactly. CUZ WE LOOOOOOOOOOVE HAVING EFFICIENT CODE! <3
View ourView = null;
if (null == convertView) {
final Context context = getContext();
final LayoutInflater inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
ourView = inflater.inflate(companiesBuilderResource, null);
} else {
ourView = convertView;
}
return ourView;
}
private rowItem getrowItem(final View ourView) {
// Recycling and reusing tags and objects is the name of the game!
final Object tag = ourView.getTag();
rowItem rowItem = null;
/*
* Sets up the listview's rowitems with their corresponding listview
* items (textviews and images).
*/
if (null == tag || !(tag instanceof rowItem)) {
rowItem = new rowItem();
rowItem.titleView_right = (TextView) ourView
.findViewById(R.id.title_right);
rowItem.titleView_left = (TextView) ourView
.findViewById(R.id.title_left);
rowItem.subTitleView_left = (TextView) ourView
.findViewById(R.id.subtitle_left);
rowItem.subTitleView_right = (TextView) ourView
.findViewById(R.id.subtitle_right);
rowItem.imageButton = (ImageButton) ourView
.findViewById(R.id.add_button);
ourView.setTag(rowItem);
} else {
rowItem = (rowItem) tag;
}
return rowItem;
}
/*
* since views are recycled, these references will always be there to be
* reused. Again, it's all about optimization!
*/
private static class rowItem {
public TextView titleView_left;
public TextView titleView_right;
public TextView subTitleView_left;
public TextView subTitleView_right;
public ImageButton imageButton;
}
#Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
}
}
Selector for imagebutton
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="#drawable/ic_added_button" android:state_selected="true"/>
<item android:drawable="#drawable/ic_add_button" android:state_selected="false"/>
</selector>

Create model for companies (ex. Company class).
In Company class add property isSelected.
Fill array of companies from your JSONArray. Pass this array to ListView adapter.
In rowItem.imageButton.setOnClickListener update rowItem state (selected or not) in source array (array of companies, which was created from JSONArray).
Note: if you will save list row state, you should save this state in source array of your list adapter.
In MainActivity:
CompanyListAdapter adapter = new CompanyListAdapter(activity);
ArrayList<Company> companies = getCompaniesFromJsonArray();
for(Company company : companies){
adapter.add(company);
}
listView.setAdapter(adapter);
Company.java
package com.donvigo.TestCustomActionBar;
public class Company {
private String name;
private boolean isSelected;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public boolean isSelected() {
return isSelected;
}
public void setSelected(boolean isSelected) {
this.isSelected = isSelected;
}
}
CompanyListAdapter.java
package com.donvigo.TestCustomActionBar;
import android.app.Activity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.ArrayList;
public class CompanyListAdapter extends BaseAdapter {
private Activity activity;
private ArrayList<Company> companies;
public CompanyListAdapter(Activity activity){
this.activity = activity;
companies = new ArrayList<Company>();
}
public void add(Company company){
companies.add(company);
notifyDataSetChanged();
}
#Override
public int getCount() {
return companies.size();
}
#Override
public Object getItem(int i) {
return companies.get(i);
}
#Override
public long getItemId(int i) {
return i;
}
#Override
public View getView(int position, View convertView, ViewGroup viewGroup) {
ViewHolder holder;
if(convertView == null){
convertView = activity.getLayoutInflater().inflate(R.layout.list_row_layout, null);
holder = new ViewHolder();
holder.textViewName = (ImageView) convertView.findViewById(R.id.textViewName);
holder.rowImage = (ImageView) convertView.findViewById(R.id.rowImage);
convertView.setTag(holder);
}else{
holder = (ViewHolder) convertView.getTag();
}
final Company row = companies.get(position);
// refresh state of your row image
holder.rowImage.setSelected(row.isSelected());
holder.rowImage.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if (view.isSelected()) {
view.setSelected(false);
} else {
view.setSelected(true);
}
row.setSelected(view.isSelected());
}
});
return convertView;
}
private class ViewHolder{
public TextView textViewName;
public ImageView rowImage;
}
}
This is main idea. Also, if you will save row states in ListView permanently (not just 1 time when you download and show data from internet) - you have to save you companies data in database, or in another data storage (ex.: in text file) and next time when you open activity - restore previously saved companies list.

Seen your code, no where you are saving checked state of button. Point is when you navigate from MainActivity to SearchActivity your listview with custom adapter is populated and displayed, there you set some button, now once you navigate back to main activity from there you SearchAvtivity is destroyed and is completely redrawn when you navigate back. Hence you see every then fresh again.
If you want to retain checked state of button, you should save their latest state in preference and load it from there or you can keep global data variable for holding checked states of buttons so to retain it during entire life cycle of your applications.
Read about Activity life cycle and stack, when they are destroyed and created, this will throw you more insight over why this is happening.
hope it help.

How do I maintain ListView state between activity loads in android

I'm doing some background processing in my activity and have a ListView that shows the progress. I 'update' the listView with
adapter.notifyDataSetChanged();
However when I leave the activity and then come back, the background processes are still running, but the list view isn't updated. This is presumably because it's a new object, not the previous one. How do I maintain my list view object between activity loads?
This is my activity. I think the issue is that the 'adapter' variable that the download uses to bind to to show updates, is recreated in the onCreate method of the activity, and the 'adapter' variable that the download originally bound to is not in the activity anymore.
import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.ConnectivityManager;
import android.os.Bundle;
import android.os.Handler;
import android.preference.PreferenceManager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.BasicAWSCredentials;
import com.amazonaws.services.s3.model.ProgressEvent;
import com.amazonaws.services.s3.model.ProgressListener;
import com.amazonaws.services.s3.transfer.TransferManager;
//import com.amazonaws.auth.AWSCredentials;
//import com.amazonaws.auth.BasicAWSCredentials;
public class VideosActivity extends Activity {
ListView video_list;
CustomList adapter;
File storage_dir;
SharedPreferences completed_downloads; //http://developer.android.com/guide/topics/data/data-storage.html
SharedPreferences downloaded_data; //maps position to percent downloaded
SharedPreferences queue; //holds which fiiles are awaiting download
String images[]; //holds references to all thumnails for vids
String volume; //something like vol1 or vol2
String s3_dir; //the directory after the boucket that the files are stored in (do not add first slash)
String s3_bucket = "com--apps";
Handler handler = new Handler(); //'tunnel' through whci other threads communicate with main thread
Map<String, String[][]> video_config = new HashMap<String, String[][]>(); //holds info about video thumbs and filenames for all apps
ArrayList<String> arr_videos = new ArrayList<String>(); //holds video names
DownloadQueue queue_manager = new DownloadQueue();
#Override
public void onCreate(Bundle savedInstanceState) {
Log.v("dev", "onCreateCalled");
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
volume = getPackageName().split("\\.")[2]; //something like vol1 or vol2
s3_dir = "android/" + volume + "/"; //the directory after the boucket that the files are stored in (do not add first slash)
completed_downloads = getSharedPreferences("completed_downloads", 0);
downloaded_data = getSharedPreferences("downloaded_data", 0);
queue = getSharedPreferences("queue", 0);
storage_dir = getApplicationContext().getExternalFilesDir(null); //private to app, removed with uninstall
adapter = new CustomList(this, R.layout.customlist, arr_videos);
video_list = (ListView)findViewById(R.id.list);
video_list.setAdapter(adapter); //set adapter that specifies list contents
ensureStorageDirExists( storage_dir ); //make sure storage dir exists
set_video_data(); //store vid dat in array
ensure_connection_or_warn();
}
public boolean ensure_connection_or_warn()
{
if(have_connection())
{
return true;
}
else
{
Toast.makeText(this, "No Internet connection", Toast.LENGTH_LONG).show();
return false;
}
}
protected void ensureStorageDirExists( File dir )
{
if (!dir.exists())
{
dir.mkdirs();
}
}
public void set_video_data()
{
config_video_data(); //run config
images = video_config.get(getPackageName())[0]; //set images
for (String name : video_config.get(getPackageName())[1] ) { //set video info, this should be streamlined but is due to legacy code and my crap Java skills, consider doing like this: http://developer.android.com/guide/topics/resources/more-resources.html#TypedArray
arr_videos.add(name);
}
}
public SharedPreferences stored_vals()
{
return PreferenceManager.getDefaultSharedPreferences(this);
}
public boolean have_connection()
{
ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
if(cm.getActiveNetworkInfo()!=null && cm.getActiveNetworkInfo().isConnected() && cm.getActiveNetworkInfo().isAvailable())
{
Log.v("dev", "have internet connection");
return true;
}
else
{
Log.v("dev", "No internet connection");
return false;
}
}
public class DownloadQueue
{
protected void process()
{
if (queue.size() > 0 && queue.get(0).download_status == "queued") //this is meant to force one download at a time
{
queue.get(0).start();
adapter.notifyDataSetChanged();
}
}
protected void add(Integer position)
{
queue.edit.putInt(position+"");
d.download_status = "queued";
adapter.notifyDataSetChanged();
}
protected boolean position_is_queued(Integer position)
{
for (Download d : queue ) {
if(d.position == position)
{
return true;
}
}
return false;
}
protected void remove(Download d)
{
queue.remove(d);
adapter.notifyDataSetChanged();
}
}
public class CustomList extends ArrayAdapter<String>
{
View view;
int position;
Button btn;
public CustomList(Context context, int layout_id, ArrayList<String> objects)
{
super(context, layout_id, objects);
}
#Override
public View getView(final int position, View convertView, ViewGroup view_group)
{
set_view(convertView);
this.position = position;
TextView text_view = (TextView) view.findViewById(R.id.name);
ImageView image = (ImageView) view.findViewById(R.id.img);
btn = (Button) view.findViewById(R.id.play);
prepare_btn();
text_view.setText( list_text() );
image.setImageResource(
getResources().getIdentifier(images[position], "drawable", getPackageName())
);
return view;
}
public String list_text()
{
String s = arr_videos.get( position ).replace("_", " ").replace(".m4v", "");
s = s.substring(2, s.length());
return s;
}
public void set_view(View convertView)
{
if(convertView == null)
{
LayoutInflater inflater = getLayoutInflater();
view = inflater.inflate(R.layout.customlist, null);
}
else
{
view = convertView;
}
}
public Boolean is_downloaded()
{
return completed_downloads.getBoolean(position + "", false);
}
public void prepare_btn()
{
btn.setTag((Integer) position);
if(is_downloaded() == true)
{
btn.setText("Play ");
btn.setEnabled(true);
btn.setOnClickListener( new OnClickListener()
{
public void onClick(View btn)
{
int position = (Integer) btn.getTag();
Intent i = new Intent(VideosActivity.this, PlayVideoActivity.class);
String video_path = storage_dir + "/" + arr_videos.get(position);
Log.v("video_path", video_path);
i.putExtra("video_path", video_path);
startActivity(i);
}
});
}
else if( downloaded_data.contains(position+"") ) //it it's currently being downloaded
{
btn.setText(downloaded_data.getInt(position+"", 0) + "%");
btn.setEnabled(false);
}
else if( queue_manager.position_is_queued(position) ) //it's in the queue
{
btn.setText("Queued");
btn.setEnabled(false);
}
else
{
btn.setText("Download");
btn.setEnabled(true);
btn.setOnClickListener( new OnClickListener()
{
public void onClick(View btn)
{
int position = (Integer) btn.getTag();
btn.setEnabled(false);
queue_manager.add(position);
}
});
}
}
}
public class Download
{
File new_video_file;
int position;
String download_status;
com.amazonaws.services.s3.transfer.Download download;
protected void queue(int position)
{
this.position = position;
queue_manager.add(this);
queue_manager.process();
//put this download in the queue
//start downloading if it's the only one in the queue
}
protected void start()
{
if(!ensure_connection_or_warn())
{
return;
}
this.download_status = "started";
this.new_video_file = new File(storage_dir, arr_videos.get(position)); //local file to be writtent to
TransferManager tx = new TransferManager(credentials);
//http://stackoverflow.com/questions/6976317/android-http-connection-exception
this.download = tx.download(s3_bucket, s3_dir + arr_videos.get(position), new_video_file);
download.addProgressListener(new ProgressListener()
{
public void progressChanged(final ProgressEvent pe)
{
handler.post( new Runnable()
{
#Override
public void run()
{
if ( pe.getEventCode() == ProgressEvent.COMPLETED_EVENT_CODE )
{
Download.this.onComplete();
}
else
{
Download.this.onProgressUpdate();
}
}
});
}
});
}
//protected void onProgressUpdate(Double progress)
protected void onProgressUpdate()
{
this.download_status = "downloading";
Double progress = this.download.getProgress().getPercentTransfered();
Integer percent = progress.intValue();
//Log.v("runnable", percent + "");
downloaded_data.edit().putInt(position+"", percent).commit();
adapter.notifyDataSetChanged();
}
protected void onComplete()
{
Log.v("dev", "download complete!!!");
//downloaded_data.remove(position);
this.download_status = "complete";
completed_downloads.edit().putBoolean(position + "", true).commit();
queue_manager.remove(this);
queue_manager.process();
adapter.notifyDataSetChanged();
// this.download.abort();
}
}
}

Not exactly sure what happens during background processing and what do you mean by ListView state, but my suggestion would be:
try the following:
#Override
protected void onResume() {
super.onResume();
yourAdapter.clear();
yourAdapter.addAll(yourData); // API level [1..10] use for(..){ yourAdapter.add(yourData.get(index)) }
yourAdapter.notifyDataSetChanged();
}
Reason:
An adapter keeps a copy of all the elements, so when you call notifyDataSetChanged, it checks its own copy of the elements

Show Dialog depending on ViewPager state

I have a ViewPager, and lets imagine, that i am on page 0.
I have a button on this page, and on this button click, i want to show a dialog, and change page to the page 1.
When my page changes to page 1, i want the dialog to dissapear.
When i did it, i didn't see the dialog, it was appearing and dissapearing when page was changed, but i am sure, that i have 1000ms delay between this actions.
Please help, how can i show the dialog?
package com.example.ViewPagerDialog;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.os.Bundle;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
public class MyActivity extends Activity {
private int currentPage;
/**
* Called when the activity is first created.
*/
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
final MyViewPager viewPager = (MyViewPager) findViewById(R.id.view_pager);
final Button leftSwitcher = (Button) findViewById(R.id.left_switcher);
final Button rightSwitcher = (Button) findViewById(R.id.right_switcher);
final ProgressDialog progressDialog = new ProgressDialog(this);
leftSwitcher.setVisibility(View.GONE);
progressDialog.setTitle("Wait...");
viewPager.setAdapter(new MyPagerAdapter(this));
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
public void onPageScrolled(int i, float v, int i2) {
}
public void onPageSelected(int i) {
progressDialog.dismiss();
currentPage = i;
if (i == 0) {
leftSwitcher.setVisibility(View.GONE);
} else if (i == 1) {
leftSwitcher.setVisibility(View.VISIBLE);
rightSwitcher.setVisibility(View.VISIBLE);
} else if (i == 2) {
rightSwitcher.setVisibility(View.GONE);
}
}
public void onPageScrollStateChanged(int i) {
}
});
leftSwitcher.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
progressDialog.show();
sleepThread();
viewPager.setCurrentItem(currentPage - 1);
}
});
rightSwitcher.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
progressDialog.show();
sleepThread();
viewPager.setCurrentItem(currentPage + 1);
}
});
}
private void sleepThread() {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
private class MyPagerAdapter extends PagerAdapter {
View[] views = new View[3];
public MyPagerAdapter(Context context) {
TextView view1 = new TextView(context);
TextView view2 = new TextView(context);
TextView view3 = new TextView(context);
view1.setText("View 1");
view2.setText("View 2");
view3.setText("View 3");
views[0] = view1;
views[1] = view2;
views[2] = view3;
}
#Override
public int getCount() {
return views.length;
}
#Override
public boolean isViewFromObject(View view, Object o) {
return (view.equals(o));
}
#Override
public Object instantiateItem(ViewGroup collection, int position) {
collection.addView(views[position]);
return views[position];
}
#Override
public void destroyItem(android.view.ViewGroup container, int position, java.lang.Object object) {
container.removeView(views[position]);
}
}
}

First of all, never block the UI thread with Thread.sleep() like you do. By using Thread.sleep() you'll basically set the show command for the dialog(which will happen after you return from the onCLick() method), sleep one second(and your app will freeze) and then set the page on the ViewPager which will trigger the listener, dismissing the dialog. Instead you could use a Handler to
private Handler mHandler = new Handler();
// in the onClick method
progressDialog.show();
mHandler.postDelayed(new Runnable() {
#Override
public void run() {
viewPager.setCurrentItem(currentPage - 1);
}
}, 1000);

Android loaders, the way to go?

I am used to building lists in android using adapters. If I need some long-to-get data, I use an asynctask, or a simple runnable, to update the data structure on which the adapter rely, and call notifyDataChanged on the adapter.
Although it is not straightforward, I finally find this is a simple model and it allows a good separation of logic presentation (in the asynctask, update a data structure) and the view (an adapter acting as a view factory, mostly).
Nevertheless, I read recently about loaders introduced in HoneyComb and included in the backward compatibility support-library, I tried them and find the introduce a lot of complexity. They are difficult to handle and add some kind of magic to this whole process through loader managers, add a lot of code and don't decrease the number of classes or collaborating items but I may be wrong and would like to hear some good points on loaders.
What are they advantages of loaders in terms of lines of code, clarity and effort ?
What are they advantages of loaders in terms of role separation during data loading, or more broadly, in terms of design ?
Are they the way to go, should I replace all my list data loading to implement them through loaders ?
Ok, this is a developers' forum, so here is an example. Please, make it better with loaders :
package com.sof.test.loader;
import java.util.ArrayList;
import java.util.List;
import android.app.ListActivity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.widget.ArrayAdapter;
import android.widget.TextView;
/** The activity. */
public class LoaderTestActivity extends ListActivity {
private DataSourceOrDomainModel dataSourceOrDomainModel = new DataSourceOrDomainModel();
private List<Person> listPerson;
private PersonListAdapter personListAdapter;
private TextView emptyView;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
listPerson = new ArrayList<Person>();
personListAdapter = new PersonListAdapter( listPerson );
setListAdapter( personListAdapter );
setUpEmptyView();
new PersonLoaderThread().execute();
}
public void setUpEmptyView() {
emptyView = new TextView( this );
emptyView.setLayoutParams( new LayoutParams( LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT ) );
emptyView.setVisibility(View.GONE);
((ViewGroup)getListView().getParent()).addView(emptyView);
getListView().setEmptyView(emptyView);
}
/** Simulate a long task to get data. */
private class PersonLoaderThread extends AsyncTask<Void, Integer, List<Person>> {
#Override
protected List<Person> doInBackground(Void... params) {
return dataSourceOrDomainModel.getListPerson( new ProgressHandler());
}
#Override
protected void onProgressUpdate(Integer... values) {
emptyView.setText( "Loading data :" + String.valueOf( values[ 0 ] ) +" %" );
}
#Override
protected void onPostExecute(List<Person> result) {
listPerson.clear();
listPerson.addAll( result );
personListAdapter.notifyDataSetChanged();
}
private class ProgressHandler implements ProgressListener {
#Override
public void personLoaded(int count, int total) {
publishProgress( 100*count / total );
}
}
}
/** List item view factory : the adapter. */
private class PersonListAdapter extends ArrayAdapter<Person> {
public PersonListAdapter( List<Person> listPerson ) {
super(LoaderTestActivity.this, 0, listPerson );
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if( convertView == null ) {
convertView = new PersonView( getContext() );
}
PersonView personView = (PersonView) convertView;
personView.setPerson( (Person) getItem(position) );
return personView;
}
}
}
A small callback interface for progress
package com.sof.test.loader;
/** Callback handler during data load progress. */
public interface ProgressListener {
public void personLoaded(int count, int total );
}
A list item widget
package com.sof.test.loader;
import com.sof.test.loader.R;
import android.content.Context;
import android.view.LayoutInflater;
import android.widget.LinearLayout;
import android.widget.TextView;
/** List Item View, display a person */
public class PersonView extends LinearLayout {
private TextView personNameView;
private TextView personFirstNameView;
public PersonView(Context context) {
super(context);
LayoutInflater inflater= (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
inflater.inflate( R.layout.person_view,this );
personNameView = (TextView) findViewById( R.id.person_name );
personFirstNameView = (TextView) findViewById( R.id.person_firstname );
}
public void setPerson( Person person ) {
personNameView.setText( person.getName() );
personFirstNameView.setText( person.getFirstName() );
}
}
It's xml : res/person_view.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/person_view"
android:layout_width="fill_parent"
android:layout_height="wrap_content" >
<TextView
android:id="#+id/person_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true" />
<TextView
android:id="#+id/person_firstname"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="#id/person_name" />
</RelativeLayout>
The data source or model, providing data (slowly)
package com.sof.test.loader;
import java.util.ArrayList;
import java.util.List;
/** A source of data, can be a database, a WEB service or a model. */
public class DataSourceOrDomainModel {
private static final int PERSON_COUNT = 100;
public List<Person> getListPerson( ProgressListener listener ) {
List<Person> listPerson = new ArrayList<Person>();
for( int i=0; i < PERSON_COUNT ; i ++ ) {
listPerson.add( new Person( "person", "" + i ) );
//kids, never do that at home !
pause();
if( listener != null ) {
listener.personLoaded(i,PERSON_COUNT);
}//if
}
return listPerson;
}//met
private void pause() {
try {
Thread.sleep( 100 );
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
The POJO representing a person :
package com.sof.test.loader;
/** A simple POJO to be displayed in a list, can be manipualted as a domain object. */
public class Person {
private String name;
private String firstName;
public Person(String name, String firstName) {
this.name = name;
this.firstName = firstName;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
}//class

In case someone is looking for the loader version of my previous example : here it is :
package com.sof.test.loader;
import java.util.ArrayList;
import android.app.LoaderManager;
import java.util.List;
import android.app.ListActivity;
import android.content.AsyncTaskLoader;
import android.content.Context;
import android.content.Loader;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.widget.ArrayAdapter;
import android.widget.TextView;
/** The activity. */
public class LoaderTestActivity2 extends ListActivity implements
LoaderManager.LoaderCallbacks<List<Person>> {
private DataSourceOrDomainModel dataSourceOrDomainModel = new DataSourceOrDomainModel();
private List<Person> listPerson;
private PersonListAdapter personListAdapter;
private TextView emptyView;
private Loader<List<Person>> personLoader;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
listPerson = new ArrayList<Person>();
personListAdapter = new PersonListAdapter(listPerson);
setListAdapter(personListAdapter);
personLoader = new PersonLoader(this, dataSourceOrDomainModel, new ProgressHandler() );
setUpEmptyView();
getLoaderManager().initLoader(0, null, this);
personLoader.forceLoad();
}
public void setUpEmptyView() {
emptyView = new TextView(this);
emptyView.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,
LayoutParams.WRAP_CONTENT));
emptyView.setVisibility(View.GONE);
((ViewGroup) getListView().getParent()).addView(emptyView);
getListView().setEmptyView(emptyView);
}
public void publishProgress(int progress) {
emptyView.setText("Loading data :" + String.valueOf(progress) + " %");
}
#Override
public Loader<List<Person>> onCreateLoader(int arg0, Bundle arg1) {
return personLoader;
}
#Override
public void onLoadFinished(Loader<List<Person>> personLoader, List<Person> result) {
listPerson.clear();
listPerson.addAll(result);
personListAdapter.notifyDataSetChanged();
}
#Override
public void onLoaderReset(Loader<List<Person>> arg0) {
listPerson.clear();
personListAdapter.notifyDataSetChanged();
}
/** List item view factory : the adapter. */
private class PersonListAdapter extends ArrayAdapter<Person> {
public PersonListAdapter(List<Person> listPerson) {
super(LoaderTestActivity2.this, 0, listPerson);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = new PersonView(getContext());
}
PersonView personView = (PersonView) convertView;
personView.setPerson((Person) getItem(position));
return personView;
}
}
private class ProgressHandler implements ProgressListener {
#Override
public void personLoaded(final int count, final int total) {
runOnUiThread( new Runnable() {
#Override
public void run() {
publishProgress(100 * count / total);
}
});
}
}
}
class PersonLoader extends AsyncTaskLoader<List<Person>> {
private DataSourceOrDomainModel dataSourceOrDomainModel;
private ProgressListener progressHandler;
public PersonLoader(Context context, DataSourceOrDomainModel dataSourceOrDomainModel, ProgressListener progressHandler ) {
super(context);
this.dataSourceOrDomainModel = dataSourceOrDomainModel;
this.progressHandler = progressHandler;
}
#Override
public List<Person> loadInBackground() {
return dataSourceOrDomainModel.getListPerson( progressHandler );
}
}
It would be more difficult to add support (support librairy) to this example as there is no equivalent of ListAcitivity in the support librairy. I would have either to create a ListFragment or create an FragmentActivity and give it a layout including a list.

One problem your code has which loaders aim to fix is what happens if your activity is restarted (say due to device rotation or config change) while your async task is still in progress? in your case your restarted activity will start a 2nd instance of the task and throw away the results from the first one. When the first one completes you can end up with crashes due to the fact your async task has a reference is what is now a finished activity.
And yes using loaders often makes for more/more complex code, particularly if you can't use one of the provided loaders.

Android: My ListView Rows can't be selected on touch mode after adding a new row to the data

I have an Activity and a Thread. The thread handles the data (later that data will be grabbed from Internet activity, for now, it just automatically adds a new row each 10 seconds). The thing is, after a new row being add, I can't touch the items anymore, to regain focus, I must press the up or down arrow on my hardware keyboard, or the menu button.
Of course I first thought to re-set the .setFocusableOnTouchMode to true, but this didn't seem to solve my problem. Or at least, I'm not setting it on the right place. Anyway this is my code:
The Activity:
$
package com.ejemplolisbox;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnFocusChangeListener;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
public class EL extends Activity {
/**
* #see android.app.Activity#onCreate(Bundle)
*/
public Refresh actualizar;
// The thread
public static ListView g;
public static EfficientAdapter instance ;
// The adapter (is a custom made adapter, I didn't do it myself, just grabbed it from the Internet)
public static String[] abbreviations = { "Item0",
"Item1", "Item2"};
/** Called when the activity is first created. */
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
g = (ListView) findViewById(R.id.lv_country);
g.setFocusable(true);
g.setFocusableInTouchMode(true);
instance = new EfficientAdapter(this);
// The adapter is now set to this instance
g.setAdapter(instance);
actualizar = new Refresh();
actualizar.start();
//I start the thread
g.setOnFocusChangeListener(new OnFocusChangeListener() {
public void onFocusChange(View arg0, boolean arg1) {
// TODO Auto-generated method stub
// Code should be here (??)
}
});
g.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView a, View v, int position,
long id) {
//use position to get clicked position
//your code goes here
}
});
}
public static class EfficientAdapter extends BaseAdapter {
private LayoutInflater mInflater;
public EfficientAdapter(Context context) {
mInflater = LayoutInflater.from(context);
}
public int getCount() {
return abbreviations.length;
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
convertView = mInflater.inflate(R.layout.rowlayout, null);
holder = new ViewHolder();
holder.text1 = (TextView) convertView
.findViewById(R.id.TextView01);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.text1.setText(abbreviations[position]);
return convertView;
}
static class ViewHolder {
TextView text1;
}
}
}
OK now the Thread.
package com.ejemplolisbox;
public class Refresh extends Thread{
public void run(){
while(true){
String[] ex=EL.abbreviations;
String[] ne=new String[ex.length+1];
for(int i=0;i<ex.length;i++){
ne[i]=ex[i];
}
ne[ex.length]="newItem"+ex.length;
EL.abbreviations=ne;
try{
EL.instance.notifyDataSetChanged();
EL.g.setFocusableInTouchMode(true);
}
catch(Exception e){
int i = 0;
EL.g.setFocusableInTouchMode(true);
}
EL.g.setFocusableInTouchMode(true);
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
Well, thanks on advance, any solution will be appretiated

You can't directly modify UI elements from a thread that isn't the UI thread. If you want to modify a UI element from a different thread, you have to call the function runOnUiThread. That means you'll have to pass a refernce to the activity to the Refresh class in it's constructor so you can do the following call on your thread:
activity.runOnUiThread(new Runnable(){
public void run(){
EL.g.setFocusableInTouchMode(true);
}
});
That said, if I were you I'd scrap this and just use an AsyncTaskLoader instead. It's much easier and the class was specifically created for asynchronously loading up elements in things like a listview. The way you have the code written right now is not going to work very well and is prone to all kinds of error. In android, a general rule of thumb is to not use the raw Thread class unless you abosultely have to. Use either the AsyncTaskLoader, AsyncTask, or IntentService.
Final note, if you're developing for API levels less than 10, you can still access the AsyncTaskLoader class via the android Support Package.