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How do I remove my listener after finishing what I started? (JAVA)

I'm creating a media player in JavaFX. In one of my methods, I've created a way to search for metadata in a Media-file and then display it in ImageView. Works fine first time, but as soon as I want to call it again using another Media object, the image doesn't show up. I'm a bit confused and inexperienced, but I think that perhaps I need to reset/stop the listener before going to next object in line?
So my question is! How do you remove the listener when "image" has been found, what do you type to make it happen?
If you think that there's another reason why my image wont display the second time, please let me know as well.
Thanks on purpose.
private void displayAlbumCover (){
// Will start to show a blank CD
File file = new File("src/sample/images/blank_cd.jpeg");
Image image = new Image(file.toURI().toString());
albumCoverView.setImage(image);
// However if an album cover is found in the meta-data it will be displayed
ObservableMap<String,Object> meta_data=me.getMetadata();
meta_data.addListener((MapChangeListener<String, Object>) ch -> {
if(ch.wasAdded()){
String key=ch.getKey();
Object value=ch.getValueAdded();
switch(key){
case "image":
albumCoverView.setImage((Image)value);
break;
}
}
});
}

ObservableMap has removeListner method. You can keep the listener instance to variable and then remove it later.
private MapChangeListener<String, Object> listener;
private void displayAlbumCover (){
// ...
this.listener = //...
meta_data.addListener(listener);
}
private void removeListener() {
me.getMetadata().removeListener(this.listener);
}
https://docs.oracle.com/javase/8/javafx/api/javafx/collections/ObservableMap.html#removeListener-javafx.collections.MapChangeListener-

Is there a way for push notifications in libGDX (Android and iOS projects)?

Does someone knows if it is possible to add push notifications(like Amazon Simple Notification Service) in an Android and iOS with RoboVM libGDX projects? And if it is possible, are there any good tutorials or good hints how to implement such things?
I would be happy about every hint how I can implement it.

Hi I know this is an old question but I was struggling to find a solution for this specially for iOS, but I finally found a way. If the explanation below is confusing and you prefer to see an example here is a github repo with a sample project:
Repo GitHub
I only show the code for iOS see the repo for Android.
The idea is simple you need to create a class that handles sending a notification for each platform on each of your projects (Android and iOS) and have it implement an interface called NotificationsHandler.
NotificationsHandler:
public interface NotificationsHandler {
public void showNotification(String title, String text);
}
iOS Adapter:
public class AdapteriOS implements NotificationsHandler {
public AdapteriOS () {
//Registers notifications, it will ask user if ok to receive notifications from this app, if user selects no then no notifications will be received
UIApplication.getSharedApplication().registerUserNotificationSettings(UIUserNotificationSettings.create(UIUserNotificationType.Alert, null));
UIApplication.getSharedApplication().registerUserNotificationSettings(UIUserNotificationSettings.create(UIUserNotificationType.Sound, null));
UIApplication.getSharedApplication().registerUserNotificationSettings(UIUserNotificationSettings.create(UIUserNotificationType.Badge, null));
//Removes notifications indicator in app icon, you can do this in a different way
UIApplication.getSharedApplication().setApplicationIconBadgeNumber(0);
UIApplication.getSharedApplication().cancelAllLocalNotifications();
}
#Override
public void showNotification(final String title, final String text) {
NSOperationQueue.getMainQueue().addOperation(new Runnable() {
#Override
public void run() {
NSDate date = new NSDate();
//5 seconds from now
NSDate secondsMore = date.newDateByAddingTimeInterval(5);
UILocalNotification localNotification = new UILocalNotification();
localNotification.setFireDate(secondsMore);
localNotification.setAlertBody(title);
localNotification.setAlertAction(text);
localNotification.setTimeZone(NSTimeZone.getDefaultTimeZone());
localNotification.setApplicationIconBadgeNumber(UIApplication.getSharedApplication().getApplicationIconBadgeNumber() + 1);
UIApplication.getSharedApplication().scheduleLocalNotification(localNotification);
}
});
}
}
Now by default Libgdx passes your ApplicationListener or Game object to AndroidLauncher and IOSLauncher along with a configuration object. The trick is to pass the class we created earlier to the ApplicationListener so that you can use it inside your Core project. Simple enough:
public class IOSLauncher extends IOSApplication.Delegate {
#Override
protected IOSApplication createApplication() {
IOSApplicationConfiguration config = new IOSApplicationConfiguration();
// This is your ApplicationListener or Game class
// it will be called differently depending on what you
// set up when you created the libgdx project
MainGame game = new MainGame();
// We instantiate the iOS Adapter
AdapteriOS adapter = new AdapteriOS();
// We set the handler, you must create this method in your class
game.setNotificationHandler(adapter);
return new IOSApplication(game, config);
}
public static void main(String[] argv) {
NSAutoreleasePool pool = new NSAutoreleasePool();
UIApplication.main(argv, null, IOSLauncher.class);
pool.close();
}
}
Now that you have a reference to the implementation of NotificationHandler you can simply call it through your Core project.
public class MainGame extends Game {
// This is the notificatino handler
public NotificationHandler notificationHandler;
#Override
public void create () {
// Do whatever you do when your game is created
// ...
}
#Override
public void render () {
super.render();
// This is just an example but you
// can now send notifications in your project
if(condition)
notificationHandler.showNotification("Title", "Content");
}
#Override
public void dispose() {
super.dispose();
}
// This is the method we created to set the notifications handler
public void setNotificationHandler(NotificationHandler handler) {
this.notificationHandler = handler;
}
}
One last thing
If you need to run the Desktop version then you will need to do the same thing for Desktop otherwise you might get errors, it will not do anything on the Desktop, or you can check the platform before calling the method showNotfication. You can clone the repo where I do this:
Repo GitHub

I've never done it myself. But you can use this tutorial to find out how to write Android specific code in your libGDX project. Your Android code could then receive the notifications and trigger a callback in libGDX. I hope this is at least a step in the right direction.
However I' not sure about doing the same for iOS.

Android message between classes

This is my first post and I did not find anything similar, so I've decided to ask.
Im developing a Poker Game for Android to practice the SDK and refresh/improve my Java. Its a simple app that control a texas hold'em poker hand.
Initally, I wrote my classes using only Java SE and it looks fine. Each class has its own purpose and testing it with console input/output, I can see it really works :)
Last week, I decided to port it to Android to see things happening through a graphic interface, so I got the resource images, make an Activity and included my poker package.
Before port to Android I can just put a println (or readLine) to see whats going on and send my inputs. Now Im stuck in how each class can communicate to the game activity to provide what must be drawn. If possible, I don't want insert Android draw code inside game classes. Im trying find a way to exchange messages between my Activity and the game classes and Id like some suggetions. Im new in developing Android apps, so I dont know all mechanics to do this.
Below are the snippet from my activity:
package my.poker.game;
//import stuff
public class ActivityHand extends Activity
{
private static Vector<Player> Players = new Vector<Player>();
public static final int MAX_PLAYERS = 8;
public static void startEmptyTable()
{
Players.removeAllElements();
Players.setSize(MAX_PLAYERS);
}
public static void LeaveTable(int pos)
{
Players.set(pos, null);
}
public static void SitTable(int pos, Player player)
{
Players.set(pos, player);
}
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
int cash = 1000;
startEmptyTable();
SitTable(0, new Jogador("William", cash));
SitTable(2, new Jogador("Richard", cash));
SitTable(4, new Jogador("John", cash));
SitTable(6, new Jogador("Paul", cash));
SitTable(8, new Jogador("Albert", cash));
//Start a Hand.... in future this will be a loop for each Hand
Hand hand = new Hand(Players);
}
}
The object hand, will select a Dealer, deal the cards, control the small and big blinds and start the game loop.
The question is: how the hand class can tell the Activity to Draw and pass an object containing what to draw?
Thanks a lot for your help
Editing: I've decided to try implementing it using a Handler and passing simple messages. As I read from Handler at Developers a Handler object is assigned to thread's MessageQueue, so I tried to put this into my Activity Class (before Hand hand = new Hand (...) ):
Handler handler = new Handler()
{
#Override
public void handleMessage(Message msg)
{
Bundle bundle = msg.getData();
// Do something with message contents
}
};
And inside the Hand class I put this when I want to draw something:
Handler handler = new Handler();
Message msg = new Message();
Bundle bundle = new Bundle();
bundle.putString("Key", "The Key's Value");
msg.setData(bundle);
handler.sendMessage(msg);
As I understood, both handlers are from same thread, so they are assigned to same MessageQueue right? I tought when I send a message inside Hand class, the Activity class can receive it in handleMessage method and processes any message I send, but handleMessage doesn't execute.
What am I missing?
Thanks again

To call methods in the activity, you want to pass the activity to this class.
for example:
public class PokerActivity extends Activity
{
#Override
public void onCreate(Bundle savedInstanceState)
{
Hand hand = new Hand(this);
}
public void setVisibleHand(Player player)
{
<do something in the activity>
}
}
public class Hand
{
PokerActivity pokerActivity;
public Hand(PokerActivity activity)
{
this.pokerActivity = activity;
}
public void setVisibleHand()
{
pokerActivity.setVisibleHand(player1);
}
}
Now, this might not be the best way to do it. In Android you have to be carefull to not leak the context, or you might be getting trouble with the memory. (simply passing the activity/context might be the easy way, but is also the easiest way to leak the context.)
I'd advise you to look at some simple tutorials first, to get a feeling of how android activities work.

You could use a Handler and Message system to communicate between your classes.
This tutorial by Lars Vogel should help you Android Threads, Handlers and AsyncTask - Tutorial

You will have to create another class to make the interactions with your own classes and the activity itself.
From that class you can use the activity context to control the android activity.
The approach about using Handlers and Messages is good but would require you to modify your game classes.

Maybe you should extend View Class to draw the Hand.
http://developer.android.com/reference/android/view/View.html

How can I get the selected text in AutoCompleteField and send it to a server via post

I'm new to blackberry development. There is this question I've come across several times, which is "How to get the Selected item as string". The answers that were given did not fully answer the question:
AutoCompleteField autoCompleteField = new AutoCompleteField(filterList)
{
public void onSelect(Object selection, int SELECT_TRACKWHEEL_CLICK) {
ListField _list = getListField();
if (_list.getSelectedIndex() > -1) {
Dialog.alert("You selected: "+_list.getSelectedIndex());
// get text selected by user and do something...
}
}
The point is how can I get the selected text and "do something". Imagine I want to send the items as a string to a server via post. How would I do that in code?
Thank you! Michael.

These are really (at least) two different things.
To get the selected text, see this answer
To send a HTTP POST request, see this other answer
Normally, it's also bad to make network requests on the UI thread (which is what will callback your onSelect() method). So, it would be better to take the HTTP POST code from the second answer, and put it inside the run() method of a Runnable object you could run on a background thread. Something like this:
private class PostRequest implements Runnable {
private String _postParam;
public PostRequest(String param) {
_postParam = param;
}
public void run() {
// make POST request here, using _postParam
}
}
And use it like this:
AutoCompleteField acf = new AutoCompleteField(list) {
protected void onSelect(Object selection, int type) {
super.onSelect(selection, type);
if (selection != null) {
String selectionAsString = getEditField().getText();
Thread worker = new Thread(new PostRequest(selectionAsString));
worker.start();
}
}
};

GWT SuggestBox: How do I force the SuggestBox to select the first item in the suggestion list?

I have a textbox and one suggestbox. I attach a value change and key up handler to the text box such that whatever the user types (or pastes) into the text box is echo-ed inside the suggestbox. I can get the suggestbox to display the suggestion list by calling showSuggestionList on each value change and key up event.
Now, how do I get the suggestbox to automatically choose the first item in the suggestion list?
One of the methods I tried is to programatically simulate key presses, i.e
suggestBox.setFocus(true);
NativeEvent enterEvent = Document.get().createKeyPressEvent(false, false, false, false, KeyCodes.KEY_ENTER);
DomEvent.fireNativeEvent(enterEvent, suggestBox);
textBox.setFocus(true);
This doesn't work at all. The enter key isn't simulated. Another possible solution is to extend SuggestionBox.SuggestionDisplay, but I'm not too sure how to that. Any pointers appreciated.
Update: I'm still working on this and trying various methods.
Here, I tried to implement my own SuggestionDisplay by subclassing DefaultSuggestionDisplay and overriding getCurrentSelection() to make accessible from my class. This doesn't work either. Null is returned.
private class CustomSuggestionDisplay extends DefaultSuggestionDisplay {
#Override
protected Suggestion getCurrentSelection() {
return super.getCurrentSelection();
}
}
suggestBox.setAutoSelectEnabled(true);
textBox.addKeyUpHandler(new KeyUpHandler() {
public void onKeyUp(KeyUpEvent event) {
suggestBox.setValue(textBox.getText(), true);
suggestBox.showSuggestionList();
if (suggestBox.isSuggestionListShowing()) {
String s = ((CustomSuggestionDisplay) suggestBox.getSuggestionDisplay()).getCurrentSelection().getDisplayString();
Window.alert(s);
}
}
});
Here, I tried to attach a value change handler to the SuggestBox, and casting the event type to SuggestOracle.Suggestion. Again, null is returned.
suggestBox.addValueChangeHandler(new ValueChangeHandler<String>() {
public void onValueChange(ValueChangeEvent<String> event) {
String s = ((SuggestOracle.Suggestion) event).getDisplayString();
Window.alert(s);
}
});

Use suggesBox.setAutoSelectEnabled(true)
Here more info about the SuggestBox of GWT:

You could try using addSelectionHandler in conjunction with setAutoSelectEnabled to receive an event whenever a suggestion is selected. You could also have your Oracle send a message when it suggests something, or your Display send a message when it displays a list:
public class AutomaticallySelectingSuggestionDisplay extends SuggestBox.DefaultSuggestionDisplay {
#Override
protected void showSuggestions(SuggestBox box, Collection<? extends SuggestOracle.Suggestion> suggestions, boolean isDisplayHtml, boolean isAutoSelectEnabled, SuggestBox.SuggestionCallback callback) {
super.showSuggestions(box, suggestions, isDisplayHtml, isAutoSelectEnabled, callback);
fireValueChangeEventWithFirstSuggestion(suggestions);
}
}
This idea feels a little muddled to me, so I hope you can find a solution just using event handlers.