I am looking for a way to display images on my UI from a background thread. This background thread recieves streaming images in the form of byte array. I need to diplay it on my UI
Can anyone help with this please?
I already tried accessing the bitmap field from the background thread but nothing happens
Thanks
bmp = Bitmap.createBitmapFromBytes(jpegBytes, 0, jpegBytes.length, 1);
final Bitmap bit = bmp;
final byte [] jp = jpegBytes;
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run()
{
camView.jpegBytes = jp;
System.out.println(bit);
camView.bmpStream.setBitmap(bit);
//camView.bmpStream.
}
});
If you need to change the Main Screen means if you need to add field to Main Screen from the Background thread you need to call
invalidate();
method to repaint the screen otherwise no change will place in Screen
Ex:
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run()
{
camView.jpegBytes = jp;
System.out.println(bit);
camView.bmpStream.setBitmap(bit);
invalidate();
//camView.bmpStream.
}
});
Hey guys I managed to find the problem I had an issue with the used of references to my parent class. the above code I have posted in the question works perfect if you have a reference to the main class.
Related
I've got this Controller connected to a FXML-file with several buttons, labels, a table, etc.
I've got some popups that get initialized and shown when different buttons get clicked and that works fine.
I've got another popup that I'd like to 'pop up' when something goes wrong, so this is called when an event get's handled that has been sent from java-code in another class.
This message pop-up get's called, but the code within the Platform.runLater() isn't executed, actually freezing the GUI.
There's one distinction I've found that seems to cause this and that is that a Platform.isFxApplicationThread() that I call right before the Platform.runLater() returns false in this message pop-up where it returns true when one of the other pop-ups get called from a button-click.
As I've also tried one of those pop-ups that's normally called from a button-click and that also doesn't work when it's called from the code that get's executed because of the incoming event, I'm pretty sure this is the problem, but Platform.runLater states "This method, which may be called from any thread, will post the Runnable to an event queue and then return immediately to the caller." and that seems not true for me, so I'm kinda puzzled if this actually is the problem ...
Has anyone encountered this before and / or does anyone know what I'm doing wrong?
This works fine:
#FXML
private void btnCashClicked(ActionEvent event) {
screensController.getCashTransactionController().addCashTransactionListener(this);
labelToPay = new Label(eurosToPay + " euro");
sealbagTextField = new SealbagTextField();
PopupUtils.showCashPaymentPopup(btnSealbag, btnCashOk, labelPaid, labelSealbag, labelToPay, lblExchange,
labelExchange, labelReturnValue, eurosToPay, btnCash, this, sealbagTextField);
screensController.getMainController().startTransaction(amountInCents, PaymentType.Asap);
}
This code in the same controller class doesn't show a pop-up:
#Override
public void showErrorOnScreen(String message) {
// temporary usage of label and textfield
labelToPay = new Label(eurosToPay + " euro");
sealbagTextField = new SealbagTextField();
PopupUtils.showCashPaymentPopup(btnSealbag, btnCashOk, labelPaid, labelSealbag, labelToPay, lblExchange,
labelExchange, labelReturnValue, eurosToPay, btnCash, this, sealbagTextField);
//PopupUtils.showMessagePopup("Error", message, "Close", 374, 250, btnCancel);
}
I'm on Windows and using jre1.8.0_60
The code of the cashPopup:
public static int showCashPaymentPopup(Button btnSealbag, Button btnCashOk, Label labelPaid, Label labelSealbag, Label labelToPay, Label lblExchange, Label labelExchange, Label labelReturnAmount, int amount, Node node, PayScreen parent, SealbagTextField sealbagTextField) {
int paid = 0;
logger.debug("cashPopup is on GUI thread: " + Platform.isFxApplicationThread());
Platform.runLater(new Runnable() {
#Override
public void run() {
cashPopup.getContent().clear();
Rectangle rectangle = new Rectangle();
rectangle.setArcHeight(20);
rectangle.setArcWidth(20);
rectangle.setFill(Color.LIGHTBLUE);
rectangle.setWidth(466);
rectangle.setHeight(311);
rectangle.setStroke(Color.DARKBLUE);
rectangle.setStrokeType(StrokeType.INSIDE);
...
cashPopup.getContent().addAll(rectangle, textArea, headerLabel, lblDesc, lblAmount, labelAmount, lblPaid, labelPaid, lblToPay, labelToPay, btnCashOk, lblSealbag, labelSealbag, lblExchange, labelExchange, labelReturnAmount, btnSealbag, btnCancel);
cashPopup.show(node, 150, 164);
}
});
return paid;
}
And the showMessagePopup:
public static void showMessagePopup(String title, String text, String buttonText, int posX, int posY, Node parent) {
logger.debug("messagePopup is on GUI thread: " + Platform.isFxApplicationThread());
Platform.runLater(new Runnable() {
#Override
public void run() {
logger.debug("0");
messagePopup.getContent().clear();
Rectangle rectangle = new Rectangle();
rectangle.setArcHeight(20);
rectangle.setArcWidth(20);
rectangle.setFill(Color.LIGHTBLUE);
rectangle.setWidth(500);
rectangle.setHeight(300);
rectangle.setStroke(Color.DARKBLUE);
rectangle.setStrokeType(StrokeType.INSIDE);
Label headerLabel = new Label(title);
headerLabel.setStyle("-fx-font-size: 18; -fx-font-family: Arial;");
headerLabel.setLayoutX(15);
headerLabel.setLayoutY(10);
TextArea textArea = new TextArea();
textArea.setStyle("-fx-font-size: 14; -fx-font-family: Arial;");
textArea.setLayoutX(10);
textArea.setLayoutY(35);
textArea.setMaxWidth(480);
textArea.setMinHeight(190);
textArea.setMaxHeight(190);
textArea.setEditable(false);
textArea.setWrapText(true);
textArea.setText(text);
Button btnClose = new Button(buttonText);
btnClose.setLayoutX(180);
btnClose.setLayoutY(235);
btnClose.setPrefSize(120, 54);
btnClose.setStyle("-fx-font-size: 18; -fx-font-family: Arial; -fx-text-fill:white; -fx-background-color: linear-gradient(#8b9aa1, #456e84), linear-gradient(#c5dde7, #639fba), linear-gradient(#79abc1, #639fba); -fx-background-insets: 0,1,2; -fx-background-radius: 6,5,4;");
btnClose.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
messagePopup.hide();
}
});
messagePopup.getContent().addAll(rectangle, headerLabel, btnClose, textArea);
messagePopup.show(parent, posX, posY);
}
});
}
logger.debug("0") isn't even executed ...
Found it, by running in debug mode and suspending the Java FX thread to see what it is doing.
There's this 'other thread' that gets started from the main program and which needs to get started before the process can continue. This other thread looks like this:
pinPadAsSlaveThread = new Thread(pinPadAsSlave);
pinPadAsSlaveThread.start();
while (!pinPadAsSlave.isRunning()) {
// wait for pinPadAsSlave to be running
try {
Thread.sleep(10);
} catch(InterruptedException ie) {
// ignore
}
}
Normally this takes about 50 ms, but as the pin pad is unavailable on the network this becomes an infinite loop. That on itself should be handled of course, by letting this loop only try it for 50 times or so.
But the real problem is that this thread that is put to sleep for 10 ms all the time is the Java FX thread. I don't know why the Java FX thread is doing the setting up of the communication, as it shouldn't (and I didn't ask for that by putting it inside a platform.runLater or something alike), but the fact is: it is ...
I have a problem while working with JavaFX and Threads. Basically I have two options: working with Tasks or Platform.runLater. As I understand Platform.runLater should be used for simple/short tasks, and Task for the longer ones. However, I cannot use any of them.
When I call Thread, it has to pop up a captcha dialog in a middle of task. While using Task, it ignores my request to show new dialog... It does not let me to create a new stage.
On the other hand, when I use Platform.runLater, it lets me show a dialog, however, the program's main window freezes until the pop up dialog is showed.
I need any kind of solution for this. If anyone knows how to deal with this or had some similar experience and found a solution I am looking forward to hearing from you!
As puce says, you have to use Task or Service for the things that you need to do in background. And Platform.runLater to do things in the JavaFX Application thread from the background thread.
You have to synchronize them, and one of the ways to do that is using the class CountDownLatch.
Here is an example:
Service<Void> service = new Service<Void>() {
#Override
protected Task<Void> createTask() {
return new Task<Void>() {
#Override
protected Void call() throws Exception {
//Background work
final CountDownLatch latch = new CountDownLatch(1);
Platform.runLater(new Runnable() {
#Override
public void run() {
try{
//FX Stuff done here
}finally{
latch.countDown();
}
}
});
latch.await();
//Keep with the background work
return null;
}
};
}
};
service.start();
Use a Worker (Task, Service) from the JavaFX Application thread if you want to do something in the background.
http://docs.oracle.com/javafx/2/api/javafx/concurrent/package-summary.html
Use Platform.runLater from a background thread if you want to do something on the JavaFX Application thread.
http://docs.oracle.com/javafx/2/api/javafx/application/Platform.html#runLater%28java.lang.Runnable%29
It's too late to answer but for those who have the error, here is the solution XD
You can use one Thread.
Use the lambda expression for the runnable in the thread and the runlater.
Thread t = new Thread(() -> {
//Here write all actions that you want execute on background
Platform.runLater(() -> {
//Here the actions that use the gui where is finished the actions on background.
});
});
t.start();
You can user directly this code
Don't forget you can't send non-final variable in thread .
you can send final variable in thread
//final String me="ddddd";
new Thread(new Runnable() {
#Override
public void run() {
// me = me + "eee";
//...Your code....
}
}).start();
Use in
your code
try/catch
class MyCanvas extends Canvas{
protected void paint(Graphics g) {
//Process keyboard
//Update movement/position
//Draw
repaint(); //loop
}
}
Until now I used the Canvas's paint() for the game loop, but I came across some article in the web that says that another thread should be used here
Now I'm wondering if paint() is a good/safe place to process all the data.
So can I continue doing it like this?
Or should I make another thread for that?
I'm not sure of pros and cones of each so I'm not sure which method to choose but I got used to repaint method
I would not use paint() that way, no. paint() should be for painting ... drawing. I would split your monitoring of user input, and game logic processing, outside that method.
Have you considered using the GameCanvas subclass of Canvas?
It gives you some nice double-buffering features. You would create another thread, which would call your GameCanvas' run() method, where it would check for user input, update the game logic, then draw to the off-screen buffer, and finally trigger repainting of the on-screen buffer.
Something like this:
class MyGameCanvas extends GameCanvas implements Runnable {
/** start this game! */
public void start() {
Thread worker = new Thread(this);
worker.start();
}
/** run the game loop */
public void run() {
// Get the Graphics object for the off-screen buffer
Graphics g = getGraphics();
while (true) {
// Check user input and update positions if necessary
int keyState = getKeyStates();
if ((keyState & LEFT_PRESSED) != 0) {
sprite.move(-1, 0);
}
else if ((keyState & RIGHT_PRESSED) != 0) {
sprite.move(1, 0);
}
// Clear the background to white
g.setColor(0xFFFFFF);
g.fillRect(0,0,getWidth(), getHeight());
// Draw the Sprite
sprite.paint(g);
// Flush the off-screen buffer
flushGraphics();
try {
// TODO: of course, you might want a more intelligent
// sleep interval, that reflects the amount of time
// remaining (if any) in the cycle ...
Thread.sleep(10); //sleep 10 ms
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
Note that I put basically everything in the run() method, for brevity. I'm assuming your game is more complicated, and would warrant splitting off separate methods for getting user input, updating logic, and then calling graphics/paint methods. Those would all be called from run().
Usage
Start this in your MIDlet's startApp() method:
MyGameCanvas gameCanvas = new MyGameCanvas();
gameCanvas.start();
exitCommand = new Command("Exit", Command.EXIT, 1);
gameCanvas.addCommand(exitCommand);
gameCanvas.setCommandListener(this);
Display.getDisplay(this).setCurrent(gameCanvas);
References
http://www.codeproject.com/Articles/35833/Programming-2D-Games-in-J2ME
an example that shows a better implementation, if you don't use GameCanvas and just use Canvas.
PowerPoint overview of Game APIs and looping , with code and general theory
I've been reading about AsyncTasks and Hanlders and Loopers but I still can't figure out where I'm going wrong in my code. I'm trying to run code that will look over a Tic Tac Toe grid and determine the best move for the computer. I want this code to run in the background 'cause it can take some time and then I can update the UI level with a textbox that says something like "I'm Thinking". I've tried this a bunch of different ways, none with success.
private class PostTask extends AsyncTask<String, Integer, String> {
private Board _b;
private Welcome.Player _opp;
private int _depth;
#Override
protected void onPreExecute() {
super.onPreExecute();
}
protected void SetVars(Board b, Player p, int depth){
_b = b;
_opp = p;
_depth = depth;
}
#Override
protected String doInBackground(String... params) {
Looper.prepare();
try{
_bestMove = _b.GetBestMove(_opp,_depth);
}
catch(Exception err){
_bestMove = -1;
}
return "All done";
}
#Override
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values);
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
if(_bestMove == -1){
TextView tv = (TextView) findViewById(R.id.tv_Score);
tv.setText("Had and error, couldn't make a move.");
}
FollowUpComputerMove(this);
}
The above code will work for exactly 5 moves and then it crashes. When I watch in the debugger I see new theads being created named Thread<#> AsyncTask #1. Once I get to five of those AsyncTasks it goes back to try and grab the first AsyncTask and crashes. When it crashes I'm shown the ThreadPoolExecutor.class file.
I've also read that I shouldn't be using both the AsyncTask and the Looper objects together so I've tried taking the Loooper.prepare() statement out, but then my AsyncTask fails immediately with the error message:
Can't create handler inside thread that has not called Looper.prepare() - AsyncTask inside a dialog
I've read repeatedly that you shouldn't be trying to update the UI from an AsyncTask and that often the above error is because of that, but GetBestMove isn't updating the UI thread. When I trace through to see where the error comes, it fails when calling a constructor saying it can't find the class.
Can anyone point me in the right direction? My end goal is to use one main thread and only one background thread, and just keep re-using the background thread whenever the computer needs to make a move. I know that the recursive method GetBestMove works when I run this program in a single-thread manner. But the screen freezes for too long on some moves as the method is being run. Thank you so much.
-NifflerX
Apologies for answering my own question, but the issue I was facing had nothing to do with recursion. The class I was calling was extending the class Activity, and while trying to call that from an AsyncTask the program was erroring out. When I removed the extends Activity from the class definition it started working again. Sorry for the post.
-NifflerX
Hi I play with GWT in the weekends, and I really like what i've seen
so far. I have 2 questions:
I don't really understand the execution model of my app. I think
that's because I don't know javascript. I'm assuming that there is
only one logical thread from the browser running the javascript and it
is the same thread that updates the display (disregarding asynchronous
requests). So when through js I add 50 elements to a frame, the 50
elements are displayed after all of them are added to the frame. In
other words, after the js has finished executing. Do I have it
right? Are there articles out there on this topic?
Sorry this is not a great example, but it may get my question
across. What do I do in the following situation (design):
a) update the text in a label to "starting..."
b) do a bunch of js and dom manipulation
c) update the text in the label to "finished!"
Currently, all I see is the after-effect: my dom manipulation and
"finished". The label never displays "starting..."
How can I force the label to refresh between step a & b. I've seen
some posts describing that one could use the Timer and somehow force
the element to refresh. But I can't figure out how this is achieved.
Looking forward to your suggestions. Thanks in advance.
To 1): Yes, javascript is single threaded. It is up to you to implement long running operations as non-blocking. Otherwise you're likely to run into Slow Script Warnings (see next point).
To 2): Have a look at the IncrementalCommand class (it's usage is described here). With it you can divide long running operations into chunks of smaller work and display progress updates to the user. A small example:
public class Starter implements EntryPoint {
private Label text = new Label();
private Label update = new Label();
#Override
public void onModuleLoad() {
Button btn = new Button("hit me");
btn.addClickHandler(new ClickHandler() {
#Override
public void onClick(ClickEvent event) {
text.setText("starting...");
startIncrementalWork();
}
});
RootPanel.get().add(text);
RootPanel.get().add(update);
RootPanel.get().add(btn);
}
private void startIncrementalWork() {
IncrementalCommand cmd = new IncrementalCommand() {
private int count = 0;
#Override
public boolean execute() {
if (count >= 10000) {
text.setText("finished");
return false;
}
for (int i = 0; i < 100; i++) {
update.setText("count " + count);
count++;
}
return true;
}
};
DeferredCommand.addCommand(cmd);
}
}
Hope that helps.