I am a beginner with multithreading and GUI development in Java with Swing and Window Builder in Eclipse.
I am trying to get a jlabel that shows the status of the program to display text and quickly fade from red to black when a button is pressed and then to disappear in ten seconds.
I tried to combine suggestions for this from several answers on Stack Overflow using a new thread and a timed task (How to fade color from white to black?) and the code works correctly the first time the button is pressed. However, when the button is pressed again and the method is called again, it only briefly blinks red and the text disappears very quickly.
I believe that it is because when the button is pressed a second time the old thread is still running and both are trying to control the label. I obviously found several question on Stack Overflow on how to kill treads in Java (including How do you kill a thread in Java?), but none of them seemed to help in my situation. I am relatively inexperienced with multithreading and Swing GUIs, so I probably made some really dumb mistakes with my code.
Here it the method that is called by a event listener when a button is pressed (this method is in a separate "Program Main" controller class):
private static void setBriefLblStatus(String content) {
one = new Thread() {
public void run() {
setLblStatus(content);
fading = Color.RED;
TimerTask fadingTask = new TimerTask() {
#Override
public void run() {
if (fading.getRed() > 0) {
fading = new Color(fading.getRed() - 1, 0, 0);
setLblStatusColor(fading);
}
}
};
timer = new Timer();
timer.scheduleAtFixedRate(fadingTask, 7, 7);
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
setLblStatus("");
}
};
one.start();
}
Related
This question already has answers here:
Calling a method from a JButton is freezing a JFrame?
(2 answers)
Display indeterminate JProgressBar while batch file runs
(1 answer)
Something seems wrong with the layout, JButton showing unexpected behaviour at resize of the window
(4 answers)
Closed 5 years ago.
I am trying to make a program that has a toggle button (regular JButton) that when clicked, runs a while loop that runs until the button is clicked again to stop it.
I have done this, however, when I click the button, the entire JFrame freezes because of it being stuck in the while loop, as the loop will run forever until the button is pressed again. However, it is impossible to click the button again because the JFrame freezes. The button itself also just stays blue because the JFrame freezes before the colour change occurs; right before I click the button.
My code looks something like this:
boolean isRunning=false;
private void buttonClickEvent(ActionEvent evt) {
if(isRunning){
isRunning=false;
System.out.println("Stopped running!");
jButton.setText("Start Running");
} else { // BELOW IS THE CODE THAT CAUSES IT TO LOCK
isRunning=true;
jButton.setText("Stop Routine");
while(isRunning){
// DO STUFF
}
}
}
EDIT: I tried doing the following code (below) and it does print the text and allow the colour change to occur in the button, but the UI still freezes quickly afterward.
boolean isRunning=false;
private void buttonClickEvent(ActionEvent evt) {
if(isRunning){
isRunning=false;
System.out.println("Stopped running!");
jButton.setText("Start Running");
} else { // BELOW IS THE CODE THAT CAUSES IT TO LOCK
isRunning=true;
jButton.setText("Stop Routine");
new Thread(new Runnable() {
public void run() {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
while(isInRoutine){
System.out.println("lolk");
}
}
});
}
}).start();
}
}
I'm trying to build "Stick Hero" board game using javafx (JDK8). I use
scene.setOnKeyPressed(e -> {
Thread thread = new Thread() {
#Override
public void run() {
if (e.getCode().equals(KeyCode.ENTER)) {
// do some graphical changes
playGame();
}
}
};
thread.start();
});
to listen to keyboard and by pressing enter the vertical line turns into a horizontal bridge and the human pass the bridge and this will continue until the length of bridge doesn't match the distance. Now i want to update UI during playGame() method is running. When i tried to do scoreLabel.setText(String.valueOf(score)); and update the scoreLabel text i encountered Not on FX application thread error. playGame() is something like
for (int i = 0; i < cycle; i++) {
goOneCycle();
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
fixPosition();
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
and in goOneCycle(); and fixPosition(); i do some graphical changes but it does not shown until the end of the loop.
Now i have two questions. First why i can do stuff like scoreLabel.setLayoutX(500); but i cannot do scoreLabel.setText(String.valueOf(score)); i mean in the first case i do not encounter Not on FX application thread. And how i can update scoreLabel text. Notice that i already tried to use Platform.runLater() but when i use this animations and graphical changes will not shown in playGame() method, and just the final frame is shown -all of the animations is done but it does not shown.
Original Question
I'm currently working on a simple application that displays a map and will later implement pathfinding logic for units. I've implemented the map and view so far and everything runs just fine until I implemented the game loop.
With the game loop enabled, the program just freezes. I can't close the window anymore and the map isn't presented, even though the game loop is executed just fine. I've used this game loop twice in the past and never had any problems until now.
Edit: The game loop continues to execute just fine while everything else freezes.
Here are the two functions involved:
public GameController() {
paused = true;
frame = new GameFrame(this);
map = new Map(500, 500);
mvm = new MapViewModel(map.getMap(), map.getWidth(), map.getHeight());
//TODO: gameLoop() currently breaks the game.
gameLoop();
}
public void gameLoop() {
double tickTime, lastTick;
for (;;) {
tickTime = System.nanoTime();
lastTick = tickTime;
//Repaints the frame
update();
while (tickTime - lastTick < NANOSECONDS_PER_UPDATE) {
try {
Thread.sleep(1);
} catch (InterruptedException ignored) {}
tickTime = System.nanoTime();
}
}
}
edit2: I'm using Swing. The actual painting happens in the paintComponent method of my GamePanel (JPanel):
#Override
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
//Paints the map
painter.paintMap(g2, controller.getMvm());
}
Obviously, if you have any further questions feel free to ask. Thanks in advance.
Solution
Here's the code I'm using now, GameController and update haven't changed.
public void gameLoop() {
timer = new Timer(MILLISECONDS_PER_UPDATE, updater);
timer.start();
}
updater is an ActionListener that I have added as a private variable to the class.
private ActionListener updater = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("test2");
update();
}
};
You could add updater locally but I prefer it this way.
You tell us nothing about what GUI library you might be using, but assuming that it might be Swing, it looks like you're running some long-running code on the Swing event thread, the main thread responsible for doing all Swing graphics and for interacting with the user. If so, then the code will prevent Swing from redrawing the GUI, freezing your application.
My suggestions are:
Don't do this. Don't run any long-running code on the main event thread.
Instead consider using a Swing Timer to do your "game loop".
Or if you must use your while loop and Thread sleep, do it off of the event thread, but then be sure that all Swing calls that mutate the state of Swing objects be done on the event thread.
For more on Swing threading, please read Concurrency in Swing.
I am making a simple board game in java, where I want to animate a dice roll. So I flash pictures of a dice like this:
public Timer roll_dice = new Timer(50, this);
...
public void actionPerformed(ActionEvent evt) {
if(roll_dice.getDelay() > 500){
roll_dice.setDelay(50);
roll_dice.stop();
movePiece();
}else{
roll_dice.setDelay(roll_dice.getDelay() + 50);
dice_panel.repaint(0);
}
}
}
movePiece(){
//do some more painting
}
So the die is going so show random numbers for a few times, and then slowly settle on a number. After that is done I would like to call the movePiece() method. However, as it is, the the repaint occurs sporadically and screws everything up so that movePiece() gets called before the dice roll is actually finished animating.
Does anyone have any ideas how I can call movePiece only after the final repaint has happened?
So the die is going so show random numbers for a few times, and then slowly settle on a number. After that is done I would like to call the movePiece() method. However, as it is, the the repaint occurs sporadically and screws everything up so that movePiece() gets called before the dice roll is actually finished animating.
What worries me here is why your painting is occurring sporadically -- it simply shouldn't be doing that, and perhaps that is what you need to fix. I wonder if you're reading in the images from the file each time you do the drawing or some other cause for slowing the drawing down. If you need more help regarding this issue, then you'll have to give us more information on how you do your painting. Regardless, you should avoid having program logic be dependent on painting as you don't have full control over when or even if painting will occur.
Rather than redrawing images and calling repaint(), why not simply put your rolling dice images into ImageIcons on program start up, and then in your Swing Timer, swap icons in a JLabel? Then stop your Timer when the delay gets long enough and in that if block, move your piece.
So, assuming that you have several dice, each can be displayed by a JLabel that is held in an array of JLabel called diceLabels, and the ImageIcons can be held in an array called diceIcons. Then you can do something like:
public void actionPerformed(ActionEvent e) {
if (roll_dice.getDelay() > 500) {
roll_dice.setDelay(50);
roll_dice.stop();
movePiece(); // I like this -- this shouldn't change
} else {
roll_dice.setDelay(roll_dice.getDelay() + 50);
// dice_panel.repaint(0);
for (JLabel dieLabel : diceLabels) {
int randomIndex = random.nextInt(diceIcons.length);
dieLabel.setIcon(diceIcons[randomIndex]);
}
}
}
I like your logic on when you call movePiece() and I think that this should remain unchanged.
You can call the rolling in another thread and join() the current thread to the rolling one. That way the main code will wait until the roll thread dies (finished rolling).
public void actionPerformed(ActionEvent evt) {
if(roll_dice.getDelay() > 500){
Thread rollerThread = new RollerThread();
rollerThread.start();
rollerThread.join();
movePiece();
}
else{
roll_dice.setDelay(roll_dice.getDelay() + 50);
dice_panel.repaint(0);
}
}
private RollerThread extends Thread
{
public void run(){
roll_dice.setDelay(50);
roll_dice.stop();
}
}
However, this might not work with the EDT - because repaints should be scheduled to the queue. Maybe you can shedule the event using the SwingUtilities.invokeAndWait():
public void actionPerformed(ActionEvent evt) {
Thread thread = new Thread(){
public void run(){
if(roll_dice.getDelay() > 500){
SwingUtilities.invokeAndWait(new Runnable(){
public void run(){
roll_dice.setDelay(50);
roll_dice.stop();
}
});
movePiece();
}
else{
roll_dice.setDelay(roll_dice.getDelay() + 50);
dice_panel.repaint(0);
}
}
};
thread.start();
}
Does anything change if you put that call to movePiece(); in a SwingUtilities.invokeLater(Runnable);?
if(roll_dice.getDelay() > 500){
roll_dice.setDelay(50);
roll_dice.stop();
SwingUtilities.invokeLater(new Runnable() {
public void run() { movePiece(); }
});
}
...
It's been a long time since I had to deal with concurrent programming in Java (it was in concurrent programming college classes, actually) and I'm having what to seem some pretty basic problem. The sample code below might seem kinda weird since I'm not using standard JDK for UI controls, but it goes like this:
//class Screen
public class Screen{
private Frame rootContainer;
public Screen(Frame rootContainer){
this.rootContainer = rootContainer;
this.createGui();
}
private void createGui(){
Button btn = new Button("Call");
btn.setBounds(20, 20, 100, 20);
rootContainer.add(btn);
btn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
ConcurrentDialog cr = createDialog();
cr.start();
//Suposedly only to be called after the Exit button in the dialog is clicked
((Button)e.getSource()).setLabel("Called");
((Button)e.getSource()).repaint();
}
});
}
private ConcurrentDialog createDialog(){
return new ConcurrentDialog(rootContainer, this);
}
}
//Class ConcurrentDialog
public class ConcurrentDialog extends Thread {
private Frame rootContainer;
private Screen screen;
public ConcurrentDialog(Frame rootContainer, Screen screen){
this.rootContainer = rootContainer;
this.screen = screen;
}
public void run(){
createDialog();
synchronized(screen){
try {
screen.wait();
} catch (InterruptedException e1) {
e1.printStackTrace();
}
}
}
private void createDialog(){
Dialog dialog = new Dialog(rootContainer, true);
dialog.setBounds(20, 20, 110, 35);
Button btn = new Button("Exit");
btn.setBounds(5, 5, 100, 20);
btn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
Button source = (Button)e.getSource();
Dialog dialog = (Dialog)source.getParent();
synchronized(screen){
screen.notify();
}
dialog.dispose();
dialog.getOwner().remove(dialog);
dialog = null;
}
});
dialog.add(btn);
dialog.show();
}
}
Before anyone asks, yes, I'm trying to implement a modal dialog (in fact, I should rename ConcurrentDialog to ModalDialog). As I said before, I'm not using swing (just because I CAN'T... Embeded VM's are usually platform-specific when it comes to UI and that's my case) and this particular library doesn't have a native Modal Dialog (meaning no JOptionPane.showMessageDialog love for me) so I'm building one from scratch.
Anyway, here's the problem: It seems that the wait() method is executed much later than ((Button)e.getSource()).setLabel("Called"). A workaround that I found is setting btn as a global attribute with public access and refactor the run() method to this:
public void run(){
createDialog();
synchronized(screen){
try {
screen.wait();
} catch (InterruptedException e1) {
e1.printStackTrace();
}
}
screen.getBtn().setLabel("Called");
screen.getBtn().repaint();
}
It works this way, but in my "real world" scenario, this implementation would cause quite a mess when it comes to coupling. Any pointers?
your cr.start() returns immediately.
What you want is to put the wait(screen) instead of after cr.start(), and remove wait(screen) from run() method.
This way the thread will show a dialog and exit. Once the dialog is closed, screen will be notified, and your createGui().actionPerformed() will wake up.
you can't use multiple threads with swing/awt, and you can't "wait" on the thread which is running the gui, or it will stop working. the way to do asynchronous work which involves the gui is to spawn a separate thread (as you are doing), and then have that thread use SwingUtilities.invokeLater() whenever it needs to "update" the gui.