Develop Reference

Creating and Discarding JFrames that run Threads

I'm writing my Tetris using Java Swing. The Game class revolves around a JFrame (frame), which consists of a TetrisPanel extending JPanel (panel) where the blocks fall, a JLabel (pontok) point counter, a JTextArea (rekord_text) showing high scores, and another JPanel (kovi) showing the next block to fall. My idea is that the game has 3 difficulty levels, where the blocks fall with different speed.
I thought the best way of approaching this problem is to create a new JFrame with the components above, but with the blocks' speed set different. I am able to close the old JFrame. However, when the new JFrame opens up, it is only a blank frame, and it won't respond to closing the window.
I should add that TetrisPanel is running a thread, but I am 90% sure I stop that with a volatile boolean.
Constructor of the Game class:
this.difSet(nehezseg); //this function sets the falling velocity
TetrisPanel.stopped = true; //this static member is the volatile boolean responsible for stopping the thread
new_game = false;
frame = new JFrame("Tetris_alpha");
frame.setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
panel = new TetrisPanel();
TetrisPanel.stopped = false;
new Thread(panel).start();
frame.add(panel, c);
pontok = new JLabel ("0");
frame.add(pontok, c);
rekord_text = new JTextArea();
//i set up the area
frame.add(rekord_text, c);
kovi = new NextAktualPanel();
frame.add(kovi, c);
menu = new MyMenu(this);
frame.setJMenuBar(menu);
frame.addWindowListener(new WindowAdapter()
{
#Override
public void windowClosing(WindowEvent e)
{
rekordok.add(panel.getPont());
rekordok.write(f);
e.getWindow().dispose();
System.exit(0);
}
}
);
frame.pack();
frame.setVisible(true);
}
The Game.start() function containing the game loop:
public void start()
{
//game_loop
while (!panel.GameOver() && !new_game)
{
if (panel.aktualLeertDetector())
{
panel.addAktualToBlocks();
panel.addNewAktual(next);
Elem temp = new Elem(0,0,rand.nextInt(7));
while (temp.getTipus() == next.getTipus())
temp = new Elem(0,0,rand.nextInt(7));
next = temp;
kovi.setNextAktual (next);
}
if (!paused)
pontok.setText(Integer.toString(panel.getPont()));
kovi.repaint();
panel.repaint();
}
The function which opens the new frame:
Public void newGame (Game g)
{
Game.new_game = true;
g.frame.dispose();
Game new_game = new Game("easy");
g = new_game;
g.start();
}
And the run() function of TetrisPanel:
public static volatile boolean stopped = false;
#Override
public void run() {
while (!stopped)
{
aktual.zuhan();
this.sorTeleAction();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
Any help would be appreciated, including ideas about different a approach.

Do not use volatile boolean as status variable, use AtomicBoolean instead, volatile it's not the correct way to do this kind of things, and it does not either cause "immediate variable updating"... this is not volatile purpose.
It's not a good idea to start a thread on main AWT thread, you still have to use SwingUtilities.invokeLater(Runnable runnableAction). You can use something like this when launching a Gui Thread:
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
try {
new Thread(threadAction).start();
} catch (Exception e) {
}
}
});
Hope that this will solve you problem!

Not showing Swing component when running before or in the game loop

I'm actually trying to fix a problem with the component of JFrame that don't want to show up when I run my game loop (see the question after the code). I have reduced the code at the minimum possible for you to get what I mean fast:
Run.class
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
Game game = new Game();
game.loop();
}
});
}
Game.class
private Frame frame;
private HashMap<String,ActionListener> actions;
private HashMap<String,Image> ressources;
public Game() {
this.setActions();
this.setRessources();
frame = new Frame(actions,ressources);
}
public void loop() {
double FPS = 60;
double UPS = 60;
long initialTime = System.nanoTime();
final double timeU = 1000000000 / UPS;
final double timeF = 1000000000 / FPS;
double deltaU = 0, deltaF = 0;
int frames = 0, ticks = 0;
long timer = System.currentTimeMillis();
boolean running = true;
boolean RENDER_TIME = false;
while (running) {
...code for update, render, with a fps control
}
}
Frame.class
public Frame(HashMap<String,ActionListener> actions, HashMap<String,Image> ressources) {
this.setTitle(Constants.GAME_NAME);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setSize(Constants.GAME_SIZE_X, Constants.GAME_SIZE_Y);
this.setLayout(new FlowLayout());
JButton myButton = new JButton("My Button");
this.add(myButton);
this.revalidate();
this.repaint();
this.setVisible(true);
}
It's not the complete code because I don't want to give a useless thing. So here, my problem is:
If I run this code, the button not going to show up in the frame. But if I comment game.loop() in the Run.class, the windows show the button. And I don't understand WHY?
I have been trying for a few days to figure it out. I need some help for this one. Alone I'm afraid I will not find out.

To avid blocking the Event Dispatching Thread by running a long process you can use swing Timer which can handle the "looping" for you :
ActionListener animate = e -> {
game.oneFrame();
panel.repaint();
};
timer = new Timer(50, animate);
timer.start();
public void oneFrame(){
//update what is needed for one "frame"
}
For more help post mcve.

Progress Bar for a GUI application using Java

I am trying to write a progress bar for an application that is downloading information before the GUI runs. Because this is such a long process to download and organize the information, I am wanting to inform the user of the progress. I decided on using a progress bar late in the game and, as such, a majority of the code is written and I'm trying to incorporate the progress bar into the code without a drastic re-working of the code. The following is the code for the progress bar. Currently, the progress bar comes up AFTER everything runs and the GUI pops up.
static class PopulatingCardsWorker extends SwingWorker<Void, Integer> {
JProgressBar jpb;
int max;
JLabel label;
public PopulatingCardsWorker(JProgressBar jpb, int maximum, JLabel label) {
this.jpb = jpb;
this.max = maximum;
this.label = label;
}
#Override
protected void process(List<Integer> chunks) {
int i = chunks.get(chunks.size()-1);
jpb.setValue(i); // The last value in this array is all we care about.
System.out.println(i);
label.setText("Loading " + i + " of " + max);
}
#Override
protected Void doInBackground() throws Exception {
for(int i = 0; i < max; i++) {
Thread.sleep(10); // Illustrating long-running code.
publish(i);
}
return null;
}
#Override
protected void done() {
try {
get();
JOptionPane.showMessageDialog(jpb.getParent(), "Success", "Success", JOptionPane.INFORMATION_MESSAGE);
} catch (ExecutionException | InterruptedException e) {
e.printStackTrace();
}
}
}
private static void go(int max) {
JFrame frame = new JFrame();
JPanel panel = new JPanel();
JLabel label = new JLabel("Loading...");
JProgressBar jpb = new JProgressBar();
jpb.setIndeterminate(false);
jpb.setMaximum(max);
panel.add(label);
panel.add(jpb);
frame.add(panel);
frame.pack();
frame.setSize(200,90);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
new PopulatingCardsWorker(jpb, max, label).execute();
}
The program initially calls the GUI application and then runs the database acquisition code as shown below.
public static void main(String args[]) {
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new MagicTheGatheringUI().setVisible(true);
}
});
}
public MagicTheGatheringUI() {
int i, size;
colorRefinementFilter = "selected";
try {
my_list=new CardDatabase();
my_list.sortByName(my_list.all_cards);
my_list.populateSubArrays();
size = my_list.all_cards.size();
for(i = 0; i < size; i++)
{
namesList.addElement(my_list.all_cards.get(i).name);
}
} catch(Exception e) {
System.out.println(e);
System.exit(0);
}
initComponents();
}
The swing worker is created during the creation of "my_list=new CardDatabase();". In that class, I have the swing worker and the process the swing worker is supposed to monitor.
I currently call swing worker in a method called "populate_cards()" and I use the following code to create the swing worker. The swing worker is supposed to monitor what's going on in the populate_cards() method. All of the data in the swing worker methods are just temporary until I better understand how to make it work the way I want it to.
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
go(1000);
}
});
I believe the issue is that I'm calling the progress bar inside of the "invokeLater" method for the actual GUI.
I have looked at the following questions to try and solve my problem.
How to add a progress bar?
Can a progress bar be used in a class outside main?
and I have also looked at tutorials.

Your code is ok. The reason why the progressBar (and the gui itself) pops after the code ends is that by default in java, the code and the gui runs on the same Thread. Because the code has higher priority then the gui, all the code executes first and after that the gui updates.
You should do that in the "go" method:
new Thread(){
public void run(){
new PopulatingCardsWorker(jpb, max, label).execute();
}
} start();
see that article for more information about threads
Im answering from my phone, so sorry about the bad writing.
Code and GUi threads
and from Wikipedia
last one

Java repaint() method doesn't always work

There is a problem with the repaint() method in Java. I made a new thread that constantly repaints the screen. When I release the spacebar I want my player to fall smoothly by setting its position and then waiting for 50 milliseconds and looping that 20 times. Instead, it waits the whole amount of time in the loop, then repaints. I am wondering why it doesn't constantly repaint the changes in the players co-ordinates. Thank you.
(Edit) Thanks everyone for the help. This is my first time using stack overflow, and I am only 13 and still learning java, so I probably will go back to the tutorials again.
My 'a' class (main):
public class a {
public static void main(String[] args) {
JFrame frame = new JFrame("StickFigure Game");
frame.setSize(740, 580);
frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
b board = new b();
frame.add(board);
frame.addKeyListener(board);
}
}
My 'b' class (JPanel/drawing):
public class b extends JPanel implements KeyListener {
c player = new c();
public class MyRunnable implements Runnable {
public void run() {
while (true)
repaint();
}
}
MyRunnable run = new MyRunnable();
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2d = (Graphics2D) g;
g2d.drawImage(player.getImage(), player.getX(), player.getY(), 80, 140,
null);
}
public b() {
Thread thread = new Thread(new MyRunnable());
thread.start();
}
public static void slow(int n) {
long t0, t1;
t0 = System.currentTimeMillis();
do {
t1 = System.currentTimeMillis();
} while (t1 - t0 < n);
}
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_D) {
player.setPos(player.getX() + 6, player.getY());
}
if (e.getKeyCode() == KeyEvent.VK_A) {
player.setPos(player.getX() - 6, player.getY());
}
if (e.getKeyCode() == KeyEvent.VK_SPACE) {
player.setPos(player.getX(), player.getY() - 60);
}
}
public void keyReleased(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_SPACE) {
for (int i = 0; i < 20; i++) {
slow(50);
player.setPos(player.getX(), player.getY() + 2);
}
}
}
public void keyTyped(KeyEvent e) {
}
}
my 'c' class (player):
public class c {
private ImageIcon i = new ImageIcon("guy.png");
private Image img = i.getImage();
private int x = 0;
private int y = 100;
public void wait(int what) {
try {
Thread.sleep(what);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public c() {
}
public Image getImage() {
return img;
}
public int getX() {
return x;
}
public int getY() {
return y;
}
public void setPos(int mx, int my) {
x = mx;
y = my;
}
}

I haven't gone through all the code here but here are some pointers:
Swing has its own concurrency mechanisms which allow you to handle UI updates. You can use a Swing Timer rather than a raw Thread. Related is the use of Thread.sleep - don't do this, it only blocks the EDT and prevents UI updates.
The Swing paint chain mechanism requires you to override paintComponent rather than paint.
Always use Key Bindings rather than KeyListeners in Swing. KeyListeners require component focus to work to interact with the KeyEvents. Key Bindings do not have this limitation.

"There is a problem with the repaint() method in java." Did you consider that perhaps the problem is with your code instead? You are blocking the event thread and giving the system no time to do the intermediate repaints. In particular, this method:
public static void slow (int n){
long t0,t1;
t0=System.currentTimeMillis();
do{
t1=System.currentTimeMillis();
}
while (t1-t0<n);
}
and this loop:
for(int i = 0;i<20;i++){
slow(50);
player.setPos(player.getX(), player.getY()+2);
}
do not relinquish control to the system so that repaints can actually happen. Rewrite those using Swing timers. Look at this tutorial for an introduction on how to use these.
Also, your thread that constantly calls repaint() in a tight loop:
public void run(){
while(true) repaint();
}
is a terrible idea. You don't need to call repaint() at full CPU speed. Once every 30 milliseconds or so is fine for animation. Again, consider using Swing utilities to do this rather than writing your own looping thread.

The repaint is only a "request" to paint as soon as possible. so when you call it it causes a call to the paint method as soon as possible.
from here
So basically you just flooding the scheduled calls of paint or update with while(true) repaint();.
Oracle's stance on painting in AWT and Swing
One way you could do it, or should I say how I would do it, is to make your c class implement KeyListener, so that when a key is pressed (and only when it is pressed) you update it's location.
So move your KeyListener methods to class c, in your class b constructor you can add the call this.addKeyListener(player) or make a method void addPlayer(c player) that adds it.

Make a main method wait on a smaller method (java)

i really need to find better ways to word my questions.
Basically I've created a program that takes information from a webpage and displays it nicely across the screen.
When the user closes the program, they actually hide it.
I also have another method which constantly loops checking for information to see if tis been updated.
unfortunately the problem im having is that it loops to fast, i only want it to check for information every 40 seconds or so.
What i tried was inserting a wait(1000,1000) in the method itself and in the main of the program. but both of these cause IllegalMonitorStateException.
Is this the correct way to make the thread wait properly? or is there a better way?
note: the only thread i have is the main.
MAIN
class Marquee
{
public static void main(String[] args) throws InterruptedException
{
MyFrame frame = new MyFrame();
frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
frame.setVisible(true);
frame.setAlwaysOnTop(true);
frame.setBackground(Color.BLACK);
frame.setResizable(true);
while(true)
{
// this doesnt work
frame.wait(1000,1000);
frame.notifyAll();
frame.checkForNewUpdate();
System.out.println(" ____________________________next line _______________________________");
}
}
}
CHECK FOR UPDATES
public String[] checkForNewUpdate()
{
//setVisible(true);
String tempUpdate = getEngineersUpdate();
if (latestUpdate[0] != tempUpdate)
{
// do nothign
setVisible(false);
}
else if(latestUpdate[0]==tempUpdate)
{
latestUpdate[0] = tempUpdate;
//show the page again
setVisible(true);
}
else if(latestUpdate[0]!= "NULL")
{
// do nothing
//latestUpdate[0] = tempUpdate;
}
else
{
latestUpdate[0] = tempUpdate;
}
return latestUpdate;
}
1: WHat am i doing wrong to get this exception
2: Is there any other way to make a gap of time in a method
3: Am i going to have to put all these methods into another thread? Please say no
// my constructor which I failed to mention has a timer in it. only i dont know hwo to use it
class MyFrame extends JFrame implements ActionListener
{
private ActionListener listener;
private Timer t1;
private String [] latestUpdate = new String[1];
public MyFrame()
{
Dimension d = Toolkit.getDefaultToolkit().getScreenSize();// gets the maximum size of the screen
setSize(d.width,(d.height/100)*10);//sets it to max. need to change this
// this shit find the max size of screen and puts it bottom left
GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice defaultScreen = ge.getDefaultScreenDevice();
Rectangle rect = defaultScreen.getDefaultConfiguration().getBounds();
int x = (int)rect.getMinX();
int y = (int)rect.getMaxY()-getHeight();
setLocation(x,y-30);
setTitle("ALERT::OUTAGE");
MyPanel panel = new MyPanel();
add(panel);
listener = this;
t1 = new Timer(50,listener);
t1.start();
}
by request, here is getEngineersUpdate()
public String getEngineersUpdate() //gets data from page and sets it to string.
{
String update = "blank";
final WebClient webClient = new WebClient();
webClient.setJavaScriptEnabled(false);// javascript causes some serious problems.
webClient.setCssEnabled(false);
String forChecking;
HtmlPage page;
try
{
URL outageURL = new URL("file:\\C:\\Users\\0vertone\\Desktop\\version control\\OUTAGE\\Outages.html"); //local drive at home
page = webClient.getPage(outageURL);
//All this crap can be gone if we just give the table an id
Object[] dates = page.getByXPath("//span[#id='date']/text()").toArray();
Object[] sites = page.getByXPath("//span[#id='site']/text()").toArray();
Object[] issues = page.getByXPath("//span[#id='issue']/text()").toArray();
System.out.println("" + dates[0].toString());
System.out.println("" + sites[0].toString());
System.out.println("" + issues[0].toString());
update = (dates[0].toString() + " " + sites[0].toString() + " " +issues[0].toString());
forChecking = dates[0].toString();
/**some examples of the getCellAt() method*/
//update = table.getCellAt(0,0).asText(); // This returns DATE/Time
//update = table.getCellAt(1,0).asText(); // This return the actual date
//update = table.getCellAt(0,1).asText(); // This returns, SITE/Sector
//update = table.getCellAt(1,1).asText(); // This returns the actual site issue
}
catch (FailingHttpStatusCodeException a)
{
System.out.println("Failing HTTP Status Execution");
a.printStackTrace();
}
catch (MalformedURLException b)
{
System.out.println("Malformed URL");
b.printStackTrace();
}
catch (IOException c)
{
System.out.println("IO PROBLEMS!");
c.printStackTrace();
}
webClient.closeAllWindows();
return update;
}

I've changed your code so it should work as you intended. I'm not clear on what getEngineersUpdate() does, so I can't say for sure if it will work, but I've given you a start. I've included 2 options for how to handle it, with explanation in the comments. You can see how to use a Timer properly in the constructor, also. Finally, I don't have your full code, so I had to rig something together to simulate it.
class Marquee {
public static void main(String[] args) throws InterruptedException {
MyFrame frame = new MyFrame();
frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
frame.setVisible(true);
frame.setAlwaysOnTop(true);
frame.setBackground(Color.BLACK);
frame.setResizable(true);
}
}
class MyFrame extends JFrame {
private String [] latestUpdate = new String[1];
private static final int DISPLAY_TIME = 3000;
private Timer displayTimer;
/*
* Option #1:
* Ideally, you'd have the thread that generates the "Engineers Update" messages call this
* method. If you can't make this event based, then you should use option #2
*/
public void newUpdate(String message) {
setVisible(true);
// change this to whatever you need to.
text.setText(message);
displayTimer.restart();
}
// I used this to test it
private JTextField text;
public MyFrame() {
// gets the maximum size of the screen
Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
//sets it to max. need to change this
setSize(d.width, (d.height / 100) * 10);
// this shit find the max size of screen and puts it bottom left
GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice defaultScreen = ge.getDefaultScreenDevice();
Rectangle rect = defaultScreen.getDefaultConfiguration().getBounds();
int x = (int) rect.getMinX();
int y = (int) rect.getMaxY() - getHeight();
setLocation(x, y - 30);
setTitle("ALERT::OUTAGE");
//MyPanel panel = new MyPanel();
//add(panel);
text = new JTextField("Initial Text");
add(text);
// this creates a timer that when it goes off, will hide the frame
displayTimer = new Timer(DISPLAY_TIME, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
setVisible(false);
}
});
// sets the timer not to repeat
displayTimer.setRepeats(false);
//This code is for option #2:
updateTimer = new Timer(UPDATE_INTERVAL, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
checkForNewUpdate();
}
});
updateTimer.start();
}
// This is for option #2
private static final int UPDATE_INTERVAL = 1000;
private Timer updateTimer;
/*
* Option #2:
* Not ideal, but this should work.
*/
public String[] checkForNewUpdate() {
// I don't know how getEngineersUpdate() works
// which would have made it much easier to help you.
String tempUpdate = getEngineersUpdate();
// String comparison doesn't work like this in java.
// you also had a sleeping NullPointerException here
if (!tempUpdate.equals(latestUpdate[0])) {
// this is when you have a new update, correct?
newUpdate(tempUpdate);
latestUpdate[0] = tempUpdate;
} else if (tempUpdate.equals(latestUpdate[0])) {
// it's the same update as last time, so do nothing
} else if (tempUpdate.equals("NULL")) {
// You need to handle this according to what getEngineersUpdate() does
}
return latestUpdate;
}
// This code is rigged to show how it would work
private static int i = 0;
private String getEngineersUpdate() {
// 1 in 6 chance of returning "NULL"
if (Math.random() * 6 - 1 < 0)
return "NULL";
// probability of 1 in 4 of generating a new update
if(Math.random() * 4 - 1 < 0)
return "UPDATE #"+i++;
else
return "UPDATE #"+i;
}
}

I think you can't call wait() on an JFrame, but I am not sure.
You have to call wait() within a snychronized-block. (Example below)
Thread.sleep(1000l) can be used, if it runs in a Thread, but look for the class Timer
It would be much better design, if you create a thread, which checks for updates. You can notify the GUI (JFrame) with some kind of event-listener about the new date to display.
Take a look at the Timer and Callable.

You should create another thread, you should call checkforNewUpdate method from this thread. And also do not forget use SwingUtilities.invokeLater method to update your UI inside checkforNewUpdate method. here is the some part of the code;
public class Marque {
private JFrame frame;
class CheckForUpdate implements Runnable {
public void run() {
while(true) {
checkForNewUpdate();
try {
Thread.sleep(40000);
} catch (InterruptedException e1) {
e1.printStackTrace();
throw new RuntimeException(e1);
} }
}
public String[] checkForNewUpdate() {
//your code
// user interface interaction code
SwingUtilities.invokeLater(new Runnable() {
public void run() {
frame.setVisible(true);
}
});
}
}
public Marque() {
frame = new JFrame();
//....frame related code
new Thread(new CheckForUpdate()).start();
}
public static void main(String[] arg) {
Marque marque = new Marque();
}