我的程序忙时无法重新绘制JPanel

Question

I'm trying to make a visualization of algorithms. I had a working program, but is was really dirty and I decided to re-orgranize it before I continued. The problem is that it won't repaint anymore before the algorithm finishes. (and I have tried using revalidate instead/in combination with repaint)

The option menu:

public class BootScreen extends JPanel implements ActionListener {

GridBagConstraints c = new GridBagConstraints();

JFrame frame = new JFrame();

SpinnerNumberModel arraySizeModel = new SpinnerNumberModel(50, 0, 100000, 1);
SpinnerNumberModel speedModel = new SpinnerNumberModel(20, 0, 10000, 1);
SpinnerNumberModel algSelectModel = new SpinnerNumberModel(1, 1, 5, 1);

JSpinner arraySizeSpinner = new JSpinner(arraySizeModel);
JSpinner speedSpinner = new JSpinner(speedModel);
JSpinner algSelectSpinner = new JSpinner(algSelectModel);

JButton start = new JButton("Start");

BootScreen() {
    frame.setTitle("Settings");
    frame.setSize(500, 250);
    frame.setVisible(true);
    frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    frame.add(this);

    //just creating the options menu, nothing special here (deleted for simplicity)
    //...
}

@Override
public void actionPerformed( ActionEvent e ) {
    Algorithm alg = new Algorithm(Integer.parseInt(arraySizeModel.getValue().toString()), Integer.parseInt
            (speedModel.getValue().toString()));

    switch(Integer.parseInt(algSelectModel.getValue().toString())) {
        case 1:
            alg.alg1();
            break;

        case 2:
            alg.alg2();
            break;

        case 3:
            alg.alg3();
            break;

        case 4:
            alg.alg4();
            break;

        case 5:
            alg.alg5();
            break;
    }
}

public static void main(String[] Args) {new BootScreen();}
}

The main algorithm stuffs:

public class Algorithm {
int[] A;
GUI gui;
int type;
int[] pointers;
int delay;
int max;

Random r = new Random();

Algorithm( int arraySize, int delaySet) {
    A = new int[arraySize];
    delay = delaySet;
    gui = new GUI(this);
}

void generate(int maxIntSize, int pointersAmount, int typeSet) {
    max = maxIntSize;
    for( int i = 0; i < A.length; i++ ) {
        A[i] = r.nextInt(max);
    }

    pointers = new int[pointersAmount];
    for( int i = 0; i < pointers.length; i++ ) {
        pointers[i] = -1;
    }
    type = typeSet;
}

void step(boolean sleep, int updatePointer, int updatePointerVal) {
    pointers[updatePointer] = updatePointerVal;
    gui.revalidate();
    gui.repaint();
    if( sleep ) {
        try {
            Thread.sleep(delay);
        }catch( InterruptedException e ) {
        }
    }
}

//alg1(), alg2(), .... would be here. They first call generate() and call step() a couple of times. (deleted for simplicity)
}

The GUI:

public class GUI extends JPanel {
JFrame frame = new JFrame();
Algorithm alg;

GUI( Algorithm algIn ) {
    alg = algIn;

    frame.setTitle("Algorithmizer");
    frame.setSize(1080, 720);
    frame.setExtendedState(Frame.MAXIMIZED_BOTH);
    frame.setVisible(true);
    frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    frame.add(this);
}

@Override
protected void paintComponent( Graphics g ) {
    super.paintComponent(g);
    //drawing alg.A as a bar-graph by looping through it (deleted for simplicity)
}
}

When I put System.out.println("1") before the repaint() call, System.out.println("2") in the paintComponent() function and System.out.println("3") after the repaint() call it will only print: 1 3 1 3 1 3 ... I also tried printing the stack, didn't get anything usefull from that either. The program does repaint when the algorithm is done, but that isn't usefull to me.

Answer 1

Maybe take an approach like this. This will do all your calculations and stuff in a worker thread off the Event Dispatch Thread, and then call done() where you can do you GUI updates on the Event Dispatch Thread.

@Override
public void actionPerformed( ActionEvent e ) {
    new SwingWorker<Object, Object>() {
            @Override
            protected Object doInBackground() throws Exception {
                runAlg();
                return null
            }

            @Override
            protected void done() {
                //any of you gui stuff here
            }
        }.execute();
    }
}

public void runAlg(){
     Algorithm alg = new Algorithm(Integer.parseInt(arraySizeModel.getValue().toString()), Integer.parseInt
            (speedModel.getValue().toString()));

    switch(Integer.parseInt(algSelectModel.getValue().toString())) {
        case 1:
            alg.alg1();
            break;

        case 2:
            alg.alg2();
            break;

        case 3:
            alg.alg3();
            break;

        case 4:
            alg.alg4();
            break;

        case 5:
            alg.alg5();
            break;
    }
}

Answer 2

The problem is that it won't repaint anymore before the algorithm finishes.

Your algorithm is executing on the Event Dispatch Thread (EDT) which is the Thread the GUI uses to paint itself, therefore the GUI can't repaint itself until the algorithm is finished.

The solution is to use a separate Thread for the algorithm.

One way to do this is to use a Swing Worker which executes on a separate Thread and allows you to "publish" results as the algorithm is executing.

Read the section from the Swing tutorial on Concurrency for more details. The tutorial has a Swing Worker example.