JPanel不会更新或重绘，直到For循环结束

Question

I understand that this is probably a very simple problem, but as I've only been working with JPanel and JFrame for one weekend please don't bag on me too much. My issue is that I have this code:

package Game_Elements;
import java.awt.Color;
import java.awt.Desktop.Action;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.RenderingHints.Key;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.AbstractAction;
import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Game implements KeyListener
{
private JFrame frame = null;
private JPanel panel = null;
int y = 0;
int x = 0;
public boolean W_TRUE;
public boolean S_TRUE;
public boolean A_TRUE;
public boolean D_TRUE;
public void keyPressed(KeyEvent e)
{

    if(e.getKeyCode()== KeyEvent.VK_W){
            y-= 15;
            panel.setLocation(x, y);
            W_TRUE = true;

    }
    if(e.getKeyCode()== KeyEvent.VK_S){
            y+= 15;
            panel.setLocation(x, y);
            S_TRUE = true;
    }
    if(e.getKeyCode()== KeyEvent.VK_A){
            x-= 15;
            panel.setLocation(x, y);
            A_TRUE = true;
    }
    if(e.getKeyCode()== KeyEvent.VK_D){
            x+= 15;
            panel.setLocation(x, y);
            D_TRUE = true;
    }
    if(D_TRUE == true  && S_TRUE == true ){
        y+= 15;
        x+= 15;
        panel.setLocation(x, y);
    }
    if(A_TRUE == true  && W_TRUE == true ){
        y-= 15;
        x-= 15;
        panel.setLocation(x, y);
    }
    if(A_TRUE == true  && S_TRUE == true ){
        y+= 15;
        x-= 15;
        panel.setLocation(x, y);
    }
    if(D_TRUE == true && W_TRUE == true ){
        y-= 15;
        x+= 15;
        panel.setLocation(x, y);
    }
}
public void keyReleased(KeyEvent e)
{
    if(e.getKeyCode()== KeyEvent.VK_W){
        W_TRUE = false;
}
if(e.getKeyCode()== KeyEvent.VK_S){
        S_TRUE = false;
}
if(e.getKeyCode()== KeyEvent.VK_A){
        A_TRUE = false;
}
if(e.getKeyCode()== KeyEvent.VK_D){
        D_TRUE = false;
}
if(e.getKeyCode()== KeyEvent.VK_SPACE){
    System.out.println("Running JUMP");
    for(int j = y - 200; j < y; y-= 15){
        try {
            Thread.sleep(10);
        } catch (InterruptedException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
        panel.setLocation(x, y);
        panel.revalidate();
    }   
    System.out.println("Complete");

}
}

public void keyTyped(KeyEvent e) {

}

public void frameStart()
{

    frame = new JFrame();
    frame.setVisible(true);
    frame.setTitle("Desperation");
    frame.getContentPane().setLayout(new BoxLayout(frame.getContentPane(), BoxLayout.Y_AXIS)); // otherwise nice exceptions java.awt.AWTError:
    frame.setPreferredSize(new Dimension(1920, 1050));
    frame.setSize(new Dimension(1920, 1050));
    frame.setResizable(false);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    System.out.println("Frame Created");

    panel = new JPanel();
    panel.setBackground(Color.BLUE);
    panel.setMaximumSize(new Dimension(200, 200));
    panel.setLocation(1080, 500);
    panel.revalidate();
    frame.add(panel);
    System.out.println("Panel Created");

    frame.addKeyListener(this);
    System.out.println("Listener Created");
}

public static void main(String[] args){

    Game obj = new Game();

    obj.frameStart();
}

}

The panel I have, a basic 200x200 blue cube, does not seem to change location until the loop is done running, so it's more of a jump than anything. I understand that the repaint function only runs as soon as possible, and as this is likely the problem, I was wondering if any of you good folks have advice on an alternative method for refreshing it so it doesn't necessarily look smooth, but at least show some progression. Any advice is appreciated as I don't know much at all about JPanel, JFrame, or really JAnything. Thank you!

Answer 1

For refreshing

this.revalidate(); 

is a good way to "refresh" your JComponent