javaswingappletactionlistener
Why do the panels disappear when i press UP?
This is my code for a game im making. At the moment im not worried about how the game functions I've been more so worried about the fact that each time I hit the UP button the panels disappear and sometimes when i hit the LEFT button as well. Is there an explanation to this can anyone help me understand why this happens?? I have a feeling it has something to do with my if statements but im not really sure. also, im messing around with the key listener and if you could give me some advice on key listeners like some dos and donts I really appreciate the help!!
import javax.swing.*;
import java.applet.*;
import java.awt.event.*;
import java.awt.*;
public class Game extends Applet implements ActionListener,KeyListener {
Image image;
MediaTracker tr;
JLabel label,computerLabel;
JPanel panel,computerPanel;
Button start,up,down;
Label result;
Dimension SIZE = new Dimension(50,50);
int x = 0;
int y = 0;
int w = 100;
int q = 100;
int WIDTH = 50;
int HEIGHT = 50;
//Player Integers
int zeroPosX,zeroPosY,xLeft,xUp;
//Computer integers
int compZeroPosX,compZeroPosY,compXLeft,compXUp;
//--------------------------------------
public void init() {
setLayout(new FlowLayout());
start = new Button("Start");
up = new Button("UP");
down = new Button("LEFT");
//PlayerPiece stuff
ImageIcon icon = new ImageIcon("playerpiece.png");
label = new JLabel(icon);
panel = new JPanel();
label.setVisible(true);
panel.add(label);
panel.setPreferredSize(SIZE);
//ComputerPiece Stuff
ImageIcon computerIcon = new ImageIcon("computerPiece.png");
computerPanel = new JPanel();
computerLabel = new JLabel(computerIcon);
computerLabel.setVisible(true);
computerPanel.add(computerLabel);
computerPanel.setPreferredSize(SIZE);
//===============================================
result = new Label("=========");
addKeyListener(this);
setSize(650,650);
up.addActionListener(this);
down.addActionListener(this);
start.addActionListener(this);
label.setSize(WIDTH,HEIGHT);
label.setLocation(0,0);
add(computerPanel);
add(panel);
add(start);
add(up);
add(down);
add(result);
}
//--------------------------------------
public void paint(Graphics g) {
Graphics2D firstLayer = (Graphics2D)g;
Graphics2D secondLayer = (Graphics2D)g;
Graphics2D thirdLayer = (Graphics2D)g;
secondLayer.setColor(Color.BLACK);
for(x=100; x<=500; x+=100)
for(y=100; y <=500; y+=100)
{
firstLayer.fillRect(x,y,WIDTH,HEIGHT);
}
for(w=150; w<=500; w+=100)
for(q=150; q <=500; q+=100)
{
secondLayer.fillRect(w,q,WIDTH,HEIGHT);
}
}
//--------------------------------------
public void actionPerformed(ActionEvent ae) {
int [] range = {50,0,0,0,0};
int selection = (int)Math.random()*5 ;
//~~~~~~~~~~~~~~~~~~~~~~~~~
//PlayerPositioning
zeroPosX = panel.getX();
zeroPosY = panel.getY();
xLeft = zeroPosX - 50;
xUp = zeroPosY - 50;
//ComputerPositioning
compZeroPosX = computerPanel.getX();
compZeroPosY = computerPanel.getY();
compXLeft = compZeroPosX - range[selection];
compXUp = compZeroPosY - range[selection];
//~~~~~~~~~~~~~~~~~~~~~~~~~~
Button user = (Button)ae.getSource();
//Starting the game
if(user.getLabel() == "Start") {
result.setText("=========");
//playersetup
label.setLocation(0,0);
panel.setLocation(300,500);
//============================
//npc setup
computerLabel.setLocation(0,0);
computerPanel.setLocation(500,300);
}
if(compZeroPosX >= 150) {
if(compZeroPosY >= 150) {
if(zeroPosX >= 150) {
if(zeroPosY >=150) {
if(user.getLabel() == "UP") {
panel.setLocation(zeroPosX,xUp);
}
else
computerPanel.setLocation(compZeroPosX,compXUp);
if(user.getLabel() == "LEFT") {
panel.setLocation(xLeft,zeroPosY);
}
else
computerPanel.setLocation(compXLeft,compZeroPosY);
if(panel.getX() < 150)
result.setText("GAME-OVER");
if(panel.getY() < 150)
result.setText("GAME-OVER");
}
}
}
}
}
@Override
public void keyPressed(KeyEvent kp) {
int keycode = kp.getKeyCode();
switch (keycode) {
case KeyEvent.VK_W:
panel.setLocation(xLeft,zeroPosY);
break;
}
}
@Override
public void keyReleased(KeyEvent kr) {
}
@Override
public void keyTyped(KeyEvent kt) {
}
}
Solution
Issues and suggestions:
- You're mixing AWT (e.g., Applet, Button, Label) with Swing (e.g., JPanel, JLabel) dangerously and without need. Stick with Swing and get rid of all vestiges of AWT.
- You're painting directly in a top-level window, here the Applet, a dangerous thing to do. Don't. Follow the Swing graphics tutorials and do your drawing in a JPanel's paintComponent method.
- You're not calling the super method within your painting method override, another dangerous thing to do, and another indication that you're trying to do this without reading the important relevant tutorials.
- Don't compare Strings using
==or!=. Use theequals(...)or theequalsIgnoreCase(...)method instead. Understand that==checks if the two object references are the same which is not what you're interested in. The methods on the other hand check if the two Strings have the same characters in the same order, and that's what matters here. - You're trying to directly set the location of a component such as a JPanel without regard for the layout managers. Don't do this. Instead move logical (non-component) entities and display the movement in your graphics.
You can find links to the Swing tutorials and to other Swing resources here: Swing Info
Later we can talk why you should avoid applets of all flavors...
Myself, I'd move ImageIcons around a grid of JLabels and not directly use a painting method at all. For example,
To see, run the following code:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;
import javax.imageio.ImageIO;
import javax.swing.*;
@SuppressWarnings("serial")
public class Game2 extends JPanel {
private static final String CPU_PATH = "https://upload.wikimedia.org/wikipedia/commons/thumb/4/4f/"
+ "Gorilla-thinclient.svg/50px-Gorilla-thinclient.svg.png";
private static final String PERSON_PATH = "https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/"
+ "Emblem-person-blue.svg/50px-Emblem-person-blue.svg.png";
private static final int SQR_WIDTH = 50;
private static final int SIDES = 10;
private static final Dimension SQR_SIZE = new Dimension(SQR_WIDTH, SQR_WIDTH);
private static final Color DARK = new Color(149, 69, 53);
private static final Color LIGHT = new Color(240, 220, 130);
private JLabel[][] labelGrid = new JLabel[SIDES][SIDES];
private Icon playerIcon;
private Icon computerIcon;
public Game2() throws IOException {
// would use images instead
playerIcon = createIcon(PERSON_PATH);
computerIcon = createIcon(CPU_PATH);
JPanel buttonPanel = new JPanel();
buttonPanel.add(new JButton(new StartAction("Start", KeyEvent.VK_S)));
buttonPanel.add(new JButton(new UpAction("Up", KeyEvent.VK_U)));
buttonPanel.add(new JButton(new LeftAction("Left", KeyEvent.VK_L)));
JPanel gameBrd = new JPanel(new GridLayout(SIDES, SIDES));
gameBrd.setBorder(BorderFactory.createLineBorder(Color.BLACK));
for (int i = 0; i < labelGrid.length; i++) {
for (int j = 0; j < labelGrid[i].length; j++) {
JLabel label = new JLabel();
label.setPreferredSize(SQR_SIZE);
label.setOpaque(true);
Color c = i % 2 == j % 2 ? DARK : LIGHT;
label.setBackground(c);
gameBrd.add(label);
labelGrid[i][j] = label;
}
}
setLayout(new BorderLayout());
add(buttonPanel, BorderLayout.PAGE_START);
add(gameBrd);
// random placement, just for example
labelGrid[4][4].setIcon(computerIcon);
labelGrid[5][5].setIcon(playerIcon);
}
private Icon createIcon(String path) throws IOException {
URL url = new URL(path);
BufferedImage img = ImageIO.read(url);
return new ImageIcon(img);
}
private abstract class MyAction extends AbstractAction {
public MyAction(String name, int mnemonic) {
super(name);
putValue(MNEMONIC_KEY, mnemonic);
}
}
private class StartAction extends MyAction {
public StartAction(String name, int mnemonic) {
super(name, mnemonic);
}
@Override
public void actionPerformed(ActionEvent e) {
// TODO start game code
}
}
// move all icons up
private class UpAction extends MyAction {
public UpAction(String name, int mnemonic) {
super(name, mnemonic);
}
@Override
public void actionPerformed(ActionEvent e) {
// collection to hold label that needs to be moved
Map<JLabel, Icon> labelMap = new HashMap<>();
for (int i = 0; i < labelGrid.length; i++) {
for (int j = 0; j < labelGrid[i].length; j++) {
Icon icon = labelGrid[i][j].getIcon();
if (icon != null) {
int newI = i == 0 ? labelGrid.length - 1 : i - 1;
labelGrid[i][j].setIcon(null);
labelMap.put(labelGrid[newI][j], icon);
}
}
}
// move the icon after the iteration complete so as not to move it twice
for (JLabel label : labelMap.keySet()) {
label.setIcon(labelMap.get(label));
}
}
}
// move all icons left
private class LeftAction extends MyAction {
public LeftAction(String name, int mnemonic) {
super(name, mnemonic);
}
@Override
public void actionPerformed(ActionEvent e) {
Map<JLabel, Icon> labelMap = new HashMap<>();
for (int i = 0; i < labelGrid.length; i++) {
for (int j = 0; j < labelGrid[i].length; j++) {
Icon icon = labelGrid[i][j].getIcon();
if (icon != null) {
int newJ = j == 0 ? labelGrid[i].length - 1 : j - 1;
labelGrid[i][j].setIcon(null);
labelMap.put(labelGrid[i][newJ], icon);
}
}
}
for (JLabel label : labelMap.keySet()) {
label.setIcon(labelMap.get(label));
}
}
}
private static void createAndShowGui() {
Game2 mainPanel = null;
try {
mainPanel = new Game2();
} catch (IOException e) {
e.printStackTrace();
System.exit(-1);
}
JFrame frame = new JFrame("Game2");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
createAndShowGui();
});
}
}
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