Develop Reference

Setting a label text in Swing undos all button location movements

I have the weirdest bug ever.
I have this puzzle game that moves puzzle pieces (which really are buttons with images attached to them).
Everything worked fine until I tried to change the text of some label (to indicate how many steps the player has done).
Everytime I call someControl.setText("text");, the puzzle pieces that moved are set back to the their first position. I have no idea why, but they just do.
Here's my window:
It consists of two panels, each uses a GridBagLayout.
The main frame uses a gridBagLayout as well, which consists of the two panels.
I know it's weird as hell, but I can't figure out what may cause this GUI bug. Any idea?
The pieces of code:
increaseSteps which is called everytime I click a puzzle button
void increaseSteps() {
_steps++;
_lblSteps.setText("Steps: " + _steps);
}
Creation of the puzzle panel (the left panel)
private JPanel puzzlePanel() {
JPanel panel = new JPanel(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
for (int i = 0; i < _splitImage.getSize(); i++)
for (int j = 0; j < _splitImage.getSize(); j++) {
int valueAtPos = _board.getMatrix()[i][j];
if (valueAtPos == 0)
continue;
int imageRow = _board.getImageRowFromValue(valueAtPos);
int imageCol = _board.getImageColFromValue(valueAtPos);
ImageIcon imageIcon = new ImageIcon(_splitImage.getImages()[imageRow][imageCol]);
JButton btn = new JButton(imageIcon);
_tileButtons[i][j] = new TileButton(btn, i, j);
btn.setPreferredSize(new Dimension(_splitImage.getImages()[i][j].getWidth(null),
_splitImage.getImages()[i][j].getHeight(null)));
// add action listener
btn.addActionListener(this);
btn.addKeyListener(this);
gbc.gridx = j;
gbc.gridy = i;
panel.add(_tileButtons[i][j].getButton(), gbc);
}
return panel;
}
actionPerformed:
#Override
public void actionPerformed(ActionEvent e) {
if (!(e.getSource() instanceof JButton))
return;
JButton btn = (JButton) e.getSource();
TileButton tile = getTileButtonFromBtn(btn);
if (tile == null)
return;
// check if we can move the tile
String moveDir = _board.canMoveTile(tile.getRow(), tile.getCol());
if (moveDir.equals("no"))
return;
increaseSteps();
int dirx = 0;
int diry = 0;
if (moveDir.equals("left")) {
dirx = -1;
_board.move("left", true);
tile.setCol(tile.getCol() - 1);
} else if (moveDir.equals("right")) {
dirx = 1;
_board.move("right", true);
tile.setCol(tile.getCol() + 1);
} else if (moveDir.equals("up")) {
diry = -1;
_board.move("up", true);
tile.setRow(tile.getRow() - 1);
} else { // down
diry = 1;
_board.move("down", true);
tile.setRow(tile.getRow() + 1);
}
moveButton(btn, dirx, diry, MOVE_SPEED);
if (_board.hasWon())
win();
}
moveButton: (moves the button in a seperate thread, calling btn.setLocation())
private void moveButton(JButton btn, int dirx, int diry, int speed) {
Point loc = btn.getLocation();
// get start ticks, calculate distance etc...
StopWatch stopper = new StopWatch();
int distance;
if (dirx != 0)
distance = _splitImage.getImages()[0][0].getWidth(null) * dirx;
else
distance = _splitImage.getImages()[0][0].getHeight(null) * diry;
if (speed > 0) {
// run the animation in a new thread
Thread thread = new Thread() {
public void run() {
int currentTicks;
int elapsed;
do {
int newX = loc.x;
int newY = loc.y;
elapsed = stopper.getElapsed();
int moved = (int) ((double) distance * (double) (elapsed / (double) speed));
if (dirx != 0)
newX += moved;
else
newY += moved;
btn.setLocation(newX, newY);
} while (elapsed <= MOVE_SPEED);
// make sure the last location is exact
btn.setLocation(loc.x + (dirx == 0 ? 0 : distance), loc.y + (diry == 0 ? 0 : distance));
}
};
thread.start();
}
else
btn.setLocation(loc.x + (dirx == 0 ? 0 : distance), loc.y + (diry == 0 ? 0 : distance));
}

You're trying to set the absolute position of a component via setLocation(...) or setBounds(...), one that is held by a container that uses a layout manager. This may work temporarily, but will fail if the container's layout manager is triggered to re-do the layout of its contained components. When that happens, the GridBagConstraints will take over and the components will move to their gridbag constraints assigned location.
The solution is to not do this, and instead to place the location of your components in concert with the layout managers used.
Another problem is that your current code is not Swing thread-safe since you're making Swing state changes from within a background thread. This won't always cause problems, but since it's a threading issue, risks causing intermittent hard to debug problems (ones that usually only occur when your boss or instructor are trying to run your code).
Possible solutions:
For a grid of images, you could use a grid of JLabels (or JButtons if you must) held in a container that uses GridLayout. When you need to reposition components, remove all components held by that JPanel, and then re-add, using the order of addition to help you position the components.
Easiest though would be to use a grid of non-moving JLabels, give them MouseListeners, and instead of moving the JLabels, remove and add Icons to them, including a blank Icon.
If you need to do Swing animation, use a Swing Timer to drive the animation. This will allow your code to make repetitive calls with delay between the calls, and with these calls being made on the Swing event thread, the EDT (event dispatch thread).
Demo proof of concept example code that shows swapping icons, but without animation, and without test of solution yet:
import java.awt.GridLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import javax.imageio.ImageIO;
import javax.swing.*;
#SuppressWarnings("serial")
public class ImageShuffle extends JPanel {
private static final int SIDES = 3;
public static final String IMG_PATH = "https://upload.wikimedia.org/wikipedia/commons/"
+ "thumb/5/5a/Hurricane_Kiko_Sep_3_1983_1915Z.jpg/"
+ "600px-Hurricane_Kiko_Sep_3_1983_1915Z.jpg";
private List<Icon> iconList = new ArrayList<>(); // shuffled icons
private List<Icon> solutionList = new ArrayList<>(); // in order
private List<JLabel> labelList = new ArrayList<>(); // holds JLabel grid
private Icon blankIcon;
public ImageShuffle(BufferedImage img) {
setLayout(new GridLayout(SIDES, SIDES, 1, 1));
fillIconList(img); // fill array list with icons and one blank one
Collections.shuffle(iconList);
MyMouseListener myMouse = new MyMouseListener();
for (Icon icon : iconList) {
JLabel label = new JLabel(icon);
label.addMouseListener(myMouse);
add(label);
labelList.add(label);
}
}
private class MyMouseListener extends MouseAdapter {
#Override
public void mousePressed(MouseEvent e) {
JLabel selectedLabel = (JLabel) e.getSource();
if (selectedLabel.getIcon() == blankIcon) {
return; // don't want to move the blank icon
}
// index variables to hold selected and blank JLabel's index location
int selectedIndex = -1;
int blankIndex = -1;
for (int i = 0; i < labelList.size(); i++) {
if (selectedLabel == labelList.get(i)) {
selectedIndex = i;
} else if (labelList.get(i).getIcon() == blankIcon) {
blankIndex = i;
}
}
// get row and column of selected JLabel
int row = selectedIndex / SIDES;
int col = selectedIndex % SIDES;
// get row and column of blank JLabel
int blankRow = blankIndex / SIDES;
int blankCol = blankIndex % SIDES;
if (isMoveValid(row, col, blankRow, blankCol)) {
Icon selectedIcon = selectedLabel.getIcon();
labelList.get(selectedIndex).setIcon(blankIcon);
labelList.get(blankIndex).setIcon(selectedIcon);
// test for win here by comparing icons held by labelList
// with the solutionList
}
}
private boolean isMoveValid(int row, int col, int blankRow, int blankCol) {
// has to be on either same row or same column
if (row != blankRow && col != blankCol) {
return false;
}
// if same row
if (row == blankRow) {
// then columns must be off by 1 -- they're next to each other
return Math.abs(col - blankCol) == 1;
} else {
// or else rows off by 1 -- above or below each other
return Math.abs(row - blankRow) == 1;
}
}
public void shuffle() {
Collections.shuffle(iconList);
for (int i = 0; i < labelList.size(); i++) {
labelList.get(i).setIcon(iconList.get(i));
}
}
}
private void fillIconList(BufferedImage img) {
// get the width and height of each individual icon
// which is 1/3 the image width and height
int w = img.getWidth() / SIDES;
int h = img.getHeight() / SIDES;
for (int row = 0; row < SIDES; row++) {
int y = (row * img.getWidth()) / SIDES;
for (int col = 0; col < SIDES; col++) {
int x = (col * img.getHeight()) / SIDES;
// create a sub image
BufferedImage subImg = img.getSubimage(x, y, w, h);
// create icon from the image
Icon icon = new ImageIcon(subImg);
// add to both icon lists
iconList.add(icon);
solutionList.add(icon);
}
}
// create a blank image and corresponding icon as well.
BufferedImage blankImg = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
blankIcon = new ImageIcon(blankImg);
iconList.remove(iconList.size() - 1); // remove last icon from list
iconList.add(blankIcon); // and swap in the blank one
solutionList.remove(iconList.size() - 1); // same for the solution list
solutionList.add(blankIcon);
}
private static void createAndShowGui(BufferedImage img) {
JFrame frame = new JFrame("ImageShuffle");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new ImageShuffle(img));
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
URL imgUrl = null;
BufferedImage img;
try {
imgUrl = new URL(IMG_PATH);
img = ImageIO.read(imgUrl);
SwingUtilities.invokeLater(() -> createAndShowGui(img));
} catch (IOException e) {
e.printStackTrace();
}
}
}
If I wanted animation, again, I'd raise the icon into the JFrame's glasspane, animate it to the new position using a Swing Timer, and then place the icon into the new JLabel. I'd also disable the MouseListener using a boolean field, a "flag", until the animation had completed its move.

Which Swing layout should i use for moving JButtons

I have a Board 14x14 which has JButtons and every Jbutton has a different color. When you click one of those buttons, it checks the neighbors with the same color and removes them. When it removes them, theres a blank space between the board so the above buttons, should move down to fill the blank space. I tried with GridLayout but I don't know how to move the above buttons.

This actually is a case where you can hardly use a layout manager at all.
A LayoutManager is supposed to compute the layout of all components at once. It is triggered by certain events (e.g. when the parent component is resized). Then it computes the layout and arranges the child components accordingly.
In your case, the situation is quite different. There is no layout manager that can sensibly represent the "intermediate" state that appears while the upper buttons are falling down. While the components are animated, they cannot be part of a proper layout.
The animation itself may also be a bit tricky, but can fortunately be solved generically. But you still have to keep track of the information about where each component (i.e. each button) is currently located in the grid. When one button is removed, you have to compute the buttons that are affected by that (namely, the ones directly above it). These have to be animated. After the animation, you have to assign the new grid coordinates to these buttons.
The following is a MCVE that shows one basic approach. It simply removes the button that was clicked, but it should be easy to generalize it to remove other buttons, based on other conditions.
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class FallingButtons
{
public static void main(String[] args)
{
SwingUtilities.invokeLater(() -> createAndShowGui());
}
private static void createAndShowGui()
{
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
int rows = 8;
int cols = 8;
GridPanel gridPanel = new GridPanel(rows, cols);
for (int r=0; r<rows; r++)
{
for (int c=0; c<cols; c++)
{
JButton button = new JButton(r+","+c);
gridPanel.addComponentInGrid(r, c, button);
button.addActionListener(e ->
{
Point coordinates = gridPanel.getCoordinatesInGrid(button);
if (coordinates != null)
{
gridPanel.removeComponentInGrid(
coordinates.x, coordinates.y);
}
});
}
}
f.getContentPane().add(gridPanel);
f.setSize(500, 500);
f.setLocationRelativeTo(null);
f.setVisible(true);
}
}
class GridPanel extends JPanel
{
private final int rows;
private final int cols;
private final JComponent components[][];
GridPanel(int rows, int cols)
{
super(null);
this.rows = rows;
this.cols = cols;
this.components = new JComponent[rows][cols];
addComponentListener(new ComponentAdapter()
{
#Override
public void componentResized(ComponentEvent e)
{
layoutGrid();
}
});
}
private void layoutGrid()
{
int cellWidth = getWidth() / cols;
int cellHeight = getHeight() / rows;
for (int r=0; r<rows; r++)
{
for (int c=0; c<cols; c++)
{
JComponent component = components[r][c];
if (component != null)
{
component.setBounds(
c * cellWidth, r * cellHeight, cellWidth, cellHeight);
}
}
}
}
Point getCoordinatesInGrid(JComponent component)
{
for (int r=0; r<rows; r++)
{
for (int c=0; c<cols; c++)
{
if (components[r][c] == component)
{
return new Point(r, c);
}
}
}
return null;
}
void addComponentInGrid(int row, int col, JComponent component)
{
add(component);
components[row][col] = component;
layoutGrid();
}
JComponent getComponentInGrid(int row, int col)
{
return components[row][col];
}
void removeComponentInGrid(int row, int col)
{
remove(components[row][col]);
components[row][col] = null;
List<Runnable> animations = new ArrayList<Runnable>();
for (int r=row-1; r>=0; r--)
{
JComponent component = components[r][col];
if (component != null)
{
Runnable animation =
createAnimation(component, r, col, r + 1, col);
animations.add(animation);
}
}
for (Runnable animation : animations)
{
Thread t = new Thread(animation);
t.setDaemon(true);
t.start();
}
repaint();
}
private Runnable createAnimation(JComponent component,
int sourceRow, int sourceCol, int targetRow, int targetCol)
{
int cellWidth = getWidth() / cols;
int cellHeight = getHeight() / rows;
Rectangle sourceBounds = new Rectangle(
sourceCol * cellWidth, sourceRow * cellHeight,
cellWidth, cellHeight);
Rectangle targetBounds = new Rectangle(
targetCol * cellWidth, targetRow * cellHeight,
cellWidth, cellHeight);
Runnable movement = createAnimation(
component, sourceBounds, targetBounds);
return () ->
{
components[sourceRow][sourceCol] = null;
movement.run();
components[targetRow][targetCol] = component;
repaint();
};
}
private static Runnable createAnimation(JComponent component,
Rectangle sourceBounds, Rectangle targetBounds)
{
int delayMs = 10;
int steps = 20;
Runnable r = () ->
{
int x0 = sourceBounds.x;
int y0 = sourceBounds.y;
int w0 = sourceBounds.width;
int h0 = sourceBounds.height;
int x1 = targetBounds.x;
int y1 = targetBounds.y;
int w1 = targetBounds.width;
int h1 = targetBounds.height;
int dx = x1 - x0;
int dy = y1 - y0;
int dw = w1 - w0;
int dh = h1 - h0;
for (int i=0; i<steps; i++)
{
double alpha = (double)i / (steps - 1);
int x = (int)(x0 + dx * alpha);
int y = (int)(y0 + dy * alpha);
int w = (int)(w0 + dw * alpha);
int h = (int)(h0 + dh * alpha);
SwingUtilities.invokeLater(() ->
{
component.setBounds(x, y, w, h);
});
try
{
Thread.sleep(delayMs);
}
catch (InterruptedException e)
{
Thread.currentThread().interrupt();
return;
}
}
SwingUtilities.invokeLater(() ->
{
component.setBounds(x1, y1, w1, h1);
});
};
return r;
}
}

You could try using a 2-dimensional array of JButtons
JButton[][] buttons = new JButton[14][14];
for (int i=0; i < buttons.length; i++) {
for (int j=0; j < buttons[i].length; j++) {
buttons[i][j] = new JButton("Button [" + i + "][" + j + "]");
}
}
// Then do whatever,remove,change color,check next element in array
// and compare colors etc
buttons[2][3].setText("changed text");

If you want the above buttons to take more space to fill the empty space when you remove a component well, this is not possible using GridLayout, but you can add some empty components like JLabels to fill the space.
You can add a component in a container at a specific index for this purpose, by using Container's add (Component comp, int index) method.
This code snippet will replace a button at a specified index (45, just for example) with a blank component in a panel which has a GridLayout set:
JPanel boardPanel = new JPanel (new GridLayout (14, 14));
// ... add your buttons ...
// This code could be invoked inside an ActionListener ...
boardPanel.remove (45);
boardPanel.add (new JLabel (""), 45);
boardPanel.revalidate ();
boardPanel.repaint ();
This way, the rest of the components will not move, and you will just see a blank space replacing your button.
You can achieve more: if you add the empty label at index = 0, all the buttons will move to the right (remember that the number of components should not change, else the components will resize and you could obtain bad behaviour), and so on, you can "move" a single component by simply removing it and adding it at a different index.
Another way to go would be to store a 2-dimensional array of objects representing your model logic (you can store color and all the stuff you need), and painting them on your own by overriding paintComponent method.
For an example of a custom painting approach, take a look at this MadProgrammer's answer, where he shows how to highlight a specific cell in a grid (in this case he uses a List to store objects, but a 2d array will work as well).

Need a Java method that creates buttons

I'm trying to create a method myMethod in JAVA that can fill a user defined jPanel with buttons according to the panels size. It works if I change "Object j" to "jFrameScreen j" , remove Component p and change variable p to j. jPanel2 in myMethod.
But that's not what I want, I want the user to be able to determine what jFrame and jPanel the buttons will be created on when calling myMethod.
When I run the code as shown here it gives me these errors:
p.add(btn[b]); //JButton cannot be converted to PopupMenu
j.setVisible(true); //Cannot find symbol, method setVisible(boolean)
My work is as follows:
public class Main {
public static void main(String[] args) {
jFrameScreen j = new jFrameScreen();
myMethod(j, j.jPanel2, 10, 10, 600, 400);
}
public static void myMethod(Object j, Component p, int col, int row, int myWidth, int myHeight) {
int bWidth = myWidth / col;
int bHeight = myHeight / row;
int numberOfButtons = (myWidth / bWidth) * (myHeight / bHeight);
JButton btn[] = new JButton[numberOfButtons];
for (int k = 0, x = 0, b = 0; k < myWidth / bWidth; k++, x += bWidth) {
for (int i = 0, y = 0; i < myHeight / bHeight; i++, y += bHeight, b++) {
btn[b] = new JButton();
btn[b].setBounds(2 + x, 3 + y, bWidth, bHeight);
btn[b].setText(Integer.toString(b));
btn[b].setVisible(true);
p.add(btn[b]); //JButton cannot be converted to PopupMenu
}
}
p.setVisible(true);
j.setVisible(true); //Cannot find symbol, method setVisible(boolean)
}
}

A variable declared with the Object type doesn't have a setVisible() method.
And Component.add() accepts only instances of the PopupMenu class :
public void add(PopupMenu popup) {
But that's not what I want, I want the user to be able to determine
what jFrame and jPanel the buttons will be created on when calling
"myMethod".
You try to provide a generic method but you don't rely on suitable base classes according to your requirements.
Object and Component are too generic to represent respectively a JFrame and a JPanel.
If these two parameters have to represent instances of these types, just use them : replace Object j by JFrame j and Component p by JPanel p.
Besides, their naming is really not good. frame and panel are better :
public static void myMethod(JFrame frame, JPanel panel, int col, int row, int myWidth, int myHeight) {

Drawing a two colored checker board with nested for loops where each square being their own object (Java)

I am attempting to draw a checkerboard pattern in java using nested for loops, but I am having trouble doing it with two different colors. I know this question has been asked before, but it hasn't been asked with two different colors on the board that are not just using a background color. I plan on using the individual squares as an array to hold checker positions, so I do need each individual square made. Would it be better to drop the ice of a nested for loop to create each square, or should i stick with that shortcut? And if I were to stick with it, how would the nested loop be formatted (one for each color)?

When creating checker tiles, I would pass in an int for the x coordinate, and y coordinate such as:
import java.awt.Color;
import java.awt.Graphics;
public class CheckerTile {
public static final int WIDTH = 100; //width of each tile
public static final int HEIGHT = 100; //height of each tile, most likely same as width so its a square
public static int currentId = 0; //variable to reference unique id for each tile
private int id; //current id of tile
private int x; //x coordinate
private int y; //y coordinate
private int width; //width of tile
private int height; //height of tile
//Default constructor to take x and y coordinate
public CheckerTile( int x, int y ) {
this.id = currentId++;
this.x = x;
this.y = y;
width = WIDTH;
height = HEIGHT;
}
public int getId()
{
return id;
}
//draws the tile on the panel.
public void draw(Graphics g)
{
//if the checkerTile's id is divisible by 2, draw it red, otherwise draw it black.
g.setColor( id % 2 == 0 ? Color.RED : Color.black);
g.fillRect(x, y, width, height);
}
}
That way we have a way to draw the tile on the board. Now, when creating each object, we increment a currentId variable so that we can color each one individually using the modulus operator later.
I am assuming you are using Swing so I decided to add a draw(Graphics g) method so when repainting in java it would use that Graphics object. If you are using a different library, then you will have to do some research in to how to draw it on the board.
Now in your JPanel, it would look something like this:
//Creates the JPanel, which needs to be added to JFrame object in main
import java.awt.BorderLayout;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class CheckerBoard extends JPanel {
CheckerTile[][] checkerTiles; //2-dimension array of checkerTiles
public CheckerBoard() {
super();
this.setSize(800,800);
checkerTiles = new CheckerTile[9][9];
//This creates the checkerTiles.
for(int i = 0; i < 9; i++)
{
for( int j = 0; j < 9; j++)
{
checkerTiles[i][j] = new CheckerTile( j * CheckerTile.WIDTH, i * CheckerTile.HEIGHT );
}
}
this.setVisible(true);
//Repaint right away to show results.
repaint();
}
//We need to override this to paint the tiles on the board.
#Override
public void paintComponent(Graphics g)
{
for(int i = 0; i < checkerTiles.length; i++)
{
for(int j = 0; j < checkerTiles[i].length; j++)
{
//call the draw method on each tile.
checkerTiles[i][j].draw(g);
}
}
}
//A demo of adding the panel to a frame and showing the tiles.
public static void main(String[] args)
{
//Create the JFrame and add the CheckerBoard we made to it.
JFrame frame = new JFrame();
frame.setSize(800,800);
frame.setLayout(new BorderLayout());
frame.add(new CheckerBoard(), BorderLayout.CENTER);
frame.setVisible(true);
}
}

Array of JButtons is returning void

I'm attempting to create Minesweeper and I've managed to get stuck very early on with my array of JButtons returning void instead of a JButton so therefore I can't perform any actions on it.
Here is the code: (The error occurs in the last line when I want to remove the button)
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Game extends JFrame implements ActionListener
{
JButton[][] buttons;
int rows;
int cols;
int x;
int y;
public Game(int rows, int cols)
{
setTitle("Minesweeper");
setSize(500, 500);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.rows = rows;
this.cols = cols;
setLayout(new GridLayout(rows, cols));
buttons(rows, cols);
}
public void buttons(int tableX, int tableY)
{
buttons = new JButton[tableX][tableY];
for (x = 0; x < tableX; x++)
{
for (y = 0; y < tableY; y++)
{
buttons[x][y] = new JButton();
buttons[x][y].setActionCommand("Pressed");
buttons[x][y].addActionListener(this);
this.add(buttons[x][y]);
}
}
}
public void actionPerformed(ActionEvent e)
{
for (x = 0; x < rows; x++)
{
for (y = 0; y < cols; y++)
{
if (e.getActionCommand().equals("Pressed"))
{
buttons[x][y] = setVisible(false);
}
}
}
}
}

Use . instead of = for invoking methods
buttons[x][y].setVisible(false);

Are you sure that setVisible() is a stand alone method? try buttons[x][y].setVisible(false);
setVisible is a method that belongs to the JButton Object so you can't just arbitrarily call it. Think "What is being set to visibile?"
Currently you're getting a returned void because what you're actually calling is a method in your immediate class called setVisible() (which doesn't exist therefor returns void) when you want to call the JButton's setVisibile

you might don't want to hide them, you can do
buttons[x][y].setEnable(false);
when you do that you can change the icon on them according to what is behind them