Develop Reference

Unable to drawimage on null layout swing

I want to draw some images on screen alongside some JButtons placed in different places of the screen. However whenever I have setLayout(null); the images do not show up on screen. If i don't set it to null I can make the images show up but I can't place my Jbuttons on the desired places.
How can i make so i have setLayout(null); and still be able to draw multiple images on screen while placing my buttons anywhere?
My Frame Class:
public class PFrame extends JFrame {
JPanel p;
public PFrame() {
p = new PPanel();
p.setBackground(Color.WHITE);
Container c = getContentPane();
c.setLayout(null);
c.add(p);
setSize(1200,700);
JRadioButton White = new JRadioButton("White");
ButtonGroup G1 = new ButtonGroup();
White.setBounds(1000, 30, 80, 50);
G1.add(White);
this.add(White);
//rest of buttons code here...
public class PPanel extends JPanel{
public void paintComponent(Graphics g) {
super.paintComponent(g);
Image [] vi = ImgArray();
int x = 0;
int y = 0;
int i;
for (i = 0; i < vi.length / 2; i++) {
g.drawImage(vi[i],x,y,240,310,null);
x+= 250;
}
y = 320;
x = 0;
for (i = vi.length / 2; i < vi.length; i++) {
g.drawImage(vi[i],x,y,240,310,null);
x+= 250;
}
}
}
Main method:
public static void main(String[] args) {
PersonagensFrame f =new PFrame();
f.setVisible(true);
f.repaint();
}

I would recomend using anything other then a null layout for swing. You should check out the documentation for layouts such as GridBagLayout and GridLayout; since they are much more friendly in terms of compatibility.
If that isn't what you are looking for, you should also try making two seperate panels, seperating your buttons and images.
Swing was specifically built to incorporate layouts in which they provide.
I hope you figure it out! :)

How to set up a mouse dragger in Java for la labyrinth? [duplicate]

I am working on developing a Chess game. I want to have the board Container utilize a GridLayout to display an 8x8 grid of JPanels. (This will make functions such as highlighting selected squares and valid moves much easier.) I would then like to add the pieces over this layer so that they may be dragged and dropped. I initially had the pieces showing by drawing them in the individual square JPanels, but figured that would be a problem when trying to drag-and-drop them later. I have since been trying to use a JLayeredPane as the main container, but have encountered several issues.
One is that once I've specified the GridLayout for the JLayeredPane, regardless of which Integer I use to specify the layer to add the JLabel or other kind of image to, the pieces get added to the grid, making their positions set and and distorting the whole board. I have read that using LayoutManagers can interfere with layer positioning on the JLayeredPane, so this isn't too surprising. (Although the Oracle demo program from the JLayeredPane tutorial seems to do this just fine: http://download.oracle.com/javase/tutorial/uiswing/examples/components/LayeredPaneDemo2Project/src/components/LayeredPaneDemo2.java)
However, I have also tried to put the grid of JPanels into its own JPanel, then add it to a low layer of the JLayeredPane, the idea being that I could add the drag & drop icons to separate, non-opaque JPanel on a higher layer of the JLayeredPane. When I do this however, after I simply have the grid JPanel inside the JLayeredPane (i.e. before the drag-and-drop layer is added), the grid will not display.
I also have tried overriding the paintComponent (and paint) methods of the JLayeredPane to draw the piece images, but they are hidden by the JPanels (I can see that they are indeed there by setting the JPanels to non-opaque) and as far as I can tell there is no option to set the layer of the graphics on the JLayeredPane. I have also tried using the glassPane of the frame to draw the pieces, but got undesired behavior there as well.
Any help explaining some of this behavior, or where I am going wrong, would be much appreciated!

Here is a simple example that shows how you might (randomly) drag and drop a "chess piece" from one square to another:
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ChessBoard extends JFrame implements MouseListener, MouseMotionListener
{
JLayeredPane layeredPane;
JPanel chessBoard;
JLabel chessPiece;
int xAdjustment;
int yAdjustment;
public ChessBoard()
{
Dimension boardSize = new Dimension(600, 600);
// Use a Layered Pane for this this application
layeredPane = new JLayeredPane();
layeredPane.setPreferredSize( boardSize );
layeredPane.addMouseListener( this );
layeredPane.addMouseMotionListener( this );
getContentPane().add(layeredPane);
// Add a chess board to the Layered Pane
chessBoard = new JPanel();
chessBoard.setLayout( new GridLayout(8, 8) );
chessBoard.setPreferredSize( boardSize );
chessBoard.setBounds(0, 0, boardSize.width, boardSize.height);
layeredPane.add(chessBoard, JLayeredPane.DEFAULT_LAYER);
// Build the Chess Board squares
for (int i = 0; i < 8; i++)
{
for (int j = 0; j < 8; j++)
{
JPanel square = new JPanel( new BorderLayout() );
square.setBackground( (i + j) % 2 == 0 ? Color.red : Color.white );
chessBoard.add( square );
}
}
// Add a few pieces to the board
ImageIcon duke = new ImageIcon("dukewavered.gif"); // add an image here
JLabel piece = new JLabel( duke );
JPanel panel = (JPanel)chessBoard.getComponent( 0 );
panel.add( piece );
piece = new JLabel( duke );
panel = (JPanel)chessBoard.getComponent( 15 );
panel.add( piece );
}
/*
** Add the selected chess piece to the dragging layer so it can be moved
*/
public void mousePressed(MouseEvent e)
{
chessPiece = null;
Component c = chessBoard.findComponentAt(e.getX(), e.getY());
if (c instanceof JPanel) return;
Point parentLocation = c.getParent().getLocation();
xAdjustment = parentLocation.x - e.getX();
yAdjustment = parentLocation.y - e.getY();
chessPiece = (JLabel)c;
chessPiece.setLocation(e.getX() + xAdjustment, e.getY() + yAdjustment);
layeredPane.add(chessPiece, JLayeredPane.DRAG_LAYER);
layeredPane.setCursor(Cursor.getPredefinedCursor(Cursor.MOVE_CURSOR));
}
/*
** Move the chess piece around
*/
public void mouseDragged(MouseEvent me)
{
if (chessPiece == null) return;
// The drag location should be within the bounds of the chess board
int x = me.getX() + xAdjustment;
int xMax = layeredPane.getWidth() - chessPiece.getWidth();
x = Math.min(x, xMax);
x = Math.max(x, 0);
int y = me.getY() + yAdjustment;
int yMax = layeredPane.getHeight() - chessPiece.getHeight();
y = Math.min(y, yMax);
y = Math.max(y, 0);
chessPiece.setLocation(x, y);
}
/*
** Drop the chess piece back onto the chess board
*/
public void mouseReleased(MouseEvent e)
{
layeredPane.setCursor(null);
if (chessPiece == null) return;
// Make sure the chess piece is no longer painted on the layered pane
chessPiece.setVisible(false);
layeredPane.remove(chessPiece);
chessPiece.setVisible(true);
// The drop location should be within the bounds of the chess board
int xMax = layeredPane.getWidth() - chessPiece.getWidth();
int x = Math.min(e.getX(), xMax);
x = Math.max(x, 0);
int yMax = layeredPane.getHeight() - chessPiece.getHeight();
int y = Math.min(e.getY(), yMax);
y = Math.max(y, 0);
Component c = chessBoard.findComponentAt(x, y);
if (c instanceof JLabel)
{
Container parent = c.getParent();
parent.remove(0);
parent.add( chessPiece );
parent.validate();
}
else
{
Container parent = (Container)c;
parent.add( chessPiece );
parent.validate();
}
}
public void mouseClicked(MouseEvent e) {}
public void mouseMoved(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
public static void main(String[] args)
{
JFrame frame = new ChessBoard();
frame.setDefaultCloseOperation( DISPOSE_ON_CLOSE );
frame.setResizable( false );
frame.pack();
frame.setLocationRelativeTo( null );
frame.setVisible(true);
}
}

Why does setting preferred sizes in a JFrame fail when entering fullscreen?

I want to create a game with a fixed width/heigth ratio for the actual screen (so I can easily just scale the game elements and don't have to bother with complex layout). In order to do so I created a JFrame with a BorderLayout with the actual screen in the center and 4 spacing-panels on the sides. After every resize I recalculate the required spacing and set the preferred sizes accordingly so the screen gets the maximum ractangle of the given ratio that fits in the frame. The following code does that job, I replaced the actual screen with a simple blue panel and also added output to check on the calculation:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class JFrameResize {
private static JFrame frame;
private static JPanel inside = new JPanel();
private static JPanel spacingTop = new JPanel();
private static JPanel spacingBottom = new JPanel();
private static JPanel spacingLeft = new JPanel();
private static JPanel spacingRight = new JPanel();
private static JPanel compound = new JPanel();
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGUI());
}
public static void createAndShowGUI() {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
inside.setBackground(Color.BLUE);
compound.setLayout(new BorderLayout());
compound.add(inside, BorderLayout.CENTER);
compound.add(spacingTop, BorderLayout.NORTH);
compound.add(spacingBottom, BorderLayout.SOUTH);
compound.add(spacingLeft, BorderLayout.WEST);
compound.add(spacingRight, BorderLayout.EAST);
frame.add(compound);
frame.addComponentListener(new ComponentAdapter() {
#Override
public void componentResized(ComponentEvent e) {
calculateSize();
}
});
calculateSize();
frame.setVisible(true);
}
public static void calculateSize() {
double width = frame.getContentPane().getWidth();
double height = frame.getContentPane().getHeight();
double vSpacing = 0, hSpacing = 0;
System.out.println("frame: " + width + ":" + height);
// ratio is hardcoded to 3:4
if ((width * 3 - height * 4) >= 0) {
hSpacing = (width - (height * 4) / 3) / 2;
width = width - 2 * hSpacing;
} else {
vSpacing = (height - (width * 3) / 4) / 2;
height = height - 2 * vSpacing;
}
System.out.println("spacing: " + hSpacing + " + " + width + " + " + hSpacing + " : "
+ vSpacing + " + " + height + " + " + vSpacing);
spacingBottom.setPreferredSize(new Dimension((int) width, (int) vSpacing));
spacingTop.setPreferredSize(new Dimension((int) width, (int) vSpacing));
spacingLeft.setPreferredSize(new Dimension((int) hSpacing, (int) height));
spacingRight.setPreferredSize(new Dimension((int) hSpacing, (int) height));
inside.setPreferredSize(new Dimension((int) width, (int) height));
frame.revalidate();
frame.repaint();
System.out.println("inside: " + inside.getWidth() + ":" + inside.getHeight()
+ ", " + "border: " + spacingLeft.getWidth() + ":"
+ spacingTop.getHeight());
}
}
This works well for the most time, I get outputs like
frame: 510.0:445.0
spacing: 0.0 + 510.0 + 0.0 : 31.25 + 382.5 + 31.25
inside: 510:385, border: 0:30
and the frame shows the correct rectangle. However if I set the frame to fullscreen I get this output:
frame: 1366.0:705.0
spacing: 213.0 + 940.0 + 213.0 : 0.0 + 705.0 + 0.0
inside: 1366:643, border: 0:31
That is incorrect since my formular calculated the inside to be 940:705 but it became 1312:705. The rectangle also doesn't show correctly anymore. Same goes for using windows + arrow keys or dragging the frame to the screen sides . The calculation input is correct but the repaint/revalidate somehow behaves differently from a normal resize. No different combination of revalidate() and repaint() or spamming them across the code seems to change anything.
How does this happen and how do I fix this? Or is the approach in general flawed and should be replaced?

Don't use a BorderLayout and try to add spacing components.
Instead I would suggest you can set the layout manager of the content panel to be a GridBagLayout. When using the default GridBagConstraints any component added to the GridBagLayout will automatically be centered.
Then for the "inside" panel that you add to the frame you need to override the getPreferredSize() method to calculate the size of the panel.
To determine its preferred size you would get the size of its parent container and then you determine its preferred size based on your rules.
There would be no need for the ComponentListener because the layout manager is automatically invoked whenever the frame is resized.
Simple example to get you started:
import java.awt.*;
import javax.swing.*;
public class JFrameResize
{
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGUI());
}
public static void createAndShowGUI() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel inside = new JPanel()
{
#Override
public Dimension getPreferredSize()
{
Dimension parent = getParent().getSize();
Dimension child = new Dimension();
int value = (parent.width * 3) - (parent.height * 4);
if (value > 0)
{
child.height = parent.height;
child.width = (int)(child.height * 4 / 3);
}
else
{
child.width = parent.width;
child.height = (int)(child.width * 3 / 4);
}
return child;
}
};
inside.setBackground(Color.BLUE);
frame.setLayout( new GridBagLayout() );
frame.add(inside, new GridBagConstraints());
frame.pack();
frame.setVisible(true);
}
}

Regarding why my approach does not work:
This source from this question (thanks to #Andrew Thompson for linking) states:
[setPreferredSize is] used by LayoutManager as hints to balance the actual layout
So my setPreferredSize was probably overridden by the BorderLayout, in order to make sure the LayoutManager does not interfere you have to overwrite the getPreferredSize

Adding a JScrollPane to an overriden JPanel

I am trying to create a program that computes for the Round Robin algorithm. The logic works fine. My problem is with the overriden JPanel that I use to draw the timeline. The timeline goes on and on without definite line length. I want to add the overriden panel to a scroll pane so it can be scrollable.
SampleGPane.class
import java.awt.*;
import javax.swing.*;
public class
SampleGPane
{
/* Timeline elements */
Container timelineContainer;
JFrame timelineFrame = new JFrame ();
JPanel pnlDraw = new JPanel ();
JScrollPane timelineScroll;
public void
launchFrame ()
{
GPanel gpane = new GPanel ();
timelineContainer = timelineFrame.getContentPane ();
timelineScroll = new JScrollPane (gpane);
timelineContainer.add (timelineScroll);
timelineFrame.setSize (500, 250);
timelineFrame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
timelineFrame.setVisible (true);
}
private class
GPanel extends JPanel
{
#Override
public void
paintComponent (Graphics g)
{
super.paintComponent (g);
int runningLineX = 0;
int runningLineY = 0;
// g.drawLine (50, 50, orderCount * 5, 50);
runningLineX += 50;
runningLineY += 50;
for (int count = 0; count < 35; count++) {
g.drawString ("J" + (count + 1), runningLineX + 50, 25);
runningLineX += 50;
// runningLineY += 50;
g.drawLine (runningLineX, runningLineY, runningLineX + 50, runningLineY);
}
}
}
}
SampleGPane.class is called by SampleLaunch.class
public class
SampleLaunch
{
public static void main (String args[]) {
SampleGPane sgp = new SampleGPane ();
sgp.launchFrame ();
}
}
The problem is, the JScrollPane won't work. It doesn't seem to detect the line. How do I fix this?

You need to override the getPreferredSize() method of your custom panel to return a reasonable size.
The scrollbars will only appear when the preferred size of the component added to the viewport of the scroll pane is greater than the size of the scroll pane.
The timeline goes on and on without definite line length.
The line length will need to match your painting code. So you need parameters to control what to paint. These parameters will also be used in the calculation of the size of the component. In your example you iterate 35 times and increment the x by 50 so the width would be 1750 plus the starting x offset.

JLabel is being shown in wrong place

I have a problem with GUI. In my drawing simulator, I created a JLabel that show mouseclicks coordinates. I put it on southwest of my JFrame but after each click, in addition to its first place, mouse coordinates also appear on northwest of the JFrame. I didn't understand what ths problem is.The code is here.
JLabel statusBar = new JLabel( "Mouse outside JPanel" );
Container panel;
JFrame frame = new JFrame();
panel = frame.getContentPane();
panel.add(this);
frame.setJMenuBar(jmb);
frame.add(statusBar, BorderLayout.SOUTH );
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(700,700);
frame.setVisible(true);
This is how I edit JLabel
statusBar.setText( String.format( "Clicked at [%d, %d]",
e.getX(), e.getY() ) );
The whole code can be longer thats why iam copying some important parts
public class Tester extends JPanel implements MouseMotionListener, MouseListener {
....
This is how a draw a single line and I set the label's name here
else if(lineci == true){
if(mouseclicks == 0){
l1.point1.x = e.getX();
l1.point1.y = e.getY();
statusBar.setText( String.format( "Clicked at [%d, %d]",
e.getX(), e.getY() ) );
mouseclicks++;
}
else if(mouseclicks == 1){
l1.point2.x = e.getX();
l1.point2.y = e.getY();
statusBar.setText( String.format( "Clicked at [%d, %d]",
e.getX(), e.getY() ) );
mouseclicks = 0;
int a = l1.point2.y - l1.point1.y;
int b = l1.point1.x - l1.point2.x;
int c = (l1.point2.x * l1.point1.y) - (l1.point1.x * l1.point2.y);
l1.denklem[0] = a;
l1.denklem[1] = b;
l1.denklem[2] = c;
array.add(l1);
array3.add(l1);
repaint();
}
By the way, I 'm creating JLabel object outside the constructur of the class, just after creating class I mean.
Still same problem exists.

Instead of
frame.add(statusBar, BorderLayout.SOUTH );
Try
frame.getContentPane().add(statusBar, BorderLayout.SOUTH );