Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 8 years ago.
Improve this question
I have a java program that's should be doing something very simple. It contains a JPanel, on which repaint() is called 30 times each second. This JPanel overrides the paintComponent() method, and in this overwritten method, I take a BufferedImage and draw it to the JPanel.
This BufferedImage consists of a black image with a somewhat smaller blue rectangle inside of it. This displays, but the problem is that the left side, 50-80 pixels or so, of the screen flickers. On the leftmost part of what should be the blue rectangle, some of the pixels will sometimes appear black instead, as though there's some black overlay extending from the left side of the screen covering it, that flickers a bit each frame.
I wouldn't think just drawing a rectangle would be so consuming that it would cause graphical bugs with something like this; is it? I can't figure out why this would be happening, so do any of you have any idea what would cause a black "flicker" on the left of either a BufferedImage or a Graphics2D?
'Runnable example(please add the imports)':
public class Panel extends JPanel{
public int width, height;
public long lastTime;
public BufferedImage canvas;
public Panel(int a, int b){
width = a;
height = b;
canvas = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
lastTime = System.currentTimeMillis();
}
public void paintComponent(Graphics g){
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g.drawImage(canvas, 0, 0, this);
}
public void drawRect(int startX, int startY, int w, int h, int color){
for(int i=0; i<w; i++){
for(int j=0; j<h; j++){
canvas.setRGB(i + startX, j + startY, color);
}
}
}
public void render(){
drawRect(0, 0, width, height, 0x000000);
drawRect(10, 10, width - 20, height - 20, 0x0000ff);
}
public void update(){
int delta = (int)(System.currentTimeMillis() - lastTime);
if(delta >= 1000 / 30){
render();
lastTime = System.currentTimeMillis();
}
}
//in a different class, contains main()
public class Main{
public static Panel pan;
public static void main(String[] args){
JFrame frame = new JFrame();
Container c = frame.getContentPane();
c.setPreferredSize(500, 500);
pan = new Panel(500, 500);
frame.add(pan);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
new runThread().run();
}
class runThread extends Thread{
public void run(){
while(true){
pan.update();
}
}
}
}
Because your program is incorrectly synchronized in several ways, the result is indeterminate. Swing GUI objects must be constructed and manipulated only on the event dispatch thread; this is required on all supported platforms. As discussed in How to Use Swing Timers, this example runs at 50 Hz without flicker.
I have a 15-class program…
In larger programs, you can search for EDT violations using one of the approaches cited here. Also review the animation techniques suggested here.
Related
I am trying to teach myself more about graphics in Java. To do this I'm trying to build a chess game. I've hit my first roadblock at making the board. My thought here is that I would have a extension of JComponent called "Square" that would be my container for both the color of the board square and the piece on that square (if any). To start with I haven't attempted to include any representation of the piece yet, just the square colors. Later on I hope to have an abstract "Pieces" class that is extended by multiple subclasses representing all the different types of pieces, and add those to each Square as applicable.
When I execute the following, I only get one black square in the upper left hand corner.
ChessBoardTest.java
public class ChessBoardTest {
public static void main(String[] args) {
ChessBoard Board = new ChessBoard();
Board.Display();
}
}
ChessBoard.java
public class ChessBoard extends JFrame {
public static final int FRAME_WIDTH = 500;
public static final int FRAME_HEIGHT = 500;
// Declare instance variables
private Square[][] square = new Square[rows][cols];
private final static int rows = 8;
private final static int cols = 8;
public ChessBoard() {
}
public void Display() {
JPanel Board_Layout = new JPanel();
Board_Layout.setLayout(new GridLayout(8,8));
for(int i=0;i<8;i++)
{
for(int j=0;j<8;j++)
{
if((i+j) % 2 == 0) {
square[i][j] = new Square(1);
Board_Layout.add(square[i][j]);
} else {
square[i][j] = new Square(0);
Board_Layout.add(square[i][j]);
}
}
}
setTitle("Chess Mod");
setSize(FRAME_WIDTH, FRAME_HEIGHT);
setResizable(false);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
add(Board_Layout);
setVisible(true);
}
public void messageBox(String pMessage) {
JOptionPane.showMessageDialog(this, pMessage, "Message", JOptionPane.PLAIN_MESSAGE);
}
}
Square.java
public class Square extends JComponent {
private int color;
public Square(int c) {
this.color=c;
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
if (this.color == 1) {
g.setColor(new Color(0,0,0));
} else {
g.setColor(new Color(255,255,255));
}
g.fillRect(this.getX(), this.getY(), this.getWidth(), this.getHeight());
}
}
I only get one black square in the upper left hand corner.
That's mainly because of the following call:
g.fillRect(this.getX(), this.getY(), this.getWidth(), this.getHeight());
getX() returns the horizontal pixel offset/location of the Component which is invoked upon, relative to the Container that contains that Component. getY() accordingly returns the vertical pixel offset/location of the Component which is invoked upon, relative to the Container that contains the Component.
getWidth() and getHeight() return the size of the Component.
So imagine that the Component at row with index 2 and column with index 3, will have its coordinates at about x == 3 * w / 8 and y == 2 * h / 8 where w and h is the size (width and height respectively) of the parent Container (ie the Board_Layout panel). Let's assume that Board_Layout has a size of 300x300 when you show the graphical user interface... This means that the Square at the location I mentioned will only paint the region which starts at x == 112 and y == 75 and expands at one 8th of the width (and height) of Board_Layout (because there are 8 rows and 8 columns in the grid). But the size of the Square itself is also at one 8th of the width (and height) of Board_Layout, ie about 37x37. So the painted region which starts and expands from the location 112,75 will not be shown at all (because it lies completely outside the Square's size).
Only the top left Square will have some paint on it because its bounds in the parent happen to intersect the drawn region.
To fix this, the location given at the Graphics object should be relative to each Square and not its parent Board_Layout. For example:
g.fillRect(0, 0, getWidth(), getHeight());
I've never written a program with anything more than a bare-bones GUI, so I've undertaken a personal project to write a chess application.
One of my goals with this project was to make the board rescale to fit the window, and I managed to do this without too much trouble. However, in the process I ran into the issue that my pieces (which were represented as Icons on JButtons) did not rescale with the rest of the board.
I decided to represent them with the Image class instead, and made a custom class called ScalingJButton which overrode paintComponent. This actually worked quite well... for the last piece to be drawn. The rest of the pieces are not drawn, and as a result the program is broken. Here is my ScalingJButton class:
public class ScalingJButton extends JButton{
private Image image;
ScalingJButton (){
this.image = null;
}
ScalingJButton (Image image){
this.image = image;
}
public void setImage(Image image){
this.image = image;
}
public Image getImage(){
return image;
}
#Override
public void paintComponent(Graphics g){
//super.paintComponent(g);
int x = getX();
int y = getY();
int width = getWidth();
int height = getHeight();
if (image != null) {
g.drawImage(image, x, y, width, height, this);
}
}}
Additionally, here is the code responsible for instantiating the ScalingJButtons (VisualBoard is a class extending JPanel and this is its constructor).
public VisualBoard (){
white = Color.WHITE;
black = Color.GRAY;
loadPieceImages();
setLayout(new GridLayout(8, 8));
for (int i = 0; i < 8; i++){
for (int j = 0; j < 8; j++){
squares[i][j] = new ScalingJButton();
if ((i + j) % 2 != 0) {
squares[i][j].setBackground(white);
}
else{
squares[i][j].setBackground(black);
}
add(squares[i][j]);
}
}
initializeStandardBoard();
}
Finally, since the layout may be relevant, here is the code that makes the board autoscale:
public class Chess {
public static void main (String[] args){
final VisualBoard board = new VisualBoard();
final JPanel container = new JPanel(new GridBagLayout());
container.add(board);
container.addComponentListener(new ComponentAdapter() {
#Override
public void componentResized(ComponentEvent e) {
drawResizedBoard(board, container);
}
});
JFrame frame = new JFrame("Chess");
frame.setSize(1000,1000);
frame.add(container);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
private static void drawResizedBoard(JPanel innerPanel, JPanel container) {
int w = (int)Math.round(container.getWidth()*0.9);
int h = (int)Math.round(container.getHeight()*0.9);
int size = Math.min(w, h);
innerPanel.setPreferredSize(new Dimension(size, size));
container.revalidate();
}}
I have done extensive debugging, but most of it has lead nowhere. One thing to note is that the "image" variable in ScalingJButton holds the correct picture when drawImage is called, so that's not the issue. Another interesting point is that the square with the piece in it is the the last square to be drawn, and depending on what order I add squares to the Board, different pieces will be drawn (so there is no issue loading pieces).
Strangely, if I do away with super in paintComponent, rolling my mouse over the drawn pieces causes the other squares to fill with that piece when I roll my mouse over them.
I'm completely lost and don't know what to do, so any help would be greatly appreciated!
First, you need to keep the super.paintComponent(g); line. If you don’t, artifacts will appear at seemingly random times.
Second, getX() and getY() return to the component’s position in its parent. When you paint, you are given a coordinate system where 0,0 is the top left corner of the component. So you should ignore getX() and getY().
The simplest alternative is to use the upper-left corner of the button:
int x = 0;
int y = 0;
You may want to account for the button’s border:
if (image != null) {
Rectangle inner = SwingUtilities.calculateInnerArea(this, null);
g.drawImage(image, inner.x, inner.y, inner.width, inner.height, this);
}
And if you want the button to really look like a normal button, you can also account for its margin:
if (image != null) {
Rectangle inner = SwingUtilities.calculateInnerArea(this, null);
Insets margin = getMargin();
inner.x += margin.left;
inner.y += margin.top;
inner.width -= (margin.left + margin.right);
inner.height -= (margin.top + margin.bottom);
g.drawImage(image, inner.x, inner.y, inner.width, inner.height, this);
}
However, in the process I ran into the issue that my pieces (which were represented as Icons on JButtons) did not rescale
The Stretch Icon may be a simpler solution. You can use this Icon on any component that can display an Icon. The image will dynamically change size to fill the space available to the Icon.
There are two suspicious lines in your code. First one is
frame.add(container);
This line adds your Swing element to an AWT container. Instead your should replace it with
frame.setContentPane(container);
The second line is the method
public void paintComponent(Graphics g) {
Try replacing it with
public void paint(Graphics g) {
Hope this helps.
EDIT:
Also change this
g.drawImage(image, x, y, width, height, this);
to
public void paint(Graphics g) {
super.paint(g);
int width = getWidth();
int height = getHeight();
if (image != null) {
g.drawImage(image, 0, 0, width, height, this);
}
}
Your images were simply outside of the grid.
I am trying to draw circles to JFrame with different positions, in this case in a grid-like pattern.
I don't seem to have trouble drawing a single circle with an x,y position, however, when I try to draw multiple circles with different positions the other circles' positions come out obscured.
In the code below, I have two arrays: XPlacements and YPlacements that contain different X and Y positions to form a grid. For each X position there should be circles created at that X position with varying Y positions (vice versa).
When I only make the below code draw one circle, where XPlacements = {10} YPlacements = {100}, it draws a circle that appears to be at some (10,100) from the top left. Similarly when I add multiple X positions but a single Y position nothing seems to be obscured. However, when I add multiple Y positions, every descending row of circles seems to be more and more pushed to the right.
When I run it, it obscures like this: http://imgur.com/HHjhvPD
I can't seem to make it less obscured by changing the values of the JFrame. All the JFrame circle tutorials I can find only deal with 1 circle, and I don't have any issues when I use 1 circle (or only 1 row of circles).
Does anyone know why the code below isn't producing a grid like pattern?
Thanks.
public class Circle extends Canvas {
int XPos;
int YPos;
public void SetPosition(int x, int y) {
this.XPos = x;
this.YPos = y;
repaint();
}
public void paint(Graphics g) {
System.out.println("Filling oval with position ("+XPos+","+YPos+")");
g.fillOval(XPos, YPos, 15, 15);
}
}
public class MainFile extends JFrame {
static int[] XPlacements = {10,20,30};
static int[] YPlacements = {100,200,300};
static Circle[] Circles = new Circle[1000];
static int Circle_Count = 0;
public static void main(String[] args) {
JFrame frame = new JFrame("Grid of circles");
frame.setLayout(new GridLayout(1,1));
frame.setSize(800, 800);
for(int x=0;x<XPlacements.length;x++) {
for(int y=0;y<YPlacements.length;y++) {
System.out.println("Creating new circle "+Circle_Count+" with position "+XPlacements[x]+","+YPlacements[y]);
Circles[Circle_Count] = new Circle();
Circles[Circle_Count].SetPosition(XPlacements[x],YPlacements[y]);
frame.add(Circles[Circle_Count]);
Circle_Count++;
}
}
frame.setVisible(true);
}
}
First of all this is a Swing application so custom painting should be done by overriding paintComponent() of a JPanel. A Canvas is an AWT component that should not be used in a Swing application.
If you want to draw on a component then the custom painting is always done relative to offset (0, 0). So in your case the code would be:
//g.fillOval(XPos, YPos, 15, 15);
g.fillOval(0, 0, 15, 15);
Then you need to override the getPreferredSize() method of your class to set the size of the component:
#Override
public Dimension getPreferredSize()
{
return new Dimension(15, 15);
}
Read the section from the Swing tutorial on Custom Painting for more informations and working examples.
Now the layout manager has information about the component and can position each component on the panel:
So the code to add the Circles to the frame would be something like:
frame.setLayout( new GridLayout(3, 3, 50, 50) );
for (int i = 0; i < 9; i++)
{
frame.add( new Circle() );
}
This will create a 3x3 grid with a gap of 50 pixels between each component.
Is there a Java-only way to show larger pictures in a JScrollPane? I don't want to reinvent the wheel and I'm already struggling at showing 32768x400 images using the ImageIcon in a JLabel trick because there seem to be limits regarding the ImageIcon that are platform dependent. Ubuntu 16.10 won't show any ImageIcon of the size 32768x400, though it shows smaller ones. Win10 shows them all.... and there is not even any error output of any sorts, which is terrible because I just wasted time searching for the problem.
So is there any easy solution to this that does not require me to reinvent the wheel?
In particular, I want to display waveforms, ie. an array of floats, so there is actually no need to have an overall image at all.
I believe this shows how to do what you want. Note how the Graph component has a width of 65535. This could be further optimized by only drawing the visible part of the graph as you scroll, but it's fairly fast as it is.
import java.awt.*;
import javax.swing.*;
import java.util.function.Function;
class Graph extends JComponent {
private Function<Double, Double> fun;
public Graph(Function<Double, Double> fun) {
this.fun = fun;
setPreferredSize(new Dimension(65535, 300));
}
public void paintComponent(Graphics g) {
// clear background
g.setColor(Color.white);
Rectangle bounds = getBounds();
int w = bounds.width;
int h = bounds.height;
g.fillRect(bounds.x, bounds.y, w, h);
// draw the graph
int prevx = 0;
int prevy = fun.apply((double)prevx).intValue();
g.setColor(Color.black);
for (int i=1; i<w; i++) {
int y = fun.apply((double)i).intValue();
g.drawLine(prevx, prevy, i, y);
prevx = i;
prevy = y;
}
}
}
public class Wf {
public static void main(String[] args) {
JFrame f = new JFrame();
// we're going to draw A sine wave for the width of the
// whole Graph component
Graph graph = new Graph(x -> Math.sin(x/(2*Math.PI))*100+200);
JScrollPane jsp = new JScrollPane(graph);
f.setContentPane(jsp);
f.setSize(800, 600);
f.setVisible(true);
}
}
In Java, I can write pixel data to an image that is then printed to the screen by overridden methods (paint and paintComponent). I can refresh the screen easily by updating the image and calling refresh(), which calls the paint/paintComponent cycle.
I'm wanting to do this in swift (3) with a UIImage. I can update the image, but I can't figure out how to repeatedly project the image onto the screen, print the screen, and repeat as I need to refresh the screen.
Firstly, what type of swift project (Single view app., Game, etc.) is best for repeatedly refreshing the screen?
And secondly how do I go about creating a (regulated) loop in Swift that refreshes the screen every so often?
In java this would look like (in a class that extends Frame):
static int width = 1440;
static int height = 900;
private BufferedImage canvas;
static Color[][] RGBMap = new Color[width][height];
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setBackground(Color.WHITE);
g2.clearRect(0, 0, width, height);
g2.drawImage(this.canvas, null, null);
paint();
}
public void paint() {
int i = 0;
while (i < width) {
int t = 0;
while (t < height) {
this.canvas.setRGB(i, t, RGBMap[i][t].getRGB());
t++;
}
i++;
}
//Refreshes RGBMap
iterate();
repaint();
}