Is there a common reason why the paint() method may be called twice without being intended. I have the following code:
public void paint(Graphics g)
{
//Graphics2D gg;
//gg=(Graphics2D) g;
drawMatrix(g);
}
private void drawMatrix(Graphics g) {
int side = 40;
hex hexagon=new hex();
for(int i = 0; i<9; i++)
for(int k = 0; k<9; k++){
g.setColor(Color.lightGray);
g.fill3DRect(i*side,k*side, side, side, true);
if (matrix[i][k]!=null){System.out.println("i is "+i+" k is "+k);
g.setColor(Color.black);hexagon.DrawHexfromMatrix(g, i, k, Color.black);}
}
}
hex is a class that extends polygon (to model a hexagon figure), and the DrawHexfromMatrix is a function that draws a hexagon from the index of the matrix that is drawn(put the hexagon in the slot of a matrix). I can provide the whole code if you think it helps, but for now i don't understand why the system.out.println is executed twice.( for example if[1][2] and [2][3] are not null it will print:
i is 1 k is 2
i is 2 k is 3
i is 1 k is 2
i is 2 k is 3
I think this also affects my drawing because sometimes although an element exists at [i][k] is isn't drawn.(matrix is a matrix of hex).
Later edit: Is it possible somehow that g.fill3DRect(i*side,k*side, side, side, true); to overpaint the hexagons i'm trying to paint with hexagon.DrawHexfromMatrix(g, i, k, Color.black);???
First of all, you should not paint directly to a JApplet.
You should define a JPanel that is added to the JApplet. You paint to the JPanel.
Second, you should use the paintComponent() method, and call the super class behavior, like this.
protected void paintComponent(Graphics g) {
// Paint the default look.
super.paintComponent(g);
// Your custom painting here.
g.drawImage(foregroundImage, x, y, this);
}
Third, you have no control over when Swing fires the paintComponent() method. You should do the calculations in some other method, and limit the code in paintComponent() to actual drawing methods.
Related
I'm pretty new to Java and the GUI world. Right now I'm trying to create a really basic space shooter. To create it I started creating a JFrame, in which I've later on put a personal extension of a JPanel called GamePanel, on which I'm now trying to display all my components. Until here it's all pretty clear, the problem comes now: I have my GamePanel in which I display my player, and on the KeyEvent of pressing S the player should shoot the Bullets. I've managed the bullets as an Array, called Shooter[], of Bullet Objects, created by myself this way:
public class Bullet implements ActionListener{
Timer Time = new Timer(20, this);
private int BulletY = 430;
public int PlayerX;
public Rectangle Bound = new Rectangle();
public Bullet(int playerx) {
this.PlayerX = playerx;
Time.start();
}
public void draw(Graphics g){
g.setColor(Color.RED);
g.fillRect(PlayerX + 2, BulletY, 3, 10);
g.dispose();
}
#Override
public void actionPerformed(ActionEvent e) {
if (Time.isRunning()) {
BulletY = BulletY - 5;
Bound = new Rectangle (PlayerX + 2, BulletY, 3, 10);
}
}
}
I thought that calling the draw method in the GamePanel's paint() method would have allowed me to display both all the bullets shot and the player. What actually happens is that at the start it seems allright, but when I press S the player disappears and just one bullet is shot. Can you explain me why? This is how my paint() method looks like:
public void paint(Graphics g) {
g.setColor(Color.BLACK);
g.fillRect(0, 0, 500, 500);
for(int i = 0; i < BulletsCounter; i++) {
Shooter[i].draw(g);
}
g.setColor(Color.RED);
g.fillRect(PlayerX, PlayerY, 20, 20);
//System.out.println("Here I should have painted the player...");
g.dispose();
}
BulletsCounter is a counter I've created to avoid any NullPointerExceptions in painting the whole array, it increases when S is pressed and so another bullet of the array is initialized and shot.
Thank you for your patience, I'm new to the site, so warn me for any mistake.
You've several significant problems, the biggest given first:
You're disposing a Graphics object given to you by the JVM. Never do this as this will break the painting chain. Instead, only dispose of a Graphics object that you yourself have created.
You're drawing within paint which is not good for several reasons, but especially bad for animation since you don't have automatic double buffering of the image
You don't call the super painting method within your override and thus don't allow the JPanel to do house-keeping painting.
Recommendations:
Don't dispose of the Graphics object, not unless you, yourself, create it, for example if you extract one from a BufferedImage.
Override the JPanel's paintComponent method, not its paint method to give you double buffering and smoother animation.
And call super.paintComponent(g) first thing in your override to allow for housekeeping painting
I am currently working on an animation to compare two stock exchange algorithms. I am running the algorithms within the paint component extending JComponent. (not the best, but I don't care) I need to have the screen refresh half way through the paint component. I do not want it to have to get all the way through before it up dates the screen. The reason being is I have one algorithm with a nested while loop and the other without. How would I go about doing this?
public void paintComponent(Graphics g) {
//calls in the super class and calls the calibrate the graphics method
super.paintComponent(g);
Graphics2D g2D = (Graphics2D) g;
calibrateFrame( getHeight(), getWidth() );
//Clears the rectangle to avoid overlaying, makes it black
g2D.clearRect(0, 0, getWidth(), getHeight());
g2D.setColor(Color.BLACK);
g2D.fillRect(0, 0, getWidth(), getHeight());
//Draws the rectangles without the algorithm started
redraw(g2D, -1);
/**
*algorithms
*/
fastSpans[0] = 1;
slowSpans[0] = 1;
//Makes a new stack pushes 0 on the stack
Stack myStack = new Stack();
myStack.push(0);
//If it has not been sorted or paused, continue the algorithm
if (!(pause) && !(sorted)){
//The slower algorithm needs to start out at zero (j)
int j = indexValue-1;
g2D.setColor(Color.BLUE);
//Calculates the values for the X and Y coordinates for the
//new rectangle, along with the height
int slowY = calSlowY(j);
int slowX = calSlowX(j);
int curHeightSlow = (int) ((stocks[j]/maxStockValue)*maxHeight);
//Here is the actual algorithm
int k = 1;
boolean span_end = false;
//Nested While Loop
while (((j-k)>0) && !span_end){
if (stocks[j-k] <= stocks[j]){
k = k + 1;
// Draw the current component
// **********************
// DO REFRESH MID PAINT COMPONENT
}
else{ span_end = true; }
}
slowSpans[j] = k;
g2D.setColor(Color.WHITE);
for(int i = 0; i < numberOfStock ; i++){
}
if (!(indexValue >= numberOfStock)){
while (!( myStack.empty()) && (stocks[(int)myStack.peek()]) <= stocks[indexValue]){
myStack.pop();
}
if (myStack.empty()){
fastSpans[indexValue] = indexValue + 1;
}
else {
fastSpans[indexValue]= indexValue - (int) myStack.peek();
//System.out.println("Im in the else");
}
myStack.push(indexValue);
}
}
drawStrings(g2D);
}
I am running the algorithms within the paint component extending JComponent. (not the best, but I don't care)
But you should care, since this impacts on your problem and possible solution.
I need to have the screen refresh half way through the paint component. I do not want it to have to get all the way through before it up dates the screen. The reason being is I have one algorithm with a nested while loop and the other without. How would I go about doing this?
Then don't run the algorithm through paintComponent. Instead use a SwingWorker<Void, Image>, update a BufferedImage and pass that image to the GUI through the worker's publish/process method pair, calling repaint() at the same time. For more on how to use a SwingWorker, please have a look at: Lesson: Concurrency in Swing
Don't understand what half way means.
If it means half of the component, then the simple way is to using two JComponent.
If u means in same component one line updated but another line not updated.
What I understand the repaint is calling when it packs(), updateUI(), or caused by invalidate().
So in my view, the repaint() should only care about paint these lines/2D, and in another thread to execute these loops/generate these data. Once the data collection is finished just call updateUI()/paintImmediately.
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
repaint();
}
});
I am trying to draw fish at whatever location the user enters, but it will either say
drawFish.java:38: error: cannot find symbol
outer.add(sPanel1);
Or
Exception in thread "main" java.lang.IllegalArgumentException: adding a window to a container
at java.awt.Container.checkNotAWindow(Container.java:483)
at java.awt.Container.addImpl(Container.java:1084)
at java.awt.Container.add(Container.java:410)
at drawFish.main(drawFish.java:38)
I was thinking that I need to make a new panel for each fish, but how do I make a loop to create multiple panels? If that is even the problem? Also, I am supposed to use a method that takes an x and a y coordinate so the user can change the location of a fish, and draw a number of fish at different locations. But that's not what I'm doing. I've tried to make a method including the questions of x and y, but then it says that the variables aren't public and thus can't be used in the paint method. I would appreciate explanations for everything, because I want to comprehend everything that I am doing.
public class drawFish extends JPanel {
int x = Integer.parseInt(JOptionPane.showInputDialog(null, "What is the x location of the fish? "));
int y = Integer.parseInt(JOptionPane.showInputDialog(null, "What is the y location of the fish? "));
int w = 200;
int h = 100;
int a = x + 20;
int b = y + 30;
int d = 50;
public drawFish() {
setPreferredSize(
new Dimension(400,400));
}
public void paint(Graphics g) {
g.setColor(Color.GREEN);
g.fillOval(x, y, w, h);
g.fillOval((w-5), y, d, h);
g.setColor(Color.BLACK);
g.fillOval(a, b, 25, 25);
}
public static void main(String[] args) {
MyFrame frame1 = new MyFrame("Drawing Fish");
JPanel outer = new JPanel();
int fn = Integer.parseInt(JOptionPane.showInputDialog(null, "How many fish would you like to draw? "));
for(int i=0; i<fn; i++){
drawFish sPanel1 = new drawFish();
}
outer.add(sPanel1);
frame1.add(outer);
frame1.pack();
frame1.setVisible(true);
}
}
Don't make many JPanels, just make one drawing JPanel.
Create a Fish class that is not a JPanel nor a component, but has a draw(Graphics g) method so that can draw itself at its current location when asked to.
Give your JPanel an ArrayList<Fish> and fill the list with Fish objects.
In your JPanel's paintComponent(Graphics g) method (not the paint method), loop through the ArrayList calling draw(g) on each Fish object it contains.
Be sure to call super.paintComponent(g) as the first line of your drawing JPanel's paintComponent(Graphics g) method so that old drawings will be erased.
Your for loop logic is off. If you're going to create objects inside of a for loop, you need to add them to something from inside of the loop. Else all you're dong is creating objects and discarding them, never to use them.
You will want to learn and stick with Java naming conventions. Class names, such as DrawFish, should start with an upper-case letter, and methods and variables with a lower-case letter.
sPanel1 variable's scope finishes as soon as you get out of loop.
Therefore replace
for(int i=0; i<fn; i++){
drawFish sPanel1 = new drawFish();
}
outer.add(sPanel1);
with
for(int i=0; i<fn; i++){
drawFish sPanel1 = new drawFish();
outer.add(sPanel1);
}
Now all panels will be added.
Also consider using a LayeredPane.
Hope this helps.
We've just learned how to create our own class, and this particular assignment we had to work with graphics. We had to draw a crayon, and then create a test program where there are 5 crayons lined up next to one another (so we just change the color and x,y of each one). I know how to change the color and x,y coords, but my question is...
how do I 'print' each crayon? Yes, it's an applet and yes I know I need a .html file. But what exactly goes in the test program in order for the crayon to show up when I run the .html file? I've run non-applets before in test programs using System.out.println, but never any graphics. Would it just be System.out.println(Crayon); ?
Also, how do I get multiple crayons? I'm assuming it's Crayon crayons = new Crayon;, and then the next one might be 'Crayon crayons2 = new Crayons;`? I'm not sure.
The x,y coordinates need to be modified w/each crayon, but the UML for the assignment told me not to make them instance variables but instead to put it in 'public void paint (Graphics g, int x, int y)'. What I have so far for the test program (may or may not be correct):
import javax.swing.JApplet;
import java.awt.*;
public class BoxOfCrayons extends JApplet {
Crayon first = new Crayon (Color.red, 50, 250)
Start by having a read through 2D Graphics.
Basically, you will need to create some kind of list of Cryons. This can either be a Collection or array, depending on what you know. I would personally use a ArrayList as it's flexible and easy to use, but doesn't suffer from the same constraints as an array.
Next, create you're self a custom component (ie BoxOfCryons) which extends from JPanel. Override this classes paintComponent method. Within this method, run through the list of Cryons and paint each one, incrementing the x offset by the width of the last Cryon.
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
int x = 0;
int y = 0;
for (Crayon crayon : cryons) {
crayon.paint(g2d, x, y);
x += crayon.getWidth();
}
g2d.dispose();
}
Create yourself a new class that extends from JApplet. In it's init method, set the applets layout manager to BorderLayout and add an instance of the BoxOfCryons class to it.
I'm trying to make a tower of hanoi solver which simply solves the hanoi without any mouse events. The problem is when I move the rectangle the original remains, even after I repaint. I've searched the net and tried changing the code around but nonthing worked. I am using a JFrame with a JPanel inside of it if that changes anything.
I have my disk class here which is just a rectangle with colour.
class Disk extends Rectangle {
Color diskColour;
public Disk(int a, int b, int c, int d, Color colour) {
x = a;
y = b;
width = c;
height = d;
diskColour = colour;
}
public Color getColour() {
return diskColour;
}
public void paintSquare(Graphics g) {
repaint();
g.setColor(diskColour);
g.fillRect(x, y, width, height);
repaint();
}
}
Here is my code where I actually call the paintSquare method:
public void simpleMoveDisk(Disk[] disks, int n, Graphics g) {
disks[n].setLocation(30,25);
disks[n].paintSquare(g);
repaint();
}
The paintSquare method paints the disk, while the setLocation method changes its coordinates.
When this runs the rectangle occurs in the new location, however the old one still remains. Any help is appreciated, thanks in advance.
You are calling repaint() in several places and you shouldn't be.
Have your the top level class that is doing the painting, call the paintSquare method and any other method that is needed. Those methods should not be calling repaint().
Also your simple move disk is really strange in the fact that it passes an array of Disks, an index, and a graphics object. Instead make it just take in a Disk. Just pass it the one out of the array that is needed to be updated. Then let whatever class that calls simpleMoveDisk, separately make a call to repaint instead of trying to paint and update the model in the same method.