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drawImage not drawing at all, can't find the mistake

I'm new at Java and I'm trying to make a chess with it for training.
I'm having some trouble with the Graphic methods though.
I listed the functions which the mistake could have been in.
The code below shows a function called in main.
This function is inside my package that handle Graphic stuff.
public class GUI_main extends JComponent{
private final int tam = 100;
private final int tamTab = 8 * tam;
Image torre;
public void inicializaTabuleiro(Torre t)
{ //Sets the window properties and the "tile" proper image.
JFrame janela = new JFrame("Xadrez");
janela.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
janela.setSize(816, 839);
janela.getContentPane().add(new GUI_main());
janela.setLocationRelativeTo(null);
janela.setResizable(false);
janela.setVisible(true);
paintPeca(t); /*this one is the function that sets the correct image
for the tile that will be on the board*/
System.out.println("Janela inicializada com sucesso!");
}
...
next one is the "paintPeca" function, which should initialize "Image torre".
public void paintPeca(Torre t)
{
System.out.println(t.imgPeca());
torre = Toolkit.getDefaultToolkit().getImage(t.imgPeca());
}
and finally my paint function:
public void paint(Graphics g)
{
Graphics2D g2 = (Graphics2D) g;
g2.setPaint(Color.black);
int x = 0, y = 0;
while(y<tamTab) //draw board
{
if(y%200 == 0)
{
g2.draw(new Rectangle2D.Double(x, y, tam, tam));
x = x + tam;
g2.fill(new Rectangle2D.Double(x, y, tam, tam));
x = x + tam;
}
else
{
g2.fill(new Rectangle2D.Double(x, y, tam, tam));
x = x + tam;
g2.draw(new Rectangle2D.Double(x, y, tam, tam));
x = x + tam;
}
if(x == tamTab)
{
y = y + tam;
x = 0;
}
}
x = 14;
y = 19;
g2.drawImage(torre, x, y, this); //draw tower
g2.finalize();
...
Together these functions should have draw a board and a tower on it.
It's showing me the board, but not the tower (Image torre), and I do not have a clue on the reason.
"t.imgPeca()" returns a string (path to image), and it's correct, as I have tested before.
Since I'm new at Java this might be some kind of of silly mistake, but I have not found the answer in other pages of stack that talked about the drawImage function.

Restricting the drawing area on a JPanel and saving graphics states

The purpose of the black JPanel is drawing.
How can I restrict the drawing to the radius of the circle formed by the lines?
Is there a way to save the graphics object state so that more drawing can be added to it as well as adding an undo function?
public void paintComponent(Graphics g)
{
super.paintComponent(g);
sectors = 12;
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(Color.RED);
sector = new Line2D.Double(getWidth()/2, 0, getWidth()/2, getHeight());
//g2d.setClip(new Ellipse2D.Double(getWidth()/2,getHeight()/2, radius, radius));
//draws the sectors on the screen
for(int i=0; i<sectors; i++)
{
g2d.draw(sector);
g2d.rotate(Math.toRadians(30),getWidth()/2,getHeight()/2);
}
//draws the doily
if(dragging)
{
for(int i=0; i<sectors; i++)
{
g2d.fillOval((int) draw.getX(), (int) draw.getY(),20, 20);
g2d.rotate(Math.toRadians(30), getWidth()/2, getHeight()/2);
}
//saves the current drawing in a stack
graphics.push(g2d);
}
}

For your first question,
You would need to read up on Java's Custom Painting http://docs.oracle.com/javase/tutorial/uiswing/painting/
Not to discourage you but this is a tricky process,
To answer your question there is a similar post here
Java Change shape of JPanel

understanding difficulties java swing

im trying to paint random (not yet) circles on a JPanel through click on a JMenu.
Im using a JTextField (and have to keep this) for some output.
Here is my Class:
class RandomDrawer extends JPanel implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
//double x = Math.random();
//double y = Math.random();
Random generator = new Random();
int x = generator.nextInt(100)+1;
int y = generator.nextInt(100)+1;
//System.out.printf("x = %d y = %d\n", x, y);
status.setText(String.format("rnd draw x: %d y: %d", x, y));
Graphics2D gg = (Graphics2D) canvas.getGraphics();
gg.setColor(Color.BLACK);
gg.drawOval(50, 50, 50, 50);
}
}
As long i let the line
status.setText(String.format("rnd draw x: %d y: %d", x, y));
stay in there i get nothing drawn. Without it i get my circle, im not sure what the problem is. I cant figure out why nothing is drawn.
Thanks a lot
EDIT:
Hello, i tried to understand the given informations.
Sadly I have to draw using the Graphics2D class, so i guess i can not draw using shapes. So i tried this, sadly it wont draw yet, can u give me some tips?
I tried to create a new class DrawShape, my thought was that i could keep track with those objects.
In my understanding there should be a drawn oval right now
gg.drawOval(100,100,100,100);
Thank you.
class DrawShape {
public DrawShape(String string) {
// TODO Auto-generated constructor stub
}
}
class RandomDrawer extends JPanel implements ActionListener {
/* (non-Javadoc)
* #see java.awt.event.ActionListener#actionPerformed(java.awt.event.ActionEvent)
*/
private List<DrawShape> shapes = new ArrayList<DrawShape>();
public void addShape(DrawShape s) {
shapes.add(s);
repaint();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
final Graphics2D gg = (Graphics2D) g;
gg.setColor(Color.BLACK);
gg.drawOval(100, 100, 100, 100);
}
#Override
public void actionPerformed(ActionEvent e) {
Random generator = new Random();
int x = generator.nextInt(100)+100;
int y = generator.nextInt(100)+100;
if (e.getActionCommand()==("Draw RandomCircle")) {
System.out.printf("x = %d y = %d\n", x, y);
status.setText(String.format("rnd draw x:%d y:%d ", x, y));
DrawShape circle = new DrawShape("Circle");
addShape(circle);
int count = shapes.size();
System.out.printf("objects in array: %d\n", count);
}
else if (e.getActionCommand()==("Draw RandomRectangle")) {
System.out.printf("x = %d y = %d\n", x, y);
//status.setText(String.format("rnd draw x: y: "));
//Graphics2D gg = (Graphics2D) canvas.getGraphics();
//gg.setColor(Color.BLACK);
//gg.drawRect(x, y, generator.nextInt(x), generator.nextInt(y));
}
}
}

Painting and such happens event-driven. If a a piece of a component needs to be redrawn its paintComponent method is called.
This means you need a component that nows how to draw by for instance:
public class DrawShape {
public final String text;
public final Color color;
public final Shape shape;
public DrawShape(String text, Color color, Shape shape) {
this.text = text;
this.color = color;
this.shape = shape;
}
}
public class CanvasWithShapes extends JPanel {
private List<DrawShape> shapes = new ArrayList<>();
public void addShape(DrawShape shape) {
shapes.add(shape);
}
#Override
public void paintComponent(Graphics g) {
final Graphics2D gg = (Graphics2D) g;
// Java 8: shapes.stream().forEach((shape) -> gg.draw(shape));
for (DrawShape drawShape : shapes) {
gg.setColor(drawShape.color);
gg.draw(drawShape.shape);
Rectangle bounds = shape.getBounds();
gg.drawString(shape.text, bounds.x+ 10, bounds.y + 20);
}
}
}
And then just add shapes to be redrawn a bit later.
Shape oval = ...;
c.add(oval);
c.repaint(50L); // A bit later
More detailed
A Shape has many implementations of interest like rectangle and oval.
Graphics2D can draw and fill a Shape. So in your case it would be ideal to add such a Shape. Maybe together with color and text. So I took your DrawShape class to hold these properties.
Random generator = new Random();
int x = generator.nextInt(100)+100;
int y = generator.nextInt(100)+100;
if (e.getActionCommand().equals("Draw RandomCircle")) {
System.out.printf("x = %d y = %d\n", x, y);
status.setText(String.format("rnd draw x:%d y:%d ", x, y));
int w = generator.nextInt(100) + 10;
int h = w;
Shape circle = new Ellipse2D.Double(x, y, w, h);
addShape(new DrawShape(text, Color.BLACK, circle));
int count = shapes.size();
System.out.printf("objects in array: %d\n", count);
} else if (e.getActionCommand().equals("Draw RandomRectangle")) {
System.out.printf("x = %d y = %d\n", x, y);
generator.nextInt(y));
int w = generator.nextInt(100) + 10;
int h = generator.nextInt(100) + 10;
Shape rect = Rectangle2D.Double(x, y, w, h)
addShape(new DrawShape(text, Color.BLACK, rect));
}

Graphics2D gg = (Graphics2D) canvas.getGraphics();
Don't use the getGraphics() method to do painting. The painting is temporary. It will be lost if you resize the frame for example.
Instead you need to override the paintComponent() method of your panel.
If you want to paint multiple objects then you need to keep track of each object. Check out Custom Painting Approaches for the two common ways to do this:
keep of List of Objects to paint and then iterate through the List each time the component is repainted.
paint the Object directly to a BufferedImage and then just paint the BufferedImage.
The example paints Rectangles. Basically you need a method like the addRectangle(...) method to add a new object to paint. So every time you click your button you add the new random shape.

Presumably, your problem arises from the setText() invocation modifying the Graphics object in some unexpected way. It is rarely appropriate to use getGraphics() in your own code. Instead, paint with the Graphics that is given to you.
Your approach is anyway flawed. If you manage to draw on a GUI component only once, as you are trying to do, then whatever you have drawn will disappear when the component is next repainted. Repainting can happen for a wide variety of reasons, many of them unrelated to the program's own behavior.
What you need to do is store some kind of data that the component's paintComponent() method will rely upon to do your custom painting every time. It follows that you will need to override the paintComponent() method of the component on which you want the circles to be drawn. For example, you might create a class that records all the needed drawing details for one circle, and give RandomDrawer a List of those objects as a member variable. The action listener manipulates that list appropriately and schedules a repainting, and paintComponent() is overridden to perform the actual painting.

Drawing a shape but keeping the most previous shape on screen in java

I've created a function to where I can click somewhere in a Jpanel and it draws a shape at the position where the mouse clicked. The problem I am having is when I click in a new position, it moves the shape and redraws it. I would like the previous shape to "Burn" into the screen and stay there. It doesn't have to have any data tied to it, I just want the image of the shape to show where it used to be each time. I have tried many different things, but no success. here is what I mean:
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.BLUE);
g2.fillRect(n, m, 32, 32); //I want each one of these shapes to be new, not
//moving, but redrawn
////////////////////////////////////////////////
//This is just drawing a grid and doing other things(irrelevant)
g2.fill(new Ellipse2D.Double(x, y, 32, 32));
for (int i = 0; i < 500; i += 32) {
g2.drawRect(i, j, 32, 32);
for (int j = 0; j < 500; j += 32) {
g2.drawRect(i, j, 32, 32);
}
}
if (paintColBlock){
System.out.println("Drawing Block at " + n +"," + m);
paintColBlock = false;
}
/////////////////////////////////////////////////////////////////////
}

Keep an ArrayList of Points like this:
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.BLUE);
for(Point p : points)
g2.fillRect(p.x, p.y, 32, 32);
Adding a new Point to the array at each mouse click, and call repaint():
public void mousePressed(MouseEvent evt){
points.add(new Point(evt.getX(),evt.getY());
repaint();
}

Java Draw Line based on doubles (sub-pixel precision)

I am making a basic Java program and I would like to draw a line using basic swing Graphics.drawLine.
Is there a way to make the two points in terms of doubles so I can make the output more accurate, or another way that is better?

You can draw the lines using ((Graphics2D) g).draw(Shape) and pass it a Line2D.Double.
Here's a demo:
import javax.swing.*;
public class FrameTestBase extends JFrame {
public static void main(String args[]) {
FrameTestBase t = new FrameTestBase();
t.add(new JComponent() {
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
for (int i = 0; i < 50; i++) {
double delta = i / 10.0;
double y = 5 + 5*i;
Shape l = new Line2D.Double(5, y, 200, y + delta);
g2.draw(l);
}
}
});
t.setDefaultCloseOperation(EXIT_ON_CLOSE);
t.setSize(400, 400);
t.setVisible(true);
}
}
You might also want to try adding
g2.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL,
RenderingHints.VALUE_STROKE_PURE)

If you have a refernce to g, which I assume is Graphics object, you should use Java 2D APIs
Graphics2D g2 = (Graphics2D) g;
g2.draw(new Line2D.Double(x1, y1, x2, y2));
Javadocs for:
Line2D
Graphics2D