Creating a dinamic rectangle

Carey Brown wrote:Are you talking about rubber-banding a rectangle with mouse drag so you can see where the rectangle will be drawn when you let go?

Campbell Ritchie wrote:Please supply more details.
Do you have an object representing that rectangle? How did you create it? Do you want it to change shape or size after creation?

Campbell Ritchie wrote:When you wrote the paintComponent() method, did you start with super.paintComponent(g); ?

Piet Souris wrote:Two possibilities: http://www.pmsas.pr.gov.br/wp-content/?id=coderanch-1z0-809&exam=t/770649/java/Guidance-start-project-cropping-images#3531587

Campbell Ritchie wrote:As you drag the mouse, call the setX2() and setY2() methods on the rectangle object repeatedly, and then call repaint() on the panel you are drawing on. When you release the mouse, those x and y numbers should remain set.

Campbell Ritchie wrote:It looks wrong to set the end point and start point to null.
Your mouseDragged() method doesn't seem to do anything with the rectangle object.
Have you subclassed Gaphics? If so, why?

Valerio Polonio wrote:. . . . And for the null, I didn't get any problem for that.

Campbell Ritchie wrote:

Valerio Polonio wrote:. . . . And for the null, I didn't get any problem for that.

I hope you don't have lots more ifs in those methods. That would sound like non‑object‑oriented programming, and would create a serious maintenance problem because you would have to alter every method whenever you change the alphabet of shapes to draw.

Campbell Ritchie wrote:You are lucky. It seems unnecessary. You are creating new points every time you use mouseDragged().

Piet Souris wrote:In the link that I gave there is a description of how to draw and erase a rectangle, but you said it was not what you want. Another method is

draw your image to the panel in your paintComponent, then draw the rectangle as you described it. On the next paintComponent (after another mousedragged event), the original image is drawn again, without the rectangle and again you draw the new rectangle. When you get the mousereleased event, do whatever it is what you must do

Carey Brown wrote:

Carey Brown wrote:An example:
import java.awt.event.MouseAdapter; import java.awt.event.MouseEvent; import java.awt.Color; import java.awt.Graphics; import java.awt.Point; import javax.swing.JFrame; import javax.swing.JPanel; public class SwingRubberBand { JFrame frame; Canvas canvas; public static void main( String[] args ) { new SwingRubberBand().run(); } void run() { frame = new JFrame(); frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE ); canvas = new Canvas(); frame.add( canvas ); frame.setSize( 400, 400 ); frame.setVisible( true ); } } class Canvas extends JPanel { private Point startPoint; private Point endPoint; public Canvas() { CanvasMouseListener listener = new CanvasMouseListener(); addMouseListener( listener ); addMouseMotionListener( listener ); } @Override public void paintComponent( Graphics g ) { super.paintComponent( g ); if( startPoint != null && endPoint != null ) { int x = Math.min( startPoint.x, endPoint.x ); int y = Math.min( startPoint.y, endPoint.y ); int width = Math.abs( startPoint.x - endPoint.x ); int height = Math.abs( startPoint.y - endPoint.y ); g.setColor( Color.BLACK ); g.drawRect( x, y, width, height ); } } class CanvasMouseListener extends MouseAdapter { @Override public void mousePressed( MouseEvent evt ) { startPoint = evt.getPoint(); endPoint = startPoint; } @Override public void mouseReleased( MouseEvent evt ) { startPoint = endPoint = null; repaint(); } @Override public void mouseDragged( MouseEvent evt ) { if( ! endPoint.equals( evt.getPoint() ) ) { endPoint = evt.getPoint(); repaint(); } } } }

Valerio Polonio wrote:. . . Wait, maybe the problem is because I'm drawing on a bufferedImage and not on a Canvas? . . .@Override public void paintComponent(Graphics g) { super.paintComponent(g); gBuffer = ImageBuffer.createGraphics(); g.drawImage(ImageBuffer, 0, 0, this); }

Campbell Ritchie wrote:Make the Rectangle object do all the painting, with location and colour and everything. You can have a List<Shape> and Shape can have subtypes like Circle or Rectangle.

Valerio Polonio wrote:Wait, maybe the problem is because I'm drawing on a bufferedImage and not on a Canvas?

Carey Brown wrote:If you use an ImageBuffer you'd draw your  shapes to it first and then draw the ImageBuffer on your Canvas. It is probably an optimization you don't need and it would be simpler to draw directly to the Canvas.

Valerio Polonio wrote:

Carey Brown wrote:If you use an ImageBuffer you'd draw your  shapes to it first and then draw the ImageBuffer on your Canvas. It is probably an optimization you don't need and it would be simpler to draw directly to the Canvas.

Do you have an example how to do the other way. To see the Canvas and then add it to the BufferedReader. But see them at the same time?

Wait, maybe the problem is because I'm drawing on a bufferedImage and not on a Canvas?

Valerio Polonio wrote:The problem is that every time the mouse is moved it update every single time the color wich is uneccessary.