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Thread: Won't Draw??

  1. #1
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    Default Won't Draw??

    Hi, I'm having trouble trying to get my program to draw a rectangle when I click somewhere in the window. I really have no idea why it won't work, everything seems to be in place. Can someone please help?

    import java.applet.Applet;
    import java.awt.Color;
    import java.awt.Graphics;
    import java.awt.Paint;
    import java.awt.event.KeyEvent;
    import java.awt.event.KeyListener;
    import java.awt.event.MouseEvent;
    import java.awt.event.MouseListener;
     
    public class testing extends Applet implements KeyListener{
    	boolean drawRedBlock = false;
    	int x = 0;
    	int y = 0;
    		public void paint(Graphics g){
    			g.setColor(Color.white);
    			g.fillRect(0,0,500,500);
    			g.setColor(Color.black);
    			g.drawLine(0,0,500,0);
    			g.drawLine(500,500,500,0);
    			g.drawLine(500,500,0,500);
    			g.drawLine(0,500,0,0);
    			g.setColor(Color.red);
    			g.fillRect(125,125,125,125);
    		}
     
    		public void mouseClicked(MouseEvent e) {
    			drawRedBlock = true;
    			x=e.getX();
    			y=e.getY();
    			repaint();
    		}
    		public void drawRedBlock(Graphics g){
    			if(drawRedBlock=true)
    			{
    				g.setColor(Color.red);
    				g.fillRect(x, y, 125, 125);
    				repaint();
    			}
    		}
    		public void mouseEntered(MouseEvent arg0) {}
    		public void mouseExited(MouseEvent arg0) {}
    		public void mousePressed(MouseEvent arg0) {}
    		public void mouseReleased(MouseEvent arg0) {}
    		public void keyPressed(KeyEvent e) {}
    		public void keyReleased(KeyEvent e) {}
    		public void keyTyped(KeyEvent e) {}
    	}


  2. #2
    Super Moderator copeg's Avatar
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    Default Re: Won't Draw??

    You have the implementation to receive mouse and key events, but for them to work properly you also need to register the listener with a particular component, for example a JPanel.
    JPanel panel = new JPanel();
    panel.addMouseListener(this); //assuming this refers to an object that implements MouseListener
    or you can add the listener directly to an applet
    this.addMouseListener(this);
    Either of these should be done only once, such as in the init function of the applet

  3. #3
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    Default Re: Won't Draw??

    Sorry, I'm a beginner, I've inserted the registration of the MouseListener in the code yet it still has errors for some reason, under each parenthesis, any idea why?

    import java.applet.Applet;
    import java.awt.Color;
    import java.awt.Graphics;
    import java.awt.Paint;
    import java.awt.event.KeyEvent;
    import java.awt.event.KeyListener;
    import java.awt.event.MouseEvent;
    import java.awt.event.MouseListener;
     
    import javax.swing.JPanel;
     
    public class testing extends Applet implements MouseListener{
    	[B]this.addMouseListener(this);[/B]
    	boolean drawRedBlock = false;
    	int x = 0;
    	int y = 0;
    		public void paint(Graphics g){
    			g.setColor(Color.white);
    			g.fillRect(0,0,500,500);
    			g.setColor(Color.black);
    			g.drawLine(0,0,500,0);
    			g.drawLine(500,500,500,0);
    			g.drawLine(500,500,0,500);
    			g.drawLine(0,500,0,0);
    			g.setColor(Color.red);
    			g.fillRect(125,125,125,125);
    		}
     
    		public void mouseClicked(MouseEvent e) {
    			drawRedBlock = true;
    			x=e.getX();
    			y=e.getY();
    			repaint();
    		}
    		public void drawRedBlock(Graphics g){
    			if(drawRedBlock=true)
    			{
    				g.setColor(Color.red);
    				g.fillRect(x, y, 125, 125);
    				repaint();
    			}
    		}
    		public void mouseEntered(MouseEvent arg0) {}
    		public void mouseExited(MouseEvent arg0) {}
    		public void mousePressed(MouseEvent arg0) {}
    		public void mouseReleased(MouseEvent arg0) {}
    		public void keyPressed(KeyEvent e) {}
    		public void keyReleased(KeyEvent e) {}
    		public void keyTyped(KeyEvent e) {}
    	}
    So now it shows errors everywhere under each parenthesis and it seems like i didn't put it in the right place or something, yet I've tried putting it in several different places and none of them worked, even if they didn't show errors when I did.

  4. #4
    Super Moderator copeg's Avatar
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    Default Re: Won't Draw??

    As I alluded to above, applets have a method init() which is called once when a browser loads the applet. It should be overridden and any initial setup code, such as adding mouse listeners or setting up the gui, should be placed in the overridden init method. Fundamentally, you cannot reference 'this' outside of a non-static function

  5. #5
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    Default Re: Won't Draw??

    Ok, so something like this?

    import java.applet.Applet;
    import java.awt.Color;
    import java.awt.Graphics;
    import java.awt.Paint;
    import java.awt.event.KeyEvent;
    import java.awt.event.KeyListener;
    import java.awt.event.MouseEvent;
    import java.awt.event.MouseListener;
     
    import javax.swing.JPanel;
     
    public class Drawing extends Applet implements MouseListener{
    	[B]public void init() {
    		this.addMouseListener(this);
    		if(this.mouseClicked(this))
    		{
    			x=getX();
    			y=getY();
    			drawRedBlock = true;
    		}[/B]
    	}
    	private boolean mouseClicked(Drawing drawing) {
    		return false;
     
    	}
    	boolean drawRedBlock = false;
    	int x = 0;
    	int y = 0;
    		public void paint(Graphics g){
    			g.setColor(Color.white);
    			g.fillRect(0,0,500,500);
    			g.setColor(Color.black);
    			g.drawLine(0,0,500,0);
    			g.drawLine(500,500,500,0);
    			g.drawLine(500,500,0,500);
    			g.drawLine(0,500,0,0);
    			g.setColor(Color.red);
    			g.fillRect(125,125,125,125);
    		}
    		public void drawRedBlock(Graphics g){
    			if(drawRedBlock=true)
    			{
    				g.setColor(Color.red);
    				g.fillRect(x, y, 125, 125);
    				repaint();
    			}
    		}
    		public void mouseEntered(MouseEvent arg0) {}
    		public void mouseExited(MouseEvent arg0) {}
    		public void mousePressed(MouseEvent arg0) {}
    		public void mouseReleased(MouseEvent arg0) {}
    		public void keyPressed(KeyEvent e) {}
    		public void keyReleased(KeyEvent e) {}
    		public void keyTyped(KeyEvent e) {}
    		@Override
    		public void mouseClicked(MouseEvent e) {
    			// TODO Auto-generated method stub
     
    		}
    	}

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