anyone used Canvas + graphics ?

[Naveen Sharma]

hi,
i m trying to draw a string at some random position on the screen
i have extended the Canvas class and overided the paint()
now say on some clicks i am generating a random x,y positions.. and drawing a string using drawString() of Graphics class
evrything works fine,
but i want the previously written string should be cleand up... and each time the text should is written at new x,y location, it should not messed up with previous written
i have called the repaint() of graphics class to repaint the text at new location... but as i donot find any update() in canvas class... how to achieve this
any ideas?
Thanks
Naveen

[Naveen Sharma]

I am surprised no one is having ANY idea about that

[Xiao Qinglai]

First you should stroe the (x, y) of your latest panited String; Whenever you are painting the nextString, repaint both area of oldString and newString.
like this:
repaint(xOfOldString, yOfOldString, widthOfOldString, heightOfOldString);
repaint(xOfNewString, yOfNewString, widthOfNewString, heightOfNewString);

[Naveen Sharma]

hi,
as Xiao Qinglai said use repaint(int,int,int,int) instead of repaint()..
i have written the following code, my aim is to make a toggle,
when we press key "3" it should write the string..
and when we press key "9" it should delete the string from canvas...
please tell me where things are wrong
Thanks
Navi
//------ Following is the code

package mycanvas;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class MyCanvas extends MIDlet implements CommandListener
{
  private Display display; 
  private CanvasArea ca;
  
  public MyCanvas() throws Exception {
   display = Display.getDisplay(this);
   ca = new CanvasArea(this);
  }
  public void startApp() {
   display.setCurrent(ca);
  }
  public void pauseApp()  { }
  
  public void destroyApp(boolean unconditional) { }
  public void commandAction(Command c, Displayable s)  { }
  public void destroyMe() {
  destroyApp(true);
  notifyDestroyed();    
  } 
}
class CanvasArea extends Canvas implements CommandListener
{
private Command cmdExit;
private MyCanvas midlet;
private String txt = "[+]"; //text to draw
private boolean toDraw = true;

private int _x = 50;
private int _y = 100;
public CanvasArea(MyCanvas midlet){
this.midlet = midlet;
cmdExit = new Command("Exit", Command.EXIT, 5);
addCommand(cmdExit);
setCommandListener(this);
}
public void paint(Graphics g){
g.setColor(255, 0, 0);  
if(toDraw)
g.drawString(txt,50,100, Graphics.TOP | Graphics.HCENTER);

}
protected void keyPressed(int keyCode){
if(keyCode == Canvas.KEY_NUM3){
System.out.println("Drawing...");
toDraw = true;
repaint(50,100,50,50);
}
else if(keyCode == Canvas.KEY_NUM9){
toDraw = false;
System.out.println("Clearing...");
repaint(50,100,50,50);
}
}
public void commandAction(Command c, Displayable d){

if(c == cmdExit)
midlet.destroyMe();
}
};
  

//--------Code ends here

[Xiao Qinglai]

plz pay attention to this method:
/************paint() of CanvasArea************/
public void paint(Graphics g){g.setColor(255, 0, 0); if(toDraw)g.drawString(txt,50,100, Graphics.TOP | Graphics.HCENTER);}
/*****************end**************************/
if toDraw is true, paint txt to screen;
if toDraw is false, do nothing --- instead, you should do this:
/*************start********/
Font f = g.getFont();
g.setColor(0x00FFFFFF);
g.fillRect(50, 100, f.stringWidth(txt), f.getHeight());
/********end**********/
good luck
Regards,
XQL