How to add/remove a shape with a key press in Processing? - processing

Question

I want to add/remove an ellipse using a press of a button in Processing. I use void keyPressed() and void keyReleased() for the keys. But how can I use if statements to add/remove an ellipse?
Now that i can add more , and remove some ellipses. For example, if i have one i can press a button then have one more. Or press a button to remove one. But now I would like to move those ellipses (max 4) using different key sets for each of them. How can i do that?

Answer 1

What you need to do is have a boolean to be read whenever the ellipse is to be drawn. If that is true draw it, if it not don't! THe keypress should just switch that boolean. Like this:
boolean iShouldDrawTheEllipse = true;
void draw() {
background(0);
if(iShouldDrawTheEllipse) ellipse(50,50,10,10);
}
void keyPressed() {
iShouldDrawTheEllipse = !iShouldDrawTheEllipse;
}

Answer 2

You can use some booleans to determinate which ellipse you have to print and which not.
E.G.
void keyPressed(){
switch(keyCode){
case 'z':
drawingFirstEllipse = !drawingFirstEllipse;
break;
case 'x':
drawingSecondEllipse = !drawingSecondEllipse;
break;
case 'c':
drawingThirdEllipse = !drawingThirdEllipse;
break;
case 'v':
drawingFourthEllipse = !drawingFourthEllipse;
break;
}
}
Then in your void draw(void) method you can easily draw the ellipses:
void draw(){
background(0);
if(drawingFirstEllipse) ellipse(50, 50, 10, 10);
if(drawingSecondEllipse) ellipse(50, 50, 70, 10);
if(drawingThirdEllipse) ellipse(50, 50, 130, 10);
if(drawingFourthEllipse) ellipse(50, 50, 190, 10);
}
I hope I helped [;