Comments on: Example 5-4: Hold Down the Button

By: Anonymous

Anonymous — Thu, 05 May 2011 18:34:00 +0000

These are equivalent. if (button) is simple a shorter way of writing it. Since a boolean variable can only be “true” or “false” by definition, asking if it is equal to true is redundant.

By: Will Price

Will Price — Sat, 30 Apr 2011 22:03:00 +0000

For this bit ” if(button) ”
why does it not read “if(button == true)”

By: Anonymous

Anonymous — Fri, 11 Mar 2011 02:30:00 +0000

your second conditional needs to reference x1, not x. Also, you’ll want to use an if, else if, else structure, i.e.

if (button1) {
background(0,255,0);
} else if (button2) {
background(255,0,0);
} else {
background(0,0,255);
}

Object-oriented programming will really make this easier. See:

http://www.learningprocessing.com/exercises/chapter-9/exercise-9-8/

By: mhelke

mhelke — Wed, 09 Mar 2011 18:22:00 +0000

what if I want to have more than one of these rectangles?
I tried this but it doesn’t work…// Learning Processing
// Daniel Shiffman
// http://www.learningprocessing.com

// Example 5-4: Hold down the button
boolean button1 = false;

int x = 800;
int y = 230;
int w = 10;
int h = 10;

boolean button2 = false;
int x1 = 200;
int y1 = 230;
int w1 = 10;
int h1 = 10;

PImage b;
PImage c;
PImage d;
PImage e;

void setup() {
size(960,540);
noStroke();
}

void draw() {
// The button is pressed if (mouseX,mouseY) is inside the rectangle and mousePressed is true.
if (mouseX > x && mouseX y && mouseY x && mouseX y && mouseY < y1+h1 && mousePressed) {
button2 = true;
} else {
button2 = false;
}

if (button1) {
b = loadImage("first.gif");
background(b);
noStroke();
} else {
c = loadImage("second.gif");
background(c);

}

if (button2) {
d = loadImage("first.jpeg");
background(d);
noStroke();
} else {
e = loadImage("second.jpeg");
background(e);

}

fill(#e09554);
rect(x,y,w,h);
rect(x1,y1,w1,h1);
}

By: Patrick Mimran

Patrick Mimran — Tue, 02 Mar 2010 23:54:28 +0000

Thank you very much

Patrick

By: Daniel Shiffman

Daniel Shiffman — Tue, 02 Mar 2010 21:07:08 +0000

Yes, the default value of a boolean variable is false. So

boolean button = false;

and

boolean button;

are the same. However, it’s a good habit to always initialize your variables, just so that your code is more clear.

By: Patrick Mimran

Patrick Mimran — Tue, 02 Mar 2010 14:58:21 +0000

i would like to understand something please , if a boolean is anyway only t or false why do we have to specify
true or false when we declare the variable name in this example .
Or if flase is specified when variable is declared why shouldn’t we write only “button” instead of button = false when button false ?

Thank you

Patrick