Classes are one of the most important programming constructs of Java and many other languages. They are the abstract model or blueprint for an object. One could We can also see understand classes as extended data types. Unlike the primitive data types we have already looked at, classes define both variables and functions. Programmers call class variables attributes, and class functions are as methods, but otherwise they work much the same to the variables and functions we already know. But in order to get access to these attributes and methods we need to user dot syntax: a "." must be placed after the object name, followed by the name of the attribute or the method.
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BouncingBall ball1;
BouncingBall ball2;
PVector p1 = new PVector();
PVector p2 = new PVector();
boolean drag = false;
void setup()
{
size(800,600);
ball1 = new BouncingBall(100,100);
ball2 = new BouncingBall(50,50);
//
svg bild
soll zentriert sein
shapeMode(CENTER);
smooth();
}
void draw()
{
// hintergrund loeschen
//background(255);
// ghosting
fill(255,255,255,60);
rect(0,0,width,height);
if(drag)
{ // draw the zeichnedirection dieof abschussrichtungshoot
p1.set(ball1._pos.x,ball1._pos.y,0);
line(p1.x,p1.y,p2.x,p2.y);
}
// zeichnedraw denthe ballballs
ball1.draw();
ball2.draw();
}
void mousePressed()
{
drag = true;
p1.set(ball1._pos.x,ball1._pos.y,0);
p2.set(mouseX,mouseY,0);
}
void mouseDragged()
{
p2.set(mouseX,mouseY,0);
}
void mouseReleased()
{
drag = false;
// shooting abschussdirection staerkecalculation. berechnen
PVector dir = PVector.sub(p2,p1);
// shorten laengethe length verkuerzen
dir.mult(.09);
//the ball is dergiven balla wirdnew neudirection ausgerichtet
ball1.set(p1,dir,.993);
ball2.set(p1,dir,.95);
}
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class BouncingBall
{
PVector _pos;
PVector _dir;
float _dampV;
PShape _shape;
int _w;
int _h;
// constructor konstruktor
BouncingBall(int shapeWidth,int shapeHeight)
{
_pos = new PVector(width/2, height/2);
_dir = new PVector(0,0);
_dampV = 1;
_w = shapeWidth;
_h = shapeHeight;
_shape = loadShape("ball1.svg");
}
// setztset diethe neuenew posposition + richtungdirection + daempfungdampening
void set(PVector pos,PVector dir,float dampV)
{
_pos = pos.get();
_dir.add(dir);
_dampV = dampV;
}
// erneuertupdate diethe aktuellecurrent position
void calcPos()
{
// aktuellecurent position verschiebenshifted
_pos.add(_dir);
// bewegungsmovement vektorvector veraendertmodified
_dir.mult(_dampV);
// testetest horizontalhorisontal
if(_pos.x + _w/2 > width)
{
_dir.x *= -1;
_pos.x = width - _w/2;
}
else if(_pos.x - _w/2 < 0)
{
_dir.x *= -1;
_pos.x = _w/2;
}
// testetest vertikalvertical
if(_pos.y + _h/2 > height)
{
_dir.y *= -1;
_pos.y = height - _w/2;
}
else if(_pos.y - _h/2 < 0)
{
_dir.y *= -1;
_pos.y = _h/2;
}
}
// zeichnetdraw denthe ball
void draw()
{
calcPos();
shape(_shape,
_pos.x,_pos.y,
_w,_h);
}
}
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Download Example
Exercise 12 A
- Modify the program, so that several balls can be placed independently of each other
Exercise 12 B
- Extend the class again to make a third kind of ball. Modify its attributes and methods to create new kinds of behavior
Example BallKlasse Extended
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class BallEx extends BouncingBall
{
BallEx(int size)
{
super(size,size);
}
void draw()
{
super.draw();
line(0,0,_pos.x,_pos.y);
}
}
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Download Example
Exercise:
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