Learning OOP with Processing

Programming Questions

sgtoneill

in Programming Questions • 2 years ago

Hi everyone,

im trying to learn OOP and giving my first try with processing.

My goal is to make a falling image affected by gravity. However im trying to make it generic enough so i can make anything fall, be it an image or a video.

So i made:

a "Container" class that will receive an object

a "Image" class that will receive a directory and some other arguments

a "Video" class (yet to be implemented).

My problem is, i dont know how to send an Object to the Container class.

Im also getting token errors on all the arguments of the constructors of each class.

heres the code:

void setup(){
size(800,800);
background(0);
content = new Image("image.jpg", width/2, height/2, 400, 400);
block = new Container(content, width/2, height/2, tempW, tempH);
}
void draw(){
block.display();
}
class Container {
int containerPosX, containerPosY, containerW, containerH;
Object tempItem; (????????????????????)
Container(tempItem, tempPosX, tempPosY, tempW, tempH){
containerPosX = temPosX;
containerPosY = temPosY;
containerW = tempW;
containerH = tempH;
}
void display (){
Item.setPosX = containerPosX;
Item.setPosY = containerPosX;
Item.setW = containerW;
Item.setH = containerH;
}
}
class Image {
String dir;
int imagePosX, imagePosY, imageW, imageY;
Image(){
PImage img;
img = loadImage(dir);
}
void setPosX(tempPosX){
imagePosX = tempPosX;
}
void setPosY(tempPosY){
imagePosY = tempPosX;
}
void setW(tempW){
imageW = tempW;
}
void setH(tempH){
imageH = tempH;
}
}
/*
Class Video {
Video(){
}
void setPosX(){}
void setPosY(){}
void setW(){}
void setH(){}
}
*/

Maybe someone can shed a light on this :)

The gravity and other stuff isn't programmed yet, for not i'm just trying to display a video / image inside a container.

Thank you!

Replies(7)

PhiLho

Re: Learning OOP with Processing

2 years ago

Have you read the Processing tutorial on objects in the Learning section of the site?
I often see people asking how to "send" objects to classes, not sure where the concept of sending comes from.
In general, you don't declare an object with the Object type, you declare them with the exact class type.
Your constructor declaration is incorrect, you have to provide the types of the parameters in the declaration.
So, I don't know what is the type of the tempItem. I will suppose it can host either an image or a video. If so, you should have a common super-class to these two types, or, better, an common interface defining, for example, a method to display the item.
Then you create an instance of your item, and pass it as a parameter of the constructor. Well, as you did...

sgtoneill

Re: Learning OOP with Processing

2 years ago

There are some programming languages that let you declare a generic object type. This is not the case i guess.

I did read that tutorial but didn't manage to help me out, maybe because i really am new to this OOP concept :)

tempItem would be the image or video that the container class would receive. exactly as u said.

Trying not to abuse your help, could you sample some code of that last part you said?

" If so, you should have a common super-class to these two types, or, better, an common interface defining, for example, a method to display the item."

Im going to read the tutorial on OOP again. see if i missed something.

blindfish

Re: Learning OOP with Processing

2 years ago

Have a look at the Objects examples at: http://processing.org/learning/basics/ especially the one on Inheritance ;)

PhiLho

Re: Learning OOP with Processing

2 years ago

Well, Object is indeed a generic object type, but using it is seen as bad OOP practice, so since you are learning, it is better to learn good practice...

A quick sketch showing my idea:

interface DisplayableObject
{
void update(); // Takes a chance to update the object, eg. to go to the next video frame
void display(int x, int y, int w, int h);
}
class Image implements DisplayableObject
{
void update()
{
// Implementation here (can be empty)
}
void display(int x, int y, int w, int h)
{
// Implementation here
}
}
class Video implements DisplayableObject
{
void update()
{
// Implementation here
}
void display(int x, int y, int w, int h)
{
// Implementation here
}
}

class Container {
int containerPosX, containerPosY, containerW, containerH;
DisplayableObject itemToShow;
Container(DisplayableObject its, int posX, int posY, int w, int h) {
itemToShow = its;
containerPosX = posX;
containerPosY = posY;
containerW = w;
containerH = h;
}
void display () {
itemToShow.update();
itemToShow.display(containerPosX , containerPosY, containerW, containerH);
}
}

The interface guarantee we can use the defined methods, whatever the object implementing it, which can define its own internal methods too.

sgtoneill

Re: Learning OOP with Processing

2 years ago

Well i made it work... but im not sure I can do this again by myself in some other exercise.

But it worked!

Now, if i wanted to affect all the containers with gravity, should i make another object? whats the OOP thinking behind that?

Here's what i have working so far.

Image img;
Container c;
Container c1;
void setup(){
size(400,400);
img = new Image("image.jpg");
c = new Container (img, width/2, height/2, 100,100);
c1 = new Container (img, 0,0,100,100);
}
void draw(){
c.display();
c1.display();
}
class Container {
int containerPosX, containerPosY, containerW, containerH;
ListaObjectos content;
Container(ListaObjectos item, int posX, int posY, int w, int h) {
content = item;
containerPosX = posX;
containerPosY = posY;
containerW = w;
containerH = h;
}
void display () {
content.update();
content.display(containerPosX, containerPosY, containerW, containerH);
}
}
interface ListaObjectos
{
void display( int x, int y, int w, int h);
void update();
}
class Image implements ListaObjectos
{
int posX, poxY, imgW, imgH;
String directory;
PImage imagem;
Image(String dir){
imagem = loadImage(dir);
}
void display(int x, int y, int w, int h){
image(imagem, float(x),float(y),float(w/2),float(h/2));
}
void update(){
}
}

PhiLho

Re: Learning OOP with Processing

2 years ago

No, somehow, I first thought the Container wasn't needed, but then I thought it could be used to manage all the movements of the object it contains. So if you want to add gravity, this is the natural place to do it.

sgtoneill

Re: Learning OOP with Processing

2 years ago

Pretty cool, i think i managed to make it work :)

not sure if this is how you create gravity but its working, the image is falling and has a terminal velocity :)

Image img;
Container c;
void setup(){
size(700,700);
img = new Image("image.jpg");
c = new Container (img, (width/2)-25, 0, 100,100);
}
void draw(){
background(200);
c.display();
c.gravity();
}
void keyPressed() {
if(keyPressed) {
if (key == 'w' || key == 'W') {
c.moveUp(5);
}
if (key == 's' || key == 'S') {
c.moveDown(5);
}
if (key == 'a' || key == 'A') {
c.moveLeft(5);
}
if (key == 'd' || key == 'D') {
c.moveRight(5);
}
}
}
class Container {
int containerPosX, containerPosY, containerW, containerH;
float gravidade, velocidade;
ListaObjectos content;
Container(ListaObjectos item, int posX, int posY, int w, int h) {
content = item;
containerPosX = posX;
containerPosY = posY;
containerW = w;
containerH = h;
velocidade = 1.5; // VALOR DA VELOCIDADE INICIAL DO CONTAINER
gravidade = 1.02; // VALOR DA GRAVIDADE PARA O CONTAINTER
}
void display() {
content.update();
//DESENHA O CONTAINER
content.display(containerPosX, containerPosY, containerW, containerH);
}
void gravity(){
//GRAVIDADE APLICADA AO CONTAINER
if(velocidade <= 10){
velocidade = velocidade*gravidade;
}else{
velocidade = velocidade*1;
}
containerPosY += velocidade;
println("aceleraçao da gravidade: " + velocidade);
}
//CONTROLO BASICO DO CONTAINER
void moveUp(float speed){
containerPosY -= speed;
content.display(containerPosX, containerPosY, containerW, containerH);
}
void moveDown(float speed){
containerPosY += speed;
content.display(containerPosX, containerPosY, containerW, containerH);
}
void moveLeft(float speed){
containerPosX -= speed;
content.display(containerPosX, containerPosY, containerW, containerH);
}
void moveRight(float speed){
containerPosX += speed;
content.display(containerPosX, containerPosY, containerW, containerH);
}
}
interface ListaObjectos
{
void display( float x, float y, float w, float h);
void update();
}
class Image implements ListaObjectos
{
PImage imagem;
float posX, posY, imgW, imgH;
String directory;
Image(String dir){
imagem = loadImage(dir);
}
void display(float x, float y, float w, float h){
posX = x;
posY = y;
imgW = w;
imgH = h;
image(imagem, posX, posY, imgW/2, imgH/2);
}
void update(){
}
}

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