we have to implement the Dijkstra Algorithm. But at the beginning you have an empty field where you can click to create the nodes and edges between the nodes. In MousePressed we have implemented the nodes, but we dont know how we can connect two nodes with a line. Furthermore we dont really know how we can distinguish betwenn drawing a node or an edge in the funktion mousePressed.
Maybe there is someone who can help us!!
void setup() {
size(400,400);
}
void draw() {
}
void mouseClicked(){
// wenn Stelle noch nicht belegt
Node node= new Node();
// wenn an der Stelle ein Knoten ist
// -> Kante ziehen
}
static class Zaehler{
static int knotennummerzaehler = -1;
}
class Node extends Zaehler{
// number inside the node
int knotennummer;
// neuen Knoten erstellen
Node(){
hochzaehler();
fill(0);
ellipse(mouseX,mouseY,50,50);
fill(255);
textSize(20);
text(knotennummer,mouseX,mouseY);
}
void hochzaehler(){
// number increases
knotennummerzaehler ++;
knotennummer = knotennummerzaehler;
}
}
class Edge{
Edge(){
fill(0);
line(mouseX, mouseY,0,0);
}
}
When the mouse is clicked, look to see if it was clicked on a node.
If it wasn’t, that click creates a node.
If, however, the click WAS on an existing node, you’re starting to create an edge. When this occurs, you must wait for the next click to happen. If the next click is on a node, create an edge between those two nodes. If that next click is not on a node, however, then nothing happens.
You can also remove nodes and edges this way if you’re clever! If you click a node to start an edge, but then don’t click a second node, that can mean to remove the clicked node (don’t forget to remove all edges that connect to it too!).
Also, if you try to make an edge between two nodes that already have an edge, that can mean to remove that edge. Essentially it’s toggling edges between the clicked nodes, not just creating one.
Implementation of this is left as part of the exercise. Do post what you come up with - It’d be most helpful for others!
I would focus on creating the classes for the Nodes and Edges first. For instance the Node class needs to know its own position, an Edge would have 2 Node fields (for the start and the end) and a weighting (might be distance between start and end nodes).
Both the Node class and Edge class would have their own method to draw itself e.g. display()
Once you have the classes then create a small fixed network of nodes and edges and make sure they render OK
Then you can consider how to create the network dynamically with the mouse.
Finally create the path finding algorithm and test it.
Thank you guys for your answer!! @TfGuy44 can you describe how i can check if there is a node or not? My idea was to initialize a variable int noNodeexists = 0; and in mousePressed i check this with an if-clause.
So kinda like this…
@quark i understand your point. Every node needs to know where he is and every edge needs to know the beginning and ending… but i dont know how to start
I did it like this now. So the nodes are in the ArrayList. Probably not right but a beginning. But i didnt create the ArrayList inside the class Node, as you can see. Is it right?
In mouseClicked the Nodes will be added to the List.
import java.util.ArrayList;
void setup() {
size(600,600);
}
void draw() {
}
void mouseClicked(){
// loop over Array of nodes to check if there is another node
Node knoten = new Node(mouseX,mouseY);
// Adding node
NodeList.add(knoten);
// println(NodeList.size());
// println(NodeList.indexOf(knoten));
}
ArrayList<Node> NodeList = new ArrayList<Node>();
// class Node
public class Node extends Zaehler {
private float x;
private float y;
int knotennummer;
void draw(){
// display();
}
public Node(float x, float y){
hochzaehler();
this.x = x;
this.y = y;
display();
}
public void display(){
strokeWeight(2);
stroke(0); // black
fill(0);
ellipse(x, y, 60, 60);
fill(255);
textSize(20);
text(knotennummer,x,y); //number inside the node
}
void hochzaehler(){
knotennummerzaehler ++;
knotennummer = knotennummerzaehler;
}
}
static class Zaehler{
static int knotennummerzaehler = -1;
}
class Edge {
void display(){
//line();
}
Edge(){
fill(0);
line(mouseX, mouseY,0,0);
}
}
librakl didn’t have background(); at start of draw(), so it looked like it worked. Because the drawing in the constructor just stayed on the screen.
But quark is right of course: never drawing in the constructor.
I would argue the second statement (never process mouse input in the constructor) though, because when he wants to generate a new node on mouse input he needs the mouse position in the constructor (or at least pass the mouse position to the constructor).
