java - 无法弄清楚在数组中使用循环

Question

在我的作业中，有一个术语，在两个节点之间，之前单击的节点应保留在屏幕上，并且应该有线条将每个节点与下一个节点连接起来(最后一个节点连接到第一个节点)。除了这些线(当然还有网格线)之外不应该有其他线。我尝试通过在数组内使用循环来做到这一点。但这不是我正在寻找的答案......

int [] a;
int [] b;
ArrayList<Point> points = new ArrayList<Point>();

class Point {
    int x, y, r;

    Point(int x, int y, int r) {
        this.x = x;
        this.y = y;
        this.r = r;
    }

    void Draw() {
        circle(this.x, this.y, this.r*2);
    }
}

int n_part=10;
void setup(){
    size(600,360);

    a = new int [100];
    b = new int [100];
}

void draw () {

    background (255);

    int gridW = width/n_part;
    int gridH = height/n_part;

    stroke(210);
    noFill();
    for (int row = 0; row < n_part; row++){ 
        int gridY = 0 + row*gridH;
        for (int col = 0; col < n_part; col++) {
            int gridX = 0+ col* gridW;
            rect (gridX, gridY, gridW, gridH);   
        }
    }

    stroke(0, 0, 0);
    fill(0);
    for (int i = 0; i < points.size(); ++ i) {
        Point p = points.get(i);
        p.Draw();
    }
}

void mousePressed() {
    int gridW = width/n_part;
    int gridH = height/n_part;

    int x = round(mouseX / (float)gridW) * gridW;
    int y = round(mouseY / (float)gridH) * gridH;

    points.add(new Point(x, y, 5));
    {
    for (int j=0; j < a.length; j++) 
        a [j] = (mouseX / (int)gridW) * gridW;
    for (int k=0; k < b.length; k++) 
        b [k] = height;
    }
}

void mouseReleased(){
    for (int k=0; k < a.length; k++) 
        line (0, 0, a [k], b [k]);
}

Answer 1

您所要做的就是在连续点之间画线。

点i的下一个索引是i+1。对于最后一个点，它是 0。这可以通过模 (%) 运算符 (h(i+1) %points.size()) 来实现。

获取循环中的 2 个连续点并在它们之间画一条线:

for (int i = 0; i < points.size(); ++ i) {
    Point p1 = points.get(i);
    Point p2 = points.get((i+1) % points.size());
    line(p1.x, p1.y, p2.x, p2.y);   
}

参见示例:

void draw () {

    background (255);

    int gridW = width/n_part;
    int gridH = height/n_part;

    strokeWeight(1);
    stroke(210);
    noFill();
    for (int row = 0; row < n_part; row++){ 
        int gridY = 0 + row*gridH;
        for (int col = 0; col < n_part; col++) {
            int gridX = 0+ col* gridW;
            rect (gridX, gridY, gridW, gridH);   
        }
    }

    stroke(0, 0, 0);
    fill(0);
    for (int i = 0; i < points.size(); ++ i) {
        Point p = points.get(i);
        p.Draw();
    }

    strokeWeight(3);
    stroke(255, 0, 0);
    for (int i = 0; i < points.size(); ++ i) {
        Point p1 = points.get(i);
        Point p2 = points.get((i+1) % points.size());
        line(p1.x, p1.y, p2.x, p2.y);   
    }
}