Question

当且仅当两个节点之间存在边缘时，我试图从每个节点图形对象到另一个节点图形对象绘制一条线。

我的图是在二维布尔邻接矩阵中实现的。

我该如何实现？

这是我到目前为止所做的：

// Draw method which will draw the shape of the graph.
    public void paint(Graphics g) {

        //Define parameters to draw the graph in. Example taken from
        //http://www.zetcode.com/gfx/java2d/basicdrawing/
        Dimension size = getSize();
        Insets insets = getInsets();

        int w = size.width - insets.left - insets.right;
        int h = size.height - insets.top - insets.bottom;

        //Parameters for vertices, to be used later to draw vertices.
        int x = 0;
        int y = 0;

        // Extend to Graphics 2D
        Graphics2D graph = (Graphics2D) g;

        // Set preferences. This cleans up edges.
        graph.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);

        //Generate vertices as random points on JPanel.
        Random r = new Random();

        //Draw random points on JPanel for the vertices.
        for (int l = 0; l < adj_Matrix_Edges.length; l++){
            String str = Integer.toHexString(l);
            //Define where a specific vertex will fall on a x, y coordinate
            //inside the container.
            x = Math.abs(r.nextInt()) % w;
            y = Math.abs(r.nextInt()) % h;
            //Initialize a node graphics object to represent vertices.
            Graphics2D node = (Graphics2D)g;
            node.fillOval(x, y, 7, 7); //Creates filled ovals for nodes.
            graph.drawString(str, x, y + 20);
        }

            //Create a nexted for loop to see if there is an edge between vertices.
        for (int m = 0; m < adj_Matrix_Edges.length; m++){
            for (int n = 0; m < adj_Matrix_Edges[m].length; m++){
                if (adj_Matrix_Edges[m][n]){
                    graph.drawLine(node, y1, x2, y2);
                }
            }
        }

    }
}

Answer 1

正如MadProgrammer已经提到的，继承自JComponent的类中的绘制过程通常在paintComponent方法中完成：

@Override
protected void paintComponent(Graphics gr)
{
    super.paintComponent(gr);
    Graphics2D g = (Graphics2D)g;

    // Your drawing stuff goes here....
}

但是关于实际问题：我假设您想要绘制图形（或更准确地说：节点链接图）。这项任务有许多很复杂的库。除了最简单的应用程序之外，我强烈建议使用这样的库，因为手动执行此操作可能会变得相当棘手。

但是，目前的主要问题是每次重新绘制组件时都会创建新的随机点！我想知道这是什么样的。调整组件大小时，您应该会看到奇怪的闪烁点。

你必须以某种方式存储点（它们的坐标），以便稍后在这些点之间绘制线条。

只需对代码进行少量修改即可实现此目的：

//Generate vertices as random points on JPanel. // Pass "0" as the argument to the constructor of Random, so that it // will always create the same sequence of random numbers Random r = new Random(0); // Create lists that will store the point coordinates List<Integer> pointsX = new ArrayList<Integer>(); List<Integer> pointsY = new ArrayList<Integer>(); for (int l = 0; l < adj_Matrix_Edges.length; l++){ String str = Integer.toHexString(l); //Define where a specific vertex will fall on a x, y coordinate //inside the container. x = Math.abs(r.nextInt()) % w; y = Math.abs(r.nextInt()) % h; // Store the coordinates of the points: pointsX.add(x); pointsY.add(y); //Initialize a node graphics object to represent vertices. Graphics2D node = (Graphics2D)g; node.fillOval(x, y, 7, 7); //Creates filled ovals for nodes. graph.drawString(str, x, y + 20); } //Create a nexted for loop to see if there is an edge between vertices. for (int m = 0; m < adj_Matrix_Edges.length; m++){ for (int n = 0; m < adj_Matrix_Edges[m].length; m++){ if (adj_Matrix_Edges[m][n]){ // Fetch the coordinates of the points from the list int xm = pointsX.get(m); int ym = pointsY.get(m); int xn = pointsX.get(n); int yn = pointsY.get(n); graph.drawLine(xm,ym,xn,yn); } } }

但我不建议这样做。这只是一个快速的黑客，以显示如何通过对代码的最小修改来实现这一目标。通常，绘制时应 NOT 构建任何数据结构。绘画代码应尽可能简短。

相反，您应该在初始化邻接矩阵时创建表示节点的数据结构。你至少可以创建一些像
这样的类
class Node { String name; // Coordinates, between 0 and 1 double x; double y; }

在声明和初始化adj_Matrix_Edges的地方，您还可以创建一个节点列表，如下所示：

boolean adj_Matrix_Edges[][]; List<Node> nodes; void initializeMatrix() { adj_Matrix_Edges = ...; // Create the nodes Random random = new Random(0); nodes= new ArrayList<Node>(); for (int m = 0; m < adj_Matrix_Edges.length; m++) { Node node= new Node(); node.name = Integer.toHexString(m); node.x = random.nextDouble(); node.y = random.nextDouble(); nodes.add(node); } }

稍后，当您进行绘制时，您可以访问这些节点并直接绘制它们：

@Override protected void paintComponent(Graphics gr) { super.paintComponent(gr); Graphics2D g = (Graphics2D)g; for (int l = 0; l < adj_Matrix_Edges.length; l++){ // Compute the x- and y-coordinates that the // node will have in this component. (That's // why the coordinates that are stored in // the "Node" class should always be // between 0 and 1!) Node node = nodes.get(l); int ix = (int)(node.x * getWidth()); int iy = (int)(node.y * getHeight()); g.fillOval(ix, iy, 7, 7); graph.drawString(node.name, ix, iy + 20); } //Create a nested for loop to see if there is an edge between vertices. for (int m = 0; m < adj_Matrix_Edges.length; m++){ for (int n = 0; m < adj_Matrix_Edges[m].length; m++){ if (adj_Matrix_Edges[m][n]){ Node nodeM = nodes.get(m); Node nodeN = nodes.get(n); int xm = (int)(nodeM.x * getWidth()); int ym = (int)(nodeM.y * getHeight()); int xn = (int)(nodeN.x * getWidth()); int yn = (int)(nodeN.y * getHeight()); graph.drawLine(xm,ym,xn,yn); } } } }

通常，你也会有一个 edge 的表示，它类似于我在上面概述的Node类，但是你正在慢慢接近那些证明使用a的合理性。像JUNG http://jung.sourceforge.net/或JGraphX https://github.com/jgraph/jgraphx这样的图书馆（那里有很多图库，这些图库可能是最受欢迎的图库之一，但这里只应作为例子）

如何使用Graphics Class从顶点到顶点绘制一条线？

1 个答案: