Question

我想知道为什么repiant（）方法不再按预期工作...... Ex：

public class Main extends JPanel implements ActionListener, MouseListener,MouseMotionListener{

private ArrayList<Node> nodes;
private ArrayList<Edge> edges;
private boolean AddNode;
private int no_Of_Nodes;
private int width = 30, height = 30;


public static void main(String[] args){
    Main M = new Main();
    M.Start();
}

public void Start() {
    nodes = new ArrayList<Node>();
    edges = new ArrayList<Edge>();
    JFrame f = new JFrame("SFG");
    JPanel main_Panel = new JPanel(new BorderLayout());
    JPanel buttons = new JPanel();//Buttons Containser
    JPanel draw = new JPanel();
    ArrayList<JButton> bs = new ArrayList<JButton>();
    JButton b1 = new JButton("Add Node");
    b1.addActionListener(new Add_Node());
    JButton b2 = new JButton("Add Edge");
    b2.addActionListener(new Add_Edge());
    JButton b3 = new JButton("Add Arc");
    b3.addActionListener(new Add_Arc());
    JButton b4 = new JButton("Clear all");
    b4.addActionListener(new Clear());
    JButton b5 = new JButton("Solve");
    b5.addActionListener(new Solve());
    Bs.add(b1);
    Bs.add(b2);
    Bs.add(b3);
    Bs.add(b4);
    Bs.add(b5);
    for (int i = 0; i < bs.size(); i++) {
        Buttons.add(bs.get(i));
    }
    Buttons.setBackground(Color.GRAY);
    main_Panel.add(Buttons,BorderLayout.SOUTH);
    draw.setBackground(Color.darkGray);
    draw.addMouseMotionListener(this);
    draw.addMouseListener(this);
    main_Panel.add(Draw);
    main_Panel.setBackground(Color.GRAY);
    f.add(main_Panel);
    f.setSize(1024, 600);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
}

这些是方法

public void actionPerformed(ActionEvent arg0) {
    this.repaint();
}

public class Add_Node implements ActionListener{
    public void actionPerformed(ActionEvent e) {
        System.out.println("Add Node");
        addNode = true;
    }

}

现在，当我添加节点并调用重绘时，油漆区域中没有任何内容：

public void mouseClicked(MouseEvent arg0) {
    // TODO Auto-generated method stub
    if(addNode){
        addNode(arg0);
        addNode = !addNode;
    }
    System.out.println(nodes.size());
    this.repaint();
}

private void addNode(MouseEvent arg0) {
    // TODO Auto-generated method stub
    int x = arg0.getX();
    int y = arg0.getY();
    Node n = new Node(No_Of_Nodes++);
    n.setX_Pos(X);
    System.out.println(x + " " + y);
    n.setX_Pos(Y);
    nodes.add(n);
}

那是我的paint（）方法，它不再起作用了

        public void paint(Graphics g){
            super.paintComponents(g);
            FontMetrics f = g.getFontMetrics();
            int nodeHeight = Math.max(height, f.getHeight());
            System.out.println("In repaint");
        for (Node n : nodes) {
                System.out.println(n.getX_Pos() + " " + n.getY_Pos());
                int nodeWidth = Math.max(width, f.stringWidth(Integer.toString(n.getNode_ID()))+width/2);
                g.setColor(Color.white);
                g.fillOval(n.getX_Pos()-nodeWidth/2, n.getY_Pos()-nodeHeight/2, nodeWidth, nodeHeight);
                g.setColor(Color.black);
                g.drawOval(n.getY_Pos()-nodeWidth/2, n.getY_Pos()-nodeHeight/2, nodeWidth, nodeHeight);
                g.drawString(Integer.toString(n.getNode_ID()) , n.getX_Pos()-f.stringWidth(Integer.toString(n.getNode_ID()))/2, n.getY_Pos()+f.getHeight()/2);
            }
         }

TIA并抱歉长期提问：）

Answer 1

在Start方法中，您实际上从未将Main添加到JFrame。根据您提供的代码的上下文片段，我将“假设”您正在覆盖paint类的Main，这意味着，paint将永远不会被调用，因为它实际上没有附加到可显示的组件
Start不应该创建JFrame。您应该创建Main的实例，然后将其添加到JFrame的实例中，两者应该是分开的。应创建Main for Main并将其添加到paint本身
您不应该覆盖paint（作为一般规则），但是您应该通过调用其他paintComponents方法（例如paint）来躲避绘制过程。相反（再次“假设”你在Main中覆盖paintComponent），你应该覆盖super.paintComponent方法并在进行任何自定义绘画之前调用function myClickFunction(event:MouseEvent) { if (clown.visible){ clown.visible = false; elephant.visible = true; } }

请查看Performing Custom Painting和Painting in AWT and Swing了解详情。

此外，您可能希望阅读Code Conventions for the Java TM Programming Language，这样可以让人们更轻松地阅读您的代码并让您阅读其他代码

Java repaint（）无法正常工作

1 个答案: