java - 如何避免 Java Graphics2D 组件在最小化或弹出 Joptionpane 时被删除？

Question

我正在开发一个代表我的拼贴的 GRAPH 数据结构的 Java 类，现在当我使用 graphics2D 组件绘制图形时遇到问题。只是当我按下“添加顶点”按钮时，我在一个空间范围内随机地绘制图形的节点，所以我必须将绘图代码放在“添加顶点”按钮的操作上，这使我不使用 paintComponent() 或 paint() 方法，因此当我最小化或仅弹出 Joptionepane 时，我绘制的整个图形都会消失!

这是我的代码，注意:Graph、StackX 和 Queue 类实现是我在同一个包上实现的

package Graphs;

import javax.swing.JLayeredPane;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JRootPane;
import javax.swing.JTextField;
import javax.swing.JButton;
import javax.swing.border.TitledBorder;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;

import javax.swing.JScrollPane;

import DataStrucutres.Trees.BTNode;

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.util.Random;

 public class GraphGUI extends JPanel {
   private JPanel panel;

private JTextField vetxTxt;
private JButton vertxBtn;
private JTextField ed1Txt;
private JTextField ed2Txt;
private JButton edBtn;
private JPanel panel_1;
private JButton creatBtn;
private JScrollPane scrollPane;
static int j = 1;
static Graph myGraph;
private JButton btnDfs;
private JButton btnBfs;
boolean check;
int[] X = new int[10];
int[] Y = new int[10];
int w, h;
Graphics2D g;

/**
 * Create the panel.
 * 
 */

public GraphGUI() {
    setBackground(Color.DARK_GRAY);
    setLayout(null);


    panel_1 = new JPanel();
    panel_1.setBorder(new TitledBorder(null, "Controls",
            TitledBorder.LEADING, TitledBorder.TOP, null, new Color(48, 48,
                    48)));
    panel_1.setBounds(12, 117, 248, 188);
    add(panel_1);
    panel_1.setLayout(null);

    vetxTxt = new JTextField();
    vetxTxt.setEnabled(false);
    vetxTxt.setBounds(7, 23, 124, 31);
    panel_1.add(vetxTxt);
    vetxTxt.setColumns(10);

    vertxBtn = new JButton("Add Vertex");
    vertxBtn.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {

            try {

                check = true;
                String string = vetxTxt.getText().toUpperCase();
                char r = string.charAt(0);
                myGraph.addVertex(r);
                vetxTxt.setText(null);

                int x = (int) ((Math.random() * (700))  % 349 )+300;
                int y = (int) ((Math.random() * (780))  % 349);
                int width = (int) (Math.random() * (700 / 4));
                int height = (int) (Math.random() * (780 / 4));
                if (x + width > getWidth()) {
                    x = getWidth() - width;
                }
                if (y + height > getHeight()) {
                    y = getHeight() - height;
                }
                Color color = new Color((int) (Math.random() * 255),
                        (int) (Math.random() * 255),
                        (int) (Math.random() * 255));
                Graphics2D g = (Graphics2D) getGraphics();
                g.setColor(color);
                g.drawOval(x, y, 30, 30);
                g.drawString(r + "", x + 10, y + 18);

                X[h] = x;
                Y[w] = y;

                h++;
                w++;

                j++;

            } catch (ArrayIndexOutOfBoundsException e) {

                JOptionPane.showMessageDialog(null,
                        "Graph is full of vertexes", "ERORR",
                        JOptionPane.ERROR_MESSAGE);
                vetxTxt.setText(null);

            } catch (Exception ex) {

                JOptionPane.showMessageDialog(null, "Enter data pleas!",
                        "ERORR", JOptionPane.ERROR_MESSAGE);
                vetxTxt.setText(null);

            }

        }
    });
    vertxBtn.setEnabled(false);
    vertxBtn.setBounds(141, 24, 100, 29);
    panel_1.add(vertxBtn);

    ed1Txt = new JTextField();
    ed1Txt.setEnabled(false);
    ed1Txt.setBounds(7, 84, 50, 31);
    panel_1.add(ed1Txt);
    ed1Txt.setColumns(10);

    ed2Txt = new JTextField();
    ed2Txt.setEnabled(false);
    ed2Txt.setBounds(81, 84, 50, 31);
    panel_1.add(ed2Txt);
    ed2Txt.setColumns(10);

    edBtn = new JButton("Add Edge");
    edBtn.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {

            try {

                int m = Integer.parseInt(ed1Txt.getText());
                int v = Integer.parseInt(ed2Txt.getText());
                ed1Txt.setText(null);
                ed2Txt.setText(null);
                myGraph.addEdge(m, v);
                g.drawLine(X[m] + 8, Y[m] + 8, X[v] + 8, Y[v] + 8);

            } catch (Exception e) {
                JOptionPane.showMessageDialog(null,
                        "Entered edges is out of graph !", "ERORR",
                        JOptionPane.ERROR_MESSAGE);
            }

        }
    });
    edBtn.setEnabled(false);
    edBtn.setBounds(141, 85, 100, 29);
    panel_1.add(edBtn);

    btnBfs = new JButton("BFS");
    btnBfs.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            try {
                myGraph.bfs();
                JOptionPane.showMessageDialog(null,

                "BFS is : " + myGraph.getS());

            } catch (Exception e2) {
                JOptionPane.showMessageDialog(null,
                        "Graph is empty of vertexes", "ERORR",
                        JOptionPane.ERROR_MESSAGE);
                vetxTxt.setText(null);
            }
        }
    });
    btnBfs.setEnabled(false);
    btnBfs.setBounds(27, 139, 93, 29);
    panel_1.add(btnBfs);

    btnDfs = new JButton("DFS");
    btnDfs.setEnabled(false);
    btnDfs.setBounds(129, 139, 93, 29);
    panel_1.add(btnDfs);
    btnDfs.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            try {
                myGraph.dfs();
                Graphics2D g = (Graphics2D) getGraphics();

                JOptionPane.showMessageDialog(null,

                "DFS is : " + myGraph.getS());

            } catch (Exception e2) {
                JOptionPane.showMessageDialog(null,
                        "Graph is empty of vertexes", "ERORR",
                        JOptionPane.ERROR_MESSAGE);
                vetxTxt.setText(null);
            }
        }
    });

    creatBtn = new JButton("Creat Graph");
    creatBtn.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {

            g = (Graphics2D) getGraphics();
            myGraph = new Graph();
            vertxBtn.setEnabled(true);
            vetxTxt.setEnabled(true);
            ed1Txt.setEnabled(true);
            ed2Txt.setEnabled(true);
            edBtn.setEnabled(true);
            btnBfs.setEnabled(true);
            btnDfs.setEnabled(true);
            creatBtn.setVisible(false);

            JOptionPane
                    .showMessageDialog(
                            null,
                            "A graph is a structure consisting of a set of arrays (also called dimensions) and a set of edges . An edge is a pair of vertices . The two vertices are called the edge endpoints.",
                            "Graph", JOptionPane.PLAIN_MESSAGE);
        }
    });
    creatBtn.setBounds(6, 395, 125, 21);
    add(creatBtn);
}

}

Answer 1

so when i minimize or just the Joptionepane popped up , the entire graphics that i had drawn gone !

不要使用 getGraphics() 进行自定义绘画。正如您所注意到的，这幅画是暂时的。

so i have to put my drawing code on the action of add vertex button , that makes me not using paintComponent()

不，该操作应该调用自定义绘画面板上的方法来添加顶点。因此，您的类需要保留要绘制的顶点列表，然后 paintComponent() 方法中的自定义代码将迭代该列表并绘制所有顶点。

或者，另一个选项是在 BufferedImage 上绘制 Action 。然后，您可以在paintComponent() 方法中绘制BufferedImage(或者仅使用ImageIcon 将BufferedImage 添加到JLabel)。

参见Custom Painting Approaches有关使用 List 或 BufferedImage 进行自定义绘画的工作示例。