java - Swing - 使用 JTextfield 输入创建 GridLayout

Question

我正在尝试创建一个Gridlayout。我使用两个参数 - m 和 n，它们取自 JTextField 组件。

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class GUI extends JFrame
{
public static final int HEIGHT = 75;
public static final int WIDTH = 450;

    JLabel m_label, n_label;
    JTextField m_enter,n_enter;
    JButton generate;
    int m,n;
    GUI g;

public void draw()
{
    m=Integer.parseInt(m_enter.getText());
    n=Integer.parseInt(n_enter.getText());
    new Chess();
}

GUI()
{

    setPreferredSize(new Dimension(WIDTH,HEIGHT));
    setLayout(new FlowLayout());
    setVisible(true);
    setLocationRelativeTo(null);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setResizable(false);

    m_label = new JLabel("M:");
    m_enter = new JTextField(5);
    n_label = new JLabel("N:");
    n_enter = new JTextField(5);

    generate = new JButton("Generate!");

    add(m_label);
    add(m_enter);

    add(n_label);
    add(n_enter);

    add(generate);
    pack();

    generate.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e)
        {
            draw();
        }
    });
}

public static void main(String[] args)
{
    new GUI();
}}    

国际象棋课

import javax.swing.*;
import java.awt.*;

class Chess extends JDialog
{
GUI g;
public static final int HEIGHT = 600;
public static final int WIDTH = 600;
int m,n;

Chess()
{
    setPreferredSize(new Dimension(WIDTH,HEIGHT));
    setVisible(true);
    setLayout(new GridLayout(m,n));
    pack();
}
}

它会产生以下错误:

Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: rows and cols cannot both be zero
at java.awt.GridLayout.<init>(GridLayout.java:195)
at java.awt.GridLayout.<init>(GridLayout.java:166)
at Chess.<init>(Chess.java:15)
at GUI.draw(GUI.java:23)
at GUI$1.actionPerformed(GUI.java:55)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6535)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6300)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4891)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2750)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.awt.EventQueue$4.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

进程已完成，退出代码为 0

Answer 1

您的问题是您从未设置 Chess 的 m 或 n 值。为 Chess 提供一个构造函数，允许外部类能够设置这些字段，然后将它们传入。

Chess(int m, int n) {
    this.m = m;
    this.n = n;
    //if statement to check if NULL or both set to zero
    //{
        //TODO:  Check to make sure no NULLs or Zero values
    //}
    setPreferredSize(new Dimension(WIDTH,HEIGHT));
    setVisible(true);
    setLayout(new GridLayout(m,n));
    pack();
}

主要经验教训:

• 编程中没有“魔法”。您的字段不会神奇地改变，如果您希望它们改变，程序员必须改变它们。
• 不要忽略您收到的异常堆栈跟踪消息，因为它包含可帮助您解决问题的有值(value)的信息，包括问题所在以及问题是什么 。
• 您的问题最初无法回答，因为您没有发布导致错误的关键代码(请参阅上面的观点)。请查看tour ，help以及how to ask good questions有关如何改进您 future 的问题并增加获得适当帮助的机会的更多信息。