Java GridBagLayout和JPanel错误:无法添加到布局:约束必须为字符串(或为null) [英] Java GridBagLayout and JPanel Error: cannot add to layout: constraint must be a string (or null)

问题描述

我已经研究了此错误，但似乎找不到解决方法.我试图创建一个包含40列20行的800个JButton的网格.最终，它将用于控制我正在制作的多米诺骨牌设置机器人，该机器人将翻倒多米诺骨牌.我已经使用GridLayout成功创建了一个网格，但是由于项目的性质，我希望每隔一行用半个按钮偏移一次.我的意思是像设置计算机键盘上的键一样. (我会为我要解释的内容添加一张有用的图片，但是显然，在解释方面有麻烦的初学者无论如何都不允许添加图片.)

I have researched this error and I cannot seem to find a solution. I am trying to create a grid of 800 JButtons with 40 columns and 20 rows. This will eventually be used to control a domino setting up robot I am making that will tip over dominoes. I have already successfully created a grid using GridLayout, but due to the nature of the project, I would like every other row to be offset by half a button. By this I mean like how keys on a computer keyboard are set up. (I would have added a helpful picture of what I am trying to explain, but apparently beginners who have trouble explaining things aren't allowed to add pictures, whatever).

我尝试通过创建一个包含20个面板的JPanel数组(称为panel)来做到这一点.然后，将40个JButton添加到面板中.然后，我使用GridBagConstraints偏移每隔一行.我读到，您不应该混合使用awt和swing，这样可能是问题所在，但我不知道.这是代码，我是YouTube初学者，因此我从youtube教程中弄清楚了.如果我说的话没有道理，请原谅我.代码:

I try to do this by creating a JPanel array of 20 panels called panel. Then I add to the panel the 40 JButtons. Then I use GridBagConstraints to offset every other row. I read that you shouldn't mix awt and swing so that could be the problem, but i don't know. Here is the code, I figured this out from youtube tutorials as I am a very beginner. Forgive me if anything I have said does not make sense. Code:

import java.awt.GridLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
public class OffsetGrid {

    public static void main (String [] args){
        JFrame Frame = new JFrame();
        Frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        GridLayout grid= new GridLayout();


        GridBagConstraints gbca= new GridBagConstraints();
        GridBagConstraints gbcb= new GridBagConstraints();
        JPanel[] panel=new JPanel[20];


        for (int row=0;row<20; row++){
                panel[row]=new JPanel(new GridBagLayout()); 
                gbca.gridx=1;
                gbca.gridy=row;
                gbcb.gridx=0;
                gbcb.gridy=row;

        for (int y=0; y<40;y++){
                grid=new GridLayout(1,40);
                panel[row].setLayout(grid);
                JButton[] button = new JButton[40];
                button[y]=new JButton();
                button[y].setOpaque(true);
                panel[row].add(button[y]);

                }
            if (row%2==0){
                Frame.add(panel[row], gbcb);
            }
            else {
                Frame.add(panel[row], gbca);
            }

    }

        Frame.setVisible(true);
        Frame.setLocationRelativeTo(null);
        Frame.pack();
}
}

错误:

Exception in thread "main" java.lang.IllegalArgumentException: cannot add to layout: constraint must be a string (or null)
    at java.awt.BorderLayout.addLayoutComponent(BorderLayout.java:426)
    at javax.swing.JRootPane$1.addLayoutComponent(JRootPane.java:531)
    at java.awt.Container.addImpl(Container.java:1120)
    at java.awt.Container.add(Container.java:998)
    at javax.swing.JFrame.addImpl(JFrame.java:562)
    at java.awt.Container.add(Container.java:966)
    at OffsetGrid.main(OffsetGrid.java:38)

请帮助我找出问题并解决.谢谢

Please help me figure out the problem and get it working. Thanks

edit:我仍然对确切如何使用gridbagconstraints感到困惑，因此我什至不知道gridy和gridx是否适合在这里使用.或者即使我应该使用gridbagconstraints.请提供任何建议以完成工作.谢谢

edit: I am still confused on exactly how to use gridbagconstraints so I don't even know if gridy and gridx are even the right things to use here. Or even if i should use gridbagconstraints. Please offer any suggestions to get the job done. Thanks

这似乎起作用.

import java.awt.GridLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
public class OffsetGrid {

    public static void main (String [] args){
        JFrame Frame = new JFrame();
        Frame.setLayout(new GridBagLayout());
        Frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        GridLayout grid= new GridLayout();


        GridBagConstraints gbca= new GridBagConstraints();
        GridBagConstraints gbcb= new GridBagConstraints();
        JPanel[] panel=new JPanel[20];


        for (int row=0;row<20; row++){
                panel[row]=new JPanel(new GridBagLayout()); 
                gbca.insets=new Insets(0,100,0,0);
                gbca.gridy=row;
                gbcb.insets=new Insets(0,0,0,0);
                gbcb.gridy=row;

        for (int y=0; y<40;y++){
                grid=new GridLayout(1,40);
                panel[row].setLayout(grid);
                JButton[] button = new JButton[40];
                button[y]=new JButton();
                button[y].setOpaque(true);
                panel[row].add(button[y]);

                }
            if (row%2==0){
                Frame.add(panel[row], gbcb);
            }
            else {
                Frame.add(panel[row], gbca);
            }

    }

        Frame.setVisible(true);
        Frame.setLocationRelativeTo(null);
        Frame.pack();
}
}

推荐答案

您这样做:

Frame.add(panel[row], gbcb);

但是您忘记设置框架的布局:

But you forgot to set the frame's layout:

JFrame Frame = new JFrame();
Frame.setLayout(new GridBagLayout());

现在不会引发异常.但是……

Now the exception is not thrown. However......

我想知道这是否是您想要的:

I wonder if this is what you want:

在用户调整窗口大小的情况下，我对代码进行了一些更改.您仍然可以在修订版

I've made some change to my code in the case that user resize the window. You can still find the older code in revision

import static javax.swing.BorderFactory.createEmptyBorder;
import java.awt.GridLayout;
import java.awt.event.*;

import javax.swing.*;

public class OffsetGrid {
    public static final int ROWS = 10;
    public static final int COLUMNS = 10;

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setLayout(new GridLayout(ROWS, 1));
        final JPanel[] panel = new JPanel[ROWS];
        final JButton[][] button = new JButton[ROWS][COLUMNS];
        for (int row = 0; row < ROWS; row++) {
            panel[row] = new JPanel(new GridLayout(1, COLUMNS));
            for (int y = 0; y < COLUMNS; y++) {
                button[row][y] = new JButton(row + "-" + y);
                button[row][y].setOpaque(true);
                panel[row].add(button[row][y]);
            }
            int padding = button[row][0].getPreferredSize().width / 2;
            if (row % 2 == 0)
                panel[row].setBorder(createEmptyBorder(0, 0, 0, padding));
            else
                panel[row].setBorder(createEmptyBorder(0, padding, 0, 0));
            frame.add(panel[row]);
        }
        frame.addComponentListener(new ComponentAdapter() {
            @Override
            public void componentResized(ComponentEvent e) {
                for (int row = 0; row < ROWS; row++) {
                    int padding = button[row][0].getSize().width / 2;
                    panel[row].setBorder(createEmptyBorder(0, 0, 0, padding));
                    if (++row == ROWS)
                        break;
                    padding = button[row][0].getSize().width / 2;
                    panel[row].setBorder(createEmptyBorder(0, padding, 0, 0));
                }
            }
        });
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

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