GridBagConstraints不将组件放置在书写坐标处

Question

请看下面的图片：

如您所见“添加程序”，“删除程序”，“添加新单元”和“删除单元”与之前的按钮重叠。

之前的按钮位于（0,9），所述按钮位于（0,10）。

以下是代码：

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

public class guiStyle extends JFrame
{       
    Container cp = getContentPane();

    public guiStyle()
    {
        super( "Student Study Planner 2014" );
        makeFrame2();

        pack();
        setVisible(true);
        setResizable(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }


    public void makeFrame2()
    {                                
        setPreferredSize( new Dimension ( 1000 , 600 ) );

        cp.setLayout( new GridBagLayout() );
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets ( 5 , 5 , 5 , 5 );

        JLabel lblProgram , lblUnit , lblDetails;        
        JList programList , unitList;
        JTextArea pl = new JTextArea("ProgramList" , 20 , 20);
        JTextArea ul = new JTextArea("UnitList" , 20 , 20);
        JScrollPane sp , sp2;


        JButton btnAddProgram , btnDelProgram;
        JButton btnAddUnit2Prog,btnDelUnitFromProgram;

        JButton btnAddUnit, btnDelUnit;
        JButton btnAddPrere,btnDelPrere;
        JButton btnAddCoreq,btnDelCoreq;

        lblProgram = new JLabel ( "Program" );   
        lblUnit = new JLabel ( "Unit" );

        programList = new JList();        

        unitList = new JList();        

        btnAddProgram = new JButton ( "Add Program" );
        btnDelProgram = new JButton ( "Delete Program" );
        btnAddUnit2Prog=new JButton ( "Add Unit To Program" );
        btnDelUnitFromProgram=new JButton("Delete Unit From Program");

        btnAddUnit = new JButton ("Add New Unit");
        btnDelUnit = new JButton ("Delete Unit");
        btnAddPrere = new JButton("Add Prerequisite");
        btnDelPrere = new JButton("Delete Prerequisite");
        btnAddCoreq = new JButton("Add Corequisite");
        btnDelCoreq = new JButton("Delete Corequisite");

        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.gridwidth = 2 ;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        cp.add ( lblProgram , gbc );

        gbc.gridx = 0;
        gbc.gridy = 2;
        gbc.gridwidth = 2;
        gbc.gridheight= 7;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.fill = GridBagConstraints.VERTICAL;
        cp.add ( pl , gbc );

        JPanel p1 = new JPanel();
        p1.add ( btnAddProgram );
        p1.add ( btnDelProgram );
        gbc.gridx = 0;
        gbc.gridy = 9;
        cp.add ( p1 , gbc );


        JPanel p2 = new JPanel();
        p2.add ( btnAddUnit2Prog );
        p2.add ( btnDelUnitFromProgram );
        gbc.gridx = 0;
        gbc.gridy = 10;
        cp.add ( p2 , gbc );


       //Unit
        gbc.gridx = 2;
        gbc.gridy = 0;
        gbc.gridwidth = 2 ;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        cp.add ( lblUnit , gbc );       

        gbc.gridx = 2;
        gbc.gridy = 2;
        gbc.gridwidth = 2;
        gbc.gridheight= 7;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.fill = GridBagConstraints.VERTICAL;
        cp.add ( ul , gbc );        

        JPanel p3 = new JPanel();
        p3.add ( btnAddUnit );
        p3.add ( btnDelUnit );
        gbc.gridx = 2;
        gbc.gridy = 9;
        cp.add ( p3 , gbc );

        JPanel p4 = new JPanel();
        p4.add ( btnAddPrere );
        p4.add ( btnDelPrere );
        gbc.gridx = 2;
        gbc.gridy = 10;
        cp.add ( p4 , gbc );

    }

}

导致这种错误显示的原因是什么？

Answer 1

基本上，面板使用您之前设置的属性，例如......

gbc.gridx = 0;
gbc.gridy = 2;
gbc.gridwidth = 2;
gbc.gridheight = 7;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.fill = GridBagConstraints.VERTICAL;
cp.add(pl, gbc);

JPanel p1 = new JPanel();
p1.add(btnAddProgram);
p1.add(btnDelProgram);
gbc.gridx = 0;
gbc.gridy = 9;
cp.add(p1, gbc);

您为fill设置了gridwidth，gridheight和pl属性，但仅为{{1}更改了gridx和gridy }}，这意味着它仍然使用相同的p1属性。\

如果您将gridheight属性重置为gridheight，则应该可以解决问题......

1

（我添加了颜色边框，所以我看到我在做什么）

另外，

JPanel p1 = new JPanel();
p1.setBorder(new LineBorder(Color.MAGENTA));
p1.add(btnAddProgram);
p1.add(btnDelProgram);
gbc.gridheight = 1;
gbc.gridx = 0;
gbc.gridy = 9;
cp.add(p1, gbc);

不会按照您的想法行事，您可能想要使用

gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.fill = GridBagConstraints.VERTICAL;

，而不是...