修复JComboBox宽度

Question

我有一个JComboBox有一些选项.当我在另一个组件上做出选择时,我正在改变JComboBox的内容.首先我调用该removeAllItems()方法,然后逐个添加我现在需要的字符串.

问题是,默认情况下我有一些选项,其中一个是较大的文本,因此JComboBox获得了正确显示该选项所需的宽度.当我更改JComboBox内容时,该文本选项消失了,现在一个较小的文本给了JComboBox的宽度,所以当我更改内容时它会变小.

我的第一种方法是调用myComboBox.setPreferredSize(myComboBox.getSize()),然后它的尺寸是固定的,但不正确:它的高度和宽度略小一些.我认为这是因为我正在使用Nimbus Look&Feel,而我从该getSize()方法获得的维度是Java默认的Look%Feel给出的维度.

我也试过myCombo.setPreferredSize(new Dimension(myCombo.getHeight(), myCombo.getWidth()))了同样的结果.

我该如何处理这个问题？

我添加了一个代码示例,说明我如何使用布局:

    private String[] comboEventDOutputStrings = { "Run", "Stop", "Pause", "Conditioning time", "Deposition time", "Equilibration time", "Measurement time"};
    private String[] comboEventDInputStrings = { "Run", "Stop", "Pause"};
    // The first String array is the default set of values. It's obvious that the JComboBox will get smaller
    // when I change to the second array of contents

        //...   
            JPanel pane = new JPanel(new GridBagLayout());
            JPanel jPanelExterno = new JPanel(new GridBagLayout());
            GridBagConstraints cExterna = new GridBagConstraints();
            GridBagConstraints c = new GridBagConstraints();
            Border loweredetched = BorderFactory.createEtchedBorder(EtchedBorder.LOWERED);
            jPanelExterno.setBorder(loweredetched);
            jPanelExterno.setName("");

            cExterna.fill = GridBagConstraints.BOTH;
            cExterna.anchor = GridBagConstraints.NORTH;
            cExterna.gridx = 0;
            cExterna.gridy = 0;
            cExterna.insets = new Insets(10,10,5,5);

                JPanel jPanel1 = new JPanel(new GridBagLayout());
                jPanel1.setBorder(loweredetched);
                jPanel1.setName("PIO 1");

                jCheckBox1 = new JCheckBox("Enable");
                jCheckBox1.setSelected(false);
                jCheckBox1.setName("1");
                jCheckBox1.addActionListener(new PIOCheckListener());

                c.fill = GridBagConstraints.BOTH;
                c.anchor = GridBagConstraints.NORTH;
                c.gridx = 0;
                c.gridy = 0;
                c.insets = new Insets(10,5,10,10);
                jPanel1.add(jCheckBox1, c);

                c.gridy++;
                c.insets = new Insets(5,10,5,5);
                JLabel label1 = new JLabel("IO Type");
                jPanel1.add(label1, c);
                c.gridx++;
                c.insets = new Insets(5,5,5,10);

                combo1 = new JComboBox(comboIOTypeStrings);
                combo1.setEnabled(false);
                combo1.setSelectedIndex(0);
                combo1.setName("1");
                combo1.addActionListener (new PIOComboListener());
                jPanel1.add(combo1, c);

                c.gridy++;
                c.insets = new Insets(5,10,5,5);
                c.gridx=0;
                JLabel label2 = new JLabel("Active level");
                jPanel1.add(label2, c);
                c.gridx++;
                c.insets = new Insets(5,5,5,10);

                combo2 = new JComboBox(comboActiveLevelStrings);
                combo2.setEnabled(false);
                combo2.setSelectedIndex(0);
                jPanel1.add(combo2, c);

                c.gridy++;
                c.insets = new Insets(5,10,5,5);
                c.gridx=0;
                JLabel label3 = new JLabel("Event");
                jPanel1.add(label3, c);
                c.gridx++;
                c.insets = new Insets(5,5,10,10);

                combo3 = new JComboBox(comboEventDOutputStrings);
                combo3.setEnabled(false);
                combo3.setSelectedIndex(0);
                jPanel1.add(combo3, c);

                c.gridy++;
                c.insets = new Insets(5,10,5,5);
                c.gridx=0;
                JLabel label4 = new JLabel("Node");
                jPanel1.add(label4, c);
                c.gridx++;
                c.insets = new Insets(5,5,10,10);

                combo4 = new JComboBox(comboNodeStrings);
                combo4.setEnabled(false);
                combo4.setSelectedIndex(0);
                jPanel1.add(combo4, c);

            jPanelExterno.add(jPanel1, cExterna);

        pioDialog.add(pane);
        pioDialog.pack();
        pioDialog.setLocationRelativeTo(null);
        pioDialog.setVisible(true);
    //...
}   


    class PIOComboListener implements ActionListener{

        @Override
        public void actionPerformed(ActionEvent a) {
            JComboBox cb = (JComboBox)a.getSource();
            JComboBox target1 = null;
            JComboBox target2 = null;
            JComboBox target3 = null;
            switch(Integer.parseInt(cb.getName())){
                case 1:
                    target1 = combo2;
                    target2 = combo3;
                    target3 = combo4;
                    break;
                default:
                    Register.debug("PIODialog error: No target for comboBoxes");
                    break;
            }

            if(cb.getSelectedIndex()==2){ //Analog input
                target1.setEnabled(false);
                target2.setEnabled(false);
                target3.setEnabled(false);
            }
            else{
                target1.setEnabled(true);
                target2.setEnabled(true);
                target3.setEnabled(true);
                target2.removeAllItems();
                if(cb.getSelectedIndex()==0){
                    for(int i=0; i<comboEventDOutputStrings.length; i++)
                        target2.addItem(comboEventDOutputStrings[i]);
                } else {
                    for(int i=0; i<comboEventDInputStrings.length; i++)
                        target2.addItem(comboEventDInputStrings[i]);
                }
            }

        }
    }

它基本上是一个GridBagLayout,带有6个JPanel,每个都有一个新的GridBagLayout.我刚刚在这里写了jPanel1以简化操作.我希望它不是很乱.

Answer 1

最后我发现了一个简单的解决方

jComboBox1.setPrototypeDisplayValue("XXXXXXXXXXXXXXXXXX");

并且非常适合我想要的东西