使用 CardLayout 切换面板后不出现 JTextField

如何解决使用 CardLayout 切换面板后不出现 JTextField

我有 4 个面板与使用卡片布局的内容面板相关联。如果我尝试使用按钮在卡片之间切换，我可以看到 JLabels 但看不到 JTextFields。我认为它们在那里是因为 JLabels 之间有空间，所以我尝试在切换到面板后重新验证和重新绘制面板，但这不起作用。我必须在其他地方重新粉刷它们吗？还是我遗漏了什么？

package data;

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

public class Frame {

    JFrame frame;
    JPanel panelCont,panelStart,panelAns,panelGT,panelSyn;
    JButton buttonAns,buttonGT,buttonSyn,buttonSendAns,buttonSendGT,buttonSendSyn;

    JTextField jtfAnsCaseID,jtfAnsKeywords,jtfAnsAnswer;
    JLabel jlAnsCaseID,jlAnsKeywords,jlAnsAnswer;
    JTextField jtfGTID,jtfGTGenericTerm;
    JLabel jlGTID,jlGTGenericTerm;
    JTextField jtfSynSynonym,jtfSynID;
    JLabel jlSynSynonym,jlSynID;

    cardlayout cl;

    Frame() {
        frame = new JFrame("naoImporter");
        panelCont = new JPanel();
        cl = new cardlayout();
        panelCont.setLayout(cl);

        //Initialize components for start
        panelStart = new JPanel();
        buttonAns = new JButton("Answer");
        buttonGT = new JButton("Generic terms");
        buttonSyn = new JButton("Synonyms");

        //Initialize components for answers
        panelAns = new JPanel();
        jlAnsCaseID = new JLabel("CaseID:");
        jtfAnsCaseID = new JTextField();
        jlAnsKeywords = new JLabel("Keywords:");
        jtfAnsKeywords = new JTextField();
        jlAnsAnswer = new JLabel("Answer:");
        jtfAnsAnswer = new JTextField();
        buttonSendAns = new JButton("Send Data!");

        //Initialize components for generic terms
        panelGT = new JPanel();
        jlGTID = new JLabel("ID");
        jtfGTID = new JTextField();
        jlGTGenericTerm = new JLabel("Generic term:");
        jtfGTGenericTerm = new JTextField();
        buttonSendGT = new JButton("Send Data!");

        //Initialize components for synonyms
        panelSyn = new JPanel();
        jlSynSynonym = new JLabel("Synonym:");
        jtfSynSynonym = new JTextField();
        jlSynID = new JLabel("ID:");
        jtfSynID = new JTextField();
        buttonSendSyn = new JButton("Send Data!");

        //Configuring each component
        panelStart.setLayout(new FlowLayout());
        panelAns.setLayout(new FlowLayout());
        panelGT.setLayout(new FlowLayout());
        panelSyn.setLayout(new FlowLayout());

        jtfAnsCaseID.setPreferredSize(new Dimension(30,jtfAnsCaseID.getHeight()));
        jtfAnsKeywords.setPreferredSize(new Dimension(200,jtfAnsKeywords.getHeight()));
        jtfAnsAnswer.setPreferredSize(new Dimension(200,jlAnsAnswer.getHeight()));

        jtfGTID.setPreferredSize(new Dimension(30,jtfGTID.getHeight()));
        jtfGTGenericTerm.setPreferredSize(new Dimension(100,jtfGTGenericTerm.getHeight()));

        jtfSynSynonym.setPreferredSize(new Dimension(100,jtfSynSynonym.getHeight()));
        jtfSynID.setPreferredSize(new Dimension(30,jtfSynID.getHeight()));


        //Button listener logic
        buttonAns.addActionListener(e -> cl.show(panelCont,"2"));

        buttonGT.addActionListener(e -> cl.show(panelCont,"3"));

        buttonSyn.addActionListener(e -> cl.show(panelCont,"4"));

        buttonSendAns.addActionListener(e -> {
            cl.show(panelCont,"1");
        });

        buttonSendGT.addActionListener(e -> {
            cl.show(panelCont,"1");
        });

        buttonSendSyn.addActionListener(e -> {
            cl.show(panelCont,"1");
        });

        //Adding component ot each panel
        panelStart.add(buttonAns);
        panelStart.add(buttonGT);
        panelStart.add(buttonSyn);

        panelAns.add(jlAnsCaseID);
        panelAns.add(jtfAnsCaseID);
        panelAns.add(jlAnsKeywords);
        panelAns.add(jtfAnsKeywords);
        panelAns.add(jlAnsAnswer);
        panelAns.add(jtfAnsAnswer);
        panelAns.add(buttonSendAns);

        panelGT.add(jlGTID);
        panelGT.add(jtfGTID);
        panelGT.add(jlGTGenericTerm);
        panelGT.add(jtfGTGenericTerm);
        panelGT.add(buttonSendGT);

        panelSyn.add(jlSynSynonym);
        panelSyn.add(jtfSynSynonym);
        panelSyn.add(jlSynID);
        panelSyn.add(jtfSynID);
        panelSyn.add(buttonSendSyn);

        panelCont.add(panelStart,"1");
        panelCont.add(panelAns,"2");
        panelCont.add(panelGT,"3");
        panelCont.add(panelSyn,"4");


        cl.show(panelCont,"1");

        frame.add(panelCont);
        frame.pack();
        frame.setLocationRelativeto(null);
        frame.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }

}

Picture of start panel

Picture of answer panel after switching to it

解决方法

我可以看到 JLabels 但看不到 JTextFields

tfAnsCaseID.setPreferredSize(new Dimension(30,jtfAnsCaseID.getHeight()));

Swing 组件在框架被打包或可见之前没有大小。

默认高度为 0，因此您给组件的首选高度为 0。FlowLayout 将遵循首选大小，因此没有可绘制的内容。

所有 Swing 组件都负责确定自己的首选大小，因此不要尝试使用一些随机值自行管理首选大小。

改为使用：

jtfAnsCaseID = new JTextField(5);

在构造函数中指定的数字将允许文本字段根据使用的字体和边框计算其首选大小以显示 5 个“W”字符。