Question

我正在尝试将我的标签和按钮放在屏幕上。我在这里找到了一个答案，用label3.setHorizontalAlignment(SwingConstants.CENTER); label3.setVerticalAlignment(SwingConstants.CENTER);设置标签的位置，但我的代码没有任何影响。

此外，在将我的布局从Flow Layout更改为Border Layout时，屏幕上只显示一个Jbutton [CLEAR]。任何人都可以帮我纠正这个问题吗？

public class Corrected1 extends JFrame {

    public JTextField tf1;
    public JTextField tf2;
    public JLabel label1;
    public JLabel label2;
    public JLabel label3;
    public JLabel label4;
    public JButton button1;
    public JButton button2;
    public JComboBox cb,cb1;
    public String[] list={"DOLLARS","EUROS ","YEN","POUNDS","RUPEES"};

    public void init() {try {
        SwingUtilities.invokeAndWait(new Runnable(){
                public void run(){
                 Corrected();
                 }
             });
    } catch (InvocationTargetException exc) {
        System.out.println("Error occured due to "+ exc);
        exc.printStackTrace();
    } catch (InterruptedException exc1) {
        System.out.println("Error occured due to "+ exc1);

        exc1.printStackTrace();
    }


 }   




public void Corrected(){



    setLayout(new GridBagLayout());

    JLabel label1 = new JLabel("FROM  :");
    label1.setFont(new Font("Serif", Font.BOLD, 15));

    JComboBox cb = new JComboBox();


    cb= new JComboBox(list);
    cb.getSelectedIndex();

    GridBagConstraints gbc = new GridBagConstraints();
    gbc.gridx = 0;
    gbc.gridy = 0;
    add(label1, gbc);
    gbc.fill = GridBagConstraints.HORIZONTAL;
    gbc.gridx++;
    add(cb, gbc);

    JLabel label2 = new JLabel("TO :");
    label2.setFont(new Font("Serif", Font.BOLD, 15));
    JComboBox cb1 = new JComboBox();
    cb1=new JComboBox(list);
    cb1.getSelectedIndex();

    gbc.gridx = 0;
    gbc.gridy++;
    gbc.fill = GridBagConstraints.NONE;
    add(label2, gbc);
    gbc.fill = GridBagConstraints.HORIZONTAL;
    gbc.gridx++;
    add(cb1, gbc);

    JLabel label3 = new JLabel("\n\nENTER THE AMOUNT  :");
    label3.setFont(new Font("Serif", Font.BOLD, 15));
    label3.setHorizontalAlignment(SwingConstants.CENTER);
    label3.setVerticalAlignment(SwingConstants.CENTER);

    gbc.gridx = 0;
    gbc.gridy++;
    add(label3, gbc);
    JTextField tf1 = new JTextField(15);
    gbc.gridx++;
    add(tf1, gbc);

    JLabel label4 = new JLabel("CONVERTED AMOUNT :");
    label4.setFont(new Font("Serif", Font.BOLD, 15));
    label4.setDisplayedMnemonic(KeyEvent.VK_O);

    gbc.gridx = 0;
    gbc.gridy++;
    add(label4, gbc);
    JTextField tf2 = new JTextField(15);
    gbc.gridx++;
    add(tf2, gbc);

    JPanel buttons = new JPanel();

    JButton button1 = new JButton("CONVERT");
    button1.setFont(new Font("Serif", Font.BOLD, 15));
    button1.setMnemonic(KeyEvent.VK_K);
    buttons.add(button1);

    JButton button2 = new JButton("CLEAR ");
    button2.setFont(new Font("Serif", Font.BOLD, 15));
    button2.setMnemonic(KeyEvent.VK_C);
    buttons.add(button2);

    gbc.gridx = 0;
    gbc.gridy++;
    gbc.gridwidth = GridBagConstraints.REMAINDER;

    add(buttons, gbc);

    thehandler handler= new thehandler();

     cb.addActionListener(handler);
     cb1.addActionListener((ActionListener) handler);    
     button1.addActionListener((ActionListener) handler);    
     button2.addActionListener((ActionListener) handler);    
     tf1.addActionListener((ActionListener) handler);    
     tf2.addActionListener((ActionListener) handler);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//pack();
 setSize(450,250);
setVisible(true);

}


public class thehandler implements ActionListener{


    public void actionPerformed(ActionEvent e) {
        double a=0,b=0; 
        a=Double.valueOf(tf1.getText());
        {
            if(cb.getSelectedIndex()==0 && cb1.getSelectedIndex()==1)
                b=a*0.89;
            if(cb.getSelectedIndex()==0 && cb1.getSelectedIndex()==2)
                b=a*124.75;
            if(cb.getSelectedIndex()==0 && cb1.getSelectedIndex()==3)
                b=a*0.65;
            if(cb.getSelectedIndex()==0 && cb1.getSelectedIndex()==4)
                b=a*64.08;
            if(cb.getSelectedIndex()==1 && cb1.getSelectedIndex()==0)
                b=a*1.13;
            if(cb.getSelectedIndex()==1 && cb1.getSelectedIndex()==2)
                b=a*140.49;
            if(cb.getSelectedIndex()==1 && cb1.getSelectedIndex()==3)
                b=a*0.74;
            if(cb.getSelectedIndex()==1 && cb1.getSelectedIndex()==4)
                b=a*71.34;
            if(cb.getSelectedIndex()==2 && cb1.getSelectedIndex()==0)
                b=a*0.0080;
            if(cb.getSelectedIndex()==2 && cb1.getSelectedIndex()==1)
                b=a*0.0071;
            if(cb.getSelectedIndex()==2 && cb1.getSelectedIndex()==3)
                b=a*0.0052;
            if(cb.getSelectedIndex()==2 && cb1.getSelectedIndex()==4)
                b=a*0.51;
            if(cb.getSelectedIndex()==3 && cb1.getSelectedIndex()==0)
                b=a*1.53;
            if(cb.getSelectedIndex()==3 && cb1.getSelectedIndex()==1)
                b=a*1.36;
            if(cb.getSelectedIndex()==3 && cb1.getSelectedIndex()==2)
                b=a*191.26;
            if(cb.getSelectedIndex()==3 && cb1.getSelectedIndex()==4)
                b=a*97.88;
            if(cb.getSelectedIndex()==4 && cb1.getSelectedIndex()==0)
                b=a*0.0156;
            if(cb.getSelectedIndex()==4 && cb1.getSelectedIndex()==1)
                b=a*0.014;
            if(cb.getSelectedIndex()==4 && cb1.getSelectedIndex()==2)
                b=a*1.9607;
            if(cb.getSelectedIndex()==4 && cb1.getSelectedIndex()==3)
                b=a*0.0108;
            tf2.setText(String.valueOf(b));

        }

        if(e.getSource()==button2){
            tf1.setText("0000");
            tf2.setText("0000");
                        }

    }

}

}

Answer 1

首先看看How to Use BorderLayout，了解它是如何运作的。

BorderLayout只允许在其中定位五个组件，NORTH，SOUTH，EAST，WEST和CENTRE

默认情况下，如果您未另行指定，则组件会置于CENTRE位置。这意味着只添加了最后添加的组件。

JLabel#setHorizontal/VerticalAlignment会在标签尺寸较大时对齐标签内容，但在FlowLayout的情况下，它会使用标签内容的首选尺寸来制作关于如何最好地解决问题的决定，所以通常没有额外的空间

相反，您可以使用GridBagLayout，这是一个更复杂但更灵活的布局管理器。

GridBagLayout

setLayout(new GridBagLayout());

JLabel label1 = new JLabel("FROM  :");
label1.setFont(new Font("Serif", Font.BOLD, 15));

JComboBox cb = new JComboBox();

GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = 0;
add(label1, gbc);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx++;
add(cb, gbc);

JLabel label2 = new JLabel("TO :");
label2.setFont(new Font("Serif", Font.BOLD, 15));
JComboBox cb1 = new JComboBox();

gbc.gridx = 0;
gbc.gridy++;
gbc.fill = GridBagConstraints.NONE;
add(label2, gbc);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx++;
add(cb1, gbc);

JLabel label3 = new JLabel("\n\nENTER THE AMOUNT  :");
label3.setFont(new Font("Serif", Font.BOLD, 15));
label3.setHorizontalAlignment(SwingConstants.CENTER);
label3.setVerticalAlignment(SwingConstants.CENTER);

gbc.gridx = 0;
gbc.gridy++;
add(label3, gbc);
JTextField tf1 = new JTextField(15);
gbc.gridx++;
add(tf1, gbc);

JLabel label4 = new JLabel("CONVERTED AMOUNT :");
label4.setFont(new Font("Serif", Font.BOLD, 15));
label4.setDisplayedMnemonic(KeyEvent.VK_O);

gbc.gridx = 0;
gbc.gridy++;
add(label4, gbc);
JTextField tf2 = new JTextField(15);
gbc.gridx++;
add(tf2, gbc);

JPanel buttons = new JPanel();

JButton button1 = new JButton("CONVERT");
button1.setFont(new Font("Serif", Font.BOLD, 15));
button1.setMnemonic(KeyEvent.VK_K);
buttons.add(button1);

JButton button2 = new JButton("CLEAR ");
button2.setFont(new Font("Serif", Font.BOLD, 15));
button2.setMnemonic(KeyEvent.VK_C);
buttons.add(button2);

gbc.gridx = 0;
gbc.gridy++;
gbc.gridwidth = GridBagConstraints.REMAINDER;
add(buttons, gbc);

有时候，您甚至需要使用JPanel使用FlowLayout组合布局（我已在此处完成），使用primeMarker.setDraggable(false);按钮，因为它会产生所需的居中结果按钮

有关详细信息，请参阅How to Use GridBagLayout

Answer 2

组件定位与其所属的布局有关。

如果您真的想自由设置JLabel和JButton的位置，我建议您将布局设置为null：

setLayout(null);

并使用JLabel获取4个参数来定位setBounds()。 JLabel的尺寸及其坐标。

如何在指定的布局中定位JLabel？

2 个答案: