[英]How to set size of buttons same in Java Swing?
我是 Swing 新手,并试图为按钮设置相同的大小。 但是,我没有在互联网上找到确切的解决方案。 请注意,我必须使用setPreferredSize() 。 Dimension目前不是正确的解决方案。 我想获取 calcButton 的大小并在setPreferredSize() 中使用。
这是图片:
和代码:
import javax.swing.*;
/**
The KiloConverter class displays a JFrame that
lets the user enter a distance in kilometers. When
the Calculate button is clicked, a dialog box is
displayed with the distance converted to miles.
*/
public class KiloConverter extends JFrame
{
private JPanel panel; // To reference a panel
private JLabel messageLabel; // To reference a label
private JTextField kiloTextField; // To reference a text field
private JButton calcButton; // To reference a button
private JButton alertButton;
private final int WINDOW_WIDTH = 310; // Window width
private final int WINDOW_HEIGHT = 100; // Window height
/**
Constructor
*/
public KiloConverter()
{
// Set the window title.
setTitle("Kilometer Converter");
// Set the size of the window.
setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
// Specify what happens when the close button is clicked.
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Build the panel and add it to the frame.
buildPanel();
// Add the panel to the frame's content pane.
add(panel);
// Display the window.
setVisible(true);
}
/**
The buildPanel method adds a label, text field, and
and a button to a panel.
*/
private void buildPanel()
{
// Create a label to display instructions.
messageLabel = new JLabel("Enter a distance " +
"in kilometers");
// Create a text field 10 characters wide.
kiloTextField = new JTextField(10);
// Create a button with the caption "Calculate".
calcButton = new JButton("Calculate");
alertButton = new JButton("Alert");
// --------ERROR HERE----------
alertButton.setPreferredSize(new getPreferredSize(calcButton));
// Create a JPanel object and let the panel
// field reference it.
panel = new JPanel();
// Add the label, text field, and button
// components to the panel.
panel.add(messageLabel);
panel.add(kiloTextField);
panel.add(calcButton);
panel.add(alertButton);
}
/**
main method
*/
public static void main(String[] args)
{
new KiloConverter();
}
}
您的问题是 XY 问题,您会问“我如何做 'X'?” 当更好的解决方案根本不是做“X”,而是做“Y”时。
在这里,您询问如何设置按钮的首选大小以使按钮大小相等,而更好且实际上规范正确的解决方案不是这样做,而是使用更好的布局管理器,该管理器可以调整按钮的大小对你来说也是一样——一个 GridLayout。
例如,创建一个新的 JPanel 来保存按钮,比如说叫 buttonPanel,给它一个 GridLayout,说new GridLayout(1, 0, 3, 0)
,然后向它添加按钮,然后将此 JPanel 添加到主 JPanel .
例如,
import java.awt.GridLayout;
import javax.swing.*;
@SuppressWarnings("serial")
public class LayoutEg extends JPanel {
private static final int KILO_FIELD_COLS = 15;
private static final int GAP = 3;
private JTextField kiloTextField = new JTextField(KILO_FIELD_COLS);
private JButton calcButton = new JButton("Calculate");
private JButton alertButton = new JButton("Alert");
public LayoutEg() {
// add ActionListeners etc....
JPanel enterPanel = new JPanel();
enterPanel.add(new JLabel("Enter a distance in kilometers:"));
enterPanel.add(kiloTextField);
JPanel buttonPanel = new JPanel(new GridLayout(1, 0, GAP, 0));
buttonPanel.add(calcButton);
buttonPanel.add(alertButton);
setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
setLayout(new GridLayout(0, 1));
add(enterPanel);
add(buttonPanel);
}
private static void createAndShowGui() {
LayoutEg mainPanel = new LayoutEg();
JFrame frame = new JFrame("Kilometer Converter");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
}
代码说明:
千文本字段中列数的常量
private static final int KILO_FIELD_COLS = 15;
JButton 之间的间隙和主 JPanel 周围的间隙(空边框)的常量
private static final int GAP = 3;
15 列宽的 JTextField
private JTextField kiloTextField = new JTextField(KILO_FIELD_COLS);
包含 JLabel 和 JTextField 的顶级 JPanel。 它默认使用 FlowLayout:
JPanel enterPanel = new JPanel();
enterPanel.add(new JLabel("Enter a distance in kilometers:"));
enterPanel.add(kiloTextField);
这是问题的核心,创建一个使用GridLayout(1, 0, 3, 0)
的 JPanel,即具有 1 行的网格布局,具有可变列数(0 第二个参数),具有 3横向间隙,没有纵向间隙。 然后添加我们的按钮:
JPanel buttonPanel = new JPanel(new GridLayout(1, 0, GAP, 0));
buttonPanel.add(calcButton);
buttonPanel.add(alertButton);
在这个主 JPanel 周围放置一个 3 像素宽的边框
setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
为主 JPanel 提供一个具有可变行数 (0) 和 1 列的 GridLayout,并向其添加 enterPanel 和 buttonPanel:
setLayout(new GridLayout(0, 1));
add(enterPanel);
add(buttonPanel);
注释中有更多解释,尤其是关键方法.pack()
:
// create the main JPanel
LayoutEg mainPanel = new LayoutEg();
// create a JFrame to put it in, although better to put into a JDialog
JFrame frame = new JFrame("Kilometer Converter");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// add the LayoutEg JPanel into the JFrame
frame.getContentPane().add(mainPanel);
// **** key method*** that tells the layout managers to work
frame.pack();
// center and display
frame.setLocationRelativeTo(null);
frame.setVisible(true);
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