JLabel 文本在窄列中而不是展开
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【中文标题】JLabel 文本在窄列中而不是展开【英文标题】：JLabel text in narrow column instead of spread out 【发布时间】：2015-01-16 12:53:47 【问题描述】：我正在尝试制作一个带有 JLabel 的框架。我已成功将其添加到框架中，但文本显示在一个狭窄的列中，而不是在窗口中占用更多空间。我该如何解决？我尝试使用 html，但没有成功。
编辑：介绍面板是我遇到问题的面板。
import java.awt.BorderLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class Window implements ActionListener
JFrame frame = new JFrame("Loan Program");
JFrame intro = new JFrame("Welcome To The Loan Program!");
JPanel panel = new JPanel(new GridBagLayout());
JPanel panel2 = new JPanel(new GridBagLayout());
JPanel panel3 = new JPanel(new GridBagLayout());
JPanel descriptionPanel = new JPanel(new GridBagLayout());
JPanel descriptionPanel1 = new JPanel(new GridBagLayout());
GridBagConstraints g = new GridBagConstraints();
JButton calculate;
JButton cancel;
JButton reset;
JButton introOk;
JLabel loanAmount;
JLabel loanInterest;
JLabel loanPeriod;
JLabel monthlyRepayment;
JLabel introLabel;
JTextField laField;
JTextField liField;
JTextField lpField;
JTextField mrField;
DecimalFormat df = new DecimalFormat("#.##");
public Window()
g.insets = new Insets(10, 10, 20, 10); //For the spacing between elements
//Initalizing components
introLabel = new JLabel();
introOk = new JButton("Ok");
//Setting up text for intro panel
String text = "<html><h1 align='center'>Loan Program 1.0</h1>";
text = text + "This program lets you calculate the various aspects of loans <br />";
text = text + "If you are leaving a field empty then use 0 for its place <br />";
text = text + "<h1 align='center'>Text Fields To Enter</h1>";
text = text + "Monthly Payment: Enter values for: Loan Period, Loan Amount, and Loan Interest. Enter 0 for Monthly Payment. <br />";
text = text + "Loan Period: Enter Values for: Loan Amount, Loan Interest, and Monthly Payment. Enter 0 for Loan Period. <br />";
//Setting text to the label
introLabel.setText(text);
//Positioning introLabel
descriptionPanel.add(introLabel, g);
//Positioning button
descriptionPanel1.add(introOk, g);
//Actionlistener for buttont to dipose current frame.
introOk.addActionListener(new ActionListener()
@Override
public void actionPerformed(ActionEvent e)
intro.dispose();
);
intro.add(descriptionPanel);
intro.add(descriptionPanel1, BorderLayout.SOUTH);
//Initializing buttons here and adding them to panel
calculate = new JButton("Calculate");
reset = new JButton("Reset");
cancel = new JButton("Cancel");
panel.add(calculate, g);
panel.add(reset, g);
panel.add(cancel, g);
//Adding the Actionlistener for buttons
calculate.addActionListener(this);
reset.addActionListener(this);
cancel.addActionListener(this);
//Initializing the labels
loanAmount = new JLabel("Loan Amount:");
loanInterest = new JLabel("Loan Interest:");
loanPeriod = new JLabel("Loan Period:");
monthlyRepayment = new JLabel("Monthly Payment:");
//Positioning loanAmount label
g.gridx = 0;
g.gridy = 0;
panel2.add(loanAmount, g);
//Positioning loanInterest label
g.gridx = 0;
g.gridy = 2;
panel2.add(loanInterest, g);
//Positioning loanPeriod label
g.gridx = 0;
g.gridy = 3;
panel2.add(loanPeriod, g);
//Positioning monthlyRepayment label
g.gridx = 0;
g.gridy = 4;
panel2.add(monthlyRepayment, g);
//Initializing the text fields
laField = new JTextField("", 20);
liField = new JTextField("", 20);
lpField = new JTextField("", 20);
mrField = new JTextField("", 20);
//Positioning laField
g.gridx = 1;
g.gridy = 0;
panel2.add(laField, g);
//Positioning liField
g.gridx = 1;
g.gridy = 2;
panel2.add(liField, g);
//Positioning lpField
g.gridx = 1;
g.gridy = 3;
panel2.add(lpField, g);
//Positioning mrField
g.gridx = 1;
g.gridy = 4;
panel2.add(mrField, g);
//Adding panels to the frame using boarderlayout
frame.add(panel, BorderLayout.SOUTH);
frame.add(panel2, BorderLayout.WEST);
// Creating the window
frame.setSize(500, 500);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//popup window for intro
intro.setSize(500, 500);
intro.setVisible(true);
intro.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
@Override
public void actionPerformed(ActionEvent e)
Object o = e.getSource();
if(o == cancel)
//Initializing components for the window
JFrame frame1 = new JFrame("Are you sure?");
JPanel panel = new JPanel(new GridBagLayout());
JPanel panel2 = new JPanel(new GridBagLayout());
JLabel label = new JLabel("Are you sure you want to exit?");
JButton yes = new JButton("Yes");
JButton no = new JButton("No");
//Positioning Label
g.gridx = 0;
g.gridy = 0;
panel.add(label, g);
//Positioning yes button
g.gridx = 0;
g.gridy = 0;
g.gridwidth = 1;
panel2.add(yes, g);
//Positioning no button
g.gridx = 1;
g.gridy = 0;
panel2.add(no, g);
//Action to close program when yes is clicked
yes.addActionListener(new ActionListener()
@Override
public void actionPerformed(ActionEvent e)
System.exit(0);
);
//Action to close current window if no is clicked
no.addActionListener(new ActionListener()
@Override
public void actionPerformed(ActionEvent e)
frame1.dispose();
);
//Adding the panels to frame with borderlayout
frame1.add(panel, BorderLayout.NORTH);
frame1.add(panel2, BorderLayout.SOUTH);
//Setting up frame
frame1.setSize(300, 300);
frame1.setVisible(true);;
frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Adding actionListener once again for second level of menu
//No to close the current window
Object b = e.getSource();
if(b == no)
System.out.println("heres");
frame1.dispose();
//Yes to close the program completely
if(b == yes)
System.exit(0);
//New instance of window to reset it
if(o == reset)
frame.dispose();
new Window();
//Calculate buttons actions
if(o == calculate)
//Test values to see if they are being passed
System.out.println(laField.getText() + "\n" + liField.getText() + "/n" + lpField.getText() + "\n" + mrField.getText());
//If statement for monthly payment with the correct fields filled out
if(laField.getText() != null && liField.getText() != null && lpField.getText() != null && mrField.getText() == "0")
//Strings and double and ints to convert from text field number.
String sRate, sMonths, sPrincipal;
sRate = liField.getText();
sMonths = lpField.getText();
sPrincipal = laField.getText();
double rate = Double.parseDouble(sRate);
int months = Integer.parseInt(sMonths);
double principal = Double.parseDouble(sPrincipal);
//Setting up components for new window
JFrame frame = new JFrame("Monthly Payment");
JPanel panel = new JPanel(new GridBagLayout());
JPanel panel2 = new JPanel(new GridBagLayout());
JLabel label = new JLabel("The monthly payment is: " + df.format(calculateMonthlyRepayment(rate, months, principal)));
JButton button = new JButton("Ok");
//Action listener for okay button to just close current frame.
button.addActionListener(new ActionListener()
@Override
public void actionPerformed(ActionEvent e)
frame.dispose();
);
//Padding for element
g.insets = new Insets(5, 5, 5, 5);
//Adding components to panel
panel.add(label, g);
panel2.add(button, g);
//Adding panels to frame
frame.add(panel, BorderLayout.CENTER);
frame.add(panel2, BorderLayout.SOUTH);
//Intializing frame
frame.setSize(300, 300);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//If statement for period calculation checks to see proper fields filled
if(mrField.getText() != null && liField.getText() != null && laField.getText() != null && lpField.getText() == "0");
//String and doubles to convert to numbers from text box
String sMonthlyPayment, sloanAmount, sinterestRate;
sMonthlyPayment = mrField.getText();
sloanAmount = laField.getText();
sinterestRate = liField.getText();
double monthlyPayment = Double.parseDouble(sMonthlyPayment);
double loanAmount = Double.parseDouble(sloanAmount);
double interestRate = Double.parseDouble(sinterestRate);
//Initializing the components
JFrame frame = new JFrame("Total Loan Period");
JPanel panel = new JPanel(new GridBagLayout());
JPanel panel2 = new JPanel(new GridBagLayout());
JLabel label = new JLabel("Total number of periods is : " + calculatePeriod(monthlyPayment, interestRate, loanAmount));
JButton button = new JButton("Ok");
//Button listener to close current frame
button.addActionListener(new ActionListener()
@Override
public void actionPerformed(ActionEvent e)
frame.dispose();
);
//Padding for the components
g.insets = new Insets(5, 5, 5, 5);
//Adding componeents to panel with gridbag
panel.add(label, g);
panel2.add(button, g);
//Adding panels to frame
frame.add(panel, BorderLayout.CENTER);
frame.add(panel2, BorderLayout.SOUTH);
//Initializing the frame
frame.setSize(300, 300);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
public double calculateMonthlyRepayment(double rate, int months, double principal)
String input = mrField.getText();
double totalMr = Double.parseDouble(input);
double mrpayment = (rate + ((rate)/((Math.pow(1 + rate, months) - 1)))) * principal;
return mrpayment;
double calculatePeriod(double monthlyPayment, double interestRate, double loanAmount)
return (Math.log(monthlyPayment) - Math.log(monthlyPayment - (loanAmount * interestRate))) / Math.log(1 + interestRate);
【问题讨论】：
您必须在组件上使用 setPreferredSize() 设置大小，并在 setVisible(true) 之前调用 pack() @gantners: Don't usesetPreferredSize() when you really mean to override getPreferredSize().
@trashgod 你是对的，懒惰的我......
【参考方案1】：
首先，推荐一个，请尝试使用像 window builder 或 matisse 这样的 gui 设计器。它们确实减轻了您的日常工作，并限制了定义布局约束的代码。
如果您在布局和未出现或未对齐的组件方面遇到问题，这通常表明您对所需布局管理器的使用有误。在整个 *** 中都有关于它的优秀帖子。
代码中最严重的错误是重用了 GridBagConstraints，这是一个 bad idea，因为
正如您可能从上面的示例中猜到的那样，可以为多个组件重用相同的 GridBagConstraints 实例，即使这些组件具有不同的约束。但是，建议您不要重复使用 GridBagConstraints，因为如果您忘记为每个新实例重置字段，这很容易导致您引入细微的错误。
因此，只有在每个组件的约束相同时才尝试共享您的约束，例如标签的约束和文本字段列的另一个约束。
您的错误也存在于窄列上。如果您还想为所有标签指定所需的宽度，请在标签约束上设置网格宽度。这也适用于文本字段约束。
再次查看 GridBagLayout Example，以更好地了解其用法。
更多建议： 将您的类命名为 Window 可能会误导其他人，因为他们可能会认为他们正在使用 java.awt.window，这与您的类完全不同，并且您只能在 import 语句中看到它。
任何 gui 元素都必须从 EDT 调用，因此请使用 SwingUtilities 调用您的类，例如
SwingUtilities.invokeLater(new Runnable()
public void run()
new Window();
);
别忘了打电话给pack()，让布局管理器根据您的约束条件完成工作。
也尽量避免使用大量的框架，而是使用对话框。只有在需要将它们放在单独的上下文中时才应该使用框架，就像它们完全独立一样。
举个例子：
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.SwingUtilities;
import java.awt.Dimension;
import java.awt.GridBagLayout;
import java.awt.BorderLayout;
import javax.swing.JPanel;
import java.awt.GridBagConstraints;
import java.awt.Insets;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class GridExample extends JFrame
public GridExample()
initComponents();
pack();
setTitle("GridExample");
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLocationRelativeTo(null); //Center, could also be setLocationByPlatform(true);
@Override
public Dimension preferredSize()
return new Dimension(500,300);
private void initComponents()
getContentPane().setLayout(new BorderLayout(0, 0));
JPanel mainPanel = new JPanel();
getContentPane().add(mainPanel, BorderLayout.CENTER);
GridBagLayout gbl_mainPanel = new GridBagLayout();
gbl_mainPanel.columnWidths = new int[]0, 0, 0, 0;
gbl_mainPanel.rowHeights = new int[]0, 0, 0, 0, 0, 0;
gbl_mainPanel.columnWeights = new double[]0.0, 1.0, 0.0, Double.MIN_VALUE;
gbl_mainPanel.rowWeights = new double[]0.0, 0.0, 0.0, 0.0, 0.0, Double.MIN_VALUE;
mainPanel.setLayout(gbl_mainPanel);
JLabel lblLoanAmount = new JLabel("Loan Amount:");
GridBagConstraints gbc_lblLoanAmount = new GridBagConstraints();
gbc_lblLoanAmount.fill = GridBagConstraints.HORIZONTAL;
gbc_lblLoanAmount.insets = new Insets(0, 0, 5, 5);
gbc_lblLoanAmount.gridx = 0;
gbc_lblLoanAmount.gridy = 0;
mainPanel.add(lblLoanAmount, gbc_lblLoanAmount);
txtLoanAmount = new JTextField();
GridBagConstraints gbc_txtLoanAmount = new GridBagConstraints();
gbc_txtLoanAmount.gridwidth = 2;
gbc_txtLoanAmount.insets = new Insets(0, 0, 5, 0);
gbc_txtLoanAmount.fill = GridBagConstraints.HORIZONTAL;
gbc_txtLoanAmount.gridx = 1;
gbc_txtLoanAmount.gridy = 0;
mainPanel.add(txtLoanAmount, gbc_txtLoanAmount);
txtLoanAmount.setColumns(10);
JLabel lblLoanInterest = new JLabel("Loan Interest:");
GridBagConstraints gbc_lblLoanInterest = new GridBagConstraints();
gbc_lblLoanInterest.insets = new Insets(0, 0, 5, 5);
gbc_lblLoanInterest.fill = GridBagConstraints.BOTH;
gbc_lblLoanInterest.gridx = 0;
gbc_lblLoanInterest.gridy = 1;
mainPanel.add(lblLoanInterest, gbc_lblLoanInterest);
txtLoanInterest = new JTextField();
GridBagConstraints gbc_txtLoanInterest = new GridBagConstraints();
gbc_txtLoanInterest.gridwidth = 2;
gbc_txtLoanInterest.anchor = GridBagConstraints.NORTH;
gbc_txtLoanInterest.insets = new Insets(0, 0, 5, 0);
gbc_txtLoanInterest.fill = GridBagConstraints.HORIZONTAL;
gbc_txtLoanInterest.gridx = 1;
gbc_txtLoanInterest.gridy = 1;
mainPanel.add(txtLoanInterest, gbc_txtLoanInterest);
txtLoanInterest.setColumns(10);
JLabel lblLoanPeriod = new JLabel("Loan Period:");
GridBagConstraints gbc_lblLoanPeriod = new GridBagConstraints();
gbc_lblLoanPeriod.fill = GridBagConstraints.HORIZONTAL;
gbc_lblLoanPeriod.insets = new Insets(0, 0, 5, 5);
gbc_lblLoanPeriod.gridx = 0;
gbc_lblLoanPeriod.gridy = 2;
mainPanel.add(lblLoanPeriod, gbc_lblLoanPeriod);
txtLoanPeriod = new JTextField();
GridBagConstraints gbc_txtLoanPeriod = new GridBagConstraints();
gbc_txtLoanPeriod.gridwidth = 2;
gbc_txtLoanPeriod.anchor = GridBagConstraints.NORTH;
gbc_txtLoanPeriod.insets = new Insets(0, 0, 5, 0);
gbc_txtLoanPeriod.fill = GridBagConstraints.HORIZONTAL;
gbc_txtLoanPeriod.gridx = 1;
gbc_txtLoanPeriod.gridy = 2;
mainPanel.add(txtLoanPeriod, gbc_txtLoanPeriod);
txtLoanPeriod.setColumns(10);
JLabel lblMonthlyPayment = new JLabel("Monthly Payment:");
GridBagConstraints gbc_lblMonthlyPayment = new GridBagConstraints();
gbc_lblMonthlyPayment.fill = GridBagConstraints.HORIZONTAL;
gbc_lblMonthlyPayment.insets = new Insets(0, 0, 5, 5);
gbc_lblMonthlyPayment.gridx = 0;
gbc_lblMonthlyPayment.gridy = 3;
mainPanel.add(lblMonthlyPayment, gbc_lblMonthlyPayment);
txtMonthlyPament = new JTextField();
GridBagConstraints gbc_txtMonthlyPament = new GridBagConstraints();
gbc_txtMonthlyPament.gridwidth = 2;
gbc_txtMonthlyPament.insets = new Insets(0, 0, 5, 0);
gbc_txtMonthlyPament.anchor = GridBagConstraints.NORTH;
gbc_txtMonthlyPament.fill = GridBagConstraints.HORIZONTAL;
gbc_txtMonthlyPament.gridx = 1;
gbc_txtMonthlyPament.gridy = 3;
mainPanel.add(txtMonthlyPament, gbc_txtMonthlyPament);
txtMonthlyPament.setColumns(10);
JButton btnCalculate = new JButton("Calculate");
btnCalculate.addActionListener(new ActionListener()
public void actionPerformed(ActionEvent e)
calculate();
private void calculate()
//do the math here
txtResult.setText("Calculate pressed!");
);
JLabel lblResult = new JLabel("Result:");
GridBagConstraints gbc_lblResult = new GridBagConstraints();
gbc_lblResult.fill = GridBagConstraints.HORIZONTAL;
gbc_lblResult.insets = new Insets(0, 0, 0, 5);
gbc_lblResult.gridx = 0;
gbc_lblResult.gridy = 4;
mainPanel.add(lblResult, gbc_lblResult);
txtResult = new JTextField();
GridBagConstraints gbc_txtResult = new GridBagConstraints();
gbc_txtResult.insets = new Insets(0, 0, 0, 5);
gbc_txtResult.fill = GridBagConstraints.HORIZONTAL;
gbc_txtResult.gridx = 1;
gbc_txtResult.gridy = 4;
mainPanel.add(txtResult, gbc_txtResult);
txtResult.setColumns(10);
GridBagConstraints gbc_btnCalculate = new GridBagConstraints();
gbc_btnCalculate.gridx = 2;
gbc_btnCalculate.gridy = 4;
mainPanel.add(btnCalculate, gbc_btnCalculate);
private static final long serialVersionUID = 1L;
private JTextField txtLoanAmount;
private JTextField txtLoanInterest;
private JTextField txtLoanPeriod;
private JTextField txtMonthlyPament;
private JTextField txtResult;
public static void main(String[] args)
SwingUtilities.invokeLater(new Runnable()
public void run()
GridExample g = new GridExample();
String text = "<html><h1 align='center'>Loan Program 1.0</h1>";
text = text + "This program lets you calculate the various aspects of loans <br />";
text = text + "If you are leaving a field empty then use 0 for its place <br />";
text = text + "<h1 align='center'>Text Fields To Enter</h1>";
text = text + "Monthly Payment: Enter values for: Loan Period, Loan Amount, and Loan Interest. Enter 0 for Monthly Payment. <br />";
text = text + "Loan Period: Enter Values for: Loan Amount, Loan Interest, and Monthly Payment. Enter 0 for Loan Period. <br />";
g.setVisible(true);
JOptionPane.showMessageDialog(g, new JLabel(text));
);
【讨论】：
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