我正在构建我的第一个图形用户界面，它是一个相当简单的计算器应用程序。我遇到的问题是当我尝试预先形成另一个计算时，它会继续为输出添加一个新的JTextArea。我尝试了remove()，revalidate()，repaint()，但仍然继续添加新的JTextArea框。我做错了什么？
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import static java.lang.Thread.currentThread;
import java.util.concurrent.TimeUnit;
public class MovieCalculatorJFrame extends JFrame
{
private static final double PERCENT_TOTAL = 0.20;
private double grossChildTicketSold;
private double grossAdultTicketSold;
private double netChildTicketSold;
private double netAdultTicketSold;
private double grossRevenue;
private double netRevenue;
private MovieTextBoxPanel textBoxPanel;
private JPanel outPutPanel;
private JTextArea outPut;
private JButton calcButton;
private JPanel calcButtonPanel;
private final int WINDOW_WIDTH = 800;
private final int WINDOW_HEIGHT = 1500;
//Create constructor
public MovieCalculatorJFrame()
{
//Display title
setTitle("Profits Calculator");
//Set window size
setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
//Create GridLayout
// 3 row with 1 columns
setLayout(new GridLayout(3,1));
//Specify an action for the close button.
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Create custom Panels
textBoxPanel = new MovieTextBoxPanel();
//Add the components to the content pane
add(textBoxPanel);
//Build calculate button panel
buildCalculateButton();
//Allows time for splash to appear.
try
{
TimeUnit.MILLISECONDS.sleep(2000);
}
catch(Exception e)
{
System.out.println("Exception caught");
}
// Pack the contents of the window and display it
pack();
setVisible(true);
}
private void buildCalculateButton()
{
//Create a JPanel for the button
calcButtonPanel = new JPanel();
//Create Button and add it to the JPanel
calcButton = new JButton("Calculate");
calcButtonPanel.add(calcButton);
//add JPanel to content pane
add(calcButtonPanel);
//Register action listener
calcButton.addActionListener(new CalcButtonListener());
}
//inner class with action listener.
private class CalcButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
//Check fields for errors
try{
grossChildTicketSold = (textBoxPanel.getChildCost() * textBoxPanel.getChildTotal());
grossAdultTicketSold = (textBoxPanel.getAdultCost() * textBoxPanel.getAdultTotal());
netChildTicketSold = (PERCENT_TOTAL * grossChildTicketSold);
netAdultTicketSold = (PERCENT_TOTAL * grossAdultTicketSold);
grossRevenue = (grossAdultTicketSold + grossChildTicketSold);
netRevenue = (PERCENT_TOTAL * grossRevenue);
}
catch(Exception a)
{
System.out.println("Fields are not completely filled out or letters may have been enter");
}
//Create new JPanel and JText and outputs result to JText.
JPanel newPanel = new JPanel();
if(outPut !=null)
{
newPanel.remove(outPut);
newPanel.revalidate();
newPanel.repaint();
}
outPut = new JTextArea("Gross revenue for adult tickets sold: " + grossAdultTicketSold + "\n");
outPut.append("Net revenue for adult tickets sold: " + netAdultTicketSold + "\n");
outPut.append("Gross revenue for child tickets sold: " + grossChildTicketSold + "\n");
outPut.append("Net revenue for child tickets sold: " + netChildTicketSold + "\n");
outPut.append("Gross revenue: " + grossRevenue + "\n");
outPut.append("Net revenue: " + netRevenue + "\n");
//Build output JPanel and add it to the content pane
newPanel.add(outPut);
add(newPanel);
setVisible(true);
}
}
public static void main(String[] args)
{
new MovieCalculatorJFrame();
}
}
这是我用过的自定义JPanel，以防万一。
import javax.swing.*;
import java.awt.*;
public class MovieTextBoxPanel extends JPanel
{
private JLabel childTicketCostText;
private JTextField childTicketCostTextBox;
private JLabel AdultTicketCostText;
private JTextField AdultTicketCostTextBox;
private JLabel childTicketSoldText;
private JTextField childTicketSoldTextBox;
private JLabel AdultTicketSoldText;
private JTextField AdultTicketSoldTextBox;
private double childTicketCost;
private double childTicketTotal;
private double adultTicketCost;
private double adultTicketTotal;
private String input;
//Create constructor
public MovieTextBoxPanel()
{
//Create GridLayout
// 2 row with 2 columns
setLayout(new GridLayout(2,2));
//Create child price text message
childTicketCostText = new JLabel("Price per child's ticket");
//Create child price text box
childTicketCostTextBox = new JTextField(5);
//Create adult price text message
AdultTicketCostText = new JLabel("Price per adult's ticket");
//Create adult price text box
AdultTicketCostTextBox = new JTextField(5);
//Create child tickets sold text message
childTicketSoldText = new JLabel("Number of children's tickets sold");
//Create child tickets sold text box
childTicketSoldTextBox = new JTextField(5);
//Create adult tickets sold text message
AdultTicketSoldText = new JLabel("Number of adult's tickets sold");
//Create adult tickets sold text box
AdultTicketSoldTextBox = new JTextField(5);
//Create border
setBorder(BorderFactory.createLineBorder(Color.black));
//Add text boxes to MovieTheaterProfits Jpanel
add(childTicketCostText);
add(childTicketCostTextBox);
add(AdultTicketCostText);
add(AdultTicketCostTextBox);
add(childTicketSoldText);
add(childTicketSoldTextBox);
add(AdultTicketSoldText);
add(AdultTicketSoldTextBox);
}
public double getChildCost()
{
input = childTicketCostTextBox.getText();
childTicketCost = Double.parseDouble(input);
return childTicketCost;
}
public double getAdultCost()
{
input = AdultTicketCostTextBox.getText();
adultTicketCost = Double.parseDouble(input);
return adultTicketCost;
}
public double getChildTotal()
{
input = childTicketSoldTextBox.getText();
childTicketTotal = Double.parseDouble(input);
return childTicketTotal;
}
public double getAdultTotal()
{
input = AdultTicketSoldTextBox.getText();
adultTicketTotal = Double.parseDouble(input);
return adultTicketTotal;
}
}
答案 0 :(得分：0)
错误是每当你点击按钮创建一个新的 JPanel的实例（newPanel）
解决问题尝试声明你的JPanel类级别是可取的
private JPanel newPanel; // create variable of class level
private JTextArea outPut;
//Create constructor
public MovieCalculatorJFrame() //constructor
{
setTitle("Profits Calculator");
newPanel = new JPanel(); //instancia
outPut = new JTextArea();
....
// end to constructor
newPanel.add(outPut);
add(newPanel);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
pack();
}
没有必要删除TextArea，您的Panel就足以清理您的内容，然后执行jTextArea.append("New Text");
您的CalcButtonListener看起来像
private class CalcButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
try{
grossChildTicketSold = (textBoxPanel.getChildCost() * textBoxPanel.getChildTotal());
grossAdultTicketSold = (textBoxPanel.getAdultCost() * textBoxPanel.getAdultTotal());
netChildTicketSold = (PERCENT_TOTAL * grossChildTicketSold);
netAdultTicketSold = (PERCENT_TOTAL * grossAdultTicketSold);
grossRevenue = (grossAdultTicketSold + grossChildTicketSold);
netRevenue = (PERCENT_TOTAL * grossRevenue);
}
catch(Exception a)
{
System.out.println("Fields are not completely filled out or letters may have been enter");
}
outPut.setText(""); //clear text to JTextArea
outPut.append("Gross revenue for adult tickets sold: " + grossAdultTicketSold + "\n");
outPut.append("Net revenue for adult tickets sold: " + netAdultTicketSold + "\n");
outPut.append("Gross revenue for child tickets sold: " + grossChildTicketSold + "\n");
outPut.append("Net revenue for child tickets sold: " + netChildTicketSold + "\n");
outPut.append("Gross revenue: " + grossRevenue + "\n");
outPut.append("Net revenue: " + netRevenue + "\n");
}
}
答案 1 :(得分：0)
在Frame类中，在calculate按钮actionPerformed方法中，您正在创建新的JtextArea。这就是为什么每按一次按钮，它就会创建并添加一个JTextArea。
因此，您可以在类级别创建一次outPut JTextArea，并根据您的要求附加结果。