当前正在研究一个基于GUI的小型Java / Swing项目，该项目涉及将值从一种度量转换为另一种度量。我对Swing也很陌生。
我一直在跟踪用户完成了多少次转换（“ calcCount”），但是无论用户是否抛出NumberFormatException，无论用户是否输入了非数字字符，计数都在增加-我将CalcCount设置为每当转换在try / Catch内失败时为零，这不应该发生吗？ （如下）。
try {
conversionFieldValue = Double.parseDouble(text);
} catch (NumberFormatException e) {
calcCount = 0;
JOptionPane.showMessageDialog(null, "Error: the value entered may not be a valid number. \nPlease ensure that you are entering a valid double, with or without a decimal place.", "Conversion error", JOptionPane.ERROR_MESSAGE);
conversionCountLabel.setText("Conversion Count: " + calcCount);
}
当前calcCount唯一要增加的地方是convertButton的侦听器，仅当输入的值不为空/空且源为convertButton时才触发。代码处理如下。
if(e.getSource() == convertButton && text.isEmpty() == false) {
calcCount++;
conversionCountLabel.setText("Conversion Count: " + calcCount);
}
我该如何更有效地处理此问题，并确保在正确的条件下calcCount实际上增加了-而不管解析是否失败？
编辑-----------------------
由于我未能解决我的问题，因此我在下面提供了一个小程序，该程序具有核心功能和我面临的问题：
“ thing1”类-驱动程序类：
import java.io.IOException;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class thing1 {
public static void main(String[] args) throws IOException {
JFrame frame = new JFrame("Thing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
thing2 thing2 = new thing2();
frame.getContentPane().add(thing2);
frame.pack();
frame.setVisible(true);
}
}
“事物2”类，包括扩展和相关的侦听器
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
@SuppressWarnings("serial")
public class thing2 extends JPanel {
/**
* Declaring all variables and components to be used within the GUI
*/
private JTextField conversionField;
private JLabel resultLabel, conversionCountLabel, inputLabel;
private JButton convertButton, clearButton;
private int calcCount;
private String text;
double conversionFieldValue;
private double result;
thing2() {
/**
* Creating two listeners which will be used
* "convertListener" is used for conversions
* "convertDeleteListener" is used to set the values of conversionField, resultLabel, conversionCountLabel and calcCount
* all used to display details about number of conversions etc.
*/
ActionListener convertListener = new ConvertListener();
ActionListener convertDeleteListener = new convertDeleteListener();
/**
* Creating inputLabel and conversionCountLabel
*/
inputLabel = new JLabel("Enter value:");
conversionCountLabel = new JLabel("Conversion Count: ");
/**
* Creating both the convertButon and clearButton
* Adding listeners to both buttons which determine when they are clicked,
* and what action should be carried out when done so.
*/
convertButton = new JButton("Convert");
convertButton.addActionListener(convertDeleteListener);
convertButton.addActionListener(convertListener); // convert values when pressed
clearButton = new JButton("Clear");
/**
* Creating both the resultLabel and conversionField
*/
resultLabel = new JLabel();
conversionField = new JTextField(5);
/**
* Adding all created assets to the JFrame.
* Adding toolTips to each of the created assets.
* Adding Listeners to select assets to carry out certain tasks.
*/
add(inputLabel);
add(conversionField);
conversionField.addActionListener(convertListener);
add(convertButton);
add(resultLabel);
add(conversionCountLabel);
add(clearButton);
clearButton.addActionListener(convertDeleteListener);
/**
* Creating size of JFrame.
* Setting background colour.
*/
setPreferredSize(new Dimension(800, 80));
setBackground(Color.WHITE);
}
public class ConvertListener implements ActionListener {
@Override
public void actionPerformed(ActionEvent event) {
/**
* Trimming all leading and trailing white spaces from the text the user has input.
*/
text = conversionField.getText().trim();
if (text.isEmpty() == false) {
/**
* Simply trying to convert input to a double, if that fails outputting a Dialog box to users screen stating why
*/
try {
conversionFieldValue = Double.parseDouble(text);
} catch (NumberFormatException e) {
calcCount = 0;
JOptionPane.showMessageDialog(null, "Error: the value entered may not be a valid number. \nPlease ensure that you are entering a valid double, with or without a decimal place.", "Conversion error", JOptionPane.ERROR_MESSAGE);
conversionCountLabel.setText("Conversion Count: " + calcCount);
}
// the factor applied during the conversion
double factor = 0;
// the offset applied during the conversion.
double offset = 0;
// Setup the correct factor/offset values depending on required conversion
result = factor * conversionFieldValue + offset;
//formatting the value to two decimal places.
String numAsString = String.format ("%.2f", result);
resultLabel.setText(numAsString);
} else {
if(text.isEmpty() == true) {
/**
* if the text value is empty, simply display a dialog box stating so
*/
calcCount = 0;
JOptionPane.showMessageDialog(null, "Error: the text input area cannot be empty.", "Text area is empty...", JOptionPane.ERROR_MESSAGE);
conversionCountLabel.setText("Conversion Count: " + calcCount);
}
}
}
}
public class convertDeleteListener implements ActionListener{
public void actionPerformed(ActionEvent e){
/**
* Using e.getSource to determine which button was pressed, doing some actions depending on which it was.
*/
if(e.getSource() == convertButton && text.isEmpty() == false) {
calcCount++;
conversionCountLabel.setText("Conversion Count: " + calcCount);
} else
if(e.getSource() == clearButton) {
calcCount = 0;
conversionField.setText("");
resultLabel.setText("");
conversionCountLabel.setText("Conversion Count: " + calcCount);
}
}
}
}
应该能够按原样进行编译，并且如果您在双精度字段以外的字段中输入任何字符，则会出现一个错误对话框-但是您会注意到即使转换失败，“ caclCount”仍然会增加。由于必须切掉所有转换的巨大开关，结果将显示为00.00-这在完整程序中可以正确计算，只是calcCount我遇到了问题。
编辑：现在，此问题已解决，感谢大家的帮助：）。