[英]How to access a JLabel from another method?
我正在開發一個GUI應用程序,我想讓我的代碼執行的操作是,單擊您可以在基於swing的GUI中看到的唯一按鈕后,其中包含的2個jLabel使用戶可以感知字符串“工作” 。 這是我的代碼:
public class DiligentGUI extends javax.swing.JFrame {
public DiligentGUI() {
initComponents();
}
void a()
{
fahrenheitLabel.setText("Working");
}
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
tempTextField = new javax.swing.JTextField();
celsiusLabel = new javax.swing.JLabel();
convertButton = new javax.swing.JButton();
fahrenheitLabel = new javax.swing.JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setTitle("Celsius Converter");
tempTextField.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
tempTextFieldActionPerformed(evt);
}
});
celsiusLabel.setText("Celsius");
convertButton.setText("Convert");
convertButton.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
convertButtonActionPerformed(evt);
}
});
fahrenheitLabel.setText("Fahrenheit");
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addComponent(tempTextField,
javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE,
javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(12, 12, 12)
.addComponent(celsiusLabel))
.addGroup(layout.createSequentialGroup()
.addComponent(convertButton)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(fahrenheitLabel)))
.addContainerGap(59, Short.MAX_VALUE))
);
layout.linkSize(javax.swing.SwingConstants.HORIZONTAL, new java.awt.Component[] {convertButton, tempTextField});
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(tempTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(celsiusLabel))
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(convertButton)
.addComponent(fahrenheitLabel))
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void tempTextFieldActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
}
private void convertButtonActionPerformed(java.awt.event.ActionEvent evt) {
DiligentGUI b = new DiligentGUI();
b.a();
celsiusLabel.setText("Working");
}
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(DiligentGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(DiligentGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(DiligentGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(DiligentGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new DiligentGUI().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JLabel celsiusLabel;
private javax.swing.JButton convertButton;
private javax.swing.JLabel fahrenheitLabel;
private javax.swing.JTextField tempTextField;
// End of variables declaration
}
如您所見,其中有2個jLabel:fahrenheitLabel和celsiusLabel。 我創建了一個稱為“ a”的輔助方法,該方法應將fahrenheitLabel的狀態更改為“正在工作”。 我無法實現所需的輸出。 有什么建議么?
不會發生這種情況是因為您在convertButtonActionPerformed
方法中創建了DiligentGUI
類的另一個對象。 這將創建另一個JFrame
。 您看不到它,因為您沒有通過d.setVisible(true)
將其設置為可見。
在您的位置進行更改
private void convertButtonActionPerformed(java.awt.event.ActionEvent evt) {
a(); // This will call the a() method in the current running instance.
celsiusLabel.setText("Working");
}
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