wie, um text aus einem Textfeld in eine variable?
ich möchte den Wert aus der txt-Feld, val1 und val2 auf und speichern es in der Variablen n1 und n2. dann n1 und n2 werden analysiert, um den Wert für den Rechner. hier ist der code:
public class CalcUI extends javax.swing.JFrame {
String n1 = val1.getText();
String n2 = val2.getText();
double num1 = Double.parseDouble(n1);
double num2 = Double.parseDouble(n2);
/**
* Creates new form CalcUI
*/
public CalcUI() {
initComponents();
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
//<editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
val1 = new javax.swing.JTextField();
val2 = new javax.swing.JTextField();
plus = new javax.swing.JButton();
multiply = new javax.swing.JButton();
clr = new javax.swing.JButton();
exit = new javax.swing.JButton();
minus = new javax.swing.JButton();
divide = new javax.swing.JButton();
ans = new javax.swing.JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
plus.setText("+");
plus.setMaximumSize(new java.awt.Dimension(41, 41));
plus.setMinimumSize(new java.awt.Dimension(41, 41));
plus.setPreferredSize(new java.awt.Dimension(41, 41));
plus.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
plusActionPerformed(evt);
}
});
multiply.setText("*");
multiply.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
multiplyActionPerformed(evt);
}
});
clr.setText("Clear");
clr.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
clrActionPerformed(evt);
}
});
exit.setText("Exit");
exit.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
exitActionPerformed(evt);
}
});
minus.setText("-");
minus.setMaximumSize(new java.awt.Dimension(41, 41));
minus.setMinimumSize(new java.awt.Dimension(41, 41));
minus.setPreferredSize(new java.awt.Dimension(41, 41));
minus.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
minusActionPerformed(evt);
}
});
divide.setText("/");
divide.setMaximumSize(new java.awt.Dimension(41, 41));
divide.setMinimumSize(new java.awt.Dimension(41, 41));
divide.setPreferredSize(new java.awt.Dimension(41, 41));
divide.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
divideActionPerformed(evt);
}
});
ans.setBorder(javax.swing.BorderFactory.createEtchedBorder());
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)
.addComponent(val1)
.addComponent(val2)
.addGroup(layout.createSequentialGroup()
.addComponent(clr)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(exit)))
.addContainerGap())
.addGroup(layout.createSequentialGroup()
.addGap(134, 134, 134)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
.addComponent(multiply, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(plus, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
.addGap(77, 77, 77)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(minus, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(divide, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
.addGap(143, 143, 143))
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(ans, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addContainerGap())
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(46, 46, 46)
.addComponent(val1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(18, 18, 18)
.addComponent(val2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(ans, javax.swing.GroupLayout.PREFERRED_SIZE, 23, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(26, 26, 26)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(plus, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(minus, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(34, 34, 34)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(multiply, javax.swing.GroupLayout.PREFERRED_SIZE, 41, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(divide, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 31, Short.MAX_VALUE)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(clr)
.addComponent(exit))
.addContainerGap())
);
pack();
}//</editor-fold>
private void plusActionPerformed(java.awt.event.ActionEvent evt) {
double add = num1 + num2;
ans.setText(Double.toString(add));
//TODO add your handling code here:
}
private void minusActionPerformed(java.awt.event.ActionEvent evt) {
double min = num1 - num2;
ans.setText(Double.toString(min));
//TODO add your handling code here:
}
private void divideActionPerformed(java.awt.event.ActionEvent evt) {
double div = num1 / num2;
ans.setText(Double.toString(div));
//TODO add your handling code here:
}
private void exitActionPerformed(java.awt.event.ActionEvent evt) {
System.exit(0);
//TODO add your handling code here:
}
private void clrActionPerformed(java.awt.event.ActionEvent evt) {
val1.setText("");
val2.setText("");
ans.setText("");
//TODO add your handling code here:
}
private void multiplyActionPerformed(java.awt.event.ActionEvent evt) {
double mult = num1 * num2;
ans.setText(Double.toString(mult));
//TODO add your handling code here:
}
/**
* @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(CalcUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(CalcUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(CalcUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(CalcUI.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 CalcUI().setVisible(true);
}
});
}
//Variables declaration - do not modify
private javax.swing.JLabel ans;
private javax.swing.JButton clr;
private javax.swing.JButton divide;
private javax.swing.JButton exit;
private javax.swing.JButton minus;
private javax.swing.JButton multiply;
private javax.swing.JButton plus;
private javax.swing.JTextField val1;
private javax.swing.JTextField val2;
//End of variables declaration
}
das problem ist, dass in der Erklärung
String n1 = val1.getText();
String n2 = val2.getText();
bekomme ich eine Fehlermeldung whioch sagt illegal forward reference. wie kann ich dieses Problem beheben?
wurde dieses Problem behoben.
nun, wenn ich den folgenden code verwenden:
public class CalcUI extends javax.swing.JFrame {
Double num1 ;
Double num2 ;
/**
* Creates new form CalcUI
*/
public CalcUI(){
val1 = new javax.swing.JTextField();
val2 = new javax.swing.JTextField();
num1 = Double.parseDouble(val1.getText());
num2 = Double.parseDouble(val2.getText());
initComponents();
}
bekomme ich einen build-Fehler, die sagt:
Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: empty String
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1011)
at java.lang.Double.parseDouble(Double.java:540)
at CalcUI.<init>(CalcUI.java:24)
at CalcUI$7.run(CalcUI.java:227)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:701)
at java.awt.EventQueue.access$000(EventQueue.java:102)
at java.awt.EventQueue$3.run(EventQueue.java:662)
at java.awt.EventQueue$3.run(EventQueue.java:660)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:671)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)
wie kann ich dieses Problem beheben? was ist falsch an dem code?
- Tipp: Wo ist der "gleich" - Taste?
Du musst angemeldet sein, um einen Kommentar abzugeben.
Ich glaube, Ihr JTextField Komponenten nicht initialisiert worden durch die Zeit, die Sie anrufen:
Wenn Sie diesen code verwenden, werden Sie sehen, was Ihr Beitrag ist.
So, in diesem sollten Ihre Daten speichern, um n1.
Ihnen fehlt die "equals" - Taste, das wird die Berechnung. Hinzufügen eines Listeners zum button, und in den Hörer actionPerformed (), die Sie getText() und berechnen Sie die Berechnung. Auch, denke ich, es gibt keine Notwendigkeit, haben n1 und n2 als Klasse-level-Variablen.