FocusEvent没有得到JFormattedTextField的最后一个值，我怎么能得到它？
我的JFrame对象上有两个JFormattedTextField对象。 我希望通过这些JFormattedTextField对象的值进行基本的Math（加法）。 当焦点丢失第一个或第二个文本字段时，我希望它发生。 但是当“ focusLost() ”，事件没有得到最后一个值时，它会得到之前的值。
例如; tf1为0， tf2为0。 我将2写入tf1 ，当focusLost() ，结果（ tf1+tf2 ）变为静止0.当我更改其中任何一个时，结果变为2（前一个值）
如何获取focusLost上的最后一个值？
这是我的代码：
JFormattedTextField tf1,tf2; NumberFormat format=NumberFormat.getNumberInstance(); tf1=new JFormattedTextField(format); tf1.addFocusListener(this); tf2=new JFormattedTextField(format); tf2.addFocusListener(this);
和focusLost() ：
public void focusLost(FocusEvent e) { if(tf1.getValue() == null) tf1.setValue(0); if(tf2.getValue() == null) tf2.setValue(0); //because if I dont set, it throws nullPointerException for tf.getValue() BigDecimal no1 = new BigDecimal(tf1.getValue().toString()); BigDecimal no2 = new BigDecimal(tf2.getValue().toString()); System.out.println("total: " + (no1.add(no2))); }
我认为您应该使用PropertyChangeListener ，请参阅如何编写属性更改侦听器 。
有一个使用JFormattedTextField的例子：
//...where initialization occurs: double amount; JFormattedTextField amountField; ... amountField.addPropertyChangeListener("value", new FormattedTextFieldListener()); ... class FormattedTextFieldListener implements PropertyChangeListener { public void propertyChanged(PropertyChangeEvent e) { Object source = e.getSource(); if (source == amountField) { amount = ((Number)amountField.getValue()).doubleValue(); ... } ...//re-compute payment and update field... } }
你的JFormattedTextField中有一些defalut数值集tf1，tf2;
例如，对我而言，没有NPE
import java.awt.*; import java.awt.event.*; import java.math.RoundingMode; import java.text.NumberFormat; import javax.swing.*; import javax.swing.border.*; import javax.swing.event.*; public class FormatterLimit { private JFrame frame = new JFrame(); private JPanel pnl = new JPanel(); private JLabel focusLabel = new JLabel(" focusLost Handle "); private JFormattedTextField formTextField; private JLabel docLabel = new JLabel(" document Handle "); private JFormattedTextField formTextField1; private NumberFormat formTextFieldFormat; private double amount = 10000.00; public FormatterLimit() { formTextFieldFormat = NumberFormat.getNumberInstance(); formTextFieldFormat.setMinimumFractionDigits(2); formTextFieldFormat.setMaximumFractionDigits(2); formTextFieldFormat.setRoundingMode(RoundingMode.HALF_UP); focusLabel.setFont(new Font("Serif", Font.BOLD, 14)); focusLabel.setForeground(Color.blue); focusLabel.setPreferredSize(new Dimension(120, 27)); formTextField = new JFormattedTextField(formTextFieldFormat); formTextField.setValue(amount); formTextField.setFont(new Font("Serif", Font.BOLD, 22)); formTextField.setForeground(Color.black); formTextField.setBackground(Color.yellow); formTextField.setPreferredSize(new Dimension(120, 27)); formTextField.setHorizontalAlignment(SwingConstants.RIGHT); formTextField.addFocusListener(new FocusListener() { @Override public void focusGained(FocusEvent e) { formTextField.requestFocus(); formTextField.setText(formTextField.getText()); formTextField.selectAll(); } @Override public void focusLost(FocusEvent e) { Runnable doRun = new Runnable() { @Override public void run() { double t1a1 = (((Number) formTextField.getValue()).doubleValue()); if (t1a1 < 1000) { formTextField.setValue(amount); } } }; SwingUtilities.invokeLater(doRun); } }); docLabel.setFont(new Font("Serif", Font.BOLD, 14)); docLabel.setForeground(Color.blue); docLabel.setPreferredSize(new Dimension(120, 27)); formTextField1 = new JFormattedTextField(formTextFieldFormat); formTextField1.setValue(amount); formTextField1.setFont(new Font("Serif", Font.BOLD, 22)); formTextField1.setForeground(Color.black); formTextField1.setBackground(Color.yellow); formTextField1.setPreferredSize(new Dimension(120, 27)); formTextField1.setHorizontalAlignment(SwingConstants.RIGHT); formTextField1.addFocusListener(new FocusListener() { @Override public void focusGained(FocusEvent e) { formTextField1.requestFocus(); formTextField1.setText(formTextField1.getText()); formTextField1.selectAll(); } @Override public void focusLost(FocusEvent e) { } }); formTextField1.getDocument().addDocumentListener(docListener); pnl = new JPanel(); pnl.setBorder(new EmptyBorder(2, 2, 2, 2)); pnl.setLayout(new GridLayout(2, 2)); pnl.add(focusLabel); pnl.add(formTextField); pnl.add(docLabel); pnl.add(formTextField1); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.add(pnl, BorderLayout.CENTER); frame.setLocation(200, 200); frame.pack(); frame.setVisible(true); formTextFieldFocus(); } // private DocumentListener docListener = new DocumentListener() { @Override public void changedUpdate(DocumentEvent documentEvent) { printIt(documentEvent); } @Override public void insertUpdate(DocumentEvent documentEvent) { printIt(documentEvent); } @Override public void removeUpdate(DocumentEvent documentEvent) { printIt(documentEvent); } private void printIt(DocumentEvent documentEvent) { DocumentEvent.EventType type = documentEvent.getType(); double t1a1 = (((Number) formTextField1.getValue()).doubleValue()); if (t1a1 < 1000) { Runnable doRun = new Runnable() { @Override public void run() { formTextField1.setValue(amount); } }; SwingUtilities.invokeLater(doRun); } } }; public void formTextFieldFocus1() { Runnable doRun = new Runnable() { @Override public void run() { formTextField1.grabFocus(); formTextField1.requestFocus(); formTextField1.setText(formTextField1.getText()); formTextField1.selectAll(); } }; SwingUtilities.invokeLater(doRun); } public void formTextFieldFocus() { Runnable doRun = new Runnable() { @Override public void run() { formTextField.grabFocus(); formTextField.requestFocus(); formTextField.setText(formTextField.getText()); formTextField.selectAll(); formTextFieldFocus1(); } }; SwingUtilities.invokeLater(doRun); } public static void main(String args[]) { EventQueue.invokeLater(new Runnable() { @Override public void run() { FormatterLimit fl = new FormatterLimit(); } }); } }
焦点侦听器上的JFormattedTextField的默认行为是COMMIT_OR_REVERT ，因此一种方法是在焦点侦听器结束后执行更新。 延续效果很好，如下所示。
import java.awt.EventQueue; import java.awt.GridLayout; import java.awt.event.FocusAdapter; import java.awt.event.FocusEvent; import java.text.NumberFormat; import javax.swing.JFormattedTextField; import javax.swing.JFrame; import javax.swing.JPanel; /** @see http://stackoverflow.com/questions/6803976 */ public class Adder extends JPanel { private final NumberFormat format = NumberFormat.getNumberInstance(); private final JFormattedTextField a = new JFormattedTextField(format); private final JFormattedTextField b = new JFormattedTextField(format); private final JFormattedTextField sum = new JFormattedTextField(format); public Adder() { this.setLayout(new GridLayout(0, 1)); this.add(init(a)); this.add(init(b)); sum.setEditable(false); sum.setFocusable(false); this.add(sum); } private JFormattedTextField init(JFormattedTextField jtf) { jtf.setValue(0); jtf.addFocusListener(new FocusAdapter() { @Override public void focusLost(FocusEvent e) { EventQueue.invokeLater(new Runnable() { @Override public void run() { Number v1 = (Number) a.getValue(); Number v2 = (Number) b.getValue(); sum.setValue(v1.longValue() + v2.longValue()); } }); } }); return jtf; } private void display() { JFrame f = new JFrame("Adder"); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.add(this); f.pack(); f.setLocationRelativeTo(null); f.setVisible(true); } public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { @Override public void run() { new Adder().display(); } }); } }