JComboBox: adding automatic completion-Ignore input that does not match
//Code from: http://www.orbital-computer.de/JComboBox/
/*
Inside JComboBox: adding automatic completion
Author: Thomas Bierhance
thomas@orbital-computer.de
*/
/*
Ignore input that does not match
If the user entered a key that does not match any item you get a NullPointerException.
Of course this is not acceptable. A small enhancement in the insertString method will
ignore 'invalid' input.
*/
import javax.swing.*;
import javax.swing.text.*;
public class S07IgnoreNoMatch extends PlainDocument {
JComboBox comboBox;
ComboBoxModel model;
JTextComponent editor;
// flag to indicate if setSelectedItem has been called
// subsequent calls to remove/insertString should be ignored
boolean selecting=false;
public S07IgnoreNoMatch(final JComboBox comboBox) {
this.comboBox = comboBox;
model = comboBox.getModel();
editor = (JTextComponent) comboBox.getEditor().getEditorComponent();
}
public void remove(int offs, int len) throws BadLocationException {
// return immediately when selecting an item
if (selecting) return;
super.remove(offs, len);
}
public void insertString(int offs, String str, AttributeSet a) throws BadLocationException {
// return immediately when selecting an item
if (selecting) return;
// insert the string into the document
super.insertString(offs, str, a);
// lookup and select a matching item
Object item = lookupItem(getText(0, getLength()));
if (item != null) {
setSelectedItem(item);
} else {
// keep old item selected if there is no match
item = comboBox.getSelectedItem();
// imitate no insert (later on offs will be incremented by str.length(): selection won't move forward)
offs = offs-str.length();
// provide feedback to the user that his input has been received but can not be accepted
comboBox.getToolkit().beep(); // when available use: UIManager.getLookAndFeel().provideErrorFeedback(comboBox);
}
setText(item.toString());
// select the completed part
highlightCompletedText(offs+str.length());
}
private void setText(String text) throws BadLocationException {
// remove all text and insert the completed string
super.remove(0, getLength());
super.insertString(0, text, null);
}
private void highlightCompletedText(int start) {
editor.setSelectionStart(start);
editor.setSelectionEnd(getLength());
}
private void setSelectedItem(Object item) {
selecting = true;
model.setSelectedItem(item);
selecting = false;
}
private Object lookupItem(String pattern) {
Object selectedItem = model.getSelectedItem();
// only search for a different item if the currently selected does not match
if (selectedItem != null && startsWithIgnoreCase(selectedItem.toString(), pattern)) {
return selectedItem;
} else {
// iterate over all items
for (int i=0, n=model.getSize(); i < n; i++) {
Object currentItem = model.getElementAt(i);
// current item starts with the pattern?
if (startsWithIgnoreCase(currentItem.toString(), pattern)) {
return currentItem;
}
}
}
// no item starts with the pattern => return null
System.out.println("No item matches pattern '" + pattern + "'");
return null;
}
// checks if str1 starts with str2 - ignores case
private boolean startsWithIgnoreCase(String str1, String str2) {
return str1.toUpperCase().startsWith(str2.toUpperCase());
}
private static void createAndShowGUI() {
// the combo box (add/modify items if you like to)
JComboBox comboBox = new JComboBox(new Object[] {"Ester", "Jordi", "Jordina", "Jorge", "Sergi"});
// has to be editable
comboBox.setEditable(true);
// get the combo boxes editor component
JTextComponent editor = (JTextComponent) comboBox.getEditor().getEditorComponent();
// change the editor's document
editor.setDocument(new S07IgnoreNoMatch(comboBox));
// create and show a window containing the combo box
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(3);
frame.getContentPane().add(comboBox);
frame.pack(); frame.setVisible(true);
}
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
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