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@schoettl
Last active October 11, 2015 16:18
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UnixPasswordField -- A unix style password input
/*
* UnixPasswordField -- A unix style password input
* Copyright (C) 2012 Jakob Schöttl
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package kj.scotlyard.board;
import java.awt.event.KeyEvent;
import javax.swing.JPasswordField;
import javax.swing.UIManager;
/**
* This class implements a unix style password input. Similar like this:
* <p>
* <tt>read -s -p "Password: " VARIABLE</tt>
* </p>
* <tt>-s</tt> silent, no echo; <tt>-p</tt> prompt text, not implemented here of
* course; into <tt>VARIABLE</tt>, can be retrieved by
* <code>getPassword()</code>. Neither copy, cut nor paste are supported.
*
* Note that there is <i>no</i> protection mechanism against spy progs which
* look into the program memory.
*
* @author Jakob Schöttl
*
*/
@SuppressWarnings("serial")
public class UnixPasswordField extends JPasswordField {
private StringBuffer password = new StringBuffer();
public UnixPasswordField() { }
public UnixPasswordField(int columns) {
super(columns);
}
private void provideErrorFeedback() {
UIManager.getLookAndFeel().provideErrorFeedback(this);
}
@Override
public char getEchoChar() {
return 0;
}
/**
* Not supported; This method will do NOTHING. The echo character is not
* changeable and will always be <tt>0</tt> (on the surface), that is
* <i>no</i> echo character is displayed.
*/
@Override
public void setEchoChar(char c) { }
@Override
public char[] getPassword() {
final int l = password.length();
char[] result = new char[l];
password.getChars(0, l, result, 0);
return result;
}
@Override
protected void processKeyEvent(KeyEvent e) {
if (e.getID() == KeyEvent.KEY_TYPED) {
char c = e.getKeyChar();
switch (c) {
case KeyEvent.VK_BACK_SPACE:
int l = password.length();
if (l > 0) {
password.deleteCharAt(l - 1);
} else {
// Ein UnixPasswordField soll NICHTS ueber das Passwort verraten
// Also soll man auch nicht nach Passworteingabe, die Anzahl der
// eingegebenen Zeichen zaehlen koennen.
// Ansonsten waere folgendes aber ganz nett:
// provideErrorFeedback();
}
break;
default:
password.append(c);
break;
}
} else {
super.processKeyEvent(e);
}
}
@Override
public void cut() {
provideErrorFeedback();
}
@Override
public void copy() {
provideErrorFeedback();
}
@Override
public void paste() {
provideErrorFeedback();
}
@Override
public void setText(String s) {
password.setLength(0);
password.append(s);
}
/**
* Clear the password (like <code>setText("")</code>
* for normal text fields).
*/
public void clear() {
password.setLength(0);
}
/**
* Check weather the password is blank.
* @return <code>true</code> if the password is empty
*/
public boolean isPasswordEmpty() {
return password.length() == 0;
}
}
@schoettl
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Automatisch clear() on FOCUS_GAINED ist doch keine gute Idee.
Entweder auskommentieren, dass der Anwender am Ende entscheiden kann, oder so etwas wie setClearOnFocusGained(boolean), default false.

@schoettl
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Vielleicht zusaetzlich etwas wie setFeedbackWhenEmpty(boolean), default false. Zum ein-/ausschalten des "ErrorFeedback" bei Backspace und leerem Passwort.

@schoettl
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Zum Abfragen ob Passwort eingegeben wurde bzw. ob es leer ist:

boolean isPasswordEmpty() {
    return password.length() == 0;
}

Empty oder Blank? Empty kommt in Java schon haeufiger vor ...

@schoettl
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Bugfix: setText musste noch überschrieben werden: Damit wird, wie bei JPasswordField, das Passwort gesetzt. Allerdings dürfen beim UnixPasswordField keine echoChars im Textfeld erscheinen!

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