The  JPasswordField ComponentThe  JPasswordField component is a child class of  JTextField and so has similar functionality, except that it masks the entered text with a character, the default mask being '*'. Figure 9.9, “A Password Field Example” shows this example running. When the text is entered (without being visible) the user can press the enter key and an  ActionEvent object will be generated. This  ActionEvent can be passed to the  actionPerformed() method, where it can be identified and then the password field can be interrogated using  getPassword() that returns an array of char. The use of the char array is for security reasons and each element of the array should be set to blank after the password has be validated. You can use the  setEchoChar('X') to change the echo character to whatever is required. Figure 9.9. A Password Field Example The source code for this example is as below and as in JPasswordFieldExample.java 12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849 | /** Java Swing Examples - Written by Derek Molloy, Dublin City University, Ireland * see: http://ee402.eeng.dcu.ie/ */
package ee402;
import javax.swing.*; import java.awt.event.*; import javax.swing.border.*;
@SuppressWarnings("serial") public class JPasswordFieldExample extends JFrame implements ActionListener { JLabel l1 = new JLabel("This is a Test Swing Application"); JButton b1, b2; JPasswordField pwd; public JPasswordFieldExample() { super("JPassword Field Example");
JPanel p = new JPanel(); p.setLayout(new BoxLayout(p, BoxLayout.Y_AXIS)); p.setBorder(new TitledBorder("Enter Your Password:"));
pwd = new JPasswordField(20); pwd.addActionListener(this); p.add(pwd); this.getContentPane().add(p);
this.pack(); // set the size automatically this.setVisible(true); } public void actionPerformed(ActionEvent e) { if (e.getSource().equals(pwd)) { char[] thePassword = pwd.getPassword(); String s = new String(thePassword); System.out.println("Password is " + s); } } public static void main(String[] args) { new JPasswordFieldExample(); } }
|
The  JSlider ComponentThe  JSlider component is a replacement for the  Scrollbar AWT component. It is mentioned here, because there is quite a range of new functionality available with this component. For example if you look at the second  JSlider object from the top (the middle one) in Figure 9.10, “A  JSlider Example”, you will see that it has a title, tick marks for intervals. The code for this component is shown below: 343536373839404142434445 | // Slider 2 p = new JPanel(); p.setLayout(new BoxLayout(p, BoxLayout.Y_AXIS)); p.setBorder(new TitledBorder("Major Ticks")); s = new JSlider(100, 1000, 400); s.setPaintTicks(true); s.setMajorTickSpacing(100); s.getAccessibleContext().setAccessibleName("Major Ticks"); s.getAccessibleContext().setAccessibleDescription("A slider showing major tick marks"); //s.addChangeListener(this); p.add(s); hp.add(p);
|
A  JPanel object is created for each  JSlider object. The layout of this  JPanel object is set to  BoxLayout , which allows multiple components to be laid out either vertically or horizontally, without wrapping. In this case the components are laid out in BoxLayout.Y_AXIS allowing the components to be laid out vertically, and these components will remain vertical, even when the  JFrame is resized. For a  BoxLayout you also have to pass the container that you wish to lay out - in this case p .  TitleBorder is another border that you can use, that places a title around the border frame - in this case "Major Ticks" . The  JSlider object is then created with a minimum of 100, a maximum of 1000, and an initial value of 400. The  setPaintTicks() enables/disables the tick lines below the  JSlider component. The  setMajorTickSpacing(100) method call sets spacing to 100, so we will have 10 ticks in this case. The next two lines demonstrate the Accessibility API (part of the JFCs) that sets the Accessible name of this component to "Major Ticks" and the description to "A slider showing major tick marks", so that if the user has a visual disability that speech synthesis software would be capable of identifying the reason for the component to allow that person to use it. Figure 9.10. A  JSlider Example
Other constructors that can be used with  JSlider are: Constructors Constructor and Description |
---|
JSlider() Creates a horizontal slider with the range 0 to 100 and an initial value of 50. | JSlider(BoundedRangeModel brm) Creates a horizontal slider using the specified BoundedRangeModel. | JSlider(int orientation) Creates a slider using the specified orientation with the range 0 to 100 and an initial value of 50 . | JSlider(int min, int max) Creates a horizontal slider using the specified min and max with an initial value equal to the average of the min plus max. | JSlider(int min, int max, int value) Creates a horizontal slider using the specified min, max and value. | JSlider(int orientation, int min, int max, int value) Creates a slider with the specified orientation and the specified minimum, maximum, and initial values. | The Full code for this example can be seen in JSliderExample.java The  JProgressBar ComponentA  JProgressBar component displays an  Integer value within a bounded interval. A progress bar typically communicates the progress of an event by displaying its percentage of completion and possibly also provides a textual description. See Figure 9.11, “A  JProgressBar Example” for a basic example. Figure 9.11. A  JProgressBar Example
The code for this is in JProgressBarExample.java There are several constructors for  JProgressBar : Constructors Constructor and Description |
---|
JProgressBar() Creates a horizontal progress bar that displays a border but no progress string. | JProgressBar(BoundedRangeModel newModel) Creates a horizontal progress bar that uses the specified model to hold the progress bar's data. | JProgressBar(int orient) Creates a progress bar with the specified orientation, which can be either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL . | JProgressBar(int min, int max) Creates a horizontal progress bar with the specified minimum and maximum. | JProgressBar(int orient, int min, int max) Creates a progress bar using the specified orientation, minimum, and maximum. | You can set the value of the progress bar by using the  setValue(int) method and you can get the value by using the  getValue() method. The  JToggleButton ComponentThe  JToggleButton component is very similar to a checkbox, in that it can be selected or not selected. Figure 9.12, “The  JToggleButton component example (a) selected (b) not selected.” shows a selected  JToggleButton object and a non-selected component. It is very similar to the  JButton class except that it can have two states. Figure 9.12. The  JToggleButton component example (a) selected (b) not selected.
The code for this example is in JToggleButtonExample.java There are several constructors for a  JToggleButton : Constructors Constructor and Description |
---|
JToggleButton() Creates an initially unselected toggle button without setting the text or image. | JToggleButton(Action a) Creates a toggle button where properties are taken from the Action supplied. | JToggleButton(Icon icon) Creates an initially unselected toggle button with the specified image but no text. | JToggleButton(Icon icon, boolean selected) Creates a toggle button with the specified image and selection state, but no text. | JToggleButton(String text) Creates an unselected toggle button with the specified text. | JToggleButton(String text, boolean selected) Creates a toggle button with the specified text and selection state. | JToggleButton(String text, Icon icon) Creates a toggle button that has the specified text and image, and that is initially unselected. | JToggleButton(String text, Icon icon, boolean selected) Creates a toggle button with the specified text, image, and selection state. | If you wish to find the current state of the  JToggleButton object using the  isSelected() method that returns a boolean value. Exercise. Write an Egg TimerTask: Write an egg timer Swing application that counts to two minutes (well for runny eggs), updating the time as a progress bar and playing a sound when it is finished. You should be able to stop the timer at any stage using the "stop" button. My version is in Figure 9.13, “The Egg Timer Exercise”. You can use this sound ready.wav if you wish. Figure 9.13. The Egg Timer Exercise
Hints: Don't set the delay to 1 second until you have finished, otherwise you will have to wait a full two minutes every time you are debugging your application. To load a sound clip in an application you have to use something like: URL clipLocation = this.getClass().getResource("ready.wav"); AudioClip theSound = Applet.newAudioClip(clipLocation); and to play: theSound.play();
And this involves importing the  java.applet.* package. You may also (depending on the way you write your code) have to add a sleep call after you call the  play() method of the  AudioClip as the application/function may finish before the sound clip has played completely. Solution: My solution is here - EggTimerApplication.java . Once again have a good attempt at the exercise before reading my solution (as yours may be better!).
|