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Dacj 4 2-c

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  • 1. CollaborateKnowledge Byte In this section, you will learn about: • Property Sheets and Property Editor • The PropertyEditorSupport and PropertyDescriptor Class • The BeanInfo Interface ©NIIT Collaborate Lesson 2C / Slide 1 of 23
  • 2. CollaborateProperty Sheets and Property Editor • Property sheets and property editors enable easy access to the exposed JavaBean properties. • Property sheet or the Properties window of BDK displays a list of all the exposed properties of a JavaBean. • A property editor window is used to edit the values of JavaBean properties, which cannot be edited in property sheets. • The property editor is always associated with a specific JavaBean property. • The property editor is displayed whenever an attempt is made to modify the value of the associated JavaBean property during the build phase. ©NIIT Collaborate Lesson 2C / Slide 2 of 23
  • 3. CollaborateThe PropertyEditorSupport andPropertyDescriptor Class • The PropertyEditorSupport Class: • Enables you to create a text-based or a GUI based customized property editor. • Implements the PropertyEditor interface of the java.beans package. • Is extended by a class to create a customized property editor. ©NIIT Collaborate Lesson 2C / Slide 3 of 23
  • 4. CollaborateThe PropertyEditorSupport andPropertyDescriptor Class (Contd.) • The following table lists some methods of the PropertyEditorSupport Class: Method Description void addPropertyChangeListener( Registers a new PropertyChangeListener pcl) PropertyChangeListener to handle the PropertyChange events. The method accepts an object of PropertyChangeListener interface. void firePropertyChange() Informs all the listeners when there is a change in the JavaBean property. ©NIIT Collaborate Lesson 2C / Slide 4 of 23
  • 5. Collaborate The PropertyEditorSupport and PropertyDescriptor Class (Contd.) • The methods of PropertyEditorSupport class: (Contd.) Method Descriptionvoid paintValue(Graphics g, Paints a graphics object in a rectangle on theRectangle rec) screen area. The graphics to paint and the area in which the graphics is painted are passed as parameters to the paintValue() method.boolean isPaintable() Returns a boolean value that specifies if the JavaBean supports the paintValue() method.void Removes a registered PropertyChangeListenerremovePropertyChangeListener( from the list of listeners for the PropertyChangePropertyChangeListener plist) events. ©NIIT Collaborate Lesson 2C / Slide 5 of 23
  • 6. CollaborateThe PropertyEditorSupport andPropertyDescriptor Class (Contd.) • The methods of PropertyEditorSupport class: (Contd.) Method Descriptionboolean Returns a boolean value that determines whether thesupportsCustomEditor() property editor object supports the custom editor or not.String getAsText() Returns the string value of a JavaBean property.Component Returns a custom property editor as a component thatgetCustomEditor() enables you to edit the value of JavaBean properties.void setAsText(String Sets the value of a property to the string passed as atext) parameter to this method. ©NIIT Collaborate Lesson 2C / Slide 6 of 23
  • 7. CollaborateThe PropertyEditorSupport andPropertyDescriptor Class (Contd.) • The methods of PropertyEditorSupport class: (Contd.) Method Description String[] getTags() Returns an array of tag values that consists of all the possible values for a JavaBean property. void setValue(Object value) Sets the value of a JavaBean property to the value passed as parameter. Object getValue() Enables you to retrieve the value of a JavaBean property. ©NIIT Collaborate Lesson 2C / Slide 7 of 23
  • 8. CollaborateThe PropertyEditorSupport andPropertyDescriptor Class (Contd.) • The PropertyDescriptor Class • The PropertyDescriptor Class restricts the JavaBean properties that are displayed in the Properties window. • To create customized properties window, you need to create an information class that contains information about the properties, events, and methods of a JavaBean. • The information class extends the SimpleBeanInfo class and have a name ending with BeanInfo. For example, class PropBeanInfo extends SimpleBeanInfo { //Class body } ©NIIT Collaborate Lesson 2C / Slide 8 of 23
  • 9. CollaborateThe PropertyEditorSupport andPropertyDescriptor Class (Contd.) • You also need to override the getPropertyDescriptors() method that returns an array of PropertyDescriptor objects in the PropBeanInfo class. For example, public PropertyDescriptor[] getPropertyDescriptors() { //Method_body } ©NIIT Collaborate Lesson 2C / Slide 9 of 23
  • 10. CollaborateThe BeanInfo Interface • The BeanInfo interface provides the methods that enable you to specify and retrieve the information about a JavaBean. • The following table lists some of the methods of BeanInfo interface: Method Description MethodDescriptor[] Returns an array of the method descriptor objects getMethodDescriptors( of a JavaBean. The method descriptor objects are ) used to determine information about the various methods defined in a JavaBean. EventDescriptor[] Returns an array of the event descriptor objects of getEventDescriptors() a JavaBean. The event descriptor objects determine the information about the events associated with a JavaBean. ©NIIT Collaborate Lesson 2C / Slide 10 of 23
  • 11. CollaborateThe BeanInfo Interface(Contd.) • The methods of BeanInfo interface: (Contd.) Method Description PropertyDescriptor[] Returns an array of the property descriptor objects getPropertyDescriptor of a JavaBean. The property descriptor objects are s() used to determine information about the various custom properties of a JavaBean. Image getIcon( int Returns a corresponding image object for one of icon_type ) the fields of the BeanInfo interface passed as a parameter to this method. The BeanInfo interface defines int fields, such as ICON_COLOR_32x32 and ICON_MONO_32x32 to represent icons. ©NIIT Collaborate Lesson 2C / Slide 11 of 23
  • 12. CollaborateFrom the Expert’s Desk In this section, you will learn: • Tips on: • Using the sample JavaBeans of BDK1.1 in Java 2 SDKv1.4.x • Creating a single manifest file that contains entries for multiple JavaBeans • FAQs on JavaBeans ©NIIT Collaborate Lesson 2C / Slide 12 of 23
  • 13. CollaborateTipsUsing the Sample JavaBeans of BDK1.1 in Java 2SDK v 1.4.x • The steps to use the sample JavaBeans of BDK in Java 2 SDK 1.4.x are: • Open the C:BDK1.1beansdemosunwdemobuttons folder using the Windows Explorer. • Open the folder for the sample JavaBean, for example, open the folder for ExplicitButton JavaBean that is not supported by Java 2 SDK 1.4.x. ©NIIT Collaborate Lesson 2C / Slide 13 of 23
  • 14. CollaborateTipsUsing the Sample JavaBeans of BDK1.1 in Java 2SDK v 1.4.x (Contd.) • Change the code in the public EventSetDescriptor[] getEventSetDescriptors() method. For example, to load the ExplicitButton JavaBean, you need to change the following code: EventSetDescriptor push = new EventSetDescriptor(beanClass, "actionPerformed", java.awt.event.ActionListener.class, "actionPerformed"); The preceding code should be changed to the following code: EventSetDescriptor push = new EventSetDescriptor(beanClass, "action", java.awt.event.ActionListener.class, "actionPerformed"); ©NIIT Collaborate Lesson 2C / Slide 14 of 23
  • 15. CollaborateTipsUsing the Sample JavaBeans of BDK1.1 in Java 2SDK v 1.4.x (Contd.) • Compile all files of C:BDK1.1beansdemosunwdemobuttons directory. • Download Microsoft nmake utility to the C:BDK1.1beansbeanbox directory from the following url: ftp://ftp.microsoft.com/Softlib/MSLFILES/nmake15.exe • Add the C:BDK1.1beansbeanbox directory path to your system path. • Go to C:BDK1.1beansdemo and type: nmake buttons.mk 7. Run BDK. The ExplicitButton JavaBean will get loaded in the BDK. ©NIIT Collaborate Lesson 2C / Slide 15 of 23
  • 16. CollaborateTipsCreating Manifest File for Multiple JavaBeans • The syntax to define the entries for multiple JavaBean files in the same manifest file is: Name: <beanFile1.class> Java-Bean: <status> Name: <beanFile2.class> Java-Bean: <status> Name: <file3.gif> In the preceding syntax, a blank line is left between each of the file declarations. ©NIIT Collaborate Lesson 2C / Slide 16 of 23
  • 17. CollaborateFAQs • What type of JavaBean will you use to display the current time in an application? You can display the current time in a Java application using a control JavaBean. The control JavaBean adds a new feature to an existing Java application. • How can you count the number of hits for a particular Web page using JavaBeans? You can count the number of hits for a Web page using an invisible runtime JavaBean. This JavaBean performs a hidden background function. ©NIIT Collaborate Lesson 2C / Slide 17 of 23
  • 18. CollaborateFAQs (Contd.) • How would you change the foreground color of a component using JavaBeans? The foreground color of a component can be changed using the JavaBean properties. You need to create a JavaBean for the component and define a property, foreground color for the component. The setForegroundColor() method for the JavaBean property can be used to specify and change the value of the foreground color for the JavaBean component. ©NIIT Collaborate Lesson 2C / Slide 18 of 23
  • 19. CollaborateFAQs (Contd.) • What is introspection? Introspection is the process of examining the class structure of a JavaBean and determining the properties, methods, and events supported by the JavaBean. Introspection helps you to find only the list of methods and the method signatures of a JavaBean. It does not help you to find the source code of the methods and how the JavaBean functionality has been implemented. The introspection technique is used by a programmer during the design and build phases to identify the JavaBean functionality. The end user will not be interested in knowing the internal functionalities of a JavaBean. ©NIIT Collaborate Lesson 2C / Slide 19 of 23
  • 20. CollaborateFAQs (Contd.) • Where is the manifest file of a JavaBean stored in the JAR file? The manifest file is stored inside the directory, META-INF inside the JAR file. • How does the compiler recognize the file to execute while running a JAR file? When a JAR file is executed, the Main-Class entry in the manifest file instructs the java -jar command about the class to execute. The java -jar command enables you to execute a runnable JAR file on the command prompt. The -jar option enables the Java Runtime Environment (JRE) to recognize that the specified file is a runnable JAR file. The command to execute a runnable JAR file, SampleJar.jar, on the command prompt is: java -jar SampleJar.jar ©NIIT Collaborate Lesson 2C / Slide 20 of 23
  • 21. CollaborateChallenge 1. Select the option that allows you to view the sequence of method invocation in BDK 1.1: a. ToolBox Window b. BeanBox Window c. Method Tracer Window d. Properties Window • What is the use of the addPropertyChangeListener() method of the PropertyEditorSupport class? • Select the class that you need to use for implementing bound properties in JavaBeans: • PropertyChangeSupport class • VetobaleChangeSupport class • ProperyChangeEvent class • PropertyDescriptor class ©NIIT Collaborate Lesson 2C / Slide 21 of 23
  • 22. CollaborateChallenge (Contd.) • The PropertyEditorSupport class implements the __________interface. • What is the purpose of implementing the BeanInfo interface for a JavaBean? • The ___________enables you to modify the JavaBean properties that are displayed in the property sheet. ©NIIT Collaborate Lesson 2C / Slide 22 of 23
  • 23. CollaborateSolutions to Challenge • c. Method Tracer Window • The addPropertyChangeListener() method registers a new listener to handle the PropertyChange events. • a. PropertyChangeSupport class • PropertyEditor • The BeanInfo interface enables you to provide the information about the properties, events, and methods of a JavaBean in the JavaBean information class. • Property Editors ©NIIT Collaborate Lesson 2C / Slide 23 of 23