JAP Hybrid 3

Terminology

• A Layout Manager is a specialized class responsible for arranging GUI components in a container

• All layout managers implement the java.awt.LayoutManager interface

• Developers can use predefined layout managers or create their own, but it's not easy

• The current Java API offers layout managers for java.awt, javax.swing, and javafx.scene.layout

• java.awt layout managers include:

  • BorderLayout
  • FlowLayout
  • GridLayout
  • CardLayout
  • GridBagLayout

• javax.swing layout managers include:

  • BoxLayout
  • SpringLayout
  • GroupLayout

• javafx.scene.layout layout managers include:

  • AnchorPane
  • BorderPane
  • FlowPane
  • GridPane
  • Pane
  • StackPane
  • TilePane
  • TextFlow
  • HBox and VBox

• In Swing, all containers have a default layout manager

• The default layout manager for JFrame, JWindow, and JDialog is BorderLayout

• The default layout for JPanel and JApplet is FlowLayout

• The setLayout() method changes a container's layout after creation

• Setting the layout manager to null requires the developer to arrange components manually, which can be done in JavaFX using Pane

General View

• There are three ways to arrange components in a GUI container:

  • Using existing layout managers
  • Using absolute positioning
  • Using visual programming in an IDE

• Using existing layout managers is the easiest method for uncomplicated UIs

  • The layout manager determines all arrangements, including size and positioning
  • Containers can be placed inside other containers
  • Different layout managers for different containers create sophisticated GUIs

• Absolute positioning provides complete control over the GUI

  • Setting a container's layout to null allows specifying each component's size and absolute position relative to the container's upper-left corner
  • Programming a GUI this way can be time-consuming

• Visual programming (GUI design tools) in an IDE allows developers to "paint" the GUI

  • The IDE tool generates the Java code
  • Event handling code remains the developer's responsibility
  • NetBeans IDE provides such a tool
  • Painting tools can use absolute positioning or pre-existing layout managers
  • GridBagLayout and GroupLayout are frequently used and created specifically for GUI building tools
  • JavaFX has similar layout managers called layout Panes.

Layout Tutorial

• Layouts define how components are organized in a layer

Swing Layout Managers

• Swing provides several layout managers:
• Flow: Default for panels; lays out components one after another until there's no more room, then starts a new row.
• Border: Default for frames; divides the container into five regions: North, South, East, West, and Center. Components can be placed in a specific region.
• Box: Arranges components in a single row or column, depending on the specified alignment.
• Grid: Ideal for creating a grid of identically sized components.
• GridBag: A more flexible grid layout than Grid, allowing rows and columns of different sizes. Components can span multiple rows or columns, and the layout manager can handle components smaller or larger than the allotted space.
• Group: Works best with visual tools; describes an arrangement from left to right and top to bottom.

Choosing Layout Managers

• The most common problem is deciding which layout manager to choose

• Consider flexible layout managers like GridBagLayout and SpringLayout if none seem right or if you can't use a builder tool

• GridLayout or BorderLayout are best if you need to display a component in as much space as possible and there is only one component in the container. otherwise GridBagLayout may be a good choice

• For a few components in a compact row, use a JPanel with the default FlowLayout or the BoxLayout manager

• GridLayout is the best choice for components of the same size in rows and columns

• For complex layouts with many components, use a flexible layout manager like GridBagLayout or SpringLayout, or group components into JPanels, each with its own layout manager

Common Layout Problems

• Working with layouts often involves trial and error

• Check if the layout manager you're using allows specifying component sizes

• Ensure you need to set the component's exact size; component sizes are affected by the look and feel of your system

• Use setSize or setBounds to set a component's size if it is not controlled by a layout manager

• Override getMinimumSize, getPreferredSize, and getMaximumSize methods to give size hints when extending a Swing component class

• GridBagLayout can have issues with components and text fields if the container size is smaller than the preferred size

• Use setMinimumSize, setPreferredSize, and setMaximumSize methods to give size hints

• Call the revalidate method on a component after setting size hints on a visible component to trigger a layout update

• Invoke revalidate and repaint if a component isn't showing up after being added

• Implement getPreferredSize and getMinimumSize methods for small components

• Check the available space in your layout manager

Class Diagram

• A class diagram shows a static view of an application
• It shows the types of objects and the relationships between them
• A class contains objects and may inherit properties from other classes
• It visualizes, describes, documents and constructs executable software code

Purpose of Class Diagrams

• The main purpose of class diagrams is to build a static view of an application
• It is widely used for construction and can be mapped with object-oriented languages

Benefits of Class Diagrams

• It can represent the object model for complex systems
• It reduces maintenance time by providing a structural overview
• It provides a general schematic of an application for better understanding
• It shows a detailed chart highlighting the code to be programmed
• It is helpful for stakeholders and developers

Components of a Class Diagram

• The class diagram consists of three sections:

  • Upper Section
  • Middle Section
  • Lower Section

• Upper Section:

  • Contains the class name
  • Represents similar objects sharing relationships, attributes, operations, and semantics
  • Rules for representing a class:
    • Capitalize the initial letter of the class name.
    • Place the class name in the center of the upper section.
    • Write the class name in bold format.
    • Write the name of an abstract class in italics.

• Middle Section:

  • Contains attributes that describe the quality of the class.
  • Characteristics of attributes:
    • Attributes are written with visibility factors: public (+), private (-), protected (#), and package (~).
    • The visibility factors illustrate the accessibility of an attribute class.
    • A meaningful name should explain the attribute's usage.

• Lower Section:

  • Contains methods or operations
  • Methods are represented in list form, with each method on a single line
  • Demonstrates how a class interacts with data

Relationships

• In UML, relationships are of three types:
  • Dependency
  • Generalization
  • Association
• Dependency:
  • A semantic relationship where a change in one class affects another
  • Is known as a weaker relationship
  • E.g., Student_Name depends on Student_Id
• Generalization:
  • A relationship between a parent (superclass) and child class (subclass)
  • The child class inherits from the parent class
  • E.g., Current Account, Saving Account, and Credit Account are generalized forms of Bank Account
• Association:
  • Describes a static or physical connection between objects
  • Depicts the number of objects in the relationship
  • E.g., a department is associated with the college
• Multiplicity:
  • Defines a range of allowable instances of attributes
  • If a range is unspecified, it is considered a default multiplicity
  • E.g., multiple patients are admitted to one hospital
• Aggregation:
  • A subset of association that represents a relationship
  • Defines a part-whole or part-of relationship
  • The child class can exist independently of its parent class
  • A company encompasses employees, and the company still exists if an employee resigns
• Composition:
  • A subset of aggregation that portrays the dependency between a parent and its child
  • If one part is deleted, the other part is discarded
  • Represents a whole-part relationship
  • A contact book consists of contacts, and all contacts are lost if the contact book is deleted