Getting started with GUI programming in Java_1

GETTING STARTED WITH GUI PROGRAMMING

By .Muhammad Shebl

OBJECTIVES
1. To create user interfaces using frames.
2. GUI components
3. Adding Component
4. To understand the role of layout managers
5. Panels
6. Actions
7. Set & Get

FRAMES
 Frame is a window that is not contained
inside another window.
 Frame is the basis to contain other user
interface components in Java GUI
applications.
 For Swing GUI programs, use JFrame class to
create widows.

CREATING FRAMES
import javax.swing.*;
public class Main extends JFrame {
public Main() {
setSize(200, 150);
setTitle("MUFIX");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
setVisible(true);
}

public static void main(String[] args) {
Main m=new Main();
}
}

CENTERING FRAMES
By default, a frame is displayed in the upper-left
corner of the screen.
To display a frame at a specified location, you can
use the setLocation(x,y) method in the JFrame
class. (0, 0)

Screen

(x, y)

Frame
getHeight() screenHeight

getWidth()

screenWidth

CREATING GUI OBJECTS
Label Text Check Radio
field Box Button

Button

// Create a button with text OK
JButton jbtOK = new JButton("OK");

// Create a label with text "Enter your name: "
JLabel jlblName = new JLabel("Enter your name: ");

// Create a text field with text "Type Name Here" Combo
JTextField jtfName = new JTextField("Type Name Here"); Box

// Create a check box with text bold
JCheckBox jchkBold = new JCheckBox("Bold");

// Create a radio button with text red
JRadioButton jrbRed = new JRadioButton("Red");

// Create a combo box with choices red, green, and blue
JComboBox jcboColor = new JComboBox(new String[]{"Red", "Green", "Blue"});

LAYOUT MANAGERS
 The GUI components are placed in containers. Each
container has a layout manager to arrange the GUI
components within the container.
 Layout managers are set in containers using the
setLayout(LayoutManager) method in a container.
◦ FlowLayout

◦ GridLayout

◦ BorderLayout

FlowLayout MANAGER
The components are arranged in the container from
left to right in the order in which they were added.
When one row becomes filled, a new row is started.
container.setLayout(newFlowLayout(FlowLayout.LEFT,5,5));

FlowLayout CONSTRUCTORS
 public FlowLayout(int align, int hGap, int vGap)
Constructs a new FlowLayout with a specified alignment,
horizontal gap, and vertical gap. The gaps are the distances in
pixel between components.
 public FlowLayout(int alignment)
Constructs a new FlowLayout with a specified alignment
and a default gap of five pixels for both horizontal and
vertical.
 public FlowLayout()
Constructs a new FlowLayout with a default center alignment and
a default gap of five pixels for both horizontal and vertical.

GridLayout MANAGER
 The GridLayout manager arranges components in a grid
(matrix) formation with the number of rows and columns
container.setLayout(newGridLayout(3,2,5,5));

GridLayout CONSTRUCTORS
 public GridLayout(int rows,int columns)

Constructs a new GridLayout with the specified
number of rows and columns.
 public GridLayout(int rows, int columns,
int hGap, int vGap)
Constructs a new GridLayout with the specified
number of rows and columns, along with specified
horizontal and vertical gaps between components.

BorderLayout MANAGER
 The BorderLayout manager divides the container
into five areas: East, South, West, North, and Center.
container.setLayout(new BorderLayout(5,10));
container.add(jbtOK,BorderLayout.NORTH);

USING PANELS AS SUB-CONTAINERS
 Panels act as sub-containers for grouping user interface
components.

 It is recommended that you place the user interface
components in panels and place the panels in a frame. You
can also place panels in a panel.

 To add a component to JFrame, you actually add it to the
content pane of JFrame. But to add a component to a panel,
you add it directly to the panel using the add method.

CREATING A JPanel
 You can use
 new JPanel()
to create a panel with a default FlowLayout manager
 new JPanel(LayoutManager)
to create a panel with the specified layout manager.

Use method add(Component)
to add a component to the panel.
For example :
1. JPanel p = new JPanel();
2. p.add(new JButton("OK"));
3. The following statement places panel p into fram add(p);

EVENT AND EVENT SOURCE
 When you run Java GUI programs, the program
interacts with the user and the events drive its
execution. An event can be defined as a signal to
the program that something has happened. Events
are triggered either by external user actions, such
as mouse movements, button clicks, and
keystrokes, or by internal program activities, such
as a timer. The program can choose to respond to or
ignore an event.

ADDING EVENT
 JButton jbt = new JButton("OK");
 ActionListener listener = new
OKListener();
jbt.addActionListener(this );

SET & GET TEXT :
 getText()
Returns the string from the text field.
ex:txt1.getText();

 setText(String text)
Puts the given string in the text field.
ex:txt1.setText(“MUFIX”);

Getting started with GUI programming in Java_1

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