SASA JAVA

Border Layout

2010-07-08T04:36:00.000-07:00

BorderLayout divides the container into five Geographical regions namely
North,South,East,West and Center.This is very commonly used Lyout
Manager.You can add at most one component to each region of a BorderLayout.
To put more than one component in a section, put them in a JPanel (with its own layout),
then add that panel to the border layout.
When you add components to a container which uses BorderLayout, specify the target region as the second parameter as, for example, BorderLayout.SOUTH.
If nothing is added to a region then neighbouring regions go on to fill up space.

Construcors:-
new BorderLayout();
new BorderLayout(int hgap,int vgap);

Example
Source Code:-
import javax.swing.*;
import java.awt.*;

class borderlayout extends JFrame{
public static void main(String a[]){
//initializing frames
JFrame jf=new JFrame("BorderLayout");
JFrame jf1=new JFrame("BorderLayout");
//initializing panels
JPanel panel=new JPanel();
//initializing buttons
JButton jbn=new JButton("North");
JButton jbs=new JButton("South");
JButton jbe=new JButton("East");
JButton jbw=new JButton("West");
JButton jbc=new JButton("Central");
//setting up layout
panel.setLayout(new BorderLayout());
panel.add(jbn,BorderLayout.NORTH);
panel.add(jbs,BorderLayout.SOUTH);
panel.add(jbe,BorderLayout.EAST);
panel.add(jbw,BorderLayout.WEST);
panel.add(jbc,BorderLayout.CENTER);
//adding to frame
jf.getContentPane().add(panel);
jf.setSize(250,200);
jf.setVisible(true);
}
}

Card Layout Manager

2010-07-08T04:35:00.002-07:00

One of the most complex Layout Manager is Card Layout manager.Using this manager you can create a stack of cards and flip from one layout to another.This type of organization is similar to tabbed dialogs.Card Layout provides following

Costructors:-

public CardLayout(); //Constructor creates new CardLayout

public CardLayout(int hgap,int vgap);//Constructor creates a new card layout with specified horizontal and vertical gap.

To Create a Card Layout Manager with card layout manager object,you first create a parent panel to hold the cards .Then you create an object of the CardLayout class and set it as the layout manager of the panel.Finally ,you add each card to the layout by creating the component and adding the to the panel.

Following are the methods to switch between cards that are in stack of layout.

1.void first(Container parent) //Display first card
2.void last(Container parent) //Display last card
3.void next(Container parent) //Display next card
4.void previous(Container parent) //Display previous card
5.void first(Container parent,String name) //Display specified card

Example
code snippet:-

/*
CardLayout c1;
JPanel panel;
JButton jb 1;
cardlayout()
{
JFrame jf1=new JFrame("Card Layout demo");
JPanel panel=new JPanel();
JButton jb1=new JButton("Next Button>>");
JButton jb2=new JButton("Last Button>>");
CardLayout c1=new CardLayout();
panel.setLayout(c1);
panel.add("button1",jb1);
panel.add("button2",jb2);
jb1.addActionListener(this);
jb2.addActionListener(this);
jf1.getContentPane().add(panel);
jf1.setVisible(true);
jf1.setSize(200,200);
}
public void actionPerformed(ActionEvent ae)
{
c1.next(panel);

}*/

Grid Bag Layout

2010-07-08T04:35:00.000-07:00

The GridBag Layout manager is the most flexible and complex layout manager that the AWT provides. It places components in rows and columns allowing specific components by assigning weights to individual components in the gridbag layout.

When you specify the size and position of components,you also need to specify the constraint for each component.To specify constraint ,you need to set the variables in GridBagConstraints Object and specify theGridBagLayout manager object with the setConstraint() method, to associate the constraint with the component.

The GridBagLayout class has a single constructor that does not take any arguments.Since the position of each component in a layout is controlled by a GridBagLayout object and is determined by the currently setGridBagConstraints object,you need to create the GridBagConstraintsobject before the layout can be built.

GridBagLayout g=new GridBagLayout();
GridBagConstraints cons=new GridBagConstraints();

You can assign following values to GridBagConstraints attributes:-

anchor:-It is used when the component is smaller than its display area to determine where to place the compoenent.valid values are shown below:

GridBagConstraints.CENTER
GridBagConstraints.NORTH
GridBagConstraints.NORTHEAST
GridBagConstraints.EAST
GridBagConstraints.SOUTHEAST
GridBagConstraints.SOUTH
GridBagConstraints.SOUTHWEST
GridBagConstraints.WEST
GridBagConstraints.NORTHWEST

fill:- It is used when the display area of component is larger than the requested size of the component to determine whether to resize the component.valid values are:-
GridBagConstraints.NONE
GridBagConstraints.HORIZONTAL
GridBagConstraints.VERTICAL
GridBagConstraints.BOTH

gridwidth,gridheight:-It specifies number of columns or rows in display area of components the default value is 1,valid values are:
GridBagConstraints.REMAINDER
GridBagConstraints.RELATIVE

gridx,gridy:-They specify the row and column at the upper left of the components display area.The leftmost column has the address gridx=0 and topmost cell has the address gridy=0.

insets:- They specify the extenal padding of the component ,that is ,the minimum amount of space between the components and the edges of its display area.The value is specified as an Insets object .By default ,each component does not have external padding.The default padding value is insets(0,0,0,0).

ipadx,ipady:-They specify the internal padding to be added to the minimum size of the component.The default value is 0.The width of the component will be its minimum width plus ipadx*2 pixels.Similarly ,the height of the component will be its minimum height plus ipady*2 pixels.

weightx,weighty:- They determine whether the component stretch horizontally to fill the display area of the applet or vertically.The default value is 0 for both.

Example
Source code:-

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class GridBagWindow extends JFrame {
boolean inAnApplet = true;
final boolean shouldFill = true;
final boolean shouldWeightX = true;

public GridBagWindow() {
JButton button;
Container contentPane = getContentPane();
GridBagLayout gridbag = new GridBagLayout();
GridBagConstraints c = new GridBagConstraints();
contentPane.setLayout(gridbag);
if (shouldFill) {
//natural height, maximum width
c.fill = GridBagConstraints.HORIZONTAL;
}

button = new JButton("Button 1");
if (shouldWeightX) {
c.weightx = 0.5;
}
c.gridx = 0;
c.gridy = 0;
gridbag.setConstraints(button, c);
contentPane.add(button);

button = new JButton("2");
c.gridx = 1;
c.gridy = 0;
gridbag.setConstraints(button, c);
contentPane.add(button);

button = new JButton("Button 3");
c.gridx = 2;
c.gridy = 0;
gridbag.setConstraints(button, c);
contentPane.add(button);

button = new JButton("Long-Named Button 4");
c.ipady = 40; //make this component tall
c.weightx = 0.0;
c.gridwidth = 3;
c.gridx = 0;
c.gridy = 1;
gridbag.setConstraints(button, c);
contentPane.add(button);

button = new JButton("Button 5");
c.ipady = 0; //reset to default
c.weighty = 1.0; //request any extra vertical space
c.anchor = GridBagConstraints.SOUTH; //bottom of space
c.insets = new Insets(10,0,0,0); //top padding
c.gridx = 1; //aligned with button 2
c.gridwidth = 2; //2 columns wide
c.gridy = 2; //third row
gridbag.setConstraints(button, c);
contentPane.add(button);

addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
if (inAnApplet) {
dispose();
} else {
System.exit(0);
}
}
});
}

public static void main(String args[]) {
GridBagWindow window = new GridBagWindow();
window.inAnApplet = false;

window.setTitle("GridBagLayout");
window.pack();
window.setVisible(true);
}
}

JButton

2010-07-08T04:34:00.002-07:00

JButton

Jbutton is the standrad command button used in Java.It is mainly used for event driven programming.A JButton when clicked fires an event which is handled by an event handler which in response do some work as indicated in hadler.On click the JButton takes some set of input and process that.The JButton is a Swing Component.

JButton Class has following constructors:-

JButton() // Creates a button with no text or icon

JButton(Action a) //Creates a button where are properties are tak

en from action supplied

JButton(Icon icon)//Creates a button with a icon

JButton(String text)//Creates a button with some text

JButton(String text ,Icon icon)//Creates button with both text and icon

Features of JButton:-

1.JButton applies event handling.

2.JButton has a different look and feel for enabled and disabled buttons.

3.You can set mnemonics for JButtons.

4.TooltipText can also be set for JButtons.

Following example shows the application of all above mentioned features:-
In this example there are buttons which on click disable and enable the corresponding buttons.
The program follows:-

import javax.swing.*;

import java.awt.event.*;

public class ButtonDemo extends JPanel

implements ActionListener {

protected JButton but1, but2, but3;

public ButtonDemo() {

ImageIcon leftButtonIcon = createImageIcon("d:/image/left.gif");

ImageIcon middleButtonIcon = createImageIcon("c:/image/middle.gif");

ImageIcon rightButtonIcon = createImageIcon("c:/image/right.gif");

but1 = new JButton("Disable middle button", leftButtonIcon);

but1.setActionCommand("disable");

//setting up mnemonics

but1.setMnemonic(KeyEvent.VK_D);

but2 = new JButton("Middle button", middleButtonIcon);

but2.setMnemonic(KeyEvent.VK_M);

but3 = new JButton("Enable middle button", rightButtonIcon);

//Use the default text position of CENTER, TRAILING (RIGHT).

but3.setMnemonic(KeyEvent.VK_E);

but3.setActionCommand("enable");

//enabling the command button

but3.setEnabled(false);

//Listeners for actions on buttons 1 and 3.

but1.addActionListener(this);

but3.addActionListener(this);

but1.setToolTipText("Click this button to disable the middle button.");

but3.setToolTipText("Click this button to enable the middle button.");

//Add Components to this container, using the default FlowLayout.

add(but1);

add(but2);

add(but3);

}

public void actionPerformed(ActionEvent e) {

if ("disable".equals(e.getActionCommand())) {

but2.setEnabled(false);

but1.setEnabled(false);

but3.setEnabled(true);

} else {

but2.setEnabled(true);

but1.setEnabled(true);

but3.setEnabled(false);

}

/** Returns an ImageIcon, or null if the path was invalid. */

protected static ImageIcon createImageIcon(String path) {

java.net.URL imgURL = ButtonDemo.class.getResource(path);

if (imgURL != null) {

return new ImageIcon(imgURL);

} else {

System.err.println("Couldn't find file: " + path);

return null;

}

// Create the GUI.

private static void createAndShowGUI() {

//Create and set up the JFrame.

JFrame frame = new JFrame("ButtonDemo");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

//Create and set up the content pane.

ButtonDemo newContentPane = new ButtonDemo();

newContentPane.setOpaque(true); //content panes must be opaque

frame.setContentPane(newContentPane);

//Display the JFrame.

frame.pack();

frame.setVisible(true);

}

public static void main(String[] args) {

//creating and showing this application's GUI.

javax.swing.SwingUtilities.invokeLater(new Runnable() {

public void run() {

createAndShowGUI();

}

});

}

JLabel

2010-07-08T04:34:00.000-07:00

JLabels in Swing can contain text, images or both.
JLabel do not generate an action event though
it works on Mouse Events.Like MouseMotion,MouseListener etc.
We can also add non-functional labels in our interface(GUI).
You can also specify the position of the text relative to the image.
Also we can align,specify border,size and many more properties.
Constructors:-JLabel class has following Constructors

JLabel() // Creates a JLabel without an image and with empty string title
JLabel(Icon icon) //Creates a JLabel instance with specified image as title
JLabel(Icon image,int horizontalAlignment)// Creates a JLabel object with image and alignment
JLabel(String text)//JLabel with some text as title
JLabel(String text,Icon image,int horizontalAlignment)
JLabel(String text ,int horizontalalignment)
Example:-
The following exmaple is for simple label showing only text:-

import javax.swing.*;

public class SimpleJLabel extends JFrame{

public static void main(String[] args) {

JLabel label = new JLabel("A Simple Text Label");

JFrame frame = new JFrame();

frame.getContentPane().add(label);

frame.pack();

frame.setVisible(true);
}
}
Example:-
The Following Example shows setting up an Icon on Label

import javax.swing.*;

public class SimpleJLabel extends JFrame{

public static void main(String[] args) {

JLabel label = new JLabel();

label.setIcon(new ImageIcon("e1.png"));

JFrame frame = new JFrame();

frame.getContentPane().add(label);

frame.pack();

frame.setVisible(true);

}

}

You can also set many more properties like mnemonics,tooltiptext alignment etc.

JTextField

2010-07-08T04:33:00.001-07:00

JTextField

A text field is a basic text control that enables the user to type a small amount of text.

The text field is editable. It is handy in cases

where a single line of input is required or a little information is neede.

It is mostly used in forms and does most work on Event handling.There are certain methods which copies the contents of TextField whenever an action is fired.

Constructors:-

JTextField has four types of constructors which are as follows

1.JTextField()

2.JTextField(String) //Creates a TextField with initial text as String

3.JTextField(String,int) //creates a TextField with length of cloumn being chars and default text is as String

4.JTextField(int) //creates s TextField with length of column being chars.

Note: Always try to specify the number of columns for each text field. If you do not specify the number of columns or a preferred size, then the field's preferred size changes whenever the text changes, which can result in unwanted layout changes.

Example:-Creating a form with JTextField

//textfield.java

import javax.swing.*;

class textfield extends JFrame{

public static void main(String a[]){

JFrame frame=new JFrame("JTextFieldDemo");

JPanel panel=new JPanel();

JTextField txt=new JTextField(10);

JTextField txtf=new JTextField("Default",20); //with default text written and size of 20

panel.add(txt);

panel.add(txtf);

frame.getContentPane().add(panel);

frame.setVisible(true);

frame.pack();

}

We have several methods for getting and setting values from and to JTextField

1.String getText()

2.void setText(String)

Edit methods of JTextField component

1.void setEditable(boolean) //set whether the text in the JTextField is editable or not

2. boolean isEditable() //returns whether the tetfield is editable or not

For setting and getting the width of JTextField use

void setColumns(int) //specifies the width of textfield

int getColumns() //obtains number of columns of the TextField

For selecting whole field at once use following

void selectAll()

For adding ActionListeners use following

void addActionListener(ActionListener) //adds action listener

void removeActionListener(ActionListener) //removes ActionListener

Setting ToolTip and Icon

2010-07-08T04:32:00.004-07:00

Adding Icons and ToolTips

Tooltips are shot information messages which are displayed when your mouse pointer rests at some components.That is if suppose your mose pointer is at a button whose tooltiop is set as "click here" the if your pointer comes over button the a small message will appear saying "click here".

For setting ToolTip we can use setToolTipText() method of JComponent class.

ToolTip Example:-

// tooltip.java

import javax.swing.*;
public class tooltip
{
public static void main(String a[])
{
JFrame frm=new JFrame("ToolTip Demo");
JPanel panel=new JPanel();
JLabel labeltool=new JLabel("ToolTio DemoPlace mouse over it");
labeltool.setToolTipText("This is ToolTip");
panel.add(labeltool);
frm.getContentPane().add(panel);
frm.setVisible(true);
frm.pack();
}
}

SettingIcon Example:-

// settingicon.java

import java.awt.*;
import javax.swing.*;
public class settingicon
{
public static void main(String a[])
{
JFrame frm=new JFrame("Setting Icon Demo");
JPanel panel=new JPanel();
JLabel label=new JLabel(new ImageIcon("BAK.png"));
panel.add(label);
frm.getContentPane().add(panel);
frm.setVisible(true);
frm.pack();
}
}

Setting Mnemonics and Shortcut Keys

2010-07-08T04:32:00.002-07:00

Setting a Shrotcut Key(Mnemonic)

A shortcut key is an underlined character you may in labels,buttons,menus etc.These are called as mnemonics.You can select a control by pressing the combination of Alt key and the character.For example if underlined character is 's' then in order to activate control press Alt+s.You can set mnemonic by using setMnemonic(Char ch)

Syntax:-

component.setMnemonic(Char ch);

Exapmle:-
In the Screen shot the mnemonic is set as 'M'.
So this button can be activated by pressing Alt+M.
// memonic.java

import java.awt.*;
import javax.swing.*;
public class mnemonic
{
public static void main(String a[])
{
JFrame frm=new JFrame("Mnemonic Demo");
JPanel panel=new JPanel();
JButton Button=new JButton("Setting Mnemonic");
Button.setMnemonic('M');
panel.add(Button);
frm.getContentPane().add(panel);
frm.setVisible(true);
frm.pack();
}
}

DropDown Menu or Choice menu

2010-07-08T04:32:00.000-07:00

DropDown Menu or The Choice class

A choice menu is a dropdown menu which upon clicking presents a list of menus(choices) from which user may choose one.That is when a user clicks on the choice control a list of option drops down from which a user can select only one choice.It enforces user to choose from the list of options provided.

Constructor:-

// Choice();
creating an object of Choice class
e.g. Choice choice=new Choice();

Adding Items:-

Items in the list of menu are added by using addItem(String Item) method.
e.g. choice.addItem("Option 1");

Example:-
//choice.java

import java.awt.*;

public class choice
{
public static void main(String a[])
{
Frame frm=new Frame("Choice menu demo");
Panel panel=new Panel();
Choice choice=new Choice();
frm.add(panel);
choice.addItem("Option 1");
choice.addItem("Option 2");
choice.addItem("Option 3");
choice.addItem("Option 4");
panel.add(new Label("This is DropDown MENU"));
panel.add(choice);
frm.show();
frm.pack();
frm.setBounds(100,100,250,200);
}
}

Useful Methods of Choice Class:-

How to create and use Check Boxes

2010-07-08T04:31:00.001-07:00

CheckBox is a unique java control which lets user select one or more options.This control becomes handy where some sort of selection is to be made.I will explain here the CheckBoxes In Java Swings.Which are created using JCheckBox class.

Constructors:-There are five constructors of CheckBox

1.Checkbox() --> Creates a check box with an empty string for its label.

2.Checkbox(String label, boolean state) --> Creates a check box with the specified label and sets the specified state.

3.Checkbox(String label) --> Creates a check box with the specified label.

4.Checkbox(String label, boolean state, CheckboxGroup group) --> Constructs a Checkbox with the specified label, set to the specified state, and in the specified check box group.

5.Checkbox(String label, CheckboxGroup group, boolean state) --> Creates a check box with the specified label, in the specified check box group, and set to the specified state.

Example:-This simple swing example illustrates how checkboxes are added.

//test.java

import javax.swing.*;

public class test{
public static void main(String[] args){
JFrame frame = new JFrame("Check Box Frame");
JCheckBox chkop1 = new JCheckBox("option 1");
JCheckBox chkop2 = new JCheckBox("option 2");
JCheckBox chkop3 = new JCheckBox("option 3");
JPanel panel=new JPanel();
panel.add(chkop1);
panel.add(chkop2);
panel.add(chkop3);
frame.getContentPane().add(panel);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

Selecting Checkboxes:-In this example the checkboxes are default selected using setSelected(boolean state) method of JCheckBox class.

//test1.java

import javax.swing.*;

public class test{
public static void main(String[] args){
JFrame frame = new JFrame("Check Box Frame");
JCheckBox chkop1 = new JCheckBox("option 1");
chkop1.setSelected(true);
JCheckBox chkop2 = new JCheckBox("option 2");
chkop2.setSelected(true);
JCheckBox chkop3 = new JCheckBox("option 3");
JPanel panel=new JPanel();
panel.add(chkop1);
panel.add(chkop2);
panel.add(chkop3);
frame.getContentPane().add(panel);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

Other useful methods:-

setLabel() :-Sets Label as provided string to this CheckBox.
getLabel() :-Returns Label of CheckBox.
addItemListener() :-Only ItemListeners can be added to CheckBox control for event handling purposes.

How to Use CheckBoxGroup

2010-07-08T04:30:00.004-07:00

CheckboxGroup class is used to group togather the Checkboxes,from which only one can be selected at a time.
That is exactly one Checkbox in that goup will be "on" else remain "false".By clicking on Checkbox we may "on" or "off" the desired Checkbox.This control is mostly used in making selection ,where exactly one selection is needed form given choices.

more on Checkboxes Visit Checkbox Tutorial
Constructor:-

CheckboxGroup() ---> Creates a new instance of CheckboxGroup.
Important Methods:-

void getSelectedCheckbox() ----> Gets the current choice from this check box group.
void setSelectedCheckbox(Checkbox cb) ----> Turn "on" the specified CheckBox.
How to Use CheckboxGroup:-

Example:-

// test.java

import javax.swing.*;
import java.awt.*;

public class test{
public static void main(String[] args){
JFrame frame = new JFrame("Check Box Frame");
CheckboxGroup cb=new CheckboxGroup();
Checkbox chkop1 = new Checkbox("option1",false,cb);
Checkbox chkop2 = new Checkbox("option2",false,cb);
Checkbox chkop3 = new Checkbox("option3",true,cb);
JPanel panel=new JPanel();
panel.add(chkop1);
panel.add(chkop2);
panel.add(chkop3);
frame.getContentPane().add(panel);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

Using JTextField and JTextArea

2010-07-08T04:30:00.002-07:00

TextFields are used to take input from user also it can be used to display results.
The various constructors and methods are defined in the previous JTextField tutorials.

Values from a TextField is extracted using String getText() and set usingvoid setText(String txt).
The user can select a portion from the JTextField and JTextArea usingString getSelectedText() and void select(int start_index,int end_index)
String getSelectedText() retrurns the String portion selected by the user from the textfield.
You can also enable or disable the TextField that is if you want TextField to be editable the use the methos void setEditable(boolean value) to true else set false.If you want to get value of editable TextField useboolean isEditable().

Sometimes you wish to set a password field in which the entered character must not be shown.It has to be replaced by some other sign or value.To set a password field you must use void setEchoChar(Char ch)character you specified in 'ch' will be shown when some charater is typed.
If you want to get the Charcter specified the use char getEchoChar().
Example :-
getting selected value from a text field and displaying it to other and use of Password field.

// textfield.java

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class textfield extends JFrame implements ActionListener
{
JFrame frame;
JPanel panel;
JTextField txtname,txtdisplay;
TextField txtpass;
JButton button;
public textfield()
{
frame=new JFrame("Text Field usage demo");
panel=new JPanel();
txtname=new JTextField(25);
txtpass=new TextField(25);
txtpass.setEchoChar('#');
txtdisplay =new JTextField(25);
JButton button=new JButton("Display selected");
button.addActionListener(this);
panel.setLayout(new GridLayout(3,2));
panel.add(new JLabel("Name :"));
panel.add(txtname);
panel.add(new JLabel("Password :"));
panel.add(txtpass);
panel.add(txtdisplay);
panel.add(button);
frame.getContentPane().add(panel);
frame.show();
frame.pack();

}

public void actionPerformed(ActionEvent ae)
{

txtdisplay.setText("Name :"+txtname.getSelectedText()+" Pass :"+txtpass.getText());

}
public static void main(String a[])
{
new textfield();
}
}

Example:-
getting selected value from a text area and displaying selected in textfield.

// textarea.java

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class textarea extends JFrame implements ActionListener
{
JFrame frame;
JPanel panel;
JTextField txtname,txtdisplay;
TextField txtpass;
JTextArea area;
JButton button;
public textarea()
{
frame=new JFrame("Text Area usage demo");
panel=new JPanel();
txtdisplay =new JTextField(25);
area = new JTextArea("vaibhav pandey has made this programme",5,5);
JButton button=new JButton("Display selected");
button.addActionListener(this);
panel.add(area);
panel.add(txtdisplay);
panel.add(button);

frame.getContentPane().add(panel);
frame.show();
frame.pack();

}

public void actionPerformed(ActionEvent ae)
{
txtdisplay.setText("Selected String :"+area.getSelectedText());
}
public static void main(String a[])
{
new textarea();
}
}.

Loading Image on JFrame using JFileChooser

2010-07-08T04:30:00.000-07:00

JFileChooser is a very handy utility in java Swings to choose any particular file of an extension.
Sometimes in our applications we need to load images onto our main container .In java we can use either JFrame or JPanel to load images.Statically we can provide the path of image into our program,but most of times it is not feasible for us to give image path statically.For specifying image path dynamically we use JFileChooser which returns path of a selected image.You can also select the desierd file extensions for whom you are looking.In following Example it is elaborated how to use JFileChooser and using it how we can load an image on a container.

Example (Source code ):-

//imageloading.java

//Program developed by Vaibhav Pandey

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;

public class imageloading extends JFrame
{
BufferedImage mImage;
String name,name1;
public imageloading()
{
JFrame frm=new JFrame("image loading test");
String source=filechoose();
File inputFile = new File(source);
try {
mImage = ImageIO.read(inputFile);
} catch (IOException ex) {
//Logger.getLogger(index.class.getName()).log(Level.SEVERE, null, ex);
}
JLabel lb=new JLabel(new ImageIcon(mImage));
frm.getContentPane().add(lb);
frm.show();
frm.pack();
}

String filechoose()
{
JFileChooser chooser = new JFileChooser();
chooser.setCurrentDirectory(new File("."));

chooser.setFileFilter(new javax.swing.filechooser.FileFilter() {
public boolean accept(File f) {
name = f.getName().toLowerCase();
return name.endsWith(".gif") || name.endsWith(".jpg")
|| name.endsWith(".jpeg") || f.isDirectory();
}

public String getDescription() {
return "Image files";
}
});

int r = chooser.showOpenDialog(this);

if (r == JFileChooser.APPROVE_OPTION) {
name1 = chooser.getSelectedFile().getAbsolutePath();
StringBuffer sb=new StringBuffer();
sb.append(name1);

int l=sb.length();
for(int i=0;i
{
if(sb.charAt(i)=='\\')
{
sb.insert(i, "\\");i++;
}
}
}
return name1;
}
public static void main(String a[])
{
new imageloading();
}
}

Output Windows:-

Following first widow shows the JFileChooser() instance opened and asking to
select a file of given extension,and in second window you can see the loaded image.

Elaboration:-In the given code we have used the ImageIO class to read the image file whose file is being specified and consequently is buffered.Later this buffered image is set on a Label as a ImageIcon to display it on the frame.

JFileChooser() is used to choose the files of desired extension here FileFilter() method is used to filter the files on the basis of extensions .Here we have considered only .jpeg and .gif images.Since the '/' is treated as a escape sequence in Java thus in when we are fetching path name in variable 'name1' using method 'JFileChoose.getSelectedFile().getAbsolutePath()' ,in order to omit the escape sequence we embed '//' in the path when we have some path selected.

We have used 'JFileChooser.APPROVE_OPTION' because to verify that we have selected a legitimate file or not.Any queries and comments are most welcome.In Java JFileChooser is a nice utility ,use it and tell me about the tutorial.

Menus In Java Swings

2010-07-08T04:29:00.000-07:00

Every window can have a menu associated with it.Menu Bars basic function is to provide a list of choices.Each choice has its own drop-down menu(is provided otherwise none).This is implemented in Java by using following classes:-

MenuBar
Menu
MenuItem
CheckboxMenuItem

A menu bar can contains many menu objects.Each menu object may contain many MenuItem objects.In this implementation it is also possible to include checkable menu items.These can be implemented by CheckboxMenuItem class and will place a check mark next to them when they get selected.

First look at the constructors involved in creation of a menubar application.

1. MenuBar:-MenuBar is the highest class in this application and it will contain all the menu's inside it.It has only default constructor.

//MenuBar () only default constructor

2.Menu:-The constructors for Menu is as following.Menu's object will hold menu item's in them.

//Menu()
//Menu(String optionName)
//Menu(String optionName,boolean Removable)

In this case optionName provides the name of menu selection.If removable are set to true then menu can be removed and allowed to roam free.Otherwise it will remain with the menu bar.

3.MenuItem:-The Individual menuitems are of type MenuItem .These controls are to be placed on Menu object.

//MenuItem()
//MenuItem(String itemName)
//MenuItem(String itemName,MenuShortcut key)

here itemName is the name of item shown on menu and key is the menu shortcut for this item.

4.CheckboxMenuItem:-CheckboxMenuItem creates the checkboxes which can be placed as a menu and show their state by checked or unchecked.

//CheckboxMenuItem()
//CheckboxMenuItem(String itemName)
//CheckboxMenuItem(String itemName,boolean on)

itemName refers to the name of checkbox displayed on menu and on refers its state checked or unchecked.

Important Methods:-There are methods with various functionality lets see

1.void setEnabled(boolean flagvalue):-This method sets any menuitem to enabled or disabled state.Which specifies whether the menuitem is active or not(Click works or not).

2.boolean isEnabled():-This method returns the value whether the menuitem is active or inactive.That is either true or false.

3.void setLabel(String newName):-This method changes the name of a menuitem.

4.String getLabel():-It returns the name of the menuitem.

5.boolean getState():-This method returns the value (checked or unchecked) of
CheckboxMenuItem object.

6.void setState(boolean checked):-You can set the value of CheckboxMenuItem to true or false using this method.