NetBeans Tutorial for Colors & Counter Bean

weaverchurchSoftware and s/w Development

Aug 15, 2012 (5 years ago)

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a. Colors Bean Example

1.Creating a Bean

Let's begin with a Color Bean that has a method
change()
which will change the color

whenever a button
actionPerformed

event is generated.

Create a java file with the given source code below and name it as Colors.
java.

import java.awt.*;

import java.awt.event.*;

import java.io.*;

public class Colors extends Canvas implements Serializable{



private Color color;



private boolean rect;

public Colors(){



rect=false; setSize(200,100);



change();



}

public boolean g
etRect(){



return rect;

}

public void setRect(boolean flag){this.rect=flag;
repaint();}

public void change(){ color = randomColor(); repaint();}

private Color randomColor(){


int r=(int)(255*Math.random());


int g =(int)(255*Math.random()); int
b=(in
t)(255*Math.random());


return new Color(r,g,b);}

public void paint(Graphics g){ Dimension d = getSize();



int h=d.height; int
w=d.width; g.setColor(color);



if(rect){g.fillRect(0,0,w
-
1,h
-
1);}




else{g.fillOval(0,0,w
-
1,h
-
1);



}




}



}



2.


Compile the source code for the Bean and generate the Colors.class in the command prompt :



javac Colors.java



3.


Create a manifest file in a text

editor.

The manifest file specifies the name of the class file and indicates that it is a
JavaBean. The manifest file becomes part of the JAR file. You can name the
manifest file
manifest.tmp.

It contains the following two lines:

Name: Colors.class

Java
-
Bean: True



(On Windows, be sure to include a carriage return at the end of the text in the
manifest file.)

4 .


Create the executable JAR file.

Use the form of the
jar

command to include the manifest file along with the
Colors.class

file (Type the co
mmand on one line):

jar cvfm colors.jar manifest.tmp Colors.class




NetBean 6.1

IDE


For


Colors JavaBean



Click

File | New Project
to create a new
project
, a grouping of related files
.

Follow the wizard steps below.

1.

Choose Project

-

General | Java Appli
cation

2.

Name and Location
-

Uncheck
Create Main Class
, check
Set as Main
Project




Click

File | New File
to create a new
file
.

Follow the wizard steps below.

1.

Choose File Type

-

Java GUI Forms | JApplet Form
(from swing GUI


Forms)

2.

Class Name


Use

the

De
fault

class name






Installing Counter JavaBeans
-

JavaBeans that have been jarr'ed can be
downloaded and added to the
Palette

.

o

Tools | Pallette
---

Swing/AWT components

1.

Click

Add from JAR


2.

Select JAR file
-

Locate and select
colors.jar


3.

Select Component
s
-

Highlight
Colors


4.

Select Palette Category
-

Highlight

Beans


o

Beans
should now contain

colors
class



Visual programming
-

Since applets are visual it is possible to program by
dragging and dropping components from the toolbar.

o

Click

Design

tab.

o

To see

the layout manager:



Right click in gray design area

| Set Layout | Flow Layout


o

To add a visual object, right click the gray area:



Add From Palette | Swing | JButton




Add From Palette | Beans | colors


Then the net beans IDE look like this:


Connecting

the Button to the Colors Bean

NetBeans and other Java development environments can automatically generate the code
needed to connect events and listeners. First connect the JButton event
actionPerformed

with the Colors
change
(

)
method.



Right click

the j
Button1.
Select
Events | Action | actionPerformed.

The source code will be generated to call
jButton1ActionPerformed

method on a
JButton event.






Edit
jButton1ActionPerformed
,
adding code to increment the counter:




private void jButton1ActionPerformed(
java.awt.event.ActionEvent evt) {



colors1.change();

}



Running the Applet



Shift+F6 to run the applet.





when clicked on the button


the oval changes its color .








b. Counter Bean Exam
ple

1. Creating a Bean



The easiest way to learn to build a Bean is to start with a basic Bean, then add a property to it.


Let's begin
with a Counter Bean

that has a method
increment()
which increment a Counter bean whenever a button
actionPerformed

eve
nt is generated.

Create a java file with the given


source code below and name it as Counter.java.

import java.awt.*;



public class Counter extends Panel {



private long count=0;



private Label label;



private long maxValue=20;



public void setMaxValu
e(long max) {



maxValue = max;



}



public long getMaxValue() { return maxValue; }



public Counter() {



setBackground(Color.blue);



setForeground(Color.white);



label = new Label(""+count);



add(label);



}



pu
blic void increment () {



if (count < maxValue) {



count++;



label.setText(count+" ");



}



else label.setText("!!");



}

}



2 .


Compile the source code for the Bean and generate the Counter.class in the command pro
mpt :



javac Counter.java

3.


Create a manifest file in a text editor.

The manifest file specifies the name of the class file and indicates that it is a
JavaBean. The manifest file becomes part of the JAR file. You can name the
manifest file
manife
st.man.

It contains the following two lines:

Name: Counter.class

Java
-
Bean: True



(On Windows, be sure to include a carriage return at the end of the text in the
manifest file.)

4.


Create the executable JAR file.

Use the form of the
jar

command to in
clude the manifest file along with the
Counter.class

file (Type the command on one line):

jar cfm counterEvent.jar manifest.man Counter.class



NetBean 6
.
1

IDE


For


Counter JavaBean



Click

File | New Project
to create a new
project
, a grouping of related
files
.

Follow the wizard steps below.

1.

Choose Project

-

General | Java Application

2.

Name and Location
-

Uncheck
Create Main Class
, check
Set as Main
Project




Click

File | New File
to create a new
file
.

Follow the wizard steps below.

1.

Choose File Type

-

Jav
a GUI Forms | JApplet Form

2.

Class Name
-

Use Default






Installing Counter JavaBeans
-

JavaBeans that have been jarr'ed can be
downloaded and added to the
Palette

.

o

Tools | Pallette Manager

1.

Click

Add from JAR


2.

Select JAR file
-

Locate and select
counterE
vent.jar


3.

Select Components
-

Highlight
Counter


4.

Select Palette Category
-

Highlight

Beans


o

Beans
should now contain

Counter
class



Visual programming
-

Since applets are visual it is possible to program by
dragging and dropping components from the toolbar
.

o

Click

Design

tab.

o

To see the layout manager:



Right click in gray design area

| Set Layout | Flow Layout


o

To add a visual object, right click the gray area:



Add From Palette | Swing | JButton




Add From Palette | Beans | Counter


Then the net beans IDE

look like this:




Connecting the Button to the Counter Bean

Previous examples illustrated how events generated by clicking the mouse could be
connected to a listener method by manually writing code such as:

button.addActionListener(new ActionListener(
) {



public void actionPerformed(ActionEvent e) {



counter.increment();




}



}

);

NetBeans and other Java development environments can automatically generate the code
needed to connect events and listeners. First connect the

JButton event
actionPerformed

with the Counter
increment( )
method.



Right click

the j
Button1.
Select
Events | Action | actionPerformed.

The source code will be generated to call
jButton1ActionPerformed

method on a
JButton event.






Edit
jButton1ActionPer
formed
,
adding code to increment the counter:




private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {



counter1.increment();

}



Running the Applet



Shift+F6 to run the applet.



Label shows the number of times the button is clicked

.