Download Lecture_27__intro_to_the_Java_GUI_features

Lesson 27:
Introduction to the Java GUI
The Java Button
// helloworldbutton.java
import java.awt.*;
import javax.swing.*;
Invoking the graphics libraries
called the abstract window toolkit
and the swing. We will use the
classes provided in these standard
java libraries to create our Java
GUI.
class HelloButton{
While we can code this ourselves,
this saves us a lot of work.
public static void main (String[] args){
JFrame frame = new JFrame("HelloButton");
Container pane = frame.getContentPane();
JButton hello = new JButton("HelloWorld");
pane.add(hello);
frame.pack();
frame.show();
}
}
The Java Button
// helloworldbutton.java
import java.awt.*;
import javax.swing.*;
Our own class. The file it is stored
in must therefore be called
HelloButton.java.
class HelloButton{
public static void main (String[] args){
JFrame frame = new JFrame("HelloButton");
Container pane = frame.getContentPane();
JButton hello = new JButton("HelloWorld");
pane.add(hello);
frame.pack();
Our main section. This means that
frame.show();
this will be an executable file that
}
we can call using the command
}
“java HelloButton”.
As all main sections must do, it
accepts arguments
The Java Button
// helloworldbutton.java
import java.awt.*;
import javax.swing.*;
Here we create a java frame
(JFrame), also known as a window.
The JFrame is available since we
imported the Swing library.
class HelloButton{
public static void main (String[] args){
JFrame frame = new JFrame("HelloButton");
Container pane = frame.getContentPane();
This is the title of the frame
JButton hello = new JButton("HelloWorld");
pane.add(hello);
frame.pack();
frame.show();
}
}
This is a constructor statement. We
identify it through the keyword “new”
The Java Button
// helloworldbutton.java
import java.awt.*;
import javax.swing.*;
A container is a component to which we can add
other components. A JFrame is actually a container,
but we should not add components directly to a
JFrame. Instead, we should add all components to a
special container in the JFrame.
class HelloButton{
public static void main (String[] args){
JFrame frame = new JFrame("HelloButton");
Container pane = frame.getContentPane();
JButton hello = new JButton("HelloWorld");
pane.add(hello);
frame.pack();
frame.show();
}
}
We use the method getContentPane()
to get a reference to JFrame’s special
container.
The Java Button
// helloworldbutton.java
import java.awt.*;
import javax.swing.*;
Here we create a Javax.swing.JButton object and give
it a string which is used as a label.
class HelloButton{
public static void main (String[] args){
JFrame frame = new JFrame("HelloButton");
Container pane = frame.getContentPane();
JButton hello = new JButton("HelloWorld");
pane.add(hello);
frame.pack();
frame.show();
}
}
The object is called hello
The Java Button
// helloworldbutton.java
import java.awt.*;
import javax.swing.*;
The method add in the class Container is
used to add a component to the JFrame’s
content pane (later we will add many
components to a frame).
class HelloButton{
public static void main (String[] args){
JFrame frame = new JFrame("HelloButton");
Container pane = frame.getContentPane();
JButton hello = new JButton("HelloWorld");
pane.add(hello);
frame.pack();
frame.show();
}
}
Note: For now, we do not tell the container how to arrange this component,
nor where this component is to be displayed (we will do this later).
The Java Button
// helloworldbutton.java
import java.awt.*;
import javax.swing.*;
The pack method from JFrame is used to minimize
the window to smallest size that can accommodate the
content of the container
class HelloButton{
public static void main (String[] args){
JFrame frame = new JFrame("HelloButton");
Container pane = frame.getContentPane();
JButton hello = new JButton("HelloWorld");
pane.add(hello);
frame.pack();
frame.show();
}
}
Since we have only one component in the container, the window will be
minimized to the size of the button, which is determined by the size of the label.
The Java Button
// helloworldbutton.java
import java.awt.*;
import javax.swing.*;
The show method from JFrame is
used to display the frame.
class HelloButton{
public static void main (String[] args){
JFrame frame = new JFrame("HelloButton");
Container pane = frame.getContentPane();
JButton hello = new JButton("HelloWorld");
pane.add(hello);
frame.pack();
frame.show();
}
}
The result
The source file
Compiling and running the program
The output
The Java Button
// helloworldbutton.java
The Pack method caused the frame to
cut off the label of the frame.
import java.awt.*;
import javax.swing.*;
class HelloButton{
public static void main (String[] args){
JFrame frame = new JFrame("HelloButton");
Container pane = frame.getContentPane();
JButton hello = new JButton("HelloWorld");
pane.add(hello);
frame.pack();
frame.show();
}
}
The Java Button
// helloworldbutton.java
The Pack method caused the frame to
cut off the label of the frame.
import java.awt.*;
import javax.swing.*;
class HelloButton{
public static void main (String[] args){
JFrame frame = new JFrame("HelloButton");
Container pane = frame.getContentPane();
JButton hello = new JButton("HelloWorld");
pane.add(hello);
frame.pack();
frame.show();
}
}
The Java Button
// helloworldbutton.java
We can set the size of the frame by using the method
setSize from JFrame.
import java.awt.*;
import javax.swing.*;
class HelloButton{
public static void main (String[] args){
JFrame frame = new JFrame("HelloButton");
Container pane = frame.getContentPane();
JButton hello = new JButton("HelloWorld");
pane.add(hello);
frame.setSize(300,200);
frame.show();
}
}
This method accepts 2 parameters (width, height),
which passed in terms of number of pixels.
The new result
The source file
The output
Compiling and running the program
Exercise # 5
Complete exercise 5 of the Java code handed out in-class.
Upload your *.java file (not the class file) on BlackBoard by
Friday March 21st 2003 (10 am).
1. Write the psudocode and the deployment diagram for what you are planning
to do
2. Separate the Ball class into 2 classes:
•
Ball.java that known the location, its size and how to paint itself
•
MovableBall.java that extends the class Ball and adds all behaviors
related to motion. Such as the data fields dx and dy, the functions
setMotions, move and so on.
3. Rewrite the MultiBallWorld to use an instance of MovableBall.
IMPORTANT: Don’t built on what we did in exercise #4 or earlier exercises.
Instead use the original files for Ball and MultiBallWorld posted on BlackBoard.