Java has been around in the industry for quite some time now. It has its roots deep in various domains of the programming world, be it a web application, mobile application or embedded systems. Even if you talk about GUI programming, Java provides a rich set of libraries for developing highly interactive GUIs wrapped within AWT API. In this Java AWT Tutorial, I will be giving you a brief introduction to it along with its components.
Below are the topics covered in this Java AWT Tutorial:
- What is Java AWT?
- Features of AWT in Java
- AWT UI Aspects
- Hierarchy of Java AWT
- AWT Components
- Developing a Calculator with Java AWT
Let’s get started.
What is AWT in Java?
Abstract Window Toolkit acronymed as AWT is a toolkit of classes in Java which helps a programmer to develop Graphics and Graphical User Interface components. It is a part of JFC (Java Foundation Classes) developed by Sun Microsystems. The AWT API in Java primarily consists of a comprehensive set of classes and methods that are required for creating and managing the Graphical User Interface(GUI) in a simplified manner. It was developed for providing a common set of tools for designing the cross-platform GUIs. One of the important features of AWT is that it is platform dependent. This means that the AWT tools use the native toolkits of the platforms they are being implemented. This approach helps in preserving the look and feel of each platform. But as said everything comes with a price, there is a major drawback of this approach. When executed on various platforms because of platform dependency it will look different on each platform. This hampers the consistency and aesthetics of an application.
Apart from being platform-dependent, there are several other features of AWT classes about which I will be talking in the next section of this Java AWT Tutorial.
Features of AWT in Java
- AWT is a set of native user interface components
- It is based upon a robust event-handling model
- It provides Graphics and imaging tools, such as shape, color, and font classes
- AWT also avails layout managers which helps in increasing the flexibility of the window layouts
- Data transfer classes are also a part of AWT that helps in cut-and-paste through the native platform clipboard
- Supports a wide range of libraries that are necessary for creating graphics for gaming products, banking services, educational purposes, etc.
Now that you are aware of the various features of AWT let me now introduce the aspects of GUI in the next section of this Java AWT tutorial.
AWT UI Aspects
Any UI will be made of three entities:
- UI elements: These refers to the core visual elements which are visible to the user and used for interacting with the application. AWT in Java provides a comprehensive list of widely used and common elements.
- Layouts: These define how UI elements will be organized on the screen and provide the final look and feel to the GUI.
- Behavior: These define the events which should occur when a user interacts with UI elements.
I hope, by now you have a brief idea about AWT and what is its role in any application. In the next section of this Java AWT Tutorial, I will be throwing some light on the complete AWT hierarchy.
Hierarchy Of AWT
Below I have shown the general class description of java.awt.Component:
public abstract class Component
extends Object
implements ImageObserver, MenuContainer, Serializable{
//class body
}AWT Components
1. Containers
Container in Java AWT is a component that is used to hold other components such as text fields, buttons, etc. It is a subclass of java.awt.Component and is responsible for keeping a track of components being added. There are four types of containers provided by AWT in Java.
Types of Containers
- Window: It is an instance of the Window class having neither border nor title. It is used for creating a top-level window.
- Frame: Frame is a subclass of Window and contains title, border and menu bars. It comes with a resizing canvas and is the most widely used container for developing AWT applications. It is capable of holding various components such as buttons, text fields, scrollbars, etc. You can create a Java AWT Frame in two ways:
- By Instantiating Frame class
- By extending Frame class
- Dialog: Dialog class is also a subclass of Window and comes with the border as well as the title. Dialog class’s instance always needs an associated Frame class instance to exist.
- Panel: Panel is the concrete subclass of Container and doesn’t contain any title bar, menu bar or border. Panel class is a generic container for holding the GUI components. You need the instance of the Panel class in order to add the components.
That was all about the container and its types let us now move further in this Java AWT Tutorial article and learn about the rest of the components.
2. Button
java.awt.Button class is used to create a labeled button. GUI component that triggers a certain programmed action upon clicking it. The Button class has two constructors:
//Construct a Button with the given label public Button(String btnLabel); //Construct a Button with empty label public Button();
A few of the methods provided by this class have been listed below:
//Get the label of this Button instance public String getLabel(); //Set the label of this Button instance public void setLabel(String btnLabel); //Enable or disable this Button. Disabled Button cannot be clicked public void setEnable(boolean enable);
3. Text Field
A java.awt.TextField class creates a single-line text box for users to enter texts. The TextField class has three constructors which are:
//Construct a TextField instance with the given initial text string with the number of columns. public TextField(String initialText, int columns); //Construct a TextField instance with the given initial text string. public TextField(String initialText); //Construct a TextField instance with the number of columns. public TextField(int columns);
A few of the methods provided by TextField class are:
// Get the current text on this TextField instance public String getText(); // Set the display text on this TextField instance public void setText(String strText); //Set this TextField to editable (read/write) or non-editable (read-only) public void setEditable(boolean editable);
4. Label
The java.awt.Label class provides a descriptive text string that is visible on GUI. An AWT Label object is a component for placing text in a container. Label class has three constructors which are:
// Construct a Label with the given text String, of the text alignment public Label(String strLabel, int alignment); //Construct a Label with the given text String public Label(String strLabel); //Construct an initially empty Label public Label();
This class also provides 3 constants which are:
public static final LEFT; // Label.LEFT public static final RIGHT; // Label.RIGHT public static final CENTER; // Label.CENTER
Below I have listed down the public methods provided by this class:
public String getText(); public void setText(String strLabel); public int getAlignment(); //Label.LEFT, Label.RIGHT, Label.CENTER public void setAlignment(int alignment);
5. Canvas
A Canvas class represents the rectangular area where you can draw in an application or receive inputs created by the user.
6. Choice
Choice class is used to represent a pop-up menu of choices. The selected choice is shown on the top of the given menu.
7. Scroll Bar
The Scrollbar class object is used to add horizontal and vertical scrollbar in the GUI. It enables a user to see the invisible number of rows and columns.
8. List
The object of List class represents a list of text items. Using the List class a user can choose either one item or multiple items.
9. CheckBox
The Checkbox is a class is a graphical component that is used to create a checkbox. It has two state options; true and false. At any point in time, it can have either of the two.
So, that was all you need to know about the AWT components. Now, I hope you are ready to get your feet wet with Java AWT application.
In the next section of this Java AWT tutorial, I will show you how to build a calculator using AWT components.
Developing a Calculator with Java AWT
Here I will show you how to create a calculator using AWT, where you will be able to perform basic mathematical operations. Below is a screenshot of how your Calculator will look like:
Now in order to build this, you need to type in the following code:
package edureka.awt;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
class Calculator extends Frame implements ActionListener
{
Label lb1,lb2,lb3;
TextField txt1,txt2,txt3;
Button btn1,btn2,btn3,btn4,btn5,btn6,btn7;
public Calculator()
{
lb1 = new Label("Var 1");
lb2 = new Label("Var 2");
lb3 = new Label("Result");
txt1 = new TextField(10);
txt2 = new TextField(10);
txt3 = new TextField(10);
btn1 = new Button("Add");
btn2 = new Button("Sub");
btn3 = new Button("Multi");
btn4 = new Button("Div");
btn5 = new Button("Mod");
btn6 = new Button("Reset");
btn7 = new Button("Close");
add(lb1);
add(txt1);
add(lb2);
add(txt2);
add(lb3);
add(txt3);
add(btn1);
add(btn2);
add(btn3);
add(btn4);
add(btn5);
add(btn6);
add(btn7);
setSize(200,200);
setTitle("Calculator");
setLayout(new FlowLayout());
//setLayout(new FlowLayout(FlowLayout.RIGHT));
//setLayout(new FlowLayout(FlowLayout.LEFT));
btn1.addActionListener(this);
btn2.addActionListener(this);
btn3.addActionListener(this);
btn4.addActionListener(this);
btn5.addActionListener(this);
btn6.addActionListener(this);
btn7.addActionListener(this);
}
public void actionPerformed(ActionEvent ae) {
double a=0,b=0,c=0;
try
{
a = Double.parseDouble(txt1.getText());
}
catch (NumberFormatException e) {
txt1.setText("Invalid input");
}
try
{
b = Double.parseDouble(txt2.getText());
}
catch (NumberFormatException e) {
txt2.setText("Invalid input");
}
if(ae.getSource()==btn1)
{
c = a + b;
txt3.setText(String.valueOf(c));
}
if(ae.getSource()==btn2)
{
c = a - b;
txt3.setText(String.valueOf(c));
}
if(ae.getSource()==btn3)
{
c = a * b;
txt3.setText(String.valueOf(c));
}
if(ae.getSource()==btn4)
{
c = a / b;
txt3.setText(String.valueOf(c));
}
if(ae.getSource()==btn5)
{
c = a % b;
txt3.setText(String.valueOf(c));
}
if(ae.getSource()==btn6)
{
txt1.setText("0");
txt2.setText("0");
txt3.setText("0");
}
if(ae.getSource()==btn7)
{
System.exit(0);
}
}
public static void main(String[] args)
{
Calculator calC = new Calculator();
calC.setVisible(true);
calC.setLocation(300,300);
}
}As you might have noticed that here we have used just functionalities. You can always add more functions to your application and create a full-fledged Calculator.
With this, we come to an end of this Java AWT Tutorial. If you want to know more about Java you can refer to our other Java Blogs.
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