Java AWT Tutorial

Java AWT (Abstract Window Toolkit) is an API to develop Graphical User Interface (GUI) or windows-based applications in Java.

Java AWT components are platform-dependent i.e. components are displayed according to the view of operating system. AWT is heavy weight i.e. its components are using the resources of underlying operating system (OS).

The java.awt package provides classes for AWT API such as TextField, Label, TextArea, RadioButton, CheckBox, Choice, List etc.

The AWT tutorial will help the user to understand Java GUI programming in simple and easy steps.

Why AWT is platform independent?

Java AWT calls the native platform calls the native platform (operating systems) subroutine for creating API components like TextField, ChechBox, button, etc.

For example, an AWT GUI with components like TextField, label and button will have different look and feel for the different platforms like Windows, MAC OS, and Unix. The reason for this is the platforms have different view for their native components and AWT directly calls the native subroutine that creates those components.

In simple words, an AWT application will look like a windows application in Windows OS whereas it will look like a Mac application in the MAC OS.

Java AWT Hierarchy

The hierarchy of Java AWT classes are given below.

Components

All the elements like the button, text fields, scroll bars, etc. are called components. In Java AWT, there are classes for each component as shown in above diagram. In order to place every component in a particular position on a screen, we need to add them to a container.

Container

The Container is a component in AWT that can contain another components like buttons, textfields, labels etc. The classes that extends Container class are known as container such as Frame, Dialog and Panel.

It is basically a screen where the where the components are placed at their specific locations. Thus it contains and controls the layout of components.

Note: A container itself is a component (see the above diagram), therefore we can add a container inside container.

Types of containers:

There are four types of containers in Java AWT:

1. Window
2. Panel
3. Frame
4. Dialog

Window

The window is the container that have no borders and menu bars. You must use frame, dialog or another window for creating a window. We need to create an instance of Window class to create this container.

Panel

The Panel is the container that doesn't contain title bar, border or menu bar. It is generic container for holding the components. It can have other components like button, text field etc. An instance of Panel class creates a container, in which we can add components.

Frame

The Frame is the container that contain title bar and border and can have menu bars. It can have other components like button, text field, scrollbar etc. Frame is most widely used container while developing an AWT application.

Useful Methods of Component Class

Method	Description
public void add(Component c)	Inserts a component on this component.
public void setSize(int width,int height)	Sets the size (width and height) of the component.
public void setLayout(LayoutManager m)	Defines the layout manager for the component.
public void setVisible(boolean status)	Changes the visibility of the component, by default false.

Java AWT Example

To create simple AWT example, you need a frame. There are two ways to create a GUI using Frame in AWT.

1. By extending Frame class (inheritance)
2. By creating the object of Frame class (association)

AWT Example by Inheritance

Let's see a simple example of AWT where we are inheriting Frame class. Here, we are showing Button component on the Frame.

AWTExample1.java

1. // importing Java AWT class  
2. import java.awt.*;    
3.   
4. // extending Frame class to our class AWTExample1  
5. public class AWTExample1 extends Frame {    
6.   
7.    // initializing using constructor  
8.    AWTExample1() {  
9.   
10.       // creating a button   
11.       Button b = new Button("Click Me!!");  
12.   
13.       // setting button position on screen  
14.       b.setBounds(30,100,80,30);  
15.   
16.       // adding button into frame    
17.       add(b);  
18.   
19.       // frame size 300 width and 300 height    
20.       setSize(300,300);  
21.   
22.       // setting the title of Frame  
23.       setTitle("This is our basic AWT example");   
24.           
25.       // no layout manager   
26.       setLayout(null);   
27.   
28.       // now frame will be visible, by default it is not visible    
29.       setVisible(true);  
30. }    
31.   
32. // main method  
33. public static void main(String args[]) {   
34.   
35. // creating instance of Frame class   
36. AWTExample1 f = new AWTExample1();    
37.   
38. }  
39.   
40. }    

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The setBounds(int x-axis, int y-axis, int width, int height) method is used in the above example that sets the position of the awt button.

Output:

AWT Example by Association

Let's see a simple example of AWT where we are creating instance of Frame class. Here, we are creating a TextField, Label and Button component on the Frame.

AWTExample2.java

1. // importing Java AWT class  
2. import java.awt.*;    
3.   
4. // class AWTExample2 directly creates instance of Frame class  
5. class AWTExample2 {    
6.   
7.    // initializing using constructor  
8.    AWTExample2() {  
9.   
10.       // creating a Frame  
11.       Frame f = new Frame();  
12.   
13.       // creating a Label  
14.       Label l = new Label("Employee id:");   
15.   
16.       // creating a Button  
17.       Button b = new Button("Submit");  
18.   
19.       // creating a TextField  
20.       TextField t = new TextField();  
21.   
22.       // setting position of above components in the frame  
23.       l.setBounds(20, 80, 80, 30);  
24.       t.setBounds(20, 100, 80, 30);  
25.       b.setBounds(100, 100, 80, 30);  
26.   
27.       // adding components into frame    
28.       f.add(b);  
29.       f.add(l);  
30.       f.add(t);  
31.   
32.       // frame size 300 width and 300 height    
33.       f.setSize(400,300);  
34.   
35.       // setting the title of frame  
36.       f.setTitle("Employee info");   
37.           
38.       // no layout  
39.       f.setLayout(null);   
40.   
41.       // setting visibility of frame  
42.       f.setVisible(true);  
43. }    
44.   
45. // main method  
46. public static void main(String args[]) {   
47.   
48. // creating instance of Frame class   
49. AWTExample2 awt_obj = new AWTExample2();    
50.   
51. }  
52.   
53. }    

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Output: