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Bài giảng Phát triển phần mềm phân tán - Bài 12: GUI and event programming - Vũ Thị Hương Giang

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LESSON XII. GUI and Event  
Programming (1/2)  
Vu Thi Huong Giang  
1
Objectives  
• After this lesson, students (learners) can:  
– Understand the concept of “GUI Progamming”  
– Understand the concepts of “Container” and  
“Component”  
– Know how to create AWT containers and AWT  
components  
– Know how to organize AWT components inside an AWT  
container.  
– Understand how to handle AWT events, using different  
ways  
– Write many demo AWT applications.  
2
Content  
I. Introduction  
II. Programming GUI with AWT  
III. AWT Event-Handling  
3
I. Introduction  
• A graphical user interface - GUI (pronounced  
"GOO-ee"):  
– is a type of user interface  
– allows users to interact with electronic devices using  
images rather than text commands  
• Why use term GUI?  
– The first interactive user interfaces to computers were  
not graphical  
4
1. Introduction  
Title bar  
Menus  
Menu bar  
Combo box  
Button  
Scroll bar  
5
Java APIs for graphics programming  
• Two core sets of Java APIs for graphics programming:  
– AWT (Abstract Windowing Toolkit)  
– Swing  
• AWT:  
– introduced in JDK 1.0  
– should be replaced by newer Swing components  
• Swing:  
– enhances AWT  
– integrated into core Java since JDK 1.2  
• Others:  
– Eclipse's Standard Widget Toolkit (SWT)  
– Google Web Toolkit (GWT)  
– 3D Graphics API such as Java bindings for OpenGL (JOGL)  
and Java3D.  
6
Content  
I. Introduction  
II. Programming GUI with AWT  
III. AWT Event-Handling  
7
II. Programming GUI with  
AWT  
2.1 AWT Packages  
2.2 Containers and Components  
2.3 AWT Container Classes  
2.4 AWT Component Classes  
2.5. Layout Managers  
8
2.1. AWT Packages  
• Huge: there are 12 packages.  
– Only 2 packages: java.awt & java.awt.event are commonly-used  
– Platform-independent & device-independent  
• Core graphics classes of java.awt:  
– GUI Component classes (such as Button, TextField, and Label),  
– GUI Container classes (such as Frame, Panel, Dialog and  
ScrollPane),  
– Layout managers (such as FlowLayout, BorderLayout and  
GridLayout),  
– Custom graphics classes (such as Graphics, Color and Font).  
• java.awt.event package supports event handling  
– Event classes (such as ActionEvent, MouseEvent, KeyEvent and  
WindowEvent),  
– Event Listener Interfaces (such as ActionListener, MouseListener,  
KeyListener and WindowListener),  
– Event Listener Adapter classes (such as MouseAdapter,  
KeyAdapter, and WindowAdapter).  
9
2.2. Containers and Components  
• Two types of GUI elements:  
– Component: elementary GUI entities (Button, Label,  
TextField.)  
– Container (Frame, Panel and Applet): hold components  
in a specific layout. A container can also hold sub-  
containers  
10  
2.3. AWT Container Classes  
• Top-level AWT containers: Frame, Dialog  
and Applet.  
• Frame:  
– provides cluding:  
• a title ize,  
maxim
• an opti
• the con
• Dialog: a "pop-up window“, including:  
– a title-bar (containing an icon, a title and a close button)  
– a content dis
• Applet: top-lean applet - a Java  
program runnser  
11  
2.3. AWT Container Classes  
• Secondary Containers: Panel, ScrollPane  
– are placed inside a top-level container or another  
secondary container  
• Panel:  
– a rectangular box (partition) under a higher-level  
container,  
– used to layout a set of related GUI components  
• ScrollPane: provides automatic horizontal and/or  
vertical scrolling for a single child component  
12  
2.3. AWT Container Classes  
• Hierarchy of the AWT Container Classes  
13  
2.4. AWT Component Classes  
• AWT provides many GUI components:  
– Button, TextField, Label, Checkbox, CheckboxGroup  
(radio buttons), List, and Choice  
14  
2.4. AWT Component Classes  
• java.awt.Label: provides a text description message.  
• Constructors:  
– // Construct a Label with the given text String, of the text alignment  
– public Label(String strLabel, int alignment);  
– public Label(String strLabel); // Construct a Label with the given text  
– public Label(); // Construct an initially empty Label  
• Constants:  
– public static final LEFT; // Label.LEFT  
– public static final RIGHT; // Label.RIGHT  
– public static final CENTER; // Label.CENTER  
• Public methods:  
– public String getText();  
– public void setText(String strLabel);  
– public int getAlignment();  
– public void setAlignment(int alignment);  
15  
2.4. AWT Component Classes  
• To construct a Component and add into a  
Container:  
– Declare the component with an identifier  
– Construct the component  
– Identify the container designed to hold this component.  
Use addmethod:  
• Ex: aContainer.add(aComponent)  
• Example:  
Label lblInput;  
lblInput = new Label("Enter ID");  
this.add(lblInput);  
lblInput.setText("Enter password");  
lblInput.getText();  
16  
2.4. AWT Component Classes  
• java.awt.Button: triggers a certain programmed action  
upon clicking.  
• Constructors:  
– public Button(String buttonLabel);  
– public Button(String buttonLabel);  
• Public Methods  
– public String getLabel();  
– public void setLabel(String buttonLabel);  
– public void setEnable(boolean enable);  
• Example:  
– Button btnColor = new Button("Red");  
– this.add(btnColor);  
– ...  
– btnColor.setLabel("green");  
– btnColor.getLabel();  
17  
2.4. AWT Component Classes  
• java.awt.TextField: single-line text box to enter  
texts. (TextArea: multiple-line text box)  
• Constructor:  
– public TextField(String strInitialText, int columns);  
– public TextField(String strInitialText);  
– public TextField(int columns);  
• Public methods:  
– public String getText();  
– public void setText(String strText);  
– public void setEditable(boolean editable);  
18  
2.5. Layout Managers  
• Layout manager: arranges a container’s  
components  
• Layout managers from AWT: (in package  
java.awt)  
– FlowLayout  
– GridLayout  
– BorderLayout  
– GridBagLayout  
– BoxLayout  
– CardLayout  
19  
Set a layout manager  
• A container has a setLayout() method to set its layout  
manager:  
– public void setLayout(LayoutManager mgr)  
• To set up the layout of a Container:  
– Construct an instance of the chosen layout object, e.g., new  
FlowLayout()  
– Invoke the setLayout() method, with the layout object created as  
the argument;  
– Place the GUI components into the Container using the add()  
method in the correct order; or into the correct zones.  
• Example:  
Panel p = new Panel();  
p.setLayout(new FlowLayout());  
p.add(new JLabel("One"));  
p.add(new JLabel("Two"));  
p.add(new JLabel("Three"));  
20  
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