GUI and its COmponent Textfield, Button & Label. By Iqtidar Ali

Transcription

1 GUI and its COmponent Textfield, Button & Label By Iqtidar Ali

2 GUI (Graphical User Interface) GUI is a visual interface to a program. GUI are built from GUI components. A GUI component is an object with which the user interacts via of mouse or keyboard. The java.awt or javax.swing package, Both these packages provide rich set of user interface component.

3 Java.awt packages AWT the Abstract Window Toolkit. It contains original GUI components that came with the first release of JDK. AWT components are called Heavy Weight Component as they rely on local platform. when AWT is created corresponding process on the O.S is created which make it heavy.

4 Java Swing class hierarchy

5 Jframe & its Features JFrame is a window with border, title and buttons. The component added to frame are referred to as its contents & are managed by the content pane. To add a component to JFrame, we must use its contentpane and will add it to content Pane. When JFrame is set visible, an event dispatching thread is started. It can be moved, resized.

6 JFrame Location By default, JFrame is displayed in upper-left corner of screen. To display frame at specified location, You can use the setlocation(x,y) method in JFrame class. This method places the upper-left corner of a frame at location(x,y).

7 Steps for creating a JFrame Window Construct an object of the JFrame. Set the size of the Jframe. Set the title of the Jframe to appear in title bar. Set the default close operation. When the user clicks close button, the program stops running. Make the Jframe visible.

8 Creating a JFrame There are two ways to create a JFrame Window. By instantiating JFrame class By extending JFrame class

9 import java.awt.*; public class test { public static void main(string s[]) { Frame frame = new Frame("JFrame Source Demo"); frame.setvisible(true); } }

10 import javax.swing.*; import java.awt.*; class controlclass extends JFrame{ JLabel jlb; public controlclass() { super("title"); setlayout(new GridLayout()); jlb=new JLabel("Hello"); add(jlb); } } public class mainclass { public static void main(string[] args) { controlclass obj=new controlclass(); obj.setsize(200, 200); obj.setvisible(true); obj.setdefaultcloseoperation(jframe.exit_on_close); } }

11 import java.awt.*; public class test extends Frame{ public test(){ settitle("my Window"); Label lb=new Label("Hello window"); add(lb); setlayout(new FlowLayout()); setsize(300, 200 ); // Set the frame size setvisible( true); // Display the frame } public static void main(string[] args) { new test(); } }

12 Text Fields

13 Text Fields Text Fields provide an area where one can edit or enter a single line of text. Text Fields are usually used for getting inputs from a user. It is created using any of the following constructor. TextField():- Blank TextField(int):- int indicate minimum no s of character to be displayed. TextField(String):- Welcome msg to be displayed by default. TextField(String, int):- Combination of two.

14 import java.awt.*; import javax.swing.*; public class MyTextField extends JFrame { public MyTextField() { JTextField txf=new JTextField(20); add(txf); setlayout(new FlowLayout()); setsize(300, 200 ); // Set the frame size setdefaultcloseoperation(jframe.exit_on_close); setvisible( true); // Display the frame } public static void main(string[] args) { new MyTextField(); } }

15 Button

16 Button The most widely used control is the push button. A push button is a component that contains a label and that generates an event when it is pressed. Push buttons are objects of type Button.

17 Button (Cont--) Button defines these two constructors: Button( ):- The first version creates an empty button. Button(String):- The second creates a button that contains string as a label.

18 import java.awt.*; import javax.swing.*; public class test extends JFrame{ public test(){ settitle("my Window"); Button btn=new Button("OK"); add(btn); setlayout(new FlowLayout()); setsize(300, 200 ); // Set the frame size setdefaultcloseoperation(jframe.exit_on_close); setvisible( true); // Display the frame } public static void main(string[] args) { test obj=new test(); } }

19 LABEL To include a control in a window, you must add it to the window To do this, you must first create an instance of the desired control Then add it to a window by calling add() The syntax is Label compobj=new label() add(compobj); Here, compobj is an instance of the control that you want to add.

20 Label The easiest control to use is a label A label is an object of type Label, and it contains a string, which it displays Labels are passive controls that do not support any interaction with the user Label defines the following constructors: -Label( ) :- create empty label Label(String):- create label with given string Label(String, int):- Label with string & alignment

21 import java.awt.*; import javax.swing.*; public class test extends JFrame{ public test(){ settitle("my Window"); Label lb=new Label("Hello window"); add(lb); setlayout(new FlowLayout()); setsize(300, 200 ); // Set the frame size setdefaultcloseoperation(jframe.exit_on_close); setvisible( true); // Display the frame } public static void main(string[] args) { test obj=new test(); } }

22 THE END