CompSci 125 Lecture 17. GUI: Graphics, Check Boxes, Radio Buttons

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Sheena Sharleen Crawford
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1 CompSci 125 Lecture 17 GUI: Graphics, Check Boxes, Radio Buttons

2 Announcements

3 GUI Review

4 Review: Inheritance Subclass is a Parent class Includes parent s features May Extend May Modify extends! Parent Class Subclass

pane Re-position the frame Re-size the frame

5 JFrame Container Title Bar includes the title text, and the minimize, maximize and close buttons Content pane Re-position the frame Re-size the frame

6 Content Pane Is not a class! Is the area of the JFrame where we can add/draw stuff JFrame constructs it as a JComponent but getcontentpane returns a reference to a Container We can add other graphical components to it Has a LayoutManager getcontentpane from the JFrame setcontentpane in the JFrame add a component to the content pane

7 JPanel Is a Container to which you may add other Components May have a LayoutManager Can be configured as double-buffered You may add a JPanel to the content pane Use setcontentpane to replace the content pane with a JPanel Implements a paintcomponent(graphics g) method You may subclass a JPanel and override paintcomponent Then you can draw on the Graphics context

8 JLabel Displays text string, an icon or both Write only --- no user input possible

9 JButton Displays a button Our class implements the ActionListener interface Java calls ActionListener s actionperformed method when user clicks button

10 ActionListener Interface Our class includes implements ActionListener clause Java ensures we implement the actionperformed method Java passes an ActionEvent parameter to actionperformed ActionEvent s getsource method returns a reference to the object (e.g. an instance of a JButton or JTextField) in which the event occurred

11 JTextField Displays text (like a JLabel) Unlike a JLabel, user can enter text Our class implements ActionListener Java calls actionperformed when user modifies text ActionEvent s getsource method identifies source of event JTextField s gettext returns reference to user s text String Many, many methods!

12 The Graphics Context

13 Graphics Context 2-D canvas --- we can draw graphical shapes on it Integer coordinate system in pixels Java passes reference to a Graphics to paintcomponent

14 The Graphics State Includes Current clip rectangle Current color Current font

15 Graphics Operations Include drawarc drawimage drawline drawoval drawrect drawstring fillarc filloval fillrect

16 Graphics Etc clearrect getcliprect setcolor setfont more

17 CheckBoxes

18 JCheckBox Labeled stateful check box Text label describes an attribute Check box displays associated state (selected or not) Clicking box toggles its associated state Useful methods JCheckBox( Label Text String ) isselected() Our class implements either ActionListener or ItemListener interface

19 ItemListener Interface public void itemstatechanged(itemevent event) Called when check box s state changes: User interaction (clicking) Programmatically (unlike ActionListener) ItemEvent methods include: getitemselectable: Returns reference to source of event getstatechange: Returns reason for the event

20 Radio Buttons

21 Radio Buttons JRadioButton --- only one can be selected at any time ButtonGroup --- manages group of related JRadioButtons ActionListener

22 JRadioButton Labeled stateful button Text label describes an attribute Button displays associated state (selected or not) Clicking button toggles its associated state Only one button in group selected at any time Useful methods JRadioButton( Selected Button s Text String,true) JRadioButton( Unselected Button Text ) isselected() Define a ButtonGroup and add each JRadioButton to it Our class typically implements ActionListener interface

23 ButtonGroup Use add method to add a JRadioButton to a ButtonGroup Ensures only one JRadioButton will be selected at a time

Graphic User Interfaces. - GUI concepts - Swing - AWT

Graphic User Interfaces. - GUI concepts - Swing - AWT Graphic User Interfaces - GUI concepts - Swing - AWT 1 What is GUI Graphic User Interfaces are used in programs to communicate more efficiently with computer users MacOS MS Windows X Windows etc 2 Considerations