Downloaded 97 times
![GUI construction
public static void main(String[] args)
{
JFrame theFrame = new JFrame();
theFrame.setBounds(200, 200, 720, 450);
theFrame.setVisible(true);
JPanel thePanel = new JPanel();
theFrame.add(thePanel);
}
RHS – SOC 6](https://image.slidesharecdn.com/gui-20programming-20using-20netbeans-20-281-29-150117003413-conversion-gate01/85/GUI-Programming-using-NetBeans-1-pptx-6-320.jpg)
![GUI construction
public static void main(String[] args)
{
JFrame theFrame = new JFrame();
theFrame.setBounds(200, 200, 240, 150);
theFrame.setVisible(true);
JPanel thePanel = new JPanel();
thePanel.setLayout(new BorderLayout());
thePanel.add(new Button("Center"), BorderLayout.CENTER);
theFrame.add(thePanel);
}
RHS – SOC 10](https://image.slidesharecdn.com/gui-20programming-20using-20netbeans-20-281-29-150117003413-conversion-gate01/85/GUI-Programming-using-NetBeans-1-pptx-10-320.jpg)
![List box / Combo box
Object[] choices =
{"One", "Two", "Three", "Four"};
JComboBox theBox = new JComboBox(choices);
theBox.setEditable(true);
thePanel.add(theBox, BorderLayout.NORTH);
RHS – SOC 17](https://image.slidesharecdn.com/gui-20programming-20using-20netbeans-20-281-29-150117003413-conversion-gate01/85/GUI-Programming-using-NetBeans-1-pptx-17-320.jpg)
![GUI construction
public static void main(String[] args)
{
JFrame theFrame = new JFrame();
theFrame.setBounds(200, 200, 720, 450);
theFrame.setVisible(true);
JPanel thePanel = new JPanel();
theFrame.add(thePanel);
}
RHS – SOC 6](https://image.slidesharecdn.com/gui-20programming-20using-20netbeans-20-281-29-150117003413-conversion-gate01/75/GUI-Programming-using-NetBeans-1-pptx-6-2048.jpg)
![GUI construction
public static void main(String[] args)
{
JFrame theFrame = new JFrame();
theFrame.setBounds(200, 200, 240, 150);
theFrame.setVisible(true);
JPanel thePanel = new JPanel();
thePanel.setLayout(new BorderLayout());
thePanel.add(new Button("Center"), BorderLayout.CENTER);
theFrame.add(thePanel);
}
RHS – SOC 10](https://image.slidesharecdn.com/gui-20programming-20using-20netbeans-20-281-29-150117003413-conversion-gate01/75/GUI-Programming-using-NetBeans-1-pptx-10-2048.jpg)
![List box / Combo box
Object[] choices =
{"One", "Two", "Three", "Four"};
JComboBox theBox = new JComboBox(choices);
theBox.setEditable(true);
thePanel.add(theBox, BorderLayout.NORTH);
RHS – SOC 17](https://image.slidesharecdn.com/gui-20programming-20using-20netbeans-20-281-29-150117003413-conversion-gate01/75/GUI-Programming-using-NetBeans-1-pptx-17-2048.jpg)
Uploaded bySumalee Sonamthiang
GUI Programming using NetBeans (1).pptx
This document discusses GUI programming using the Swing API in Java. It covers constructing GUIs manually by creating frames, panels, and adding GUI controls like text fields, lists, buttons, and handling events. Specifically, it explains how to: 1) Create frames and panels to hold GUI elements and use layouts like border layout to position them. 2) Add common controls like text fields, lists, radio and check boxes programmatically. 3) Handle events from controls by implementing listener interfaces and writing event handlers. 4) Retrieve data from and set selections in GUI elements using their methods. 5) Create example applications to demonstrate concepts like grouping radio buttons and handling multiple button clicks.
GUI Programming using NetBeans (1).pptx
- 1.
- 2. GUI construction • Elementsin a (simple) GUI – Frames, Panes and Dialogs – Text fields – Lists and Combo boxes – Check and Radio buttons • How to use GUI controls in an application? RHS – SOC 2
- 3. GUI construction • Ingeneral, we have two options when constructing a GUI – Build it ”by hand” using Swing API – Use the NetBeans GUI Builder • Using the GUI Builder is usually much easier than hand-coding the GUI • Does not give you complete control, however… RHS – SOC 3
- 4.
- 5. GUI construction • Ifyou wish to construct a GUI manually, you usually begin by creating a JFrame • A JFrame object is essentially an empty window, into which you can add containers for GUI controls • Typically, you will add a JPanel to the frame – the JPanel object will contain the actual GUI controls RHS – SOC 5
- 6. GUI construction public staticvoid main(String[] args) { JFrame theFrame = new JFrame(); theFrame.setBounds(200, 200, 720, 450); theFrame.setVisible(true); JPanel thePanel = new JPanel(); theFrame.add(thePanel); } RHS – SOC 6
- 7. GUI construction • Onthe JPanel object, various layout strategies can be used – Flow layout – left to right – Border layout – groups into areas – Grid layout – groups into a grid • Border layout is default, and also most commonly used RHS – SOC 7
- 8. GUI construction • Usingborder layout, the panel is divided into five areas – Center – North – South – East – West RHS – SOC 8
- 9. GUI construction • Ifa control is put into an area, it will expand to fill out the area • Good when resizing, but may look weird… • If you need a finer level of control, put a panel inside a panel… • …or maybe consider a different layout RHS – SOC 9
- 10. GUI construction public staticvoid main(String[] args) { JFrame theFrame = new JFrame(); theFrame.setBounds(200, 200, 240, 150); theFrame.setVisible(true); JPanel thePanel = new JPanel(); thePanel.setLayout(new BorderLayout()); thePanel.add(new Button("Center"), BorderLayout.CENTER); theFrame.add(thePanel); } RHS – SOC 10
- 11. Exercises • Try outcreate an application which looks like the picture to the right, without using the GUI Builder. • That is, create it only by using the Swing API methods as shown in the presentation. • Remember that you can put panels within panels… RHS – SOC 11
- 12. Text field • Twocommon purposes: – Allow the user to enter data as text – Display text data to the user • A text field can be ”enabled” or ”disabled” – Enabled: Data can be entered – Disabled: Data can only be displayed • At some point we need to set or extract the text from the text field RHS – SOC 12
- 13. Text field JFrame theFrame= new JFrame(); theFrame.setBounds(200, 200, 300, 300); JPanel thePanel = new JPanel(); thePanel.setLayout(new BorderLayout()); JTextField theTextField = new JTextField(); thePanel.add(theTextField, BorderLayout.NORTH); theFrame.add(thePanel); theFrame.setVisible(true); RHS – SOC 13
- 14. Text field RHS –SOC 14 Text field
- 15. Text field • Enablinga text field theTextField.setEditable(true); • Disabling a text field theTextField.setEditable(false); • Setting the text in a text field theTextField.setText("Greeting earthlings!"); • Getting the text from a text field String s = theTextField.getText(); RHS – SOC 15
- 16. List box /Combo box • A list (or combo) box enables the user to choose an option between many alternatives • List box: User can only choose between specified alternatives • Combo box: User can choose between specified alternatives, or specify choice manually (type it in) RHS – SOC 16
- 17. List box /Combo box Object[] choices = {"One", "Two", "Three", "Four"}; JComboBox theBox = new JComboBox(choices); theBox.setEditable(true); thePanel.add(theBox, BorderLayout.NORTH); RHS – SOC 17
- 18. List box /Combo box RHS – SOC 18 Combo box (editable)
- 19. List box /Combo box • Enabling a Combo box theBox.setEditable(true); • Disabling a Combo box theBox.setEditable(false); • Setting the selection in a Combo box theBox.setSelectedItem(”Three"); • Getting the selection from a Combo box String s = (String)theBox.getSelectedItem(); RHS – SOC 19
- 20. Check boxes • Insome cases, the set of possible choices is limited to two options • Often a case of either/or, or perhaps on/off • A Check box can only be in two states; checked or unchecked • Nice fit for binary choices RHS – SOC 20
- 21. Check boxes JCheckBox theBBox= new JCheckBox("Bold"); JCheckBox theIBox = new JCheckBox("Italic"); JCheckBox theUBox = new JCheckBox("Underline"); thePanel.add(theBBox,BorderLayout.WEST); thePanel.add(theIBox,BorderLayout.NORTH); thePanel.add(theUBox,BorderLayout.EAST); RHS – SOC 21
- 22. Check boxes RHS –SOC 22
- 23. Check boxes • Enablinga Check box theCBox.setEnabled(true); • Disabling a Check box theCBox.setEnabled(false); • Setting the selection in a Check box theCBox.setSelected(isSelected); • Getting the selection from a Check box boolean isSelected = theCBox.isSelected(); RHS – SOC 23
- 24. Radio buttons • Ifthe number of choices is few, and they are mutually exclusive, use a group of Radio buttons • Only one button in a group of Radio buttons can be selected RHS – SOC 24
- 25. Radio buttons JRadioButton small= new JRadioButton("Small"); JRadioButton medium = new JRadioButton("Medium"); JRadioButton large = new JRadioButton("Large"); ButtonGroup theGroup = new ButtonGroup(); theGroup.add(small); theGroup.add(medium); theGroup.add(large); RHS – SOC 25
- 26. Radio buttons RHS –SOC 26
- 27. Radio buttons • Enablinga Radio button theRB.setEnabled(true); • Disabling a Radio button theRB.setEnabled(false); • Setting the selection in a Radio button theRB.setSelected(isSelected); • Getting the selection from a Radio button boolean isSelected = theRB.isSelected(); RHS – SOC 27
- 28. Radio buttons • Notethat even though only one Radio button in a group can be selected, we must call isSelected() until we find it… • Putting Radio buttons in a group does not make them appear grouped visually RHS – SOC 28
- 29. Exercises • Try outcreate an applica-tion which looks like the picture to the right, without using the GUI Builder. • Only one radio button should be selected at all times • Font for a control can be set using the setFont method (see the docu-mentation) RHS – SOC 29
- 30. The concept ofevents • On the inside (code), GUI code has a very different structure than ”usual” code • Usual code is driven by con- ditions and various control structures (if, while,…) • GUI code is driven by events RHS – SOC 30
- 31. The concept ofevents • Execution of GUI code is much more unpredictable than for usual code • We cannot predict – or dictate – what the user does, so we must always handle any possible action the user can do • A user action related to the GUI is called an event RHS – SOC 31
- 32. The concept ofevents RHS – SOC 32
- 33. The concept ofevents • Almost all actions the user performs will ”trigger” an event for us to handle – Moving the mouse – Clicking on a button – Writing text in a text box – ….and so on • There are hundreds of possible events! RHS – SOC 33
- 34. The concept ofevents • Fortunately, is it optional to respond to an event • We only need to do so, if we want any special action to happen • If that is the case, we must write an event handler for that particular event RHS – SOC 34
- 35. Relevant events • Unlesswe need more sophisticated behavior, we only need to handle two types of events – Choosing a menu item – Clicking on a push button • In both cases, we must create an object which can listen for events from the control in question RHS – SOC 35
- 36. Relevant events • Anevent listener class must implement a …Listener interface (there are several) • From pushbuttons and menu items, we get ”action events”, so a listener class must implement the ActionListener interface • This interface has a single method: actionPerformed RHS – SOC 36
- 37. Relevant events public classMyListener implements ActionListener { public void actionPerformed(ActionEvent event) { System.out.println("Button clicked"); } } private ActionListener theListener; theListener = new MyListener(); ... JButton theButton = new JButton("Click Me!"); theButton.addActionListener(theListener); RHS – SOC 37
- 38. Relevant events • Avery common dialog construction: – Add an ”OK” button – In the event listener for the button • Retrieve data from the relevant controls • Process the data • Close the dialog • Pressing ”OK” means: ”Now my input is ready, do something with it!” RHS – SOC 38
- 39. Wrapping up • GUIprogramming is somewhat difficult and tedious • Unless you need something special, use the NetBeans GUI Builder! • Always nice to know what does on under the hood… • You can – to some degree – mix manual coding and using the GUI Builder RHS – SOC 39
- 40. Exercises • Try outcreate an application which looks like the picture to the right, without using the GUI Builder. • Create event listeners for the buttons, that print the texts: – ”Brrr” for Arctic and Antarctic – ”Puhh” for America and Asia – ”Wet!” for Atlantic • You should not write more than three event listeners! RHS – SOC 40