Gui programming using netbeans
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GUI Programming using NetBeans. What is a GUI ?. GUI – Graphical User Interface The (visual) interface between humans and computers Ranging from command lines to ”Minority Report” – style GUI Why? Makes interfaces more intuitive – most humans don’t like command lines…. GUI Programming.

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Gui programming using netbeans

GUI Programming using NetBeans


What is a gui

What is a GUI ?

  • GUI – Graphical User Interface

  • The (visual) interface between humans and computers

  • Ranging from command lines to ”Minority Report” – style GUI

  • Why? Makes interfaces more intuitive – most humans don’t like command lines…

SWC


Gui programming

GUI Programming

  • Creating a proper GUI can be as important – and large – a task as creating the logic

  • Quite a lot of topics in GUI programming

    • Human perception

    • Task analysis

    • User analysis

    • Actual programming

SWC


Simple gui example

Simple GUI - example

Text label

Text Field

(input)

Text Field

(output)

Pushbutton

SWC


Elements in a gui

Elements in a GUI

  • A GUI is usually composed by controls

  • A control can be a

    • Text field (enabled, disabled)

    • Pushbutton (OK, Cancel,…)

    • List box (multiple items to choose from)

    • Check box (yes-or-no)

  • Many types of GUI controls

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Starting simple

Starting simple…

  • For now, we will limit ourselves to just a few GUI controls:

    • Text label

    • Text field

    • List

    • Check box

    • Pushbutton

    • Picture

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Text labels

Text labels

  • Probably the simplest control of all…

  • Usually just used for adding ”static” text – text that does not change – to the GUI

  • Such texts will typically be ”helper text” for other controls

  • No code needed!

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Text labels1

Text labels

SWC


Text field

Text field

  • Two common 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

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Text field1

Text field

SWC


List box

List box

  • Essentially serves the same purpose as a text field – get text input from user

  • However, in some situations we may only allow certain inputs, for instance members of a set of legal input

  • When using a list control, the user can only select an item from the list

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List box1

List box

SWC


Check box

Check box

  • In some cases, the set of possible choices is limited to two options

  • Often a case of either/or, or perhaps on/off

  • A Checkbox can only be in two states; checked or unchecked

  • Nice fit for binary choices

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Check box1

Check box

SWC


Pushbutton

Pushbutton

  • A pushbutton is usually used to start some kind of processing of data

  • The ”input” is simply the user clicking on the pushbutton!

  • Typical use: ”Now my input is ready, do something with it!”

  • We all know the ”OK” button 

SWC


Pushbutton1

Pushbutton

SWC


Picture

Picture

  • Related to text labels – does not really have any functionality, but should be helpful for the user

  • Increases ”recognisability” – the user can see that (s)he is at the right place

  • When programming in NetBeans, a picture is just a special kind of text label…

SWC


Picture1

Picture

SWC


Gui construction

GUI construction

  • In general, 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…

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Gui construction1

GUI construction

  • Swing is a class library for creating GUIs in Java

  • Quite large…

  • API: See package javax.swing in the Java documentation

  • Tutorial:http://docs.oracle.com/javase/tutorial/uiswing/components/index.html

  • Most classes begin with ”J”…

SWC


Gui construction2

GUI construction

  • If you wish to construct a GUI manually using Swing, 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 add a JPanel to the frame – the JPanel object contains the actual GUI controls

SWC


Gui construction3

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);

}

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Gui construction4

GUI construction

  • On the 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

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Gui construction5

GUI construction

  • Using border layout, the panel is divided into five areas

    • Center

    • North

    • South

    • East

    • West

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Gui construction6

GUI construction

  • If a 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

SWC


Gui construction7

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);

}

SWC


Exercise time

Exercise time

SWC


Text field2

Text field

  • Two common 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

SWC


Text field3

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);

SWC


Text field4

Text field

Text field

SWC


Text field5

Text field

  • Enabling a 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();

SWC


List box combo box

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)

SWC


List box combo box1

List box / Combo box

Object[] choices =

{"One", "Two", "Three", "Four"};

JComboBox theBox = new JComboBox(choices);

theBox.setEditable(true);

thePanel.add(theBox, BorderLayout.NORTH);

SWC


List box combo box2

List box / Combo box

Combo box (editable)

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List box combo box3

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();

SWC


Check boxes

Check boxes

  • In some 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

SWC


Check boxes1

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);

SWC


Check boxes2

Check boxes

SWC


Check boxes3

Check boxes

  • Enabling a 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();

SWC


Radio buttons

Radio buttons

  • If the 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

SWC


Radio buttons1

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);

JPanel theRadioPanel = new JPanel();

theRadioPanel.setLayout(new FlowLayout());

theRadioPanel.add(small);

theRadioPanel.add(medium);

theRadioPanel.add(large);

thePanel.add(theRadioPanel, BorderLayout.NORTH);

SWC


Radio buttons2

Radio buttons

SWC


Radio buttons3

Radio buttons

  • Enabling a 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();

SWC


Radio buttons4

Radio buttons

  • Note that 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

SWC


Exercise time1

Exercise time

SWC


Menus

Menus

  • Pull-down menu is a classic choice for choosing between options that have a hierarchical structure – menus form a hierarchy

  • Usually only one main menu in an application; possible choices may vary depending on current circumstances

SWC


Menus1

Menus

  • Swing menu classes:

  • JMenuBar – the actual menu bar, attached to a frame window

  • JMenu – an element in the menu bar, with other menus or menu items in it.

  • JMenuItem – a specific choice, with no sub-choices

SWC


Menus2

Menus

  • ”A menu bar contains menus”

  • ”A menu contains other menus and menu items”

  • ”A menu item just contains itself”

SWC


Menus3

Menus

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Menus4

Menus

  • How to create a menu bar

    • Create a JMenuBar object

      • JMenuBar theMenuBar = new JMenuBar();

    • Add all relevant menus to the menu bar

    • Attach the menu bar to the main frame of the application

      • frame.setJMenuBar(theMenuBar);

SWC


Menus5

Menus

  • How to add menus to the menu bar

    • Create relevant menus, like

      • JMenu borrowerMenu = new JMenu(”Borrower”);

    • Add other menus or menu item to the menu

    • Add the menu to the menu bar

      • theMenuBar.add(borrowerMenu);

SWC


Menus6

Menus

  • How to add other (sub)menus to a menu

    • Create relevant menus, like

      • JMenu borrowerManageMenu = new JMenu(”Manage Borrower”);

    • Add other menus or menu item to the menu

    • Add the menu to the relevant menu

      • borrowerMenu.add(borrowerManageMenu);

SWC


Menus7

Menus

  • How to add menu items to a menu

    • Create relevant menu items, like

      • JMenuItem borrowerDeleteMenuItem = new JMenuItem(”Delete Borrower”);

    • Add the menu item to the relevant menu

      • borrowerManageMenu.add(borrowerDeleteMenuItem);

SWC


Menus8

Menus

  • You can do some more ”fun” – and maybe even useful – things with menus:

    • Add images

    • Define accelerator keys

    • Use controls in menus (radio buttons, check boxes,…)

  • Explore the documentation, but only use features that are indeed useful…

SWC


Exercise time2

Exercise time

SWC


The concept of events

The concept of events

  • 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

SWC


The concept of events1

The concept of events

  • 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

SWC


The concept of events2

The concept of events

  • 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!

SWC


The concept of events3

The concept of events

SWC


The concept of events4

The concept of events

  • 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

SWC


Relevant events

Relevant events

  • Unless we 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

SWC


Relevant events1

Relevant events

  • An event 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

SWC


Relevant events2

Relevant events

public class MyListener 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);

SWC


Relevant events3

Relevant events

  • A very 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 (maybe)

  • Pressing ”OK” means: ”Now my input is ready, do something with it!”

SWC


Exercise time3

Exercise time

SWC


Gui development in netbeans

GUI Development in NetBeans

  • Manual GUI programming is somewhat difficult and tedious

  • Unless you need something special, use the NetBeans GUI Builder!

  • Enables you to ”drag-and-drop” controls into a pane, create event handler methods almost automatically, etc.

SWC


Gui development in netbeans1

GUI Development in NetBeans

  • We will often start out by creating a ”main” frame for the application

  • This frame could be called e.g. AppFrame

  • This frame will only contain a menu, to open other – use-case specific – frames

  • Could e.g. also contain a logo, but should not contain controls as such

SWC


Gui development in netbeans2

GUI Development in NetBeans

Choose New | JFrame Form

SWC


Gui development in netbeans3

GUI Development in NetBeans

Name, etc as usual…

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Gui development in netbeans4

GUI Development in NetBeans

Palette of controls

Frame properties

Graphical view of frame

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Gui development in netbeans5

GUI Development in NetBeans

You can switch between ”Design” view and ”Source” view

SWC


Gui development in netbeans6

GUI Development in NetBeans

SWC


Gui development in netbeans7

GUI Development in NetBeans

SWC


Gui development in netbeans8

GUI Development in NetBeans

  • Looks somewhat confusing at first…

  • Good news is: You can literaly drag controls onto the frame, move them around, adjust their size, alignment, etc.

  • Code that implements your ”design” is automatically generated!

SWC


Gui development in netbeans9

GUI Development in NetBeans

  • Once we add a control, we can

    • Give the variable representing the control a suitable name

    • Graphically move, resize, etc. the control

    • Set various properties for the control

    • Also, we can add event handlers to a control

  • While all this goes on, Java code is being generated for us

SWC


Gui development in netbeans10

GUI Development in NetBeans

Choosing this will generate an (empty) event handler method

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Gui development in netbeans11

GUI Development in NetBeans

As said, fill in the code to execute when the button is clicked!

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Gui development in netbeans12

GUI Development in NetBeans

  • Once we add the event handler, it cannot be removed!

  • However, we can always change the code

  • In a sense, the event handler is always there; we just make it visible…

  • In general, we are not allowed to change the automatically generated code

SWC


Gui development in netbeans13

GUI Development in NetBeans

  • Simplistic GUIs often work as follows:

    • Fill in data in the controls

    • Press the OKbutton

    • Data is ”dealt with” (sent to a handler, etc.)

  • The only code we need to write is the event handler for pressing the OK button

  • In the event handler, data is retrieved from the other controls

SWC


Gui development in netbeans14

GUI Development in NetBeans

SWC


Gui development in netbeans15

GUI Development in NetBeans

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Gui development in netbeans16

GUI Development in NetBeans

private voidjButtonDoneActionPerformed(

java.awt.event.ActionEvent evt)

{

String name = jTextFieldName.getText();

String job = jListJob.getSelectedValue().toString();

boolean isMale = jCheckBoxMale.isSelected();

String gender;

if (isMale)

gender = "Male";

else

gender = "Female";

String announce = name + " , " + gender + " , " + job;

JOptionPane.showMessageDialog(null, announce);

}

RHS – SOC


Exercise time4

Exercise time

SWC


Gui development guide

GUI Development guide

  • No two applications will need the same GUI…

  • ..but a typical 1. or 2.semester application will usually follow a certain pattern

SWC


Gui development guide1

GUI Development guide

  • What should the application be able to do…?

    • Probably some generic tasks (Quit, Help,…)

    • General data management (Load, Save,…)

    • Implement use cases!

    • Uses cases often fall in groups according to their purposes (maybe a Customer-related group, a Boat-related group, etc.)

SWC


Gui development guide2

GUI Development guide

  • The set of tasks can be used to outline a menu structure, like e.g.

    • File (Load, Save, Quit,…)

    • Customer (Register, Delete, View All, …)

    • Boat (Register, Delete, View All)

    • Rental (Create, Delete, View All,…)

SWC


Gui development guide3

GUI Development guide

  • Create a main frame for the application, and add a menu bar with proper menus

  • Do this using the Net-Beans GUI builder

SWC


Gui development guide4

GUI Development guide

  • Create an event handler for each menu item, create and display the proper frame in the event handler

    private void jMenuItemRegisterBoatActionPerformed

    (java.awt.event.ActionEvent evt)

    {

    JFrame theRegBoatFrame = new RegisterBoatFrame();

    theRegBoatFrame.setVisible(true);

    }

SWC


Gui development guide5

GUI Development guide

  • Create frames with controls for each of the Use Cases, again using the GUI builder

  • Remember to give the control variables proper names 

SWC


Gui development guide6

GUI Development guide

  • In each Use Case – specific frame, retrieve data from controls, do e.g. conversions and validation if needed, and forward data to business logic

  • The above is usually done when the user clicks an ”OK”/”Register”/”Done” button

SWC


Gui development guide7

GUI Development guide

  • Create an event handler for the button, and do data retrieval, conversion, validation and forwarding in the event handler

    private void jButtonRegisterBoatActionPerformed

    (java.awt.event.ActionEvent evt)

    {

    // Retrieve data from controls, etc..

    }

SWC


Gui development guide8

GUI Development guide

  • Remember that even though the code for a frame is auto-generated, you can still e.g. add instance fields to the class and parameters to the constructor

SWC


Gui development guide9

GUI Development guide

  • Typical use: Give a reference to the ”System” class to the frame in its constructor, so it can be used for calling a proper method in the ”System” class with the retrieved data

SWC


Gui development guide10

GUI Development guide

// Code in red added manually

public class RegisterBoatFrame extends javax.swing.JFrame

{

private BoatRentalSystem theSystem;

public RegisterBoatFrame(BoatRentalSystem theSystem)

{

this.theSystem = theSystem;

initComponents();

}

...

SWC


Gui development guide11

GUI Development guide

private void jButtonRegisterBoatActionPerformed

(java.awt.event.ActionEvent evt)

{

// Retrieve data from controls, etc..

theSystem.registerBoat(...);

}

GUI

App.

System

Handler

SWC


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