1. Lab 4: GUIs, Panels, Mouse and Key Listeners ICOM4015: FALL 2014 A N I NTRODUCTION TO P ANELS AND L AYOUTS CREATED BY KATYA I. BORGOS REVISED BY AMIR H. CHINAEI

2. JPanels  The JPanel class provides general- purpose containers, known as panels.  These panels allow us to organize the components that make up our GUI; Each component will represent an important element of our GUI such as a button, label, etc.  JPanels can be given specific layouts to reflect how we want the GUI components to be organized.

3. JPanel(cont.)  To create a new JPanel, we need to use the default constructor.  To add a component to a panel, we invoke the add(Component comp) method on the panel. Keep in mind that you can only add objects of classes that extend/inherit from JComponent. You can easily look this up in the Java API. Note: The order in which you add Components can matter. It depends on the Layout you are working with.  Finally, to set the layout of a panel to a specifc layout manager, we invoke the setLayout(LayoutManager mgr) method on the panel. We can create a new object of the corresponding Layout class as a parameter.

4. Our Goal

5. GridLayout  A JPanel with a GridLayout manager places the components that are added to it in a grid of cells.  Each component takes all the available space within its cell, and each cell is exactly the same size.  Components are added starting at the first row until it is filled, then the second row, and so on.  Example:  JPanel grid = new JPanel();  grid.setLayout(new GridLayout(5, 4));  JButton rTCButton = new JButton(“Rtc”);  grid.add(rTCButton);  JButton cEButton = new JButton(“CE”);  grid.add(cEButton);

6. BoxLayout  A BoxLayout manager arranges components either on top of each other or in a row.  The way to state which orientation you would like the BoxLayout to have is by establishing a constant when you use its constructor. These constants are:  BoxLayout.Y_AXIS (stacks components on top of each other)  BoxLayout.X_AXIS (places components in a row)  Example:  JPanel box = new JPanel();  box.setLayout(box, BoxLayout.Y_AXIS);

7. BorderLayout  A JPanel with a set BorderLayout manager arranges and resizes its components to fit in five regions: north, south, east, west, and center.  Each region may contain only one component. However, that one component may have several components.  Just like the BoxLayout, the regions are identified by a corresponding constant:  BorderLayout.NORTH  BorderLayout.WEST  BorderLayout.CENTER  BorderLayout.SOUTH  BorderLayout.EAST

8. BorderLayout(cont.)  Example:  JPanel myPanel = new JPanel();  myPanel.setLayout(new BorderLayout());  JButton button = new Jbutton();  myPanel.add(button, BorderLayout.EAST); Unlike BoxLayout, you specify locations on the BorderLayout when you add a component.

9. Listeners Hints:  Use the methods added to the WindowMainPanel class to your convenience (setDisplayText(), getDisplayText(), setStatusBarText() and getStatusBarText().  Consider using substrings and String concatenation.  Look up the String class method substring(int beginIndex, int endIndex) in the Java API.  String concatenation is the operation of joining character strings end-to-end using the plus (+) operator.  For example, System.out.println(“Hello, “ + “world!”); prints “Hello, world!” to the console.