Screen
How do you create a graphical user interface?
designScreen()
The designScreen() method first creates a button object with this statement
Button emailButton = new Button("Send Mail");.
A new object is created by declaring the object name and then using the "new" statement to create an instance of the object. The object parameter list supplies data specific to the object. In this case the "Send Mail" text string is used to define the emailButton label.
The listLabel object is created with this statement,
Label listLabel = new Label("Directory");.
A panel called listPanel is created with
Panel listPanel = new Panel(); and
listPanel.setLayout(new BorderLayout());
The setLayout method of the Panel class specifies the type of layout manger to use for the listPanel. There are five standard layout managers. The default layout manager is called FlowLayout which arranges components in a panel from left to right in a row. However, we wanted to arrange our components differently so we defined listPanel to use the BorderLayout manager. The BorderLayout manager allows components to be placed in the regions North, South, East, West and Center. The other layout managers provide additional flexibility to allow the programmer to provide more specific suggestions in order to layout the components. Yes I said, suggestions because the programmer doesn't actually place components at certain pixels on the screen he/she only provides suggestions to encourage the placement of components relative to other components in approximate locations on the panel.
The following statements specify formatting characteristics of the panel components.
listLabel.setAlignment(Label.CENTER);
Center the label text.
listPanel.setBackground(Color.lightGray);
Set the color of the listPanel to light gray.
itemList.setBackground(Color.yellow);
Set the color of the itemList to yellow.
setBackground(Color.white);
Set the color of the entire applet panel to white.
The add method of the Panel class adds the components to the listPanel as follows:
listPanel.add("North",listLabel);
listPanel.add("Center",itemList);
listPanel.add("South",sendButton);
The
add(listPanel); statement adds the listPanel to the Applet panel, which puts it in our HTML document.
For simplicity, the foreground color and font of the text have assumed the default values. A good enhancement to this program would be to read in the color and font as parameters and set the foreground text color and font.
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