AWT controls

 AWT controls

• The java GUI classes are contained in the java.awt package.
•  AWT package provides full support for user interface, components like labels, buttons, checkboxes, textfields, scrollbars, menus etc.

1)Labels

•  A Label is a string that appears on a graphical user interface.
• these class defines three constructors.

            1)Label()

            2)Label(String str)

            3)Label(String str, int align)

•  Here, str is the text for the label.

2)Buttons

•  A Button is a component that appears as a push button.
•  A button is a component that contain a label and that generates an event when it is pressed.
•  this class defines two constructor.

            1)Button()

            2)Button(String str)

•  Here str is the text for the button.

3)Checkbox

• A Checkbox is a component that combines a label and a small box.
•  it is a control that is used to turn an option on or off.
• the constructor are as follow:

            1)Checkbox()

            2)Checkbox(String str)

            3)Checkbox(String str,boolean state)

            4)Checkbox(String str,boolean state,CheckboxGroup grp)

•  The first form creates a checkbox whose label is blank.
•  In the second form str is the text for the check box.
•  In the third form if state is true, a check mark appears in the box.
• The fourth form used to group several check boxes together.
• The parameter grp is referenced to the check box group.

4)CheckboxGroup 

•  A CheckboxGroup is a set of check boxes.
•  in this group only one check box in the group can be checked at one time.
• These check box group are often called radio buttons.
•  For, this type of Checkbox you must first define the group to which they will belong and then specify that group whenyou construct the checkbox.
• CheckboxGroup()

5)Choice

• A choice is a component that provides a list of menu. When user clicks on a choice, it displays whole list of choice and then a selection can be made.
• it can have only one item selected at a time. Choice shows the currently selected item.
•  Choice define the only one constructor:
• Choice()

6)List

•  A List is a component that allows a user to select one or more items. If the list is large then it will automatically provide scroll bars so that user may see the entire list.
•  An item event is generated when a user selects or deselects one of the item.
•  It defines the following constructor:

              1)List()

              2)List(int rows)

              3)List(int rows,boolean multiple)

• Here, in the second form rows is the number of items that are visible to user.
•  In the third form if multiple is true , a user may select multiple entries in a list.
• Otherwise only one item may be selected.

7)Scrollbar

•  Scrollbars are used to select any int values between a specified minimum and maximum.
• A scroll bar contains a slider that may be dragged to continuously vary its value.
• it defines the following constructor:
• Scrollbar()
• Scrollbar(int orientation)
• Scrollbar(int orientation,int value,int width,int min,int max)

8)TextField 

•  A textField allows a user to enter one line of text.
• TextField allow the user to enter strings and to edit the text using the arrow keys, cut and paste keys, and mouse selection.
• It defines the following constructor:
• TextField()
• TextField(String str)
• TextField(int cols)
• TextField(String str, int cols)
•  Here, str is the text for the field. The argument cols indicate the width of a field in character.

9)TextArea 

•  A textArea allows a user to enter multiple lines of text. Sometimes a single line of text input is not enough for a given task.
•  To handle these situation, the AWT includes a simple multiline editor called TextArea.
•  It has the following constructor:
• TextArea()
• TextArea(String str)
• TextArea(int rows,int cols)
• TextArea(String str,int rows,int cols)
• TextArea(String str,int rows,int cols,int scrollbars)
•  Here, str is the text for the area. The rows and cols arguments indicate the number of rows and columns in the component.

10)Canvas

• A canvas provides a rectangular area on which we can draw. This is valuable because we can create graphs and other diagrams on the canvas by using methods of the Graphics class.
•  The canvas class extends component class.
• it defines the following constructor.
• Canvas()

11)Menubars and Menus

•  A window can have a menubar associated with it.A menu bar displays a list of top level menu choice.
•  Each choice is associate wiuth a drop down menu. This concept is implemented by the following classes:Menubar, Menu and MenuItem 

•  In short, a menu object contains a list of MenuItem objects.
•  Each menu object contains a list of MenuItem objects. Each MenuItem object represents something that can be selected by the user.
•  Menu is a superclass of MenuItem. We can also create a hierarchy of nested submenus.
• It is also possible to include checkable MenuItem.