JOptionPane
makes it easy to pop up a standard dialog box that
prompts users for a value or informs them of something.
For information about using
JOptionPane
, see
How to Make Dialogs,
a section in
The Java Tutorial.
While the JOptionPane
class may appear complex because of the large number of methods, almost
all uses of this class are one-line calls to one of the static
showXxxDialog
methods shown below:
Method Name |
Description |
showConfirmDialog |
Asks a confirming question, like yes/no/cancel. |
showInputDialog |
Prompt for some input. |
showMessageDialog |
Tell the user about something that has happened. |
showOptionDialog |
The Grand Unification of the above three. |
Each of these methods also comes in a
showInternalXXX
flavor, which uses an internal frame to hold the dialog box (see
JInternalFrame
).
Multiple convenience methods have also been defined -- overloaded
versions of the basic methods that use different parameter lists.
All dialogs are modal. Each showXxxDialog
method blocks
the caller until the user's interaction is complete.
icon |
message |
input value |
option buttons |
The basic appearance of one of these dialog boxes is generally
similar to the picture at the right, although the various
look-and-feels are
ultimately responsible for the final result. In particular, the
look-and-feels will adjust the layout to accommodate the option pane's
ComponentOrientation
property.
Parameters:
The parameters to these methods follow consistent patterns:
- parentComponent
-
Defines the
Component
that is to be the parent of this
dialog box.
It is used in two ways: the Frame
that contains
it is used as the Frame
parent for the dialog box, and its screen coordinates are used in
the placement of the dialog box. In general, the dialog box is placed
just below the component. This parameter may be null
,
in which case a default Frame
is used as the parent,
and the dialog will be
centered on the screen (depending on the L&F).
- message
-
A descriptive message to be placed in the dialog box.
In the most common usage, message is just a
String
or
String
constant.
However, the type of this parameter is actually Object
. Its
interpretation depends on its type:
- Object[]
- An array of objects is interpreted as a series of
messages (one per object) arranged in a vertical stack.
The interpretation is recursive -- each object in the
array is interpreted according to its type.
- Component
- The
Component
is displayed in the dialog.
- Icon
- The
Icon
is wrapped in a JLabel
and displayed in the dialog.
- others
- The object is converted to a
String
by calling
its toString
method. The result is wrapped in a
JLabel
and displayed.
- messageType
- Defines the style of the message. The Look and Feel
manager may lay out the dialog differently depending on this value, and
will often provide a default icon. The possible values are:
ERROR_MESSAGE
INFORMATION_MESSAGE
WARNING_MESSAGE
QUESTION_MESSAGE
PLAIN_MESSAGE
- optionType
- Defines the set of option buttons that appear at
the bottom of the dialog box:
DEFAULT_OPTION
YES_NO_OPTION
YES_NO_CANCEL_OPTION
OK_CANCEL_OPTION
You aren't limited to this set of option buttons. You can provide any
buttons you want using the options parameter.
- options
- A more detailed description of the set of option buttons
that will appear at the bottom of the dialog box.
The usual value for the options parameter is an array of
String
s. But
the parameter type is an array of Objects
.
A button is created for each object depending on its type:
- Component
- The component is added to the button row directly.
- Icon
- A
JButton
is created with this as its label.
- other
- The
Object
is converted to a string using its
toString
method and the result is used to
label a JButton
.
- icon
- A decorative icon to be placed in the dialog box. A default
value for this is determined by the
messageType
parameter.
- title
- The title for the dialog box.
- initialValue
- The default selection (input value).
When the selection is changed, setValue
is invoked,
which generates a PropertyChangeEvent
.
If a JOptionPane
has configured to all input
setWantsInput
the bound property JOptionPane.INPUT_VALUE_PROPERTY
can also be listened
to, to determine when the user has input or selected a value.
When one of the showXxxDialog
methods returns an integer,
the possible values are:
YES_OPTION
NO_OPTION
CANCEL_OPTION
OK_OPTION
CLOSED_OPTION
Examples:
- Show an error dialog that displays the message, 'alert':
JOptionPane.showMessageDialog(null, "alert", "alert", JOptionPane.ERROR_MESSAGE);
- Show an internal information dialog with the message, 'information':
JOptionPane.showInternalMessageDialog(frame, "information",
"information", JOptionPane.INFORMATION_MESSAGE);
- Show an information panel with the options yes/no and message 'choose one':
JOptionPane.showConfirmDialog(null,
"choose one", "choose one", JOptionPane.YES_NO_OPTION);
- Show an internal information dialog with the options yes/no/cancel and
message 'please choose one' and title information:
JOptionPane.showInternalConfirmDialog(frame,
"please choose one", "information",
JOptionPane.YES_NO_CANCEL_OPTION, JOptionPane.INFORMATION_MESSAGE);
- Show a warning dialog with the options OK, CANCEL, title 'Warning', and
message 'Click OK to continue':
Object[] options = { "OK", "CANCEL" };
JOptionPane.showOptionDialog(null, "Click OK to continue", "Warning",
JOptionPane.DEFAULT_OPTION, JOptionPane.WARNING_MESSAGE,
null, options, options[0]);
- Show a dialog asking the user to type in a String:
String inputValue = JOptionPane.showInputDialog("Please input a value");
- Show a dialog asking the user to select a String:
Object[] possibleValues = { "First", "Second", "Third" };
Object selectedValue = JOptionPane.showInputDialog(null,
JOptionPane.INFORMATION_MESSAGE, null,
possibleValues, possibleValues[0]);
Direct Use:
To create and use an
JOptionPane
directly, the
standard pattern is roughly as follows:
JOptionPane pane = new JOptionPane(arguments);
pane.set.Xxxx(...); // Configure
JDialog dialog = pane.createDialog(parentComponent, title);
dialog.show();
Object selectedValue = pane.getValue();
if(selectedValue == null)
return CLOSED_OPTION;
//If there is not an array of option buttons:
if(options == null) {
if(selectedValue instanceof Integer)
return ((Integer)selectedValue).intValue();
return CLOSED_OPTION;
}
//If there is an array of option buttons:
for(int counter = 0, maxCounter = options.length;
counter < maxCounter; counter++) {
if(options[counter].equals(selectedValue))
return counter;
}
return CLOSED_OPTION;
Warning: Swing is not thread safe. For more
information see Swing's Threading
Policy.
Warning:
Serialized objects of this class will not be compatible with
future Swing releases. The current serialization support is
appropriate for short term storage or RMI between applications running
the same version of Swing. As of 1.4, support for long term storage
of all JavaBeansTM
has been added to the java.beans
package.
Please see XMLEncoder
.