A Dialog window is an independent subwindow meant to carry temporary notice apart from the main Swing Application Window. Most Dialogs present an error message or warning to a user, but Dialogs can present images, directory trees, or just about anything compatible with the main Swing Application that manages them.
For convenience, several Swing component classes can directly instantiate and display dialogs. To create simple, standard dialogs, you use the
JOptionPane
class. The ProgressMonitor
class can put up a dialog that shows the progress of an operation. Two other classes, JColorChooser
and JFileChooser
, also supply standard dialogs. To bring up a print dialog, you can use the
Printing API. To create a custom dialog, use the
JDialog
class directly.
The code for simple dialogs can be minimal. For example, here is an informational dialog:
Here is the code that creates and shows it:
JOptionPane.showMessageDialog(frame, "Eggs are not supposed to be green.");
The rest of this section covers the following topics:
Every dialog is dependent on a Frame component. When that Frame is destroyed, so are its dependent Dialogs. When the frame is iconified, its dependent Dialogs also disappear from the screen. When the frame is deiconified, its dependent Dialogs return to the screen. A swing JDialog class inherits this behavior from the AWT Dialog
class.
A Dialog can be modal. When a modal Dialog is visible, it blocks user input to all other windows in the program. JOptionPane creates JDialog
s that are modal. To create a non-modal Dialog, you must use the JDialog
class directly.
Starting with JDK 6, you can modify dialog window modality behavior using the new Modality API. See The New Modality API for details.
The JDialog
class is a subclass of the AWT
java.awt.Dialog
class. It adds a root pane container and support for a default close operation to the Dialog
object . These are the same features that JFrame
has, and using JDialog
directly is very similar to using JFrame
. If you're going to use JDialog
directly, then you should understand the material in Using Top-Level Containers and How to Make Frames, especially Responding to Window-Closing Events.
Even when you use JOptionPane
to implement a dialog, you're still using a JDialog
behind the scenes. The reason is that JOptionPane
is simply a container that can automatically create a JDialog
and add itself to the JDialog
's content pane.
Here is a picture of an application that displays dialogs.
Using JOptionPane
, you can quickly create and customize several different kinds of dialogs. JOptionPane
provides support for laying out standard dialogs, providing icons, specifying the dialog title and text, and customizing the button text. Other features allow you to customize the components the dialog displays and specify where the dialog should appear onscreen. You can even specify that an option pane put itself into an internal frame (JInternalFrame
) instead of a JDialog
.
When you create a JOptionPane
, look-and-feel-specific code adds components to the JOptionPane
and determines the layout of those components.
JOptionPane
's icon support lets you easily specify which icon the dialog displays. You can use a custom icon, no icon at all, or any one of four standard JOptionPane
icons (question, information, warning, and error). Each look and feel has its own versions of the four standard icons. The following figure shows the icons used in the Java (and Windows) look and feel.
Icon description | Java look and feel | Windows look and feel |
---|---|---|
question |
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information |
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warning |
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error |
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For most simple modal dialogs, you create and show the dialog using one of JOptionPane
's showXxxDialog
methods. If your dialog should be an internal frame, then add Internal
after show
for example, showMessageDialog
changes to showInternalMessageDialog
. If you need to control the dialog window-closing behavior or if you do not want the dialog to be modal, then you should directly instantiate JOptionPane
and add it to a JDialog
instance. Then invoke setVisible(true)
on the JDialog
to make it appear.
The two most useful showXxxDialog
methods are showMessageDialog
and showOptionDialog
. The showMessageDialog
method displays a simple, one-button dialog. The showOptionDialog
method displays a customized dialog it can display a variety of buttons with customized button text, and can contain a standard text message or a collection of components.
The other two showXxxDialog
methods are used less often. The showConfirmDialog
method asks the user to confirm something, but presents standard button text (Yes/No or the localized equivalent, for example) rather than button text customized to the user situation (Start/Cancel, for example). A fourth method, showInputDialog
, is designed to display a modal dialog that gets a string from the user, using either a text field, an uneditable combo box or a list.
Here are some examples, taken from
DialogDemo.java
, of using showMessageDialog
, showOptionDialog
, and the JOptionPane
constructor. For more example code, see
DialogDemo.java
and the other programs listed in Examples that Use Dialogs.
showMessageDialog
showMessageDialog
:
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//default title and icon JOptionPane.showMessageDialog(frame, "Eggs are not supposed to be green."); |
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//custom title, warning icon JOptionPane.showMessageDialog(frame, "Eggs are not supposed to be green.", "Inane warning", JOptionPane.WARNING_MESSAGE); |
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//custom title, error icon JOptionPane.showMessageDialog(frame, "Eggs are not supposed to be green.", "Inane error", JOptionPane.ERROR_MESSAGE); |
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//custom title, no icon JOptionPane.showMessageDialog(frame, "Eggs are not supposed to be green.", "A plain message", JOptionPane.PLAIN_MESSAGE); |
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//custom title, custom icon JOptionPane.showMessageDialog(frame, "Eggs are not supposed to be green.", "Inane custom dialog", JOptionPane.INFORMATION_MESSAGE, icon); |
showOptionDialog
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//Custom button text Object[] options = {"Yes, please", "No, thanks", "No eggs, no ham!"}; int n = JOptionPane.showOptionDialog(frame, "Would you like some green eggs to go " + "with that ham?", "A Silly Question", JOptionPane.YES_NO_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE, null, options, options[2]); |
JOptionPane
(constructor)JOptionPane
with the specified buttons, icons, message, title, and so on. You must then add the option pane to a JDialog
, register a property-change listener on the option pane, and show the dialog. See Stopping Automatic Dialog Closing for details.
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final JOptionPane optionPane = new JOptionPane( "The only way to close this dialog is by\n" + "pressing one of the following buttons.\n" + "Do you understand?", JOptionPane.QUESTION_MESSAGE, JOptionPane.YES_NO_OPTION); |
The arguments to all of the showXxxDialog
methods and JOptionPane
constructors are standardized, though the number of arguments for each method and constructor varies. The following list describes each argument. To see the exact list of arguments for a particular method, see The Dialog API.
Component parentComponent
showXxxDialog
method is always the parent component, which must be a Frame, a component inside a Frame, or null. If you specify a Frame or Dialog, then the Dialog will appear over the center of the Frame and follow the focus behavior of that Frame. If you specify a component inside a Frame, then the Dialog will appear over the center of that component and will follow the focus behavior of that component's Frame. If you specify null, then the look and feel will pick an appropriate position for the dialog generally the center of the screen and the Dialog will not necessarily follow the focus behavior of any visible Frame or Dialog.
The JOptionPane
constructors do not include this argument. Instead, you specify the parent frame when you create the JDialog
that contains the JOptionPane
, and you use the JDialog
setLocationRelativeTo
method to set the dialog position.
Object message
\n
) characters inside the message string. For example:
"Complete the sentence:\n \"Green eggs and...\""
String title
int optionType
DEFAULT_OPTION
, YES_NO_OPTION
, YES_NO_CANCEL_OPTION
, OK_CANCEL_OPTION
.int messageType
PLAIN_MESSAGE
(no icon), ERROR_MESSAGE
, INFORMATION_MESSAGE
, WARNING_MESSAGE
, QUESTION_MESSAGE
.Icon icon
Object[] options
Object initialValue
You can either let the option pane display its default icon or specify the icon using the message type or icon argument. By default, an option pane created with showMessageDialog
displays the information icon, one created with showConfirmDialog
or showInputDialog
displays the question icon, and one created with a JOptionPane
constructor displays no icon. To specify that the dialog display a standard icon or no icon, specify the message type corresponding to the icon you desire. To specify a custom icon, use the icon argument. The icon argument takes precedence over the message type; as long as the icon argument has a non-null value, the dialog displays the specified icon.
When you use JOptionPane
to create a dialog, you can either use the standard button text (which might vary by look and feel and locale) or specify different text. By default, the option pane type determines how many buttons appear. For example, YES_NO_OPTION
dialogs have two buttons, and YES_NO_CANCEL_OPTION
dialogs have three buttons.
The following code, taken from
DialogDemo.java
, creates two Yes/No dialogs. The first dialog is implemented with showConfirmDialog
, which uses the look-and-feel wording for the two buttons. The second dialog uses showOptionDialog
so it can customize the wording. With the exception of wording changes, the dialogs are identical.
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//default icon, custom title int n = JOptionPane.showConfirmDialog( frame, "Would you like green eggs and ham?", "An Inane Question", JOptionPane.YES_NO_OPTION); |
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Object[] options = {"Yes, please", "No way!"}; int n = JOptionPane.showOptionDialog(frame, "Would you like green eggs and ham?", "A Silly Question", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE, null, //do not use a custom Icon options, //the titles of buttons options[0]); //default button title |
As the previous code snippets showed, the showMessageDialog
, showConfirmDialog
, and showOptionDialog
methods return an integer indicating the user's choice. The values for this integer are YES_OPTION
, NO_OPTION
, CANCEL_OPTION
, OK_OPTION
, and CLOSED_OPTION
. Except for CLOSED_OPTION
, each option corresponds to the button the user pressed. When CLOSED_OPTION
is returned, it indicates that the user closed the dialog window explicitly, rather than by choosing a button inside the option pane.
Even if you change the strings that the standard dialog buttons display, the return value is still one of the pre-defined integers. For example, a YES_NO_OPTION
dialog always returns one of the following values: YES_OPTION
, NO_OPTION
, or CLOSED_OPTION
.
The only form of showXxxDialog
that does not return an integer is showInputDialog
, which returns an Object
instead. This Object
is generally a String
reflecting the user's choice. Here is an example of using showInputDialog
to create a dialog that lets the user choose one of three strings:
Object[] possibilities = {"ham", "spam", "yam"}; String s = (String)JOptionPane.showInputDialog( frame, "Complete the sentence:\n" + "\"Green eggs and...\"", "Customized Dialog", JOptionPane.PLAIN_MESSAGE, icon, possibilities, "ham"); //If a string was returned, say so. if ((s != null) && (s.length() > 0)) { setLabel("Green eggs and... " + s + "!"); return; } //If you're here, the return value was null/empty. setLabel("Come on, finish the sentence!");
If you do not care to limit the user's choices, you can either use a form of the showInputDialog
method that takes fewer arguments or specify null
for the array of objects. In the Java look and feel, substituting null
for possibilities
results in a dialog that has a text field and looks like this:
Because the user can type anything into the text field, you might want to check the returned value and ask the user to try again if it is invalid. Another approach is to create a custom dialog that validates the user-entered data before it returns. See
CustomDialog.java
for an example of validating data.
If you're designing a custom dialog, you need to design your dialog's API so that you can query the dialog about what the user chose. For example, CustomDialog
has a getValidatedText
method that returns the text the user entered.
By default, when the user clicks a JOptionPane
-created button, the dialog closes. But what if you want to check the user's answer before closing the dialog? In this case, you must implement your own property change listener so that when the user clicks a button, the dialog does not automatically close.
DialogDemo
contains two dialogs that implement a property change listener. One of these dialogs is a custom modal dialog, implemented in
CustomDialog
, that uses JOptionPane
both to get the standard icon and to get layout assistance. The other dialog, whose code is below, uses a standard Yes/No JOptionPane
. Though this dialog is rather useless as written, its code is simple enough that you can use it as a template for more complex dialogs.
Besides setting the property change listener, the following code also calls the JDialog
's setDefaultCloseOperation
method and implements a window listener that handles the window close attempt properly. If you do not care to be notified when the user closes the window explicitly, then ignore the bold code.
final JOptionPane optionPane = new JOptionPane( "The only way to close this dialog is by\n" + "pressing one of the following buttons.\n" + "Do you understand?", JOptionPane.QUESTION_MESSAGE, JOptionPane.YES_NO_OPTION); final JDialog dialog = new JDialog(frame, "Click a button", true); dialog.setContentPane(optionPane); dialog.setDefaultCloseOperation( JDialog.DO_NOTHING_ON_CLOSE); dialog.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent we) { setLabel("Thwarted user attempt to close window."); } }); optionPane.addPropertyChangeListener( new PropertyChangeListener() { public void propertyChange(PropertyChangeEvent e) { String prop = e.getPropertyName(); if (dialog.isVisible() && (e.getSource() == optionPane) && (prop.equals(JOptionPane.VALUE_PROPERTY))) { //If you were going to check something //before closing the window, you'd do //it here. dialog.setVisible(false); } } }); dialog.pack(); dialog.setVisible(true); int value = ((Integer)optionPane.getValue()).intValue(); if (value == JOptionPane.YES_OPTION) { setLabel("Good."); } else if (value == JOptionPane.NO_OPTION) { setLabel("Try using the window decorations " + "to close the non-auto-closing dialog. " + "You can't!"); }
The following tables list the commonly used JOptionPane
and JDialog
constructors and methods. Other methods you're likely to call are defined by the
Dialog
,
Window
and
Component
classes and include pack
, setSize
, and setVisible
.
The API is listed as follows:
JOptionPane
Class Methods)JOptionPane
s DirectlyJDialog
Constructors and MethodsMethod | Purpose |
---|---|
static void showMessageDialog(Component, Object) static void showMessageDialog(Component, Object, String, int) static void showMessageDialog(Component, Object, String, int, Icon) |
Show a one-button, modal dialog that gives the user some information. The arguments specify (in order) the parent component, message, title, message type, and icon for the dialog. See Creating and Showing Simple Dialogs for a discussion of the arguments and their effects. |
static int showOptionDialog(Component, Object, String, int, int, Icon, Object[], Object) | Show a customized modal dialog. The arguments specify (in order) the parent component, message, title, option type, message type, icon, options, and initial value for the dialog. See Creating and Showing Simple Dialogs for a discussion of the arguments and their effects. |
static int showConfirmDialog(Component, Object) static int showConfirmDialog(Component, Object, String, int) static int showConfirmDialog(Component, Object, String, int, int) static int showConfirmDialog(Component, Object, String, int, int, Icon) |
Show a modal dialog that asks the user a question. The arguments specify (in order) the parent component, message, title, option type, message type, and icon for the dialog. See Creating and Showing Simple Dialogs for a discussion of the arguments and their effects. |
static String showInputDialog(Object) static String showInputDialog(Component, Object) static String showInputDialog(Component, Object, String, int) static String showInputDialog(Component, Object, String, int, Icon, Object[], Object) |
Show a modal dialog that prompts the user for input. The single-argument version specifies just the message, with the parent component assumed to be null. The arguments for the other versions specify (in order) the parent component, message, title, message type, icon, options, and initial value for the dialog. See Creating and Showing Simple Dialogs for a discussion of the arguments and their effects. |
static void showInternalMessageDialog(...) static void showInternalOptionDialog(...) static void showInternalConfirmDialog(...) static String showInternalInputDialog(...) |
Implement a standard dialog as an internal frame. See the
JOptionPane API documentation for the exact list of arguments. |
Method or Constructor | Purpose |
---|---|
JOptionPane() JOptionPane(Object) JOptionPane(Object, int) JOptionPane(Object, int, int) JOptionPane(Object, int, int, Icon) JOptionPane(Object, int, int, Icon, Object[]) JOptionPane(Object, int, int, Icon, Object[], Object) |
Creates a JOptionPane instance. See Creating and Showing Simple Dialogs for a discussion of the arguments and their effects. |
static Frame getFrameForComponent(Component) static JDesktopPane getDesktopPaneForComponent(Component) |
Handy JOptionPane class methods that find the frame or desktop pane, respectively, that the specified component is in. |
int getMaxCharactersPerLineCount() | Determines where line breaks will be automatically inserted in the option pane text. (The default is Integer.MAX_VALUE .) To use this method, you must create a JOptionPane subclass. For example, the following code results in an option pane with one word per line, due to the fact that each word in the string is 5 characters or less:
JOptionPane op = new JOptionPane("This is the text.") { public int getMaxCharactersPerLineCount() { return 5; } }; |
Method or Constructor | Purpose |
---|---|
JDialog() JDialog(Dialog) JDialog(Dialog, boolean) JDialog(Dialog, String) JDialog(Dialog, String, boolean) JDialog(Dialog, String, boolean, GraphicsConfiguration) JDialog(Frame) JDialog(Frame, boolean) JDialog(Frame, String) JDialog(Frame, String, boolean) JDialog(Frame, String, boolean, GraphicsConfiguration) JDialog(Window owner) JDialog(Window owner, Dialog.ModalityType modalityType) JDialog(Window owner, String title) JDialog(Window owner, String title, Dialog.ModalityType modalityType) JDialog(Window owner, String title, Dialog.ModalityType modalityType, GraphicsConfiguration gc) |
Creates a JDialog instance. The Frame argument, if any, is the frame (usually a JFrame object) that the dialog depends on. Make the boolean argument true to specify a modal dialog, false or absent to specify a non-modal dialog. You can also specify the title of the dialog, using a string argument. |
void setContentPane(Container) Container getContentPane() |
Get and set the content pane, which is usually the container of all the dialog's components. See Using Top-Level Containers for more information. |
void setDefaultCloseOperation(int) int getDefaultCloseOperation() |
Get and set what happens when the user tries to close the dialog. Possible values: DISPOSE_ON_CLOSE , DO_NOTHING_ON_CLOSE , HIDE_ON_CLOSE (the default). See Responding to Window-Closing Events for more information. |
void setLocationRelativeTo(Component) | Centers the dialog over the specified component. |
static void setDefaultLookAndFeelDecorated(boolean) static boolean isDefaultLookAndFeelDecorated() |
Set or get a hint as to whether the dialog's window decorations (such as borders, or widgets to close the window) should be provided by the current look and feel. Otherwise the dialog's decorations will be provided by the current window manager. See Specifying Window Decorations for more information. |
This table lists examples that use JOptionPane
or JDialog
. To find other examples that use dialogs, see the example lists for progress bars, color choosers, and file choosers.
Example | Where Described | Notes |
---|---|---|
DialogDemo ,CustomDialog |
This section | Creates many kinds of dialogs, using JOptionPane and JDialog . |
Framework |
| Brings up a confirmation dialog when the user selects the Quit menu item. |
ListDialog |
How to Use BoxLayout | Implements a modal dialog containing a scrolling list and two buttons. Does not use JOptionPane , except for the utility method getFrameForComponent . |