How to Make Dialogs

http://docs.oracle.com/javase/tutorial/uiswing/components/dialog.html#input

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:

An Overview of Dialogs
The DialogDemo Example
JOptionPane Features
Creating and Showing Simple Dialogs
Customizing Button Text
Getting the User's Input from a Dialog
Stopping Automatic Dialog Closing
The Dialog API
Examples that Use Dialogs

An Overview of Dialogs

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.

The DialogDemo Example

Here is a picture of an application that displays dialogs.



Try this::

Click the Launch button to run the Dialog Demo using
Java™ Web Start (download JDK 6 or later). Alternatively, to compile and run the example yourself, consult the

example index.



Click the Show it! button.

A modal dialog will appear. Until you close it, the application will be unresponsive, although it will repaint itself if necessary. You can close the dialog either by clicking a button in the dialog or explicitly, such as by using the dialog window decorations.
In the More Dialogs pane, click the bottom radio button and then the Show it! button.

A non-modal dialog will appear. Note that the DialogDemo window remains fully functional while the non-modal dialog is up.
While the non-modal dialog is showing, iconify the DialogDemo window.

The dialog will disappear from the screen until you deiconify the DialogDemo window.

JOptionPane Features

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.

Icons used by JOptionPane

Icon description	Java look and feel	Windows look and feel
question
information
warning
error

Creating and Showing Simple Dialogs

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

Displays a modal dialog with one button, which is labeled "OK" (or the localized equivalent). You can easily specify the message, icon, and title that the dialog displays. Here are some examples of using

showMessageDialog

:

	//default title and iconJOptionPane.showMessageDialog(frame, "Eggs are not supposed to be green.");
	//custom title, warning iconJOptionPane.showMessageDialog(frame, "Eggs are not supposed to be green.", "Inane warning",JOptionPane.WARNING_MESSAGE);
	//custom title, error iconJOptionPane.showMessageDialog(frame, "Eggs are not supposed to be green.", "Inane error",JOptionPane.ERROR_MESSAGE);
	//custom title, no iconJOptionPane.showMessageDialog(frame, "Eggs are not supposed to be green.", "A plain message",JOptionPane.PLAIN_MESSAGE);
	//custom title, custom iconJOptionPane.showMessageDialog(frame, "Eggs are not supposed to be green.", "Inane custom dialog",JOptionPane.INFORMATION_MESSAGE, icon);

showOptionDialog

Displays a modal dialog with the specified buttons, icons, message, title, and so on. With this method, you can change the text that appears on the buttons of standard dialogs. You can also perform many other kinds of customization.

//Custom button textObject[] 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)Creates a

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.

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

The first argument to each

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

This required argument specifies what the dialog should display in its main area. Generally, you specify a string, which results in the dialog displaying a label with the specified text. You can split the message over several lines by putting newline (

\n

)
characters inside the message string. For example:

"Complete the sentence:\n \"Green eggs and...\""

String title

The title of the dialog.

int optionType

Specifies the set of buttons that appear at the bottom of the dialog. Choose from one of the following standard sets:

DEFAULT_OPTION

,

YES_NO_OPTION

,

YES_NO_CANCEL_OPTION

,

OK_CANCEL_OPTION

.

int messageType

This argument determines the icon displayed in the dialog. Choose from one of the following values:

PLAIN_MESSAGE

(no icon),

ERROR_MESSAGE

,

INFORMATION_MESSAGE

,

WARNING_MESSAGE

,

QUESTION_MESSAGE

.

Icon icon

The icon to display in the dialog.

Object[] options

Generally used to specify the string displayed by each button at the bottom of the dialog. See

Customizing Button Text in a Standard Dialog for more information. Can also be used to specify icons to be displayed by the buttons or non-button components to be added to the button row.

Object initialValue

Specifies the default value to be selected.
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.

Customizing Button Text

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.

	//default icon, custom title int n = JOptionPane.showConfirmDialog( frame, "Would you like green eggs and ham?", "An Inane Question",JOptionPane.YES_NO_OPTION);
	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

.

Getting the User's Input from a Dialog

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.

Stopping Automatic Dialog Closing

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 Dialog API

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:

Showing Standard Modal Dialogs (using

JOptionPane

Class Methods)
Methods for Using

JOptionPane

s Directly
Frequently Used

JDialog

Constructors and Methods

Showing Standard Modal Dialogs (Using

JOptionPane

Class Methods)

Method	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.

Methods for Using

JOptionPane

s Directly

Method or Constructor	Purpose
JOptionPane() JOptionPane(Object) JOptionPane(Object, int) JOptionPane(Object, int, int) JOptionPane(Object, int, int, Icon) %29]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; } };

Frequently Used

JDialog

Constructors and Methods

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.

Examples that Use Dialogs

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 .

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