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Trail: Creating a GUI with JFC/Swing
Lesson: Using Swing Components

How to Use Internal Frames

With the JInternalFrame(in the API reference documentation) class, you can display a JFrame-like window within another window. Usually, you add internal frames to a desktop pane. The desktop pane, in turn, might be used as the content pane of a JFrame. The desktop pane is an instance of JDesktopPane(in the API reference documentation), which is a subclass of JLayeredPane that has added API for managing multiple overlapping internal frames.

You should consider carefully whether to base your program's GUI around frames or internal frames. Switching from internal frames to frames or vice versa isn't necessarily a simple task. By experimenting with both frames and internal frames, you can get an idea of the tradeoffs involved in choosing one over the other.

Here is a picture of an application that has two internal frames inside a regular frame:

InternalFrameDemo has multiple internal frames, managed by a desktop pane

As the figure shows, the window decorations on the internal frames reflect the Java Look & Feel. However, the window that contains them has the decorations for the native look and feel.

Try this: 
  1. Compile and run the application. The source files are InternalFrameDemo.java and MyInternalFrame.java.
    See Getting Started with Swing if you need help compiling or running this application.
  2. Create new internal frames using the Create item in the Document menu.
    Each internal frame comes up 30 pixels lower and to the right of the place where the previous internal frame first appeared. This functionality is implemented in the MyInternalFrame class, which is the custom subclass of JInternalFrame.

The following code, taken from InternalFrameDemo.java, creates the desktop and internal frames in the previous example. 

...//In the constructor of InternalFrameDemo, a JFrame subclass:
    desktop = new JDesktopPane(); 
    createFrame(); //Create first window
    setContentPane(desktop);
    ...
    //Make dragging faster:
    desktop.putClientProperty("JDesktopPane.dragMode", "outline");
...
protected void createFrame() {
    MyInternalFrame frame = new MyInternalFrame();
    frame.setVisible(true); //necessary as of kestrel
    desktop.add(frame);
    try {
        frame.setSelected(true);
    } catch (java.beans.PropertyVetoException e) {}
}

...//In the constructor of MyInternalFrame, a JInternalFrame subclass:
static int openFrameCount = 0;
static final int xOffset = 30, yOffset = 30;

public MyInternalFrame() {
    super("Document #" + (++openFrameCount), 
          true, //resizable
          true, //closable
          true, //maximizable
          true);//iconifiable
    //...Create the GUI and put it in the window...
    //...Then set the window size or call pack...
    ...
    //Set the window's location.
    setLocation(xOffset*openFrameCount, yOffset*openFrameCount);
}

Internal Frames vs. Regular Frames

The code for using internal frames is similar in many ways to the code for using regular Swing frames. Because internal frames have root panes, setting up the GUI for a JInternalFrame is very similar to setting up the GUI for a JFrame. JInternalFrame also provides other API, such as pack, that makes it similar to JFrame.
Note: Just as for a regular frame, you must invoke setVisible(true) or show() on an internal frame to display it. In early versions of the Java 2 platform (such as v1.2.2), this code has no effect because the internal frame is visible by default. However, starting in the Kestrel release, the internal frame does not appear until you explicitly make it visible.

Internal frames aren't windows or top-level containers, however, which makes them different from frames. For example, you must add an internal frame to a container (usually a JDesktopPane); an internal frame can't be the root of a containment hierarchy. Also, internal frames don't generate window events. Instead, the user actions that would cause a frame to fire window events cause an internal frame to fire internal frame events.

Because internal frames are implemented with platform-independent code, they add some features that frames can't give you. One such feature is that internal frames give you more control over their state and capabilities than frames do. You can programatically iconify or maximize an internal frame. You can also specify what icon goes in the internal frame's title bar. You can even specify whether the internal frame has the window decorations to support resizing, iconifying, closing, and maximizing.

Another feature is that internal frames are designed to work within desktop panes. The JInternalFrame API contains methods such as moveToFront that work only if the internal frame's container is a layered pane such as a JDesktopPane.

Rules of Using Internal Frames

If you've built any programs using JFrame and the other Swing components, then you already know a lot about how to use internal frames. The following list summarizes the rules for using internal frames. For additional information, see How to Make Frames and The JComponent Class.
You must set the size of the internal frame.
If you don't set the size of the internal frame, it will have zero size and thus never be visible. You can set the size using one of the following methods: setSize, pack, or setBounds.
As a rule, you should set the location of the internal frame.
If you don't set the location of the internal frame, it will come up at 0,0 (the upper left of its container). You can use the setLocation or setBounds method to specify the upper left point of the internal frame, relative to its container.
To add components to an internal frame, you add them to the internal frame's content pane.
This is exactly like the JFrame situation. See Adding Components to the Content Pane for details.
Dialogs that are internal frames should be implemented using JOptionPane or JInternalFrame, not JDialog.
To create a simple dialog, you can use the JOptionPane showInternalXxxDialog methods, as described in How to Make Dialogs.
You must add an internal frame to a container.
If you don't add the internal frame to a container (usually a JDesktopPane), the internal frame won't appear.
You need to call show or setVisible on internal frames.
Beginning with the Kestrel release, internal frames are invisible by default. You must invoke setVisible(true) or show() to make them visible.
Internal frames fire internal frame events, not window events.
Handling internal frame events is almost identical to handling window events. See How to Write an Internal Frame Listener for more information.
Performance Tip:  Because dragging internal frames can be slow, Swing 1.1.1 adds a way to make it zippy: outline dragging. With outline dragging, only the outline of the internal frame is painted at the current mouse position while the window's being dragged. The internal frame's innards are not repainted at a new position until dragging stops. The default, slower behavior is to reposition and repaint the entire internal frame continuously while it's being moved.

In a future release, the Swing team plans to add a method to let you specify outline dragging. Until that method is added, you can specify outline dragging by setting a client property of the desktop pane, like this: 

desktop.putClientProperty("JDesktopPane.dragMode",
                          "outline");
The preceding code has no effect in JFC implementations before Swing 1.1.1 Beta 1.

The Internal Frame API

The following tables list the commonly used JInternalFrame constructors and methods, as well as a few methods that JDesktopPane provides. Besides the API listed in this section, JInternalFrame inherits useful API from its superclasses, JComponent, Component, and Container. See The JComponent Class for lists of methods from those classes.

Like JInternalFrame, JDesktopPane descends from JComponent, and thus provides the methods described in The JComponent Class. Because JDesktopPane extends JLayeredPane, it also supports the methods described in The Layered Pane API.

The API for using internal frames falls into these categories:

Creating the Internal Frame
Constructor or Method Purpose
JInternalFrame()
JInternalFrame(String)
JInternalFrame(String, boolean)
JInternalFrame(String, boolean, boolean)
JInternalFrame(String, boolean, boolean, boolean)
JInternalFrame(String, boolean, boolean, boolean, boolean) 		Create a JInternalFrame instance. The first argument specifies the title (if any) to be displayed by the internal frame. The rest of the arguments specify whether the internal frame should contain decorations allowing the user to resize, close, maximize, and iconify the internal frame (specified in that order). The default value for each boolean argument is false, which means that the operation is not allowed.
JOptionPane class methods:
  • showInternalConfirmDialog
  • showInternalInputDialog
  • showInternalMessageDialog
  • showInternalOptionDialog
Create a JInternalFrame that simulates a dialog. See How to Make Dialogs for details.

Adding Components to the Internal Frame
Method Purpose
void setContentPane(Container)
Container getContentPane() 		Set or get the internal frame's content pane, which generally contains all of the internal frame's GUI, with the exception of the menu bar and window decorations.
void setJMenuBar(JMenuBar)
JMenuBar getJMenuBar() 		Set or get the internal frame's menu bar. Note that some early Swing releases do not include this method.

Specifying the Internal Frame's Size and Location
Method Purpose
void pack() Size the internal frame so that its components are at their preferred sizes.
void setLocation(Point)
void setLocation(int, int) 		Set the position of the internal frame. (Inherited from Component).
void setBounds(Rectangle)
void setBounds(int, int, int, int) 		Explicitly set the size and location of the internal frame. (Inherited from Component).
void setSize(Dimension)
void setSize(int, int) 		Explicitly set the size of the internal frame. (Inherited from Component).

Performing Window Operations on the Internal Frame
Method Purpose
void setDefaultCloseOperation(int)
int getDefaultCloseOperation() 		Set or get what the internal frame does when the user attempts to "close" the internal frame. The default value is HIDE_ON_CLOSE. Other possible values are DO_NOTHING_ON_CLOSE and DISPOSE_ON_CLOSE. See Responding to Window-Closing Events for details.
void addInternalFrameListener(
    InternalFrameListener)

void removeInternalFrameListener(
    InternalFrameListener) 		Add or remove an internal frame listener (JInternalFrame's equivalent of a window listener). See How to Write an Internal Frame Listener for more information.
void moveToFront()
void moveToBack() 		If the internal frame's parent is a layered pane such as a desktop pane, moves the internal frame to the front or back (respectively) of its layer.
void setClosed(boolean)
boolean isClosed() 		Set or get whether the internal frame is currently closed.
void setIcon(boolean)
boolean isIcon() 		Iconify or deiconify the internal frame, or determine whether it's currently iconified.
void setMaximum(boolean)
boolean isMaximum() 		Maximize or restore the internal frame, or determine whether it's maximized.
void setSelected(boolean)
boolean isSelected() 		Set or get whether the internal frame is the currently "selected" (activated) internal frame.

Controlling Window Decorations and Capabilities
Method Purpose
void setFrameIcon(Icon)
Icon getFrameIcon() 		Set or get the icon displayed in the title bar of the internal frame (usually in the top-left corner).
void setClosable(boolean)
boolean isClosable() 		Set or get whether the user can close the internal frame.
void setIconifiable(boolean)
boolean isIconifiable() 		Set or get whether the internal frame can be iconified.
void setMaximizable(boolean)
boolean isMaximizable() 		Set or get whether the user can maximize this internal frame.
void setResizable(boolean)
boolean isResizable() 		Set or get whether the internal frame can be resized.
void setTitle(String)
String getTitle() 		Set or get the window title.

Using the JDesktopPane API
Constructor or Method Purpose
JDesktopPane() Creates a new instance of JDesktopPane.
JInternalFrame[] getAllFrames() Returns all JInternalFrame objects that the desktop contains.
JInternalFrame[] getAllFramesInLayer(int) Returns all JInternalFrame objects that the desktop contains that are in the specified layer. See How to Use Layered Panes for information about layers.

Examples that Use Internal Frames

The following examples use internal frames. Because internal frames are similar to regular frames, you should also look at Examples that Use Frames.

Example Where Described Notes
MyInternalFrame This page. Implements an internal frame that appears at an offset to the previously created internal frame.
InternalFrameDemo This page. Lets you create internal frames (instances of MyInternalFrame) that go into the application's JDesktopPane.
InternalFrameEventDemo How to Write an Internal Frame Listener Demonstrates listening for internal frame events. Also demonstrates positioning internal frames within a desktop pane.


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