JFrame and JApplet

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JFrame and JApplet
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Primary or Application Window

• This is the type of window that appears on a
  screen when an activity or action is started.
• Required for every function or application.
• Usually contains some basic controls
• Frame or Border
• Title Bar
• Title Bar Icons
• Title Bar Text
• Title Bar Buttons
• Menu Bar
• Status Bar
• Scroll Bar
• Size Grip

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More on Primary Windows

• Should represent an independent function or
  application
• Use to present constantly used window components
  and controls
• Menu bar items that are
• Used frequently
• Used by most, or all primary and secondary
  windows
• Controls used by most applications

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Secondary, Document or Supplemental Windows

• May contain data actually being processed
• Typically associated with a single data object,
  and may appear on top of the active window
• Sizable
• Movable
• Scrollable
• Resemble primary window, but may use the primary
  window menu bar

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Window sizing

• Provide large-enough windows to
• Present all relevant and expected information for
  the task
• Avoid hiding important information
• Avoid crowding or visual confusion
• Minimize the need for scrolling
• But less than the full size of the entire screen
• If window is too large, determine
• Is all the information needed?
• Is all the information related?
• Otherwise, make the window as small as possible
• Optimum window sizes
• For text, about 12 lines
• For alphanumeric information, about 7 lines

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Advantages of different window sizes

• Larger windows
• Permit display of more information
• Facilitate learning data relationships and
  groupings are more obvious
• Less window manipulation requirements exist
• Breadth is preferred to depth
• More efficient data validation and data
  correction can be performed
• Disadvantages
• Longer pointer movements are required
• Windows are more crowded
• More visual scanning is required
• Parts are more easily obscured by other windows

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Multiple Monitors

• Do NOT assume a single monitor setup
• Default position for many windows and dialogs is
  in the center of the screen
• If you ask java what the Screen size is from the
  Toolkit, it reports the total screen size, which
  is the sum of all monitors attached to the system

Monitor 0 1600 x 1200 Origin at 0,0
Monitor 1 1600 x 1200 Origin at 1600,0
Your default positioned dialog in the Center
of the 3200 x 1200 screen
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Identifying Your Graphics Environment

• Initial reaction is to use Toolkit.getScreenSize()
  
• API says Gets the size of the screen. On
  systems with multiple displays, the primary
  display is used. Multi-screen aware display
  dimensions are available from GraphicsConfiguratio
  n and GraphicsDevice.
• Oops, on Linux with xinerma extensions (similar
  to windows), a two screen, each at 1600x1200,
  reports a window size of 3200x1200
• On Windows it is not reliable either
• Depends on video card configuration
• Many new cards drive two monitors from a single
  card
• Even if getScreenSize() did work, it still
  doesnt tell you everything you need to know
• Use the trusty GraphicsEnvironment class to get
  the information you will need.

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GraphicsEnvironment class

• Describes the collection of GraphicsDevice
  objects and Font objects available to a Java
  application on a particular platform.
• getScreenDevices() returns an array of
  GraphicsDevices for this computer
• Use the static method getLocalGraphicsEnvironment(
  ) to get a GraphicsEnvironment object for your
  system
• GraphicsEnvironment ge GraphicsEnvironment.
  getLocalGraphicsEnvironment()

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GraphicsDevices class

• Describes the graphics devices that might be
  available in a particular graphics environment.
• These include screen and printer devices.
• Use the getScreenDevices() method to pull out the
  screen devices from the GraphicsEnvironment
  object
• GraphicsDevice gs ge.getScreenDevices()
• Once you have a graphics device, you need to pull
  off the GraphicsConfiguration object that tells
  you about the current configuration a window is
  using.

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GraphicsConfiguration class

• Describes the characteristics of a graphics
  destination such as a printer or monitor.
• There can be many GraphicsConfiguration objects
  associated with a single graphics device,
  representing different drawing modes or
  capabilities.
• In a virtual device multi-screen environment in
  which the desktop area could span multiple
  physical screen devices, the bounds of the
  GraphicsConfiguration objects are relative to the
  virtual coordinate system.
• From the earlier slide, that means the bounds it
  would return are x0,y0,width1600,height1200
  andx1600,y0,width1600,height1200
• To get a GraphicsConfiguration object
• Use getDefaultConfiguration() method on a
  GraphicsDevice object
• Use the getGraphicsConfiguration() method on a
  Window object

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Managing Monitors

• There is no nice built in utility to manage
  multiple monitors
• You need to write a class that build up info for
  you
• Use that class to create different monitor tags
• Primary
• Enumeration
• Left-of, Right-of
• NEVER use null as a parent frame for a Dialog
  window, it uses a screen object and not the
  current Configuration.
• JDialog
• JOptionPane
• JFileChooser
• JColorChooser

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java.awt.Window
Object
Window
Container
Component

• Why is it Important?
• because it is a shared ancestor of the basic
  Swing windows
• because some good methods that can be accessed by
  JFrame, JWindow etc, are buried here
• public void addNotify()
• Makes this Window displayable by creating the
  connection to its native screen resource. This
  method is called internally by the toolkit and
  should not be called directly by programs.
• public void pack()
• Causes this Window to be sized to fit the
  preferred size and layouts of its subcomponents.
• public void toFront() (and toBack())
• If this Window is visible, brings this Window to
  the front and may make it the focused Window.

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More on Windows

• public Toolkit getToolkit()
• Returns the toolkit of this frame. The toolkit
  gives info on native hardware capabilities.
  Screen size, resolution, sound bell, etc
• public void setCursor(Cursor cursor)
• Set the cursor image to a specified cursor.
• public boolean isActive()
• Returns whether this Window is active. Only a
  Frame or a Dialog may be active. The native
  windowing system may denote the active Window or
  its children with special decorations, such as a
  highlighted title bar.
• public boolean isFocused()
• Returns whether this Window is focused.
• public boolean isShowing()
• Checks if this Window is showing on screen.
• public GraphicsConfiguration getGraphicsConfigurat
  ion()
• This method returns the GraphicsConfiguration
  used by this Window.
• public void setLocationRelativeTo(Component c)
• Sets the location of the window relative to the
  specified component. If the component is not
  currently showing, or c is null, the window is
  centered on the screen. If the bottom of the
  component is offscreen, the window is displayed
  to the right of the component.

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New in JDK 1.5

• Includes methods for ensuring a Window, Frame, or
  Dialog is always on top.
• This feature is not supported on all OSs (Some
  Solaris Window Managers)
• isAlwaysOnTop()
• setAlwaysOnTop(boolean)
• See example Banner.java
• Set whether a window should appear at the default
  location for the native windowing system the next
  time the Window is made visible
• setLocationByPlatform(boolean)
• Position a window and set its size
• setBounds(int x, int y, int width, int height)

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JFrame
Object
Window
Container
Component
Frame
JFrame

• Very similar to AWT Frame (at first glance)
• One of the few Swing components that do not
  inherit from JComponent. JApplet, JDialog and
  JWindow also are not children of JComponent
• Internals very different
• JDK 1.1 you make a frame, set a layout, and add
  your components
• Frame f new Frame(Foo)
• f.setLayout(new FlowLayout())
• f.add(new JButton(Press Me)
• If you try this in JDK1.2, 1.3 JDK 1.4, you
  would get a java.lang.Error when you run the
  program. JDK 1.5 does not have this limitation
• JFrame is no longer a simple container , it is
  now a compound structure
• Allows for more complex, subtle control of window
  contents

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Anatomy of a JFrame
JFrame
JRootPane
JLayeredPane
Menu Bar (optional)
Content Pane
Glass Pane
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JFrame Constructors

• JFrame()
• Constructs a new Frame that is initially
  invisible.
• JFrame(String title)
• Constructs a new, initially invisible Frame with
  the specified title.
• JFrame(GraphicsConfiguration gc)
• Constructs a new, initially invisible Frame on
  the specified configuration.
• JFrame(String title, GraphicsConfiguration gc)
• Constructs a new, initially invisible Frame with
  the specified title on the specified
  configuration.
• The GraphicsConfiguration class describes the
  characteristics of a graphics destination such as
  a printer or monitor. There can be many
  GraphicsConfiguration objects associated with a
  single graphics device. For example, on X11
  windowing systems, each visual is a different
  GraphicsConfiguration. On PCs and Macintoshes,
  the different screen resolution/color resolution
  combinations would be different
  GraphicsConfiguration objects.

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Multiple Graphics Devices

• To get the graphics devices, use the
  GraphicsEnvironment's getScreenDevices() method.
• You can get the default configuration for each
  device with the getDefaultConfiguration() method.
• Code Example MultipleJFrames.java
• GraphicsEnvironment ge GraphicsEnvironment.getLo
  calGraphicsEnvironment()
• GraphicsDevice gs ge.getScreenDevices()
• for (int j 0 j lt gs.length j)
• System.out.println("Checking Device " j)
• GraphicsDevice gd gsj
• GraphicsConfiguration gc
  gd.getConfigurations()
• System.out.println(" DefaultConfiguration
  for Device" j
• " has bounds of "
• gd.getDefaultConfiguration().getBounds()
  
• "\n and color model of "
• gd.getDefaultConfiguration().getColorMode
  l())

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Coordinates of Multiple Graphics Devices

• From the Java API
• In a virtual device multi-screen environment in
  which the desktop area could span multiple
  physical screen devices, the bounds of the
  GraphicsConfiguration objects are relative to the
  virtual coordinate system. When setting the
  location of a component, use getBounds to get the
  bounds of the desired GraphicsConfiguration and
  offset the location with the coordinates of the
  GraphicsConfiguration, as the following code
  sample illustrates
• Frame f new Frame(GraphicsConfiguration gc)
• Rectangle bounds gc.getBounds()
• f.setLocation(10 bounds.x, 10 bounds.y)

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JFrame Methods

• public void setDefaultCloseOperation(int
  operation)
• DO_NOTHING_ON_CLOSE - do not do anything -
  require the program to handle the operation in
  the windowClosing method of a registered
  WindowListener object. This is useful for
  "catching" closing events and preventing them
  from occuring until a condition is met.
• HIDE_ON_CLOSE - automatically hide the frame
  after invoking any registered WindowListener
  object. This is the default operation.
• DISPOSE_ON_CLOSE - automatically hide and dispose
  the frame after invoking any registered
  WindowListener objects
• EXIT_ON_CLOSE - Exit the application by way of
  System.exit. Only use this in applications.

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More JFrame Methods

• public void update(Graphics g)
• public JMenuBar getJMenuBar()
• public void setJMenuBar(JMenuBar menubar)
• protected void setRootPaneCheckingEnabled(boolean
  flag)
• get/set pairs for RootPane, LayeredPane,
  ContentPane and GlassPane
• public void pack()
• public void show()
• public void setResizeable(boolean b)
• public invalidate()
• public validate()
• public revalidate()
• similar to repaint() calls

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Adding components to a JFrame

• In JDK 1.5
• JFrame f new JFrame(Foo)
• f.add(new JButton(Press Me))
• or in earlier versions
• JFrame f new JFrame(Foo)
• Container cp f.getContentPane()
• cp.add(new JButton(Press Me))
• or
• f.getContentPane().add(new JButton(Press Me))

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Thread Issues and JFrames

• In December 2003, Sun issued a tutorial stating
  that the following sequence should not be used
  when creating a Jframe
• pack()
• setVisible(true)
• The pack() or setVisible() methods create the
  associated helper for the frame, and the system
  creates the event dispatch thread.
• The Thread may then call listeners while pack and
  validate() are still processing.
• May generate some event problems in more complex
  GUIs
• Recommended method is as follows
• final JFrame jf new JFrame()
• Runnable showFrame new Runnable()
• public void run()
• jf.pack()
• jf.setVisible(true)
• SwingUtilities.invokeLater(showFrame)

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Code Example, SimpleJFrame.java and
SimpleJFrame2.java
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Controlling the LF of the JFrame

• Undecorated JFrames
• You can make undecorated (no window borders)
  JFrames by doing the following
• JFrame jf new JFrame()
• jf.setUndecorated(true)
• Dont abuse this feature!
• Look and Feel Decorated JFrames
• You can let the Look and Feel decorate the
  decorate the JFrame by doing the following
• JFrame jf new JFrame()
• jf.setUndecorated(true)
• jf.getRootPane().setWindowDecorationStyle(JRootPan
  e.FRAME)

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Controlling Size/Location of JFrames

• Setting Size
• setSize(Dimension d)
• setBounds(int x, int y, int width, int height)
  JDK 1.5
• setResizable(boolean flag)
• pack()
• Setting Location
• setLocation(int x, int y)
• setLocation(Point p)
• setLocationByPlatform(boolean flag) JDK 1.5
• see next slide for example
• setLocationRelativeTo(Component c)
• setBounds(int x, int y, int width, int height)

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PlatformLocation.java
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State of JFrame on the Desktop

• You can control the state of the JFrame (or
  Frame) on the Desktop with
• setExtendedState(int state)
• This sets the state of this frame. The state is
  represented as a bitwise mask.
• NORMAL indicates that no state bits are set.
• ICONIFIED Iconifies the JFrame
• MAXIMIZED_HORIZ Maximize the JFrame Horizontally
• MAXIMIZED_VERT Maximize the JFrame Vertically
• MAXIMIZED_BOTH Concatenates MAXIMIZED_HORIZ and
  MAXIMIZED_VERT.
• Note that if the state is not supported on a
  given platform, nothing will happen. The
  application may determine if a specific state is
  available via the java.awt.ToolkitisFrameStateSup
  ported(int state) method.
• In JDKs before JDK 1.4, there is a setState()
  method which is a subset of the above methods

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JWindow
Object
Window
Container
Component
JWindow

• Borderless window, very similar to an
  undecorated JFrame
• User has no interaction with the window edges
• Splash screens
• Pop-up menus (now handled by JPopupMenu class)
• If no parent given with constructor, window
  cannot get focus
• JWindow()
• JWindow(JFrame frame)
• JWindow (Window window)
• JWindow(GraphicsConfiguration gc)
• JWindow(Window window, GraphicsConfiguration gc)
• Use for informational purposes only, be careful
  on placement, since the user can't move them!

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JApplet
Object
Panel
Container
Component
Applet
JApplet

• Swing equivalent of the AWT Applet class
• An extended version of java.applet.Applet that
  adds support for interposing input and painting
  behaviour in front of the applets children (see
  glassPane), support for special children that are
  managed by a LayeredPane (see rootPane) and for
  Swing MenuBars.
• Internal structure similar to JFrame (JRootPane,
  JContentPane)
• You can now use JMenuBar in an applet, unlike in
  JDK 1.1
• Default layout manager is BorderLayout

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JApplet methods

• Constructors
• public JApplet()
• Methods
• public void setDefaultCloseOperation(int
  operation)
• public void update(Graphics g)
• public JMenuBar getJMenuBar()
• public void setJMenuBar(JMenuBar menubar)
• protected void setRootPaneCheckingEnabled(boolean
  flag)
• get/set pairs for RootPane, LayeredPane,
  ContentPane and GlassPane
• public void pack()
• public void show()
• To disable the Warning Java Applet Window
  message
• getRootPane().putClientProperty(defeatSystemEvent
  QueueCheck, Boolean.TRUE)

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Glass Panes

• Fills the entire pane
• Instance of JPanel
• Non-opaque
• Since mouse events are normally processed by the
  top-most visible component
• Glass pane usually doesnt handle mouse input
• If it does, it will block it from the rest of the
  window
• Windows below are not disabled, they just dont
  get events
• You can use the glass pane to
• Make a status bar over an initial window, showing
  initiation progress. The bar can be in the glass
  pane, and if you handle mouse events, the app
  beneath it will not get anything yet

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JLayeredPane

• Manages its components in layers

JLayeredPane constants and their relative
positions
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Panels
JComponent
JPanel

• Swing equivalent of Panel is JPanel
• JPanel is your general purpose container/canvas
• Constructors
• JPanel()
• JPanel(boolean isDoubleBuffered)
• JPanel(LayoutManager layout)
• JPanel(LayoutManager layout, boolean
  isDoubleBuffered)
• Often used as containers for other layouts
• JPanels inherit from JComponent, so we can use
  borders
• JPanel default layout is FlowLayout
• No significant methods, only four methods for the
  class dealing with getting and updating UI,
  accessibility, paramString

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Applet/Application combinations

• A quick way to implement a file as both an
  application and an applet is as follows
• Step one let your top level window inherit from
  JApplet
• Step two attach a main method, which in turn
  creates a JFrame which shares the content pane of
  the applet
• public class Test extends JApplet
• public void init()
• public static void main(String argv)
• final JFrame f new JFrame()
• JApplet applet new Test()
• applet.init()
• f.setContentPane(applet.getContentPane())

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Case Studies
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Case Studies
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Case Studies

• Remembers Last Size
• Note hidden border that shows up during screen
  capture
• App doesn't want to use OS window style

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How does a JFrame remember its size?

• In the last example, we saw that many
  applications remember their last size and
  location on the screen.
• How can we do this in Java?
• java.util.prefs.Preferences to the rescue!
• java.util.prefs.Preferences appeared in Java
  1.4.1 as way to store configuration data for
  applications and individual users.

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Preferences

• Stores a hashtable of preferences on the native
  OS
• Windows in Registry
• Unix/Linux
• /etc/.java for system preferences
• /.java for user preferences
• Unlike property files, you don't have to manage
  the location of the Preferences, the JVM does it
  for you.
• Allows application wide preferences (system) and
  user specific (user)
• Mechanism provides for defaults when asking for a
  value that isn't there
• Preferences are package based, not class based.
  The class you provide is a map to the package
  used.

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How to use Preferences

• // get object for storing preferences for MyClass
• Preferences up Preferences.userNodeForPackage (
  MyClass.class )
• ...
• // store preferences, keyvalue
• userPrefs.putInt( "width", width )
• userPrefs.putInt( "height", height )
• ...
• // fetch preferences, key,default
• int width userPrefs.getInt( "width", 100 )
• int height userPrefs.getInt( "height", 200 )
• ...
• // write any changes in Preferences out to
  backing store
• userPrefs.flush()

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Intelligent JFrame

• MemoryFrame.java is an example of a JFrame using
  Preferences to remember its last size and location