Class ComponentUI

Constructor Detail

• ComponentUI

  public ComponentUI()

  Sole constructor. (For invocation by subclass constructors, typically implicit.)

Method Detail

• installUI

  public void installUI(JComponent c)

  Configures the specified component appropriately for the look and feel. This method is invoked when the ComponentUI instance is being installed as the UI delegate on the specified component. This method should completely configure the component for the look and feel, including the following:

  1. Install default property values for color, fonts, borders, icons, opacity, etc. on the component. Whenever possible, property values initialized by the client program should not be overridden.
  2. Install a LayoutManager on the component if necessary.
  3. Create/add any required sub-components to the component.
  4. Create/install event listeners on the component.
  5. Create/install a PropertyChangeListener on the component in order to detect and respond to component property changes appropriately.
  6. Install keyboard UI (mnemonics, traversal, etc.) on the component.
  7. Initialize any appropriate instance data.

  Parameters:

  c - the component where this UI delegate is being installed

  See Also:

  uninstallUI(javax.swing.JComponent), JComponent.setUI(javax.swing.plaf.ComponentUI), JComponent.updateUI()

• uninstallUI

  public void uninstallUI(JComponent c)

  Reverses configuration which was done on the specified component during installUI. This method is invoked when this UIComponent instance is being removed as the UI delegate for the specified component. This method should undo the configuration performed in installUI, being careful to leave the JComponent instance in a clean state (no extraneous listeners, look-and-feel-specific property objects, etc.). This should include the following:

  1. Remove any UI-set borders from the component.
  2. Remove any UI-set layout managers on the component.
  3. Remove any UI-added sub-components from the component.
  4. Remove any UI-added event/property listeners from the component.
  5. Remove any UI-installed keyboard UI from the component.
  6. Nullify any allocated instance data objects to allow for GC.

  Parameters:

  c - the component from which this UI delegate is being removed; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components

  See Also:

  installUI(javax.swing.JComponent), JComponent.updateUI()

• paint

  public void paint(Graphics g,
           JComponent c)

  Paints the specified component appropriately for the look and feel. This method is invoked from the ComponentUI.update method when the specified component is being painted. Subclasses should override this method and use the specified Graphics object to render the content of the component.

  Parameters:

  g - the Graphics context in which to paint

  c - the component being painted; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components

  See Also:

  update(java.awt.Graphics, javax.swing.JComponent)

• update

  public void update(Graphics g,
            JComponent c)

  Notifies this UI delegate that it is time to paint the specified component. This method is invoked by JComponent when the specified component is being painted.

  By default this method fills the specified component with its background color if its opaque property is true, and then immediately calls paint. In general this method need not be overridden by subclasses; all look-and-feel rendering code should reside in the paint method.

  Parameters:

  g - the Graphics context in which to paint

  c - the component being painted; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components

  See Also:

  paint(java.awt.Graphics, javax.swing.JComponent), JComponent.paintComponent(java.awt.Graphics)

• getPreferredSize

  public Dimension getPreferredSize(JComponent c)

  Returns the specified component's preferred size appropriate for the look and feel. If null is returned, the preferred size will be calculated by the component's layout manager instead (this is the preferred approach for any component with a specific layout manager installed). The default implementation of this method returns null.

  Parameters:

  c - the component whose preferred size is being queried; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components

  See Also:

  JComponent.getPreferredSize(), LayoutManager.preferredLayoutSize(java.awt.Container)

• getMinimumSize

  public Dimension getMinimumSize(JComponent c)

  Returns the specified component's minimum size appropriate for the look and feel. If null is returned, the minimum size will be calculated by the component's layout manager instead (this is the preferred approach for any component with a specific layout manager installed). The default implementation of this method invokes getPreferredSize and returns that value.

  Parameters:

  c - the component whose minimum size is being queried; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components

  Returns:

  a Dimension object or null

  See Also:

  JComponent.getMinimumSize(), LayoutManager.minimumLayoutSize(java.awt.Container), getPreferredSize(javax.swing.JComponent)

• getMaximumSize

  public Dimension getMaximumSize(JComponent c)

  Returns the specified component's maximum size appropriate for the look and feel. If null is returned, the maximum size will be calculated by the component's layout manager instead (this is the preferred approach for any component with a specific layout manager installed). The default implementation of this method invokes getPreferredSize and returns that value.

  Parameters:

  c - the component whose maximum size is being queried; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components

  Returns:

  a Dimension object or null

  See Also:

  JComponent.getMaximumSize(), LayoutManager2.maximumLayoutSize(java.awt.Container)

• contains

  public boolean contains(JComponent c,
                 int x,
                 int y)

  Returns true if the specified x,y location is contained within the look and feel's defined shape of the specified component. x and y are defined to be relative to the coordinate system of the specified component. Although a component's bounds is constrained to a rectangle, this method provides the means for defining a non-rectangular shape within those bounds for the purpose of hit detection.

  Parameters:

  c - the component where the x,y location is being queried; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components

  x - the x coordinate of the point

  y - the y coordinate of the point

  See Also:

  JComponent.contains(int, int), Component.contains(int, int)

• createUI

  public static ComponentUI createUI(JComponent c)

  Returns an instance of the UI delegate for the specified component. Each subclass must provide its own static createUI method that returns an instance of that UI delegate subclass. If the UI delegate subclass is stateless, it may return an instance that is shared by multiple components. If the UI delegate is stateful, then it should return a new instance per component. The default implementation of this method throws an error, as it should never be invoked.

• getBaseline

  public int getBaseline(JComponent c,
                int width,
                int height)

  Returns the baseline. The baseline is measured from the top of the component. This method is primarily meant for LayoutManagers to align components along their baseline. A return value less than 0 indicates this component does not have a reasonable baseline and that LayoutManagers should not align this component on its baseline.

  This method returns -1. Subclasses that have a meaningful baseline should override appropriately.

  Parameters:

  c - JComponent baseline is being requested for

  width - the width to get the baseline for

  height - the height to get the baseline for

  Returns:

  baseline or a value < 0 indicating there is no reasonable baseline

  Throws:

  NullPointerException - if c is null

  IllegalArgumentException - if width or height is < 0

  Since:

  1.6

  See Also:

  JComponent.getBaseline(int,int)

• getBaselineResizeBehavior

  public Component.BaselineResizeBehavior getBaselineResizeBehavior(JComponent c)

  Returns an enum indicating how the baseline of he component changes as the size changes. This method is primarily meant for layout managers and GUI builders.

  This method returns BaselineResizeBehavior.OTHER. Subclasses that support a baseline should override appropriately.

  Parameters:

  c - JComponent to return baseline resize behavior for

  Returns:

  an enum indicating how the baseline changes as the component size changes

  Throws:

  NullPointerException - if c is null

  Since:

  1.6

  See Also:

  JComponent.getBaseline(int, int)

• getAccessibleChildrenCount

  public int getAccessibleChildrenCount(JComponent c)

  Returns the number of accessible children in the object. If all of the children of this object implement Accessible, this method should return the number of children of this object. UIs might wish to override this if they present areas on the screen that can be viewed as components, but actual components are not used for presenting those areas. Note: As of v1.3, it is recommended that developers call Component.AccessibleAWTComponent.getAccessibleChildrenCount() instead of this method.

  Returns:

  the number of accessible children in the object

  See Also:

  getAccessibleChild(javax.swing.JComponent, int)

• getAccessibleChild

  public Accessible getAccessibleChild(JComponent c,
                              int i)

  Returns the ith Accessible child of the object. UIs might need to override this if they present areas on the screen that can be viewed as components, but actual components are not used for presenting those areas.

  Note: As of v1.3, it is recommended that developers call Component.AccessibleAWTComponent.getAccessibleChild() instead of this method.

  Parameters:

  i - zero-based index of child

  Returns:

  the ith Accessible child of the object

  See Also:

  getAccessibleChildrenCount(javax.swing.JComponent)