ComponentUI (Java SE 15 & JDK 15) (original) (raw)

Direct Known Subclasses:

[ButtonUI](ButtonUI.html "class in javax.swing.plaf"), [ColorChooserUI](ColorChooserUI.html "class in javax.swing.plaf"), [ComboBoxUI](ComboBoxUI.html "class in javax.swing.plaf"), [DesktopIconUI](DesktopIconUI.html "class in javax.swing.plaf"), [DesktopPaneUI](DesktopPaneUI.html "class in javax.swing.plaf"), [FileChooserUI](FileChooserUI.html "class in javax.swing.plaf"), [InternalFrameUI](InternalFrameUI.html "class in javax.swing.plaf"), [LabelUI](LabelUI.html "class in javax.swing.plaf"), [LayerUI](LayerUI.html "class in javax.swing.plaf"), [ListUI](ListUI.html "class in javax.swing.plaf"), [MenuBarUI](MenuBarUI.html "class in javax.swing.plaf"), [OptionPaneUI](OptionPaneUI.html "class in javax.swing.plaf"), [PanelUI](PanelUI.html "class in javax.swing.plaf"), [PopupMenuUI](PopupMenuUI.html "class in javax.swing.plaf"), [ProgressBarUI](ProgressBarUI.html "class in javax.swing.plaf"), [RootPaneUI](RootPaneUI.html "class in javax.swing.plaf"), [ScrollBarUI](ScrollBarUI.html "class in javax.swing.plaf"), [ScrollPaneUI](ScrollPaneUI.html "class in javax.swing.plaf"), [SeparatorUI](SeparatorUI.html "class in javax.swing.plaf"), [SliderUI](SliderUI.html "class in javax.swing.plaf"), [SpinnerUI](SpinnerUI.html "class in javax.swing.plaf"), [SplitPaneUI](SplitPaneUI.html "class in javax.swing.plaf"), [TabbedPaneUI](TabbedPaneUI.html "class in javax.swing.plaf"), [TableHeaderUI](TableHeaderUI.html "class in javax.swing.plaf"), [TableUI](TableUI.html "class in javax.swing.plaf"), [TextUI](TextUI.html "class in javax.swing.plaf"), [ToolBarUI](ToolBarUI.html "class in javax.swing.plaf"), [ToolTipUI](ToolTipUI.html "class in javax.swing.plaf"), [TreeUI](TreeUI.html "class in javax.swing.plaf"), [ViewportUI](ViewportUI.html "class in javax.swing.plaf")

public abstract class ComponentUI extends Object

The base class for all UI delegate objects in the Swing pluggable look and feel architecture. The UI delegate object for a Swing component is responsible for implementing the aspects of the component that depend on the look and feel. The JComponent class invokes methods from this class in order to delegate operations (painting, layout calculations, etc.) that may vary depending on the look and feel installed. Client programs should not invoke methods on this class directly.

See Also:

JComponent, UIManager

• Constructor Summary

Constructors

• Method Summary

Methods declared in class java.lang.Object

[clone](../../../../java.base/java/lang/Object.html#clone%28%29), [equals](../../../../java.base/java/lang/Object.html#equals%28java.lang.Object%29), [finalize](../../../../java.base/java/lang/Object.html#finalize%28%29), [getClass](../../../../java.base/java/lang/Object.html#getClass%28%29), [hashCode](../../../../java.base/java/lang/Object.html#hashCode%28%29), [notify](../../../../java.base/java/lang/Object.html#notify%28%29), [notifyAll](../../../../java.base/java/lang/Object.html#notifyAll%28%29), [toString](../../../../java.base/java/lang/Object.html#toString%28%29), [wait](../../../../java.base/java/lang/Object.html#wait%28%29), [wait](../../../../java.base/java/lang/Object.html#wait%28long%29), [wait](../../../../java.base/java/lang/Object.html#wait%28long,int%29)

• Constructor Details

  • ComponentUI

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

• Method Details

  • installUI

  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

  Reverses configuration which was done on the specified component duringinstallUI. This method is invoked when thisUIComponent 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

  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

  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

  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
  Returns:
  a Dimension object containing given component's preferred size appropriate for the look and feel
  See Also:
  JComponent.getPreferredSize(), LayoutManager.preferredLayoutSize(java.awt.Container)

  • getMinimumSize

  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

  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
  Returns:
  true if the specified x,y location is contained within the look and feel's defined shape for the given component
  See Also:
  JComponent.contains(int, int), Component.contains(int, int)

  • createUI

  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.
  Parameters:
  c - a JComponent for which to create a UI delegate
  Returns:
  a ComponentUI object for c

  • 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 forLayoutManagers to align components along their baseline. A return value less than 0 indicates this component does not have a reasonable baseline and thatLayoutManagers 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](../../../../java.base/java/lang/NullPointerException.html "class in java.lang") - if c is null
[IllegalArgumentException](../../../../java.base/java/lang/IllegalArgumentException.html "class in java.lang") - if width or height is < 0
  Since:
  1.6
  See Also:
  JComponent.getBaseline(int,int)

  • getBaselineResizeBehavior

  Returns an enum indicating how the baseline of the 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](../../../../java.base/java/lang/NullPointerException.html "class in java.lang") - 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 callComponent.AccessibleAWTComponent.getAccessibleChildrenCount() instead of this method.
  Parameters:
  c - JComponent for which to get count of accessible children
  Returns:
  the number of accessible children in the object
  See Also:
  getAccessibleChild(javax.swing.JComponent, int)

  • getAccessibleChild

  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 callComponent.AccessibleAWTComponent.getAccessibleChild() instead of this method.
  Parameters:
  c - a JComponent for which to get a child object
  i - zero-based index of child
  Returns:
  the ith Accessible child of the object
  See Also:
  getAccessibleChildrenCount(javax.swing.JComponent)