java.awt.FocusTraversalPolicy Maven / Gradle / Ivy

* The core responsibility of a FocusTraversalPolicy is to provide algorithms * determining the next and previous Components to focus when traversing * forward or backward in a UI. Each FocusTraversalPolicy must also provide * algorithms for determining the first, last, and default Components in a * traversal cycle. First and last Components are used when normal forward and * backward traversal, respectively, wraps. The default Component is the first * to receive focus when traversing down into a new focus traversal cycle. * A FocusTraversalPolicy can optionally provide an algorithm for determining * a Window's initial Component. The initial Component is the first to receive * focus when a Window is first made visible. * * @author David Mendenhall * @version 1.4, 01/23/03 * * @see Container#setFocusTraversalPolicy * @see Container#getFocusTraversalPolicy * @see KeyboardFocusManager#setDefaultFocusTraversalPolicy * @see KeyboardFocusManager#getDefaultFocusTraversalPolicy * @since 1.4 */ public abstract class FocusTraversalPolicy { public FocusTraversalPolicy() { } /** * Returns the Component that should receive the focus after aComponent. * focusCycleRoot must be a focus cycle root of aComponent. * * @param focusCycleRoot a focus cycle root of aComponent * @param aComponent a (possibly indirect) child of focusCycleRoot, or * focusCycleRoot itself * @return the Component that should receive the focus after aComponent, or * null if no suitable Component can be found * @throws IllegalArgumentException if focusCycleRoot is not a focus cycle * root of aComponent, or if either focusCycleRoot or aComponent is * null */ public abstract Component getComponentAfter(Container focusCycleRoot, Component aComponent); /** * Returns the Component that should receive the focus before aComponent. * focusCycleRoot must be a focus cycle root of aComponent. * * @param focusCycleRoot a focus cycle root of aComponent * @param aComponent a (possibly indirect) child of focusCycleRoot, or * focusCycleRoot itself * @return the Component that should receive the focus before aComponent, * or null if no suitable Component can be found * @throws IllegalArgumentException if focusCycleRoot is not a focus cycle * root of aComponent, or if either focusCycleRoot or aComponent is * null */ public abstract Component getComponentBefore(Container focusCycleRoot, Component aComponent); /** * Returns the first Component in the traversal cycle. This method is used * to determine the next Component to focus when traversal wraps in the * forward direction. * * @param focusCycleRoot the focus cycle root whose first Component is to * be returned * @return the first Component in the traversal cycle when focusCycleRoot * is the focus cycle root, or null if no suitable Component can be * found * @throws IllegalArgumentException if focusCycleRoot is null */ public abstract Component getFirstComponent(Container focusCycleRoot); /** * Returns the last Component in the traversal cycle. This method is used * to determine the next Component to focus when traversal wraps in the * reverse direction. * * @param focusCycleRoot the focus cycle root whose last Component is to be * returned * @return the last Component in the traversal cycle when focusCycleRoot is * the focus cycle root, or null if no suitable Component can be * found * @throws IllegalArgumentException if focusCycleRoot is null */ public abstract Component getLastComponent(Container focusCycleRoot); /** * Returns the default Component to focus. This Component will be the first * to receive focus when traversing down into a new focus traversal cycle * rooted at focusCycleRoot. * * @param focusCycleRoot the focus cycle root whose default Component is to * be returned * @return the default Component in the traversal cycle when focusCycleRoot * is the focus cycle root, or null if no suitable Component can * be found * @throws IllegalArgumentException if focusCycleRoot is null */ public abstract Component getDefaultComponent(Container focusCycleRoot); /** * Returns the Component that should receive the focus when a Window is * made visible for the first time. Once the Window has been made visible * by a call to show() or setVisible(true), the * initial Component will not be used again. Instead, if the Window loses * and subsequently regains focus, or is made invisible or undisplayable * and subsequently made visible and displayable, the Window's most * recently focused Component will become the focus owner. The default * implementation of this method returns the default Component. * * @param window the Window whose initial Component is to be returned * @return the Component that should receive the focus when window is made * visible for the first time, or null if no suitable Component can * be found * @see #getDefaultComponent * @see Window#getMostRecentFocusOwner * @throws IllegalArgumentException if window is null */ public Component getInitialComponent(Window window) { return null; } }