Module java.desktop
Package java.awt

# Class ContainerOrderFocusTraversalPolicy

java.lang.Object
java.awt.FocusTraversalPolicy
java.awt.ContainerOrderFocusTraversalPolicy

All Implemented Interfaces:
  `Serializable`

Direct Known Subclasses:
  `DefaultFocusTraversalPolicy`

public class ContainerOrderFocusTraversalPolicy extends FocusTraversalPolicy implements Serializable
A FocusTraversalPolicy that determines traversal order based on the order of child Components in a Container. From a particular focus cycle root, the policy makes a pre-order traversal of the Component hierarchy, and traverses a Container's children according to the ordering of the array returned by `Container.getComponents()`. Portions of the hierarchy that are not visible and displayable will not be searched.

By default, ContainerOrderFocusTraversalPolicy implicitly transfers focus down-cycle. That is, during normal forward focus traversal, the Component traversed after a focus cycle root will be the focus-cycle-root's default Component to focus. This behavior can be disabled using the `setImplicitDownCycleTraversal` method.

By default, methods of this class will return a Component only if it is visible, displayable, enabled, and focusable. Subclasses can modify this behavior by overriding the `accept` method.

This policy takes into account focus traversal policy providers. When searching for first/last/next/previous Component, if a focus traversal policy provider is encountered, its focus traversal policy is used to perform the search operation.

Since:
  1.4
See Also:
  - `Container.getComponents()`
  - Serialized Form

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `ContainerOrderFocusTraversalPolicy()`
  Constructs a `ContainerOrderFocusTraversalPolicy`.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `protected boolean`
  `accept(Component aComponent)`
  Determines whether a Component is an acceptable choice as the new focus owner.
  `Component`
  `getComponentAfter(Container aContainer, Component aComponent)`
  Returns the Component that should receive the focus after aComponent.
  `Component`
  `getComponentBefore(Container aContainer, Component aComponent)`
  Returns the Component that should receive the focus before aComponent.
  `Component`
  `getDefaultComponent(Container aContainer)`
  Returns the default Component to focus.
  `Component`
  `getFirstComponent(Container aContainer)`
  Returns the first Component in the traversal cycle.
  `boolean`
  `getImplicitDownCycleTraversal()`
  Returns whether this ContainerOrderFocusTraversalPolicy transfers focus down-cycle implicitly.
  `Component`
  `getLastComponent(Container aContainer)`
  Returns the last Component in the traversal cycle.
  `void`
  `setImplicitDownCycleTraversal(boolean implicitDownCycleTraversal)`
  Sets whether this ContainerOrderFocusTraversalPolicy transfers focus down-cycle implicitly.

  ### Methods declared in class java.awt.FocusTraversalPolicy

  `getInitialComponent`

  ### Methods declared in class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### ContainerOrderFocusTraversalPolicy

    public ContainerOrderFocusTraversalPolicy()
    Constructs a `ContainerOrderFocusTraversalPolicy`.

- ## Method Details

  - ### getComponentAfter

    public Component getComponentAfter(Container aContainer, Component aComponent)
    Returns the Component that should receive the focus after aComponent. aContainer must be a focus cycle root of aComponent or a focus traversal policy provider.

    By default, ContainerOrderFocusTraversalPolicy implicitly transfers focus down-cycle. That is, during normal forward focus traversal, the Component traversed after a focus cycle root will be the focus-cycle- root's default Component to focus. This behavior can be disabled using the `setImplicitDownCycleTraversal` method.

    If aContainer is focus traversal policy provider, the focus is always transferred down-cycle.

    Specified by:
      `getComponentAfter` in class `FocusTraversalPolicy`
    Parameters:
      `aContainer` - a focus cycle root of aComponent or a focus traversal policy provider
      `aComponent` - a (possibly indirect) child of aContainer, or aContainer itself
    Returns:
      the Component that should receive the focus after aComponent, or null if no suitable Component can be found
    Throws:
      `IllegalArgumentException` - if aContainer is not a focus cycle root of aComponent or focus traversal policy provider, or if either aContainer or aComponent is null

  - ### getComponentBefore

    public Component getComponentBefore(Container aContainer, Component aComponent)
    Returns the Component that should receive the focus before aComponent. aContainer must be a focus cycle root of aComponent or a focus traversal policy provider.
    Specified by:
      `getComponentBefore` in class `FocusTraversalPolicy`
    Parameters:
      `aContainer` - a focus cycle root of aComponent or focus traversal policy provider
      `aComponent` - a (possibly indirect) child of aContainer, or aContainer itself
    Returns:
      the Component that should receive the focus before aComponent, or null if no suitable Component can be found
    Throws:
      `IllegalArgumentException` - if aContainer is not a focus cycle root of aComponent or focus traversal policy provider, or if either aContainer or aComponent is null

  - ### getFirstComponent

    public Component getFirstComponent(Container aContainer)
    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.
    Specified by:
      `getFirstComponent` in class `FocusTraversalPolicy`
    Parameters:
      `aContainer` - the focus cycle root or focus traversal policy provider whose first Component is to be returned
    Returns:
      the first Component in the traversal cycle of aContainer, or null if no suitable Component can be found
    Throws:
      `IllegalArgumentException` - if aContainer is null

  - ### getLastComponent

    public Component getLastComponent(Container aContainer)
    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.
    Specified by:
      `getLastComponent` in class `FocusTraversalPolicy`
    Parameters:
      `aContainer` - the focus cycle root or focus traversal policy provider whose last Component is to be returned
    Returns:
      the last Component in the traversal cycle of aContainer, or null if no suitable Component can be found
    Throws:
      `IllegalArgumentException` - if aContainer is null

  - ### getDefaultComponent

    public Component getDefaultComponent(Container aContainer)
    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 aContainer. The default implementation of this method returns the same Component as `getFirstComponent`.
    Specified by:
      `getDefaultComponent` in class `FocusTraversalPolicy`
    Parameters:
      `aContainer` - the focus cycle root or focus traversal policy provider whose default Component is to be returned
    Returns:
      the default Component in the traversal cycle of aContainer, or null if no suitable Component can be found
    Throws:
      `IllegalArgumentException` - if aContainer is null
    See Also:
      - `getFirstComponent(java.awt.Container)`

  - ### setImplicitDownCycleTraversal

    public void setImplicitDownCycleTraversal(boolean implicitDownCycleTraversal)
    Sets whether this ContainerOrderFocusTraversalPolicy transfers focus down-cycle implicitly. If `true`, during normal forward focus traversal, the Component traversed after a focus cycle root will be the focus-cycle-root's default Component to focus. If `false`, the next Component in the focus traversal cycle rooted at the specified focus cycle root will be traversed instead. The default value for this property is `true`.
    Parameters:
      `implicitDownCycleTraversal` - whether this ContainerOrderFocusTraversalPolicy transfers focus down-cycle implicitly
    See Also:
      - `getImplicitDownCycleTraversal()`
      - `getFirstComponent(java.awt.Container)`

  - ### getImplicitDownCycleTraversal

    public boolean getImplicitDownCycleTraversal()
    Returns whether this ContainerOrderFocusTraversalPolicy transfers focus down-cycle implicitly. If `true`, during normal forward focus traversal, the Component traversed after a focus cycle root will be the focus-cycle-root's default Component to focus. If `false`, the next Component in the focus traversal cycle rooted at the specified focus cycle root will be traversed instead.
    Returns:
      whether this ContainerOrderFocusTraversalPolicy transfers focus down-cycle implicitly
    See Also:
      - `setImplicitDownCycleTraversal(boolean)`
      - `getFirstComponent(java.awt.Container)`

  - ### accept

    protected boolean accept(Component aComponent)
    Determines whether a Component is an acceptable choice as the new focus owner. By default, this method will accept a Component if and only if it is visible, displayable, enabled, and focusable.
    Parameters:
      `aComponent` - the Component whose fitness as a focus owner is to be tested
    Returns:
      `true` if aComponent is visible, displayable, enabled, and focusable; `false` otherwise