Package eu.webtoolkit.jwt

Class WLayout

java.lang.Object
eu.webtoolkit.jwt.WObject
eu.webtoolkit.jwt.WLayout
All Implemented Interfaces:
WLayoutItem
Direct Known Subclasses:
WBorderLayout, WBoxLayout, WFitLayout, WGridLayout
public abstract class WLayout
extends WObject
implements WLayoutItem
An abstract base class for layout managers.

This class is the abstract base class for any layout manager. A layout manager is associated with a container widget, and manages the layout of children inside the whole space available to the container widget.

The implementation of the layout manager depends on the container widget to which it is set, and is therefore deferred to WLayoutImpl.

A layout never assumes ownership of contained items, instead these are owned by the parent widget to which the layout is applied.

Note: When applying a layout manager to a WContainerWidget, you may not define any padding for the container widget. Instead, use setContentsMargins().

  • Constructor Details

    • WLayout

      protected WLayout()
      Create a layout.

  • Method Details

    • addItem

      public abstract void addItem​(WLayoutItem item)
      Adds a layout item.

      The item may be a widget or nested layout.

      How the item is layed out with respect to siblings is implementation specific to the layout manager. In some cases, a layout manager will overload this method with extra arguments that specify layout options.

      See Also:
      removeItem(WLayoutItem item), addWidget(WWidget w)

    • addWidget

      public void addWidget​(WWidget w)
      Adds the given widget to the layout.

      This method wraps the widget in a WWidgetItem and calls addItem().

      How the widget is layed out with respect to siblings is implementation specific to the layout manager. In some cases, a layout manager will overload this method with extra arguments that specify layout options.

      See Also:
      removeWidget(WWidget w), addItem(WLayoutItem item)

    • removeItem

      public abstract void removeItem​(WLayoutItem item)
      Removes a layout item (widget or nested layout).

      See Also:
      addItem(WLayoutItem item), removeWidget(WWidget w)

    • removeWidget

      public boolean removeWidget​(WWidget w)
      Removes the given widget from the layout.

      This method finds the corresponding WWidgetItem and calls removeItem(). The widget itself is not destroyed.

      Returns true if succesful.

      See Also:
      addWidget(WWidget w), removeItem(WLayoutItem item)

    • getCount

      public abstract int getCount()
      Returns the number of items in this layout.

      This may be a theoretical number, which is greater than the actual number of items. It can be used to iterate over the items in the layout, in conjunction with getItemAt().

    • getItemAt

      public abstract WLayoutItem getItemAt​(int index)
      Returns the layout item at a specific index.

      If there is no item at the index, null is returned.

      See Also:
      indexOf(WLayoutItem item), getCount()

    • indexOf

      public int indexOf​(WLayoutItem item)
      Returns the index of a given item.

      The default implementation loops over all items, and returns the index for which itemAt(index) equals item.

      See Also:
      getItemAt(int index)

    • findWidgetItem

      public WWidgetItem findWidgetItem​(WWidget widget)
      Finds the widget item associated with the given widget.
      Specified by:
      findWidgetItem in interface WLayoutItem

    • setLayoutHint

      public void setLayoutHint​(java.lang.String name, java.lang.String value)
      Provides a hint to the layout implementation.

      In some cases, a layout implementation may require some hints for rendering its contents. Possible hints are indicated in the reference documentation for each layout manager.

    • getWidget

      public WWidget getWidget()
      Description copied from interface: WLayoutItem
      Returns the widget that is held by this WLayoutItem.

      This implements a type-safe upcasting mechanism to a WWidgetItem.

      Specified by:
      getWidget in interface WLayoutItem

    • getLayout

      public WLayout getLayout()
      Description copied from interface: WLayoutItem
      Returns the layout that implements this WLayoutItem.

      This implements a type-safe upcasting mechanism to a WLayout.

      Specified by:
      getLayout in interface WLayoutItem

    • getParentLayout

      public WLayout getParentLayout()
      Description copied from interface: WLayoutItem
      Returns the layout in which this item is contained.
      Specified by:
      getParentLayout in interface WLayoutItem

    • getImpl

      public WLayoutItemImpl getImpl()
      Description copied from interface: WLayoutItem
      Returns the implementation for this layout item.

      The implementation of a layout item depends on the kind of container for which the layout does layout management.

      Specified by:
      getImpl in interface WLayoutItem

    • setContentsMargins

      public void setContentsMargins​(int left, int top, int right, int bottom)
      Set contents margins (in pixels).

      The default contents margins are 9 pixels in all directions.

      Note: Only used when the layout manager is applied to a WContainerWidget.

      See Also:
      setContentsMargins(int left, int top, int right, int bottom)

    • getContentsMargin

      public int getContentsMargin​(Side side)
      Returns a contents margin.

      See Also:
      setContentsMargins(int left, int top, int right, int bottom)

    • clear

      public abstract void clear()
      Removes and deletes all child widgets and nested layouts.

      This is similar to WContainerWidget.clear(), with the exception that the layout itself is not deleted.

    • update

      protected void update​(WLayoutItem item)
      Update the layout.

      Must be called whenever some properties of the layout have changed.

    • update

      protected final void update()
      Update the layout.

      Calls update((WLayoutItem)null)

    • updateAddItem

      protected void updateAddItem​(WLayoutItem item)
      Update the layout, adding the given layout item.

      Must be called from the implementation of addItem()

    • updateRemoveItem

      protected void updateRemoveItem​(WLayoutItem item)
      Update the layout, remove the given layout item.

      Must be called from the implementation of removeItem()

    • setLayoutInParent

      protected void setLayoutInParent​(WWidget parent)
      Set the layout in the parent.

      Must be called from the constructor after the layout has been fully created (since it will call virtual methods getCount() and getItemAt()).

    • clearLayoutItem

      protected void clearLayoutItem​(WLayoutItem item)
      Clears and deletes an item.

      This also deletes nested widgets and layouts.

      See Also:
      clear()

    • setParentWidget

      public void setParentWidget​(WWidget parent)
      Description copied from interface: WLayoutItem
      Internal method.
      Specified by:
      setParentWidget in interface WLayoutItem

    • setParentLayout

      public void setParentLayout​(WLayout layout)
      Description copied from interface: WLayoutItem
      Internal method.
      Specified by:
      setParentLayout in interface WLayoutItem