Package com.google.gwt.user.client.ui

Class AbsolutePanel

  • All Implemented Interfaces:
    HasAttachHandlers, HasHandlers, EventListener, HasVisibility, HasWidgets, HasWidgets.ForIsWidget, IndexedPanel, IndexedPanel.ForIsWidget, InsertPanel, InsertPanel.ForIsWidget, IsWidget, java.lang.Iterable<Widget>
    Direct Known Subclasses:
    RootPanel
    public class AbsolutePanel
extends ComplexPanel
implements InsertPanel.ForIsWidget
    An absolute panel positions all of its children absolutely, allowing them to overlap.

    Note that this panel will not automatically resize itself to allow enough room for its absolutely-positioned children. It must be explicitly sized in order to make room for them.

    Once a widget has been added to an absolute panel, the panel effectively "owns" the positioning of the widget. Any existing positioning attributes on the widget may be modified by the panel.

    Use in UiBinder Templates

    AbsolutePanel elements in UiBinder templates lay out their children with absolute position, using <g:at> elements. Each at element should have left and top attributes in pixels. They also can contain widget children directly, with no position specified.

    For example: 

     <g:AbsolutePanel>
   <g:at left='10' top='20'>
     <g:Label>Lorem ipsum...</g:Label>
   </g:at>
   <g:Label>...dolores est.</g:Label>
 </g:AbsolutePanel>

    • Constructor Detail

      • AbsolutePanel

        public AbsolutePanel()
        Creates an empty absolute panel.

      • AbsolutePanel

        protected AbsolutePanel​(Element elem)
        Creates an AbsolutePanel with the given element. This is protected so that it can be used by RootPanel or a subclass that wants to substitute another element. The element is presumed to be a <div>.
        Parameters:
        elem - the element to be used for this panel

    • Method Detail

      • add

        public void add​(Widget w)
        Description copied from class: Panel
        Adds a child widget.

        How to Override this Method

        There are several important things that must take place in the correct order to properly add or insert a Widget to a Panel. Not all of these steps will be relevant to every Panel, but all of the steps must be considered.

        1. Validate: Perform any sanity checks to ensure the Panel can accept a new Widget. Examples: checking for a valid index on insertion; checking that the Panel is not full if there is a max capacity.
        2. Adjust for Reinsertion: Some Panels need to handle the case where the Widget is already a child of this Panel. Example: when performing a reinsert, the index might need to be adjusted to account for the Widget's removal. See ComplexPanel.adjustIndex(Widget, int).
        3. Detach Child: Remove the Widget from its existing parent, if any. Most Panels will simply call Widget.removeFromParent() on the Widget.
        4. Logical Attach: Any state variables of the Panel should be updated to reflect the addition of the new Widget. Example: the Widget is added to the Panel's WidgetCollection at the appropriate index.
        5. Physical Attach: The Widget's Element must be physically attached to the Panel's Element, either directly or indirectly.
        6. Adopt: Call Panel.adopt(Widget) to finalize the add as the very last step.

        Specified by:
        add in interface HasWidgets
        Specified by:
        add in interface InsertPanel
        Overrides:
        add in class Panel
        Parameters:
        w - the widget to be added
        See Also:
        HasWidgets.add(Widget)

      • add

        public void add​(Widget w,
                int left,
                int top)
        Adds a widget to the panel at the specified position. Setting a position of (-1, -1) will cause the child widget to be positioned statically.
        Parameters:
        w - the widget to be added
        left - the widget's left position
        top - the widget's top position

      • getWidgetLeft

        public int getWidgetLeft​(Widget w)
        Gets the position of the left outer border edge of the widget relative to the left outer border edge of the panel.
        Parameters:
        w - the widget whose position is to be retrieved
        Returns:
        the widget's left position

      • getWidgetTop

        public int getWidgetTop​(Widget w)
        Gets the position of the top outer border edge of the widget relative to the top outer border edge of the panel.
        Parameters:
        w - the widget whose position is to be retrieved
        Returns:
        the widget's top position

      • insert

        public void insert​(Widget w,
                   int beforeIndex)
        Description copied from interface: InsertPanel
        Inserts a child widget before the specified index. If the widget is already a child of this panel, it will be moved to the specified index.
        Specified by:
        insert in interface InsertPanel
        Parameters:
        w - the child widget to be inserted
        beforeIndex - the index before which it will be inserted

      • insert

        public void insert​(Widget w,
                   int left,
                   int top,
                   int beforeIndex)
        Inserts a child widget at the specified position before the specified index. Setting a position of (-1, -1) will cause the child widget to be positioned statically. If the widget is already a child of this panel, it will be moved to the specified index.
        Parameters:
        w - the child widget to be inserted
        left - the widget's left position
        top - the widget's top position
        beforeIndex - the index before which it will be inserted
        Throws:
        java.lang.IndexOutOfBoundsException - if beforeIndex is out of range

      • remove

        public boolean remove​(Widget w)
        Overrides ComplexPanel.remove(Widget) to change the removed Widget's element back to static positioning.This is done so that any positioning changes to the widget that were done by the panel are undone when the widget is disowned from the panel.
        Specified by:
        remove in interface HasWidgets
        Overrides:
        remove in class ComplexPanel
        Parameters:
        w - the widget to be removed
        Returns:
        true if the child was present

      • setWidgetPosition

        public void setWidgetPosition​(Widget w,
                              int left,
                              int top)
        Sets the position of the specified child widget. Setting a position of (-1, -1) will cause the child widget to be positioned statically.
        Parameters:
        w - the child widget to be positioned
        left - the widget's left position
        top - the widget's top position

      • setWidgetPositionImpl

        protected void setWidgetPositionImpl​(Widget w,
                                     int left,
                                     int top)