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Java Standard Edition (SE)



Class FlowView

  • All Implemented Interfaces:
    Direct Known Subclasses:

    public abstract class FlowView
    extends BoxView
    A View that tries to flow it's children into some partially constrained space. This can be used to build things like paragraphs, pages, etc. The flow is made up of the following pieces of functionality.
    • A logical set of child views, which as used as a layout pool from which a physical view is formed.
    • A strategy for translating the logical view to a physical (flowed) view.
    • Constraints for the strategy to work against.
    • A physical structure, that represents the flow. The children of this view are where the pieces of of the logical views are placed to create the flow.
    See Also:
    • Field Detail

      • layoutSpan

        protected int layoutSpan
        Default constraint against which the flow is created against.
      • layoutPool

        protected View layoutPool
        These are the views that represent the child elements of the element this view represents (The logical view to translate to a physical view). These are not directly children of this view. These are either placed into the rows directly or used for the purpose of breaking into smaller chunks, to form the physical view.
      • strategy

        protected FlowView.FlowStrategy strategy
        The behavior for keeping the flow updated. By default this is a singleton shared by all instances of FlowView (FlowStrategy is stateless). Subclasses can create an alternative strategy, which might keep state.
    • Constructor Detail

      • FlowView

        public FlowView(Element elem,
                        int axis)
        Constructs a FlowView for the given element.
        elem - the element that this view is responsible for
        axis - may be either View.X_AXIS or View.Y_AXIS
    • Method Detail

      • getFlowAxis

        public int getFlowAxis()
        Fetches the axis along which views should be flowed. By default, this will be the axis orthogonal to the axis along which the flow rows are tiled (the axis of the default flow rows themselves). This is typically used by the FlowStrategy.
      • getFlowSpan

        public int getFlowSpan(int index)
        Fetch the constraining span to flow against for the given child index. This is called by the FlowStrategy while it is updating the flow. A flow can be shaped by providing different values for the row constraints. By default, the entire span inside of the insets along the flow axis is returned.
        index - the index of the row being updated. This should be a value >= 0 and < getViewCount().
        See Also:
      • getFlowStart

        public int getFlowStart(int index)
        Fetch the location along the flow axis that the flow span will start at. This is called by the FlowStrategy while it is updating the flow. A flow can be shaped by providing different values for the row constraints.
        index - the index of the row being updated. This should be a value >= 0 and < getViewCount().
        See Also:
      • createRow

        protected abstract View createRow()
        Create a View that should be used to hold a a rows worth of children in a flow. This is called by the FlowStrategy when new children are added or removed (i.e. rows are added or removed) in the process of updating the flow.
      • loadChildren

        protected void loadChildren(ViewFactory f)
        Loads all of the children to initialize the view. This is called by the setParent method. This is reimplemented to not load any children directly (as they are created in the process of formatting). If the layoutPool variable is null, an instance of LogicalView is created to represent the logical view that is used in the process of formatting.
        loadChildren in class CompositeView
        f - the view factory
        See Also:
      • getViewIndexAtPosition

        protected int getViewIndexAtPosition(int pos)
        Fetches the child view index representing the given position in the model.
        getViewIndexAtPosition in class CompositeView
        pos - the position >= 0
        index of the view representing the given position, or -1 if no view represents that position
      • layout

        protected void layout(int width,
                              int height)
        Lays out the children. If the span along the flow axis has changed, layout is marked as invalid which which will cause the superclass behavior to recalculate the layout along the box axis. The FlowStrategy.layout method will be called to rebuild the flow rows as appropriate. If the height of this view changes (determined by the preferred size along the box axis), a preferenceChanged is called. Following all of that, the normal box layout of the superclass is performed.
        layout in class BoxView
        width - the width to lay out against >= 0. This is the width inside of the inset area.
        height - the height to lay out against >= 0 This is the height inside of the inset area.
      • calculateMinorAxisRequirements

        protected SizeRequirements calculateMinorAxisRequirements(int axis,
                                                                  SizeRequirements r)
        Calculate requirements along the minor axis. This is implemented to forward the request to the logical view by calling getMinimumSpan, getPreferredSpan, and getMaximumSpan on it.
        calculateMinorAxisRequirements in class BoxView
        axis - the axis being studied
        r - the SizeRequirements object; if null one will be created
        the newly initialized SizeRequirements object
        See Also:
      • setParent

        public void setParent(View parent)
        Sets the parent of the view. This is reimplemented to provide the superclass behavior as well as calling the loadChildren method if this view does not already have children. The children should not be loaded in the constructor because the act of setting the parent may cause them to try to search up the hierarchy (to get the hosting Container for example). If this view has children (the view is being moved from one place in the view hierarchy to another), the loadChildren method will not be called.
        setParent in class CompositeView
        parent - the parent of the view, null if none


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