In this case the constraint objects used are static String s such as BorderLayout.NORTH, BorderLayout.EAST, etc.
MAKE FLOWLAYOUT BUT FILL VERTICALLY HOW TO
Method addLayoutComponent(Component comp, Object constraints) a dds a new component associated with a constraints-based object which carries information about how to lay out this component.Ī typical implementation is BorderLayout which requires a direction (north, east, etc.) to position a component. This interface extends LayoutManager to provide a framework for those layout managers that use constraints-based layouts. PreferredLayoutSize(Container parent) calculates the preferred size requirements to lay out components in the given container and returns a Dimension instance representing this size.Ībstract interface 2 LayoutContainer(Container parent) calculates and sets the bounds for all components in the given container. This interface must be implemented by any layout manager. Normally, however, the container and the layout manager are separate objects that communicate heavily with each other.įigure 4.1 LayoutManager and LayoutManager2 implementationsĪbstract interface Note: In the case of several UI components shown in figure 4.1, the container and the layout manager are the same object. The other classes-the classes we are most familar and concerned with-are built solely to provide help in laying out containers they are assigned to.Įach container should be assigned one layout manager, and no layout manager should be used to manage more than one container. Note that there are several UI classes implementing these interfaces to provide custom layout functionality for themselves. For instance, GridBagLayout uses a Hashtable to map each Component it manages to its own GridBagConstraints object.įigure 4.1 shows all the classes implementing LayoutManager and LayoutManager2. Constraints-based objects usually store position and sizing information about one component and implementations of LayoutManager2 normally store one contraints-based object per component. LayoutManager2 enhances this by adding methods intended to aid in managing component postitions and sizes using constraints-based objects. Each implementation of LayoutManager defines these methods in different ways accoring to its specific needs. LayoutManager declares a set of methods that are intended to provide a straight-forward, organized means of managing component positions and sizes in a container. But before we present these examples it is helpful to understand the big picture of layouts, which classes use their own custom layouts, and exactly what it means to be a layout manager.Īll layout managers implement one of two interfaces defined in the java.awt package: LayoutManager or its subclass, LayoutManager2. We also show how to construct a basic container for JavaBeans which must be able to manage a dynamic number of components. In this chapter we present several examples showing how to use various layouts to satisfy specific goals, and how to create two custom layout managers that simplify the construction of many common interfaces.