Thus, each component must know its space requirements the layout manager uses these to arrange the screen and your Java program never has to worry about platform-dependent positioning.
(Java 1.1 also has a getMaximumSize() method the existing layout managers don't take advantage of it.) These methods report the minimum space that a component requires to be displayed correctly and the optimal size at which it looks best. To find out how much space a component needs, a layout manager calls the component's getMinimumSize() and getPreferredSize() methods. It asks each component in the layout how much space it requires, then arranges the components on the screen as best it can, based on the component sizes on the platform in use and the space available, resizing the components as needed. A layout manager takes care of this for you.
#JAVA FLOWLAYOUT CODE#
Even for a simple layout, the code required to discover component sizes and compute absolute positions could be hundreds of lines, particularly if you concern yourself with what happens when the user resizes a window. Layout managers eliminate the need to compute component placement on your own, which would be a losing proposition since the size required for any component depends on the platform on which it is displayed. Every container has a LayoutManager that is responsible for positioning the component objects within it, regardless of the platform or the screen size. This chapter expands upon the idea of a layout manager, which was mentioned briefly in the previous chapter.
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