Can i use a single layout manager instance in swing?

Question

I'm using MiGLayout and being the freak i am, i was thinking if it's possible to create a single instance of the layout and use it for all my panels? Just curious...

Answer 1

That depends entirely on whether the layout manager retains data related to layout. Generally, any layout manager that takes constraints needs to store those, so it must be instantiated one-to-one with the container.

With particular reference to MigLayout, look at how much data it stores that would not be applicable to multiple containers:

public final class MigLayout implements LayoutManager2, Externalizable
{
    // ******** Instance part ********

    /** The component to string constraints mappings.
     */
    private final Map<Component, Object> scrConstrMap = new IdentityHashMap<Component, Object>(8);

    /** Hold the serializable text representation of the constraints.
     */
    private Object layoutConstraints = "", colConstraints = "", rowConstraints = "";    // Should never be null!

    // ******** Transient part ********

    private transient ContainerWrapper cacheParentW = null;

    private transient final Map<ComponentWrapper, CC> ccMap = new HashMap<ComponentWrapper, CC>(8);
    private transient javax.swing.Timer debugTimer = null;

    private transient LC lc = null;
    private transient AC colSpecs = null, rowSpecs = null;
    private transient Grid grid = null;
    private transient int lastModCount = PlatformDefaults.getModCount();
    private transient int lastHash = -1;
    private transient Dimension lastInvalidSize = null;

    private transient ArrayList<LayoutCallback> callbackList = null;

    private transient boolean dirty = true;

Answer 2

Some layout managers will only work with one Container (such as BoxLayout). My guess is that there's little benefit gained by trying to reuse the same layout manager.