Package edu.cnu.mdi.graphics.connection

Class ConnectionManager

java.lang.Object

edu.cnu.mdi.graphics.connection.ConnectionManager

All Implemented Interfaces:

ItemChangeListener, EventListener

public class ConnectionManager
extends Object
implements ItemChangeListener

Manages ConnectorItem objects and enforces connection rules.

This manager listens to drawable list change events so it can:

• cache connectors when they are added
• remove connectors when an endpoint item is removed

Duplicate connections are prevented: at most one connector may exist between two endpoint items (in either direction).

Method Summary

Modifier and Type	Method	Description
boolean	canConnect(AItem item1, AItem item2)	Determine whether two items can be connected.
ConnectorItem	connect(Layer layer, AItem item1, AItem item2)	Create and register a new ConnectorItem if allowed.
Set<AItem>	getConnectedItems(AItem item)	Get all items directly connected to the given item.
Set<ConnectorItem>	getConnectors()
static ConnectionManager	getInstance()	Get the singleton instance.
boolean	hasConnection(AItem item1, AItem item2)	Check whether a connection already exists between the two items.
void	itemChanged(Layer layer, AItem item, ItemChangeType type)	Drawable list change callback.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

getInstance

public static ConnectionManager getInstance()

Get the singleton instance.

Returns:

the connection manager

canConnect

public boolean canConnect(AItem item1,
 AItem item2)

Determine whether two items can be connected.

Rules:

• neither item is null
• items are not the same instance
• both items belong to the same container (cross-container connections are always rejected)
• both items are connectable
• no existing connector already connects them (either direction)

Parameters:

item1 - first endpoint

item2 - second endpoint

Returns:

true if a new connection is allowed

connect

public ConnectorItem connect(Layer layer,
 AItem item1,
 AItem item2)

Create and register a new ConnectorItem if allowed.

Note: the created item will also be discovered via ADDED events if the layer/list notifies listeners; we still add to our cache immediately so callers can rely on the returned item.

Parameters:

layer - layer to place the connector on (recommended: a connection layer)

item1 - first endpoint

item2 - second endpoint

Returns:

the created connector, or null if connection is not allowed

hasConnection

public boolean hasConnection(AItem item1,
 AItem item2)

Check whether a connection already exists between the two items. (Direction does not matter.)

getConnectors

public Set<ConnectorItem> getConnectors()

Returns:

an unmodifiable snapshot of known connectors.

itemChanged

public void itemChanged(Layer layer,
 AItem item,
 ItemChangeType type)

Drawable list change callback.

Specified by:

itemChanged in interface ItemChangeListener

Parameters:

layer - the z layer containing the chanhed item.

item - the AItem in question.

type - the type of change.

getConnectedItems

public Set<AItem> getConnectedItems(AItem item)

Get all items directly connected to the given item.

The returned set contains the opposite endpoint of every ConnectorItem that touches the given item.

The returned set is a snapshot and is not backed by the manager.

Parameters:

item - the endpoint item

Returns:

an unmodifiable set of connected items (empty if none)