AbstractDropTargetObservableSpi.java example

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/*
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package org.jowidgets.spi.impl.dnd;

import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.Set;

import org.jowidgets.spi.dnd.IDropEventSpi;
import org.jowidgets.spi.dnd.IDropResponseSpi;
import org.jowidgets.spi.dnd.IDropTargetListenerSpi;
import org.jowidgets.spi.dnd.IDropTargetObservableSpi;
import org.jowidgets.util.Assert;

public abstract class AbstractDropTargetObservableSpi implements IDropTargetObservableSpi {

    private final Set<IDropTargetListenerSpi> listeners;

    private boolean active;

    public AbstractDropTargetObservableSpi() {
        this.listeners = new LinkedHashSet<IDropTargetListenerSpi>();
        this.active = false;
    }

    @Override
    public final void addDropTargetListenerSpi(final IDropTargetListenerSpi listener) {
        Assert.paramNotNull(listener, "listener");
        final int lastSize = listeners.size();
        listeners.add(listener);
        if (lastSize == 0) {
            this.active = true;
            setActive(true);
        }
    }

    @Override
    public final void removeDropTargetListenerSpi(final IDropTargetListenerSpi listener) {
        Assert.paramNotNull(listener, "listener");
        final int lastSize = listeners.size();
        listeners.remove(listener);
        if (lastSize == 1 && listeners.size() == 0) {
            this.active = false;
            setActive(false);
        }
    }

    public final void fireDragEnter(final IDropEventSpi event, final IDropResponseSpi response) {
        for (final IDropTargetListenerSpi listener : new LinkedList<IDropTargetListenerSpi>(listeners)) {
            listener.dragEnter(event, response);
        }
    }

    public final void fireDragOver(final IDropEventSpi event, final IDropResponseSpi response) {
        for (final IDropTargetListenerSpi listener : new LinkedList<IDropTargetListenerSpi>(listeners)) {
            listener.dragOver(event, response);
        }
    }

    public final void fireDragOperationChanged(final IDropEventSpi event, final IDropResponseSpi response) {
        for (final IDropTargetListenerSpi listener : new LinkedList<IDropTargetListenerSpi>(listeners)) {
            listener.dragOperationChanged(event, response);
        }
    }

    public final void fireDragExit() {
        for (final IDropTargetListenerSpi listener : new LinkedList<IDropTargetListenerSpi>(listeners)) {
            listener.dragExit();
        }
    }

    public final void fireDropAccept(final IDropEventSpi event, final IDropResponseSpi response) {
        for (final IDropTargetListenerSpi listener : new LinkedList<IDropTargetListenerSpi>(listeners)) {
            listener.dropAccept(event, response);
        }
    }

    public final void fireDrop(final IDropEventSpi event) {
        for (final IDropTargetListenerSpi listener : new LinkedList<IDropTargetListenerSpi>(listeners)) {
            listener.drop(event);
        }
    }

    protected boolean isActive() {
        return active;
    }

    protected abstract void setActive(boolean active);

}