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SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.

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package org.scijava.ui.dnd;

import java.util.List;

import org.scijava.display.Display;
import org.scijava.plugin.Parameter;
import org.scijava.plugin.Plugin;

/**
 * Drag-and-drop handler for lists of objects.
 * 
 * @author Curtis Rueden
 * @author Barry DeZonia
 */
@Plugin(type = DragAndDropHandler.class)
public class ListDragAndDropHandler extends AbstractDragAndDropHandler>
{

	@Parameter(required = false)
	private DragAndDropService dragAndDropService;

	// -- DragAndDropHandler methods --

	@Override
	public boolean supports(final List list, final Display display) {
		if (dragAndDropService == null) return false;
		if (!super.supports(list, display)) return false;

		// empty lists are trivially compatible
		if (list.size() == 0) return true;

		// the list is deemed compatible if at least one item is compatible
		for (final Object item : list) {
			if (dragAndDropService.supports(item, display)) return true;
		}
		return false;
	}

	@Override
	public boolean drop(final List list, final Display display) {
		if (dragAndDropService == null) return false;
		check(list, display);
		if (list == null) return true; // trivial case

		// dropping an empty list trivially succeeds
		if (list.size() == 0) return true;

		// use the drag-and-drop service to handle each item separately
		boolean success = false;
		for (final Object item : list) {
			if (dragAndDropService.supports(item, display)) {
				final boolean result = dragAndDropService.drop(item, display);
				if (result) success = true;
			}
		}
		return success;
	}

	// -- Typed methods --

	@Override
	@SuppressWarnings({ "rawtypes", "unchecked" })
	public Class> getType() {
		return (Class) List.class;
	}

}