Unity3D Multi-Instance-Friendly Popup List

popup.cs

// A Popup List class that supports multiple instances in Unity
// Popup list created by Eric Haines.
// Popup list Extended by Xiaohang Miao. (xmiao2@ncsu.edu)

public class Popup{
	private int selectedItemIndex = 0;
	private bool isVisible = false;
	private bool isClicked = false;
	private static DropdownBox current;
	public int List(Rect box, GUIContent[] items, GUIStyle boxStyle, GUIStyle listStyle) {
		
		if(isVisible) {
			Rect listRect = new Rect( box.x, box.y + box.height, box.width, box.height * items.Length);

			GUI.Box( listRect, "", boxStyle );
			
			selectedItemIndex = GUI.SelectionGrid( listRect, selectedItemIndex, items, 1, listStyle );
			
			if(GUI.changed) {
				current = null;
			}
		}
		
		int controlID = GUIUtility.GetControlID( FocusType.Passive );
		
		switch( Event.current.GetTypeForControl(controlID) )
		{
		case EventType.mouseUp:
		{
			current = null;
		}
			break;
		}	
		if(GUI.Button(new Rect(box.x,box.y,box.width,box.height),items[selectedItemIndex])) {
			if(!isClicked) {
				current = this;
				isClicked = true;
			} else {
				isClicked = false;
			}
		}
		
		if(current == this) {
			isVisible = true;
		} else {
			isVisible = false;
			isClicked = false;
		}
		
		return selectedItemIndex;
	}
	
	public int GetSelectedItemIndex()
	{
		return selectedItemIndex;
	}
}