实现文件的拖拽功能importjava.awt.AlphaComposite;importjava.awt.Component;importjava.awt.Graphics2D;importjava.awt.Point;importjava.awt.Rectangle;importjava.awt.Toolkit;importjava.awt.datatransfer.DataFlavor;importjava.awt.datatransfer.StringSelection;importjava.awt.datatransfer.Transferable;importjava.awt.datatransfer.Un