【Swing】 paintImmediately 的效率问题若干

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在一个游戏里用了 paintImmediately 来刷新某 JComponent c

c 为 opaque,空布局,没有子控件

用 System.currentTimeMillis() 取时间差测得 c 的 paintComponent() 方法耗时为 0 ms

c.paintImmediatly 的每次调用却耗时 15 ~ 16 ms 不等,这正常吗?


我测量的方法正确吗?


有没有什么办法改进 paintImmediatly 的效率?

如果不用 paintImmediatly,有什么办法可以安全的得到一个往屏幕上绘制 c 的 Graphics 对象?
...全文

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实现文件的拖拽功能 import java.awt.AlphaComposite; import java.awt.Component; import java.awt.Graphics2D; import java.awt.Point; import java.awt.Rectangle; import java.awt.Toolkit; import java.awt.datatransfer.DataFlavor; import java.awt.datatransfer.StringSelection; import java.awt.datatransfer.Transferable; import java.awt.datatransfer.UnsupportedFlavorException; import java.awt.dnd.DnDConstants; import java.awt.dnd.DragGestureEvent; import java.awt.dnd.DragGestureListener; import java.awt.dnd.DragSource; import java.awt.dnd.DragSourceDragEvent; import java.awt.dnd.DragSourceDropEvent; import java.awt.dnd.DragSourceEvent; import java.awt.dnd.DragSourceListener; import java.awt.dnd.DropTarget; import java.awt.dnd.DropTargetDragEvent; import java.awt.dnd.DropTargetDropEvent; import java.awt.dnd.DropTargetEvent; import java.awt.dnd.DropTargetListener; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.KeyAdapter; import java.awt.event.KeyEvent; import java.awt.geom.AffineTransform; import java.awt.geom.Rectangle2D; import java.awt.image.BufferedImage; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.util.Iterator; import java.util.List; import javax.swing.Icon; import javax.swing.JLabel; import javax.swing.JTree; import javax.swing.Timer; import javax.swing.event.TreeExpansionEvent; import javax.swing.event.TreeExpansionListener; import javax.swing.filechooser.FileSystemView; import javax.swing.tree.DefaultMutableTreeNode; import javax.swing.tree.DefaultTreeCellRenderer; import javax.swing.tree.DefaultTreeModel; import javax.swing.tree.TreePath; class DragTree extends JTree implements DragGestureListener, DragSourceListener, DropTargetListener { /** * */ private static final long serialVersionUID = 1L; BufferedImage ghostImage; private Rectangle2D ghostRect = new Rectangle2D.Float(); private Point ptOffset = new Point(); private Point lastPoint = new Point(); private TreePath lastPath; private Timer hoverTimer; 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File f = node.getFile&#40;&#41;; try { Icon icon = FileSystemView.getFileSystemView() .getSystemIcon(f); this.setIcon(icon); this.setLeafIcon(icon); this.setOpenIcon(icon); this.setClosedIcon(icon); this.setDisabledIcon(icon); } catch (Exception e) { e.printStackTrace(); } } return super.getTreeCellRendererComponent(tree, value, selected, expanded, leaf, row, hasFocus); } }); super.setScrollsOnExpand(true); new DropTarget(this, DnDConstants.ACTION_COPY_OR_MOVE, this); // Set up a hover timer, so that a node will be automatically expanded // or collapsed // if the user lingers on it for more than a short time hoverTimer = new Timer(1000, new ActionListener() { public void actionPerformed(ActionEvent e) { if (lastPath == null) { return; } if (getRowForPath(lastPath) == 0) return; // Do nothing if we are hovering over the root node if (isExpanded(lastPath)) collapsePath(lastPath); else expandPath(lastPath); } }); hoverTimer.setRepeats(false); // Set timer to one-shot mode this.addKeyListener(new KeyAdapter() { public void keyPressed(KeyEvent e) { int code = e.getKeyCode(); 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TreePath path = getLeadSelectionPath(); if (path == null) return; FileNode node = (FileNode) path.getLastPathComponent(); sourceNode = node; // Work out the offset of the drag point from the TreePath bounding // rectangle origin Rectangle raPath = getPathBounds(path); Point ptDragOrigin = e.getDragOrigin(); ptOffset.setLocation(ptDragOrigin.x - raPath.x, ptDragOrigin.y - raPath.y); // Get the cell renderer (which is a JLabel) for the path being dragged int row = this.getRowForLocation(ptDragOrigin.x, ptDragOrigin.y); JLabel lbl = (JLabel) getCellRenderer().getTreeCellRendererComponent( this, // tree path.getLastPathComponent(), // value false, // isSelected (dont want a colored background) isExpanded(path), // isExpanded getModel().isLeaf(path.getLastPathComponent()), // isLeaf row, // row (not important for rendering) false // hasFocus (dont want a focus rectangle) ); lbl.setSize((int) raPath.getWidth(), (int) raPath.getHeight()); // <-- // The // layout // manager // would // normally // do // this // Get a buffered image of the selection for dragging a ghost image this.ghostImage = new BufferedImage((int) raPath.getWidth(), (int) raPath.getHeight(), BufferedImage.TYPE_INT_ARGB_PRE); 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