我有一个 JTree在JScrollPane . JTree 相当长，因此将节点从树的顶部拖到底部需要一些时间。拖动节点时，JScrollPane 会滚动，但速度不如使用鼠标滚轮滚动快。实现 setUnitIncrement正如所选答案中的建议 here使鼠标滚轮滚动速度更快，但不会改变拖动节点的速度。执行setBlockIncrement时也是如此.拖动节点时的滚动速度与我按住向上或向下箭头并以这种方式遍历 JTree 大致相同。
如何加快拖动节点的速度？
更新 1:
这是应要求提供的 SSCCE。我从 here 中窃取了大部分代码因为它很好地说明了我遇到的问题。只需将一个节点拖到滚动 Pane 中不可见的树的一部分，您就会看到滚动有多慢。这就是我想要加速的。
package example;
import java.awt.datatransfer.*;
import java.util.*;
import javax.swing.*;
import javax.swing.tree.*;
public class Example {
private JScrollPane getContent() {
ArrayList<String> arrayList = new ArrayList<String>();
for( int i = 0; i < 3000; i++ ) {
arrayList.add( String.format( "Node %d", i ) );
}
DefaultMutableTreeNode root = new DefaultMutableTreeNode( "Root" );
for( String s : arrayList ) {
root.add( new DefaultMutableTreeNode( s ) );
}
JTree tree = new JTree( root );
tree.setDragEnabled( true );
tree.setDropMode( DropMode.ON_OR_INSERT );
tree.setTransferHandler( new TreeTransferHandler() );
tree.getSelectionModel().setSelectionMode( TreeSelectionModel.CONTIGUOUS_TREE_SELECTION );
expandTree( tree );
return new JScrollPane( tree );
}
private void expandTree( JTree tree ) {
DefaultMutableTreeNode root = (DefaultMutableTreeNode)tree.getModel().getRoot();
Enumeration e = root.breadthFirstEnumeration();
while( e.hasMoreElements() ) {
DefaultMutableTreeNode node = (DefaultMutableTreeNode)e.nextElement();
if( node.isLeaf() ) {
continue;
}
int row = tree.getRowForPath( new TreePath( node.getPath() ) );
tree.expandRow( row );
}
}
public static void main( String[] args ) {
JFrame f = new JFrame();
f.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
f.add( new Example().getContent() );
f.setSize( 400, 400 );
f.setLocation( 200, 200 );
f.setVisible( true );
}
}
class TreeTransferHandler extends TransferHandler {
DataFlavor nodesFlavor;
DataFlavor[] flavors = new DataFlavor[1];
DefaultMutableTreeNode[] nodesToRemove;
public TreeTransferHandler() {
try {
String mimeType = DataFlavor.javaJVMLocalObjectMimeType
+ ";class=\""
+ javax.swing.tree.DefaultMutableTreeNode[].class.getName()
+ "\"";
nodesFlavor = new DataFlavor( mimeType );
flavors[0] = nodesFlavor;
} catch( ClassNotFoundException e ) {
System.out.println( "ClassNotFound: " + e.getMessage() );
}
}
public boolean canImport( TransferHandler.TransferSupport support ) {
if( !support.isDrop() ) {
return false;
}
support.setShowDropLocation( true );
if( !support.isDataFlavorSupported( nodesFlavor ) ) {
return false;
}
// Do not allow a drop on the drag source selections.
JTree.DropLocation dl = (JTree.DropLocation)support.getDropLocation();
JTree tree = (JTree)support.getComponent();
int dropRow = tree.getRowForPath( dl.getPath() );
int[] selRows = tree.getSelectionRows();
for( int i = 0; i < selRows.length; i++ ) {
if( selRows[i] == dropRow ) {
return false;
}
}
// Do not allow MOVE-action drops if a non-leaf node is
// selected unless all of its children are also selected.
int action = support.getDropAction();
if( action == MOVE ) {
return haveCompleteNode( tree );
}
// Do not allow a non-leaf node to be copied to a level
// which is less than its source level.
TreePath dest = dl.getPath();
DefaultMutableTreeNode target = (DefaultMutableTreeNode)dest.getLastPathComponent();
TreePath path = tree.getPathForRow( selRows[0] );
DefaultMutableTreeNode firstNode = (DefaultMutableTreeNode)path.getLastPathComponent();
if( firstNode.getChildCount() > 0 && target.getLevel() < firstNode.getLevel() ) {
return false;
}
return true;
}
private boolean haveCompleteNode( JTree tree ) {
int[] selRows = tree.getSelectionRows();
TreePath path = tree.getPathForRow( selRows[0] );
DefaultMutableTreeNode first = (DefaultMutableTreeNode)path.getLastPathComponent();
int childCount = first.getChildCount();
// first has children and no children are selected.
if( childCount > 0 && selRows.length == 1 ) {
return false;
}
// first may have children.
for( int i = 1; i < selRows.length; i++ ) {
path = tree.getPathForRow( selRows[i] );
DefaultMutableTreeNode next = (DefaultMutableTreeNode)path.getLastPathComponent();
if( first.isNodeChild( next ) ) {
// Found a child of first.
if( childCount > selRows.length - 1 ) {
// Not all children of first are selected.
return false;
}
}
}
return true;
}
protected Transferable createTransferable( JComponent c ) {
JTree tree = (JTree)c;
TreePath[] paths = tree.getSelectionPaths();
if( paths != null ) {
// Make up a node array of copies for transfer and
// another for/of the nodes that will be removed in
// exportDone after a successful drop.
List<DefaultMutableTreeNode> copies = new ArrayList<DefaultMutableTreeNode>();
List<DefaultMutableTreeNode> toRemove = new ArrayList<DefaultMutableTreeNode>();
DefaultMutableTreeNode node = (DefaultMutableTreeNode)paths[0].getLastPathComponent();
DefaultMutableTreeNode copy = copy( node );
copies.add( copy );
toRemove.add( node );
for( int i = 1; i < paths.length; i++ ) {
DefaultMutableTreeNode next = (DefaultMutableTreeNode)paths[i].getLastPathComponent();
// Do not allow higher level nodes to be added to list.
if( next.getLevel() < node.getLevel() ) {
break;
} else if( next.getLevel() > node.getLevel() ) { // child node
copy.add( copy( next ) );
// node already contains child
} else { // sibling
copies.add( copy( next ) );
toRemove.add( next );
}
}
DefaultMutableTreeNode[] nodes = copies.toArray( new DefaultMutableTreeNode[copies.size()] );
nodesToRemove = toRemove.toArray( new DefaultMutableTreeNode[toRemove.size()] );
return new NodesTransferable( nodes );
}
return null;
}
/**
* Defensive copy used in createTransferable.
*/
private DefaultMutableTreeNode copy( TreeNode node ) {
return new DefaultMutableTreeNode( node );
}
protected void exportDone( JComponent source, Transferable data, int action ) {
if( ( action & MOVE ) == MOVE ) {
JTree tree = (JTree)source;
DefaultTreeModel model = (DefaultTreeModel)tree.getModel();
// Remove nodes saved in nodesToRemove in createTransferable.
for( int i = 0; i < nodesToRemove.length; i++ ) {
model.removeNodeFromParent( nodesToRemove[i] );
}
}
}
public int getSourceActions( JComponent c ) {
return COPY_OR_MOVE;
}
public boolean importData( TransferHandler.TransferSupport support ) {
if( !canImport( support ) ) {
return false;
}
// Extract transfer data.
DefaultMutableTreeNode[] nodes = null;
try {
Transferable t = support.getTransferable();
nodes = (DefaultMutableTreeNode[])t.getTransferData( nodesFlavor );
} catch( UnsupportedFlavorException ufe ) {
System.out.println( "UnsupportedFlavor: " + ufe.getMessage() );
} catch( java.io.IOException ioe ) {
System.out.println( "I/O error: " + ioe.getMessage() );
}
// Get drop location info.
JTree.DropLocation dl = (JTree.DropLocation)support.getDropLocation();
int childIndex = dl.getChildIndex();
TreePath dest = dl.getPath();
DefaultMutableTreeNode parent = (DefaultMutableTreeNode)dest.getLastPathComponent();
JTree tree = (JTree)support.getComponent();
DefaultTreeModel model = (DefaultTreeModel)tree.getModel();
// Configure for drop mode.
int index = childIndex; // DropMode.INSERT
if( childIndex == -1 ) { // DropMode.ON
index = parent.getChildCount();
}
// Add data to model.
for( int i = 0; i < nodes.length; i++ ) {
model.insertNodeInto( nodes[i], parent, index++ );
}
return true;
}
public String toString() {
return getClass().getName();
}
public class NodesTransferable implements Transferable {
DefaultMutableTreeNode[] nodes;
public NodesTransferable( DefaultMutableTreeNode[] nodes ) {
this.nodes = nodes;
}
public Object getTransferData( DataFlavor flavor )
throws UnsupportedFlavorException {
if( !isDataFlavorSupported( flavor ) ) {
throw new UnsupportedFlavorException( flavor );
}
return nodes;
}
public DataFlavor[] getTransferDataFlavors() {
return flavors;
}
public boolean isDataFlavorSupported( DataFlavor flavor ) {
return nodesFlavor.equals( flavor );
}
}
}
成功!
我终于能够在拖动时加快滚动速度。事实上，我还可以根据光标离树的顶部或底部的距离来调整滚动速度。最终比我做的要简单得多。甚至不需要听众。只需比较这两个代码示例即可查看我添加的内容。
package example;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.datatransfer.*;
import java.util.*;
import javax.swing.*;
import javax.swing.tree.*;
public class Example {
private JScrollPane getContent() {
ArrayList<String> arrayList = new ArrayList<String>();
for( int i = 0; i < 3000; i++ ) {
arrayList.add( String.format( "Node %d", i ) );
}
DefaultMutableTreeNode root = new DefaultMutableTreeNode( "Root" );
for( String s : arrayList ) {
root.add( new DefaultMutableTreeNode( s ) );
}
JTree tree = new JTree( root );
tree.setDragEnabled( true );
tree.setDropMode( DropMode.ON_OR_INSERT );
tree.setTransferHandler( new TreeTransferHandler() );
tree.getSelectionModel().setSelectionMode( TreeSelectionModel.CONTIGUOUS_TREE_SELECTION );
expandTree( tree );
return new JScrollPane( tree );
}
private void expandTree( JTree tree ) {
DefaultMutableTreeNode root = (DefaultMutableTreeNode)tree.getModel().getRoot();
Enumeration e = root.breadthFirstEnumeration();
while( e.hasMoreElements() ) {
DefaultMutableTreeNode node = (DefaultMutableTreeNode)e.nextElement();
if( node.isLeaf() ) {
continue;
}
int row = tree.getRowForPath( new TreePath( node.getPath() ) );
tree.expandRow( row );
}
}
public static void main( String[] args ) {
JFrame f = new JFrame();
f.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
f.add( new Example().getContent() );
f.setSize( 400, 400 );
f.setLocation( 200, 200 );
f.setVisible( true );
}
}
class TreeTransferHandler extends TransferHandler {
DataFlavor nodesFlavor;
DataFlavor[] flavors = new DataFlavor[1];
DefaultMutableTreeNode[] nodesToRemove;
public TreeTransferHandler() {
try {
String mimeType = DataFlavor.javaJVMLocalObjectMimeType
+ ";class=\""
+ javax.swing.tree.DefaultMutableTreeNode[].class.getName()
+ "\"";
nodesFlavor = new DataFlavor( mimeType );
flavors[0] = nodesFlavor;
} catch( ClassNotFoundException e ) {
System.out.println( "ClassNotFound: " + e.getMessage() );
}
}
public boolean canImport( TransferHandler.TransferSupport support ) {
if( !support.isDrop() ) {
return false;
}
boolean isScrolling = false;
JTree tree = (JTree)support.getComponent();
JViewport vp = (JViewport)tree.getParent();
Point vpMousePosition = vp.getMousePosition();
Rectangle treeVisibleRectangle = tree.getVisibleRect();
// Don't attempt scroll if mouse isn't over tree
if( vpMousePosition != null ) {
Integer newY = null;
// Make sure we aren't already scrolled all the way down
if( tree.getHeight() - treeVisibleRectangle.y != vp.getHeight() ) {
/*
* Get Y coordinate for scrolling down
*/
if( vp.getHeight() - vpMousePosition.y < 10 ) {
newY = treeVisibleRectangle.y + 500;
} else if( vp.getHeight() - vpMousePosition.y < 20 ) {
newY = treeVisibleRectangle.y + 400;
} else if( vp.getHeight() - vpMousePosition.y < 30 ) {
newY = treeVisibleRectangle.y + 300;
} else if( vp.getHeight() - vpMousePosition.y < 40 ) {
newY = treeVisibleRectangle.y + 200;
} else if( vp.getHeight() - vpMousePosition.y < 50 ) {
newY = treeVisibleRectangle.y + 100;
} else if( vp.getHeight() - vpMousePosition.y < 60 ) {
newY = treeVisibleRectangle.y + 50;
} else if( vp.getHeight() - vpMousePosition.y < 70 ) {
newY = treeVisibleRectangle.y + 25;
} else if( vp.getHeight() - vpMousePosition.y < 80 ) {
newY = treeVisibleRectangle.y + 10;
}
}
// Make sure we aren't already scrolled all the way up
if( newY == null && treeVisibleRectangle.y != 0 ) {
/*
* Get Y coordinate for scrolling up
*/
if( 10 > vpMousePosition.y ) {
newY = treeVisibleRectangle.y - 500;
} else if( 20 > vpMousePosition.y ) {
newY = treeVisibleRectangle.y - 400;
} else if( 30 > vpMousePosition.y ) {
newY = treeVisibleRectangle.y - 300;
} else if( 40 > vpMousePosition.y ) {
newY = treeVisibleRectangle.y - 200;
} else if( 50 > vpMousePosition.y ) {
newY = treeVisibleRectangle.y - 100;
} else if( 60 > vpMousePosition.y ) {
newY = treeVisibleRectangle.y - 50;
} else if( 70 > vpMousePosition.y ) {
newY = treeVisibleRectangle.y - 25;
} else if( 80 > vpMousePosition.y ) {
newY = treeVisibleRectangle.y - 10;
}
}
// Do the scroll
if( newY != null ) {
Rectangle treeNewVisibleRectangle = new Rectangle( treeVisibleRectangle.x, newY, treeVisibleRectangle.width, treeVisibleRectangle.height );
tree.scrollRectToVisible( treeNewVisibleRectangle );
isScrolling = true;
}
}
if( isScrolling ) {
return false;
}
support.setShowDropLocation( true );
if( !support.isDataFlavorSupported( nodesFlavor ) ) {
return false;
}
// Do not allow a drop on the drag source selections.
JTree.DropLocation dl = (JTree.DropLocation)support.getDropLocation();
int dropRow = tree.getRowForPath( dl.getPath() );
int[] selRows = tree.getSelectionRows();
for( int i = 0; i < selRows.length; i++ ) {
if( selRows[i] == dropRow ) {
return false;
}
}
// Do not allow MOVE-action drops if a non-leaf node is
// selected unless all of its children are also selected.
int action = support.getDropAction();
if( action == MOVE ) {
return haveCompleteNode( tree );
}
// Do not allow a non-leaf node to be copied to a level
// which is less than its source level.
TreePath dest = dl.getPath();
DefaultMutableTreeNode target = (DefaultMutableTreeNode)dest.getLastPathComponent();
TreePath path = tree.getPathForRow( selRows[0] );
DefaultMutableTreeNode firstNode = (DefaultMutableTreeNode)path.getLastPathComponent();
if( firstNode.getChildCount() > 0 && target.getLevel() < firstNode.getLevel() ) {
return false;
}
return true;
}
private boolean haveCompleteNode( JTree tree ) {
int[] selRows = tree.getSelectionRows();
TreePath path = tree.getPathForRow( selRows[0] );
DefaultMutableTreeNode first = (DefaultMutableTreeNode)path.getLastPathComponent();
int childCount = first.getChildCount();
// first has children and no children are selected.
if( childCount > 0 && selRows.length == 1 ) {
return false;
}
// first may have children.
for( int i = 1; i < selRows.length; i++ ) {
path = tree.getPathForRow( selRows[i] );
DefaultMutableTreeNode next = (DefaultMutableTreeNode)path.getLastPathComponent();
if( first.isNodeChild( next ) ) {
// Found a child of first.
if( childCount > selRows.length - 1 ) {
// Not all children of first are selected.
return false;
}
}
}
return true;
}
protected Transferable createTransferable( JComponent c ) {
JTree tree = (JTree)c;
TreePath[] paths = tree.getSelectionPaths();
if( paths != null ) {
// Make up a node array of copies for transfer and
// another for/of the nodes that will be removed in
// exportDone after a successful drop.
List<DefaultMutableTreeNode> copies = new ArrayList<DefaultMutableTreeNode>();
List<DefaultMutableTreeNode> toRemove = new ArrayList<DefaultMutableTreeNode>();
DefaultMutableTreeNode node = (DefaultMutableTreeNode)paths[0].getLastPathComponent();
DefaultMutableTreeNode copy = copy( node );
copies.add( copy );
toRemove.add( node );
for( int i = 1; i < paths.length; i++ ) {
DefaultMutableTreeNode next = (DefaultMutableTreeNode)paths[i].getLastPathComponent();
// Do not allow higher level nodes to be added to list.
if( next.getLevel() < node.getLevel() ) {
break;
} else if( next.getLevel() > node.getLevel() ) { // child node
copy.add( copy( next ) );
// node already contains child
} else { // sibling
copies.add( copy( next ) );
toRemove.add( next );
}
}
DefaultMutableTreeNode[] nodes = copies.toArray( new DefaultMutableTreeNode[copies.size()] );
nodesToRemove = toRemove.toArray( new DefaultMutableTreeNode[toRemove.size()] );
return new NodesTransferable( nodes );
}
return null;
}
/**
* Defensive copy used in createTransferable.
*/
private DefaultMutableTreeNode copy( TreeNode node ) {
return new DefaultMutableTreeNode( node );
}
protected void exportDone( JComponent source, Transferable data, int action ) {
if( ( action & MOVE ) == MOVE ) {
JTree tree = (JTree)source;
DefaultTreeModel model = (DefaultTreeModel)tree.getModel();
// Remove nodes saved in nodesToRemove in createTransferable.
for( int i = 0; i < nodesToRemove.length; i++ ) {
model.removeNodeFromParent( nodesToRemove[i] );
}
}
}
public int getSourceActions( JComponent c ) {
return COPY_OR_MOVE;
}
public boolean importData( TransferHandler.TransferSupport support ) {
if( !canImport( support ) ) {
return false;
}
// Extract transfer data.
DefaultMutableTreeNode[] nodes = null;
try {
Transferable t = support.getTransferable();
nodes = (DefaultMutableTreeNode[])t.getTransferData( nodesFlavor );
} catch( UnsupportedFlavorException ufe ) {
System.out.println( "UnsupportedFlavor: " + ufe.getMessage() );
} catch( java.io.IOException ioe ) {
System.out.println( "I/O error: " + ioe.getMessage() );
}
// Get drop location info.
JTree.DropLocation dl = (JTree.DropLocation)support.getDropLocation();
int childIndex = dl.getChildIndex();
TreePath dest = dl.getPath();
DefaultMutableTreeNode parent = (DefaultMutableTreeNode)dest.getLastPathComponent();
JTree tree = (JTree)support.getComponent();
DefaultTreeModel model = (DefaultTreeModel)tree.getModel();
// Configure for drop mode.
int index = childIndex; // DropMode.INSERT
if( childIndex == -1 ) { // DropMode.ON
index = parent.getChildCount();
}
// Add data to model.
for( int i = 0; i < nodes.length; i++ ) {
model.insertNodeInto( nodes[i], parent, index++ );
}
return true;
}
public String toString() {
return getClass().getName();
}
public class NodesTransferable implements Transferable {
DefaultMutableTreeNode[] nodes;
public NodesTransferable( DefaultMutableTreeNode[] nodes ) {
this.nodes = nodes;
}
public Object getTransferData( DataFlavor flavor )
throws UnsupportedFlavorException {
if( !isDataFlavorSupported( flavor ) ) {
throw new UnsupportedFlavorException( flavor );
}
return nodes;
}
public DataFlavor[] getTransferDataFlavors() {
return flavors;
}
public boolean isDataFlavorSupported( DataFlavor flavor ) {
return nodesFlavor.equals( flavor );
}
}
}
最佳答案
当它不能很好地与 SDK 一起工作时，我开始使用我的 hackish 方法，在这种情况下它是一种:听鼠标。当鼠标向下移动 10 个像素时，当鼠标在同一方向上移动 100 个像素时会产生一个事件。在 Windows 中，在 Excel 中，如果您将鼠标拖到任务栏下方，它将滚动。类似的东西应该在这里，值得一试。
关于java - 在 JScrollPane 中拖动 JTree 节点时如何加快滚动速度，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/14485732/