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Java中的Drag and Drop詳解與代碼示例 (轉(zhuǎn))

通過兩種方法實(shí)現(xiàn)Drag and Drop:
1.比較初級的D&D:只利用java.awt.datatransfer.*中的類實(shí)現(xiàn).
2.高級D&D: 利用javax.awt.dnd.*中的類實(shí)現(xiàn).

比較初級D&D:只利用java.awt.datatransfer.*中的類實(shí)現(xiàn).
這種方法只支持對JComponent的拖拽.
Drag and Drop的問題簡單的說要涉及到兩個(gè)部分: Drag Source, Drop target和Transferable 即從哪里drag來的, 以及drop到哪里去, 以及傳輸?shù)臄?shù)據(jù).

Drag Source可以分為兩種:
1.第一種是這樣的JComponent, 他們有dragEnabled屬性.這些JComponent包括:
javax.swing.JColorChooser
javax.swing.JFileChooser
javax.swing.JList
javax.swing.JTable
javax.swing.JTree
javax.swing.text.JTextComponent
這些JComponent要想作為一個(gè)Drag Source只要調(diào)用setDragEnabled( true)即可, 不用多余的操作.
2. 另一種Drag Source沒有dragEnabled屬性, 也就沒有setDragEnabled方法, 要想作為Drag Source, 那就要給Component添加MouseMotionListener, 并實(shí)現(xiàn)mouseDragged方法, 后面會(huì)舉例介紹.

Drop Target, 任何JComponent都可以作為Drop Target, 但是也只有JComponent以及它的子類可以作為Drop Target, 其它的不行.

Transferable
所有的Transferable都是javax.swing.Transferable的子類, 但是細(xì)分還是可以分為兩種情況:
第一種是利用javax.swing.Transferable, 因?yàn)閖avax.swing.Transferable 是一個(gè)具體類我們可以直接調(diào)用new TransferHandler( String property )生成的transfer handler 作為Component的Transfer Handler, 這樣的transfer handler可以將 Java Bean 屬性從一個(gè)組件傳輸?shù)搅硪粋€(gè)組件的傳輸處理程序。
第二種則是自定義一個(gè)TransferHandler的子類, 你可以在這個(gè)類中實(shí)現(xiàn)復(fù)雜的拖拽操作.
下面有兩個(gè)例子.
第一個(gè)例子用簡單的javax.swing.Transferable, 第二個(gè)例子定義一個(gè)javax.swing.Transferable的子類.
例一

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.event.*;

public class LabelDnd {

private JFrame mainFrame;

private JPanel mainPanel;

private JLabel label;

private JTextField textField;

private JColorChooser colorChooser;

private JMenuBar menuBar = new JMenuBar();

private JMenu menu = new JMenu( "Menu" );

private JMenuItem menuItem = new JMenuItem( "Handle Foregound" );

private TransferHandler t1 = new TransferHandler( "text" ) ;

private TransferHandler t2 = new TransferHandler( "foreground" );

public LabelDnd() {

mainFrame = new JFrame();

mainPanel = new JPanel( new BorderLayout() );

label = new JLabel( "label" );

label.setTransferHandler( t1 );

menuItem.addActionListener( new ActionListener() {

public void actionPerformed( ActionEvent e ) {

if( label.getTransferHandler().equals( t1 ) ) {

LabelDnd.this.menuItem.setText( "Handle Text" );

label.setTransferHandler( t2 );

} else {

LabelDnd.this.menuItem.setText( "Handle Foreground" );

label.setTransferHandler( t1 );

}

});

menu.add( menuItem );

menu.setTransferHandler( t1 );

menuBar.add( menu );

mainFrame.setJMenuBar( menuBar );

label.addMouseListener( new MouseAdapter() {

public void mousePressed( MouseEvent e ) {

JComponent c = (JComponent)e.getSource();

TransferHandler handler = c.getTransferHandler();

handler.exportAsDrag( c, e, TransferHandler.COPY );

}

});

textField = new JTextField( 20 );

textField.setDragEnabled( true );

colorChooser = new JColorChooser();

colorChooser.setDragEnabled( true );

mainPanel.add( label, BorderLayout.PAGE_START );

mainPanel.add( textField, BorderLayout.PAGE_END );

mainPanel.add( colorChooser, BorderLayout.WEST );

mainFrame.getContentPane().add( mainPanel );

mainFrame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

mainFrame.pack();

mainFrame.setLocationRelativeTo( null );

mainFrame.setVisible( true );

}

public static void main( String[] args ) {

new LabelDnd();

}

效果如下:

你可以試著拖拽下。

例二
PictureDnd.java

package dt;

import java.awt.*;

import javax.swing.*;

import java.awt.event.*;

import javax.swing.event.*;

import demo.gui.PictureComponent;

import java.awt.datatransfer.*;

import java.io.*;

public class PictureDnd {

JFrame mainFrame;

JPanel mainPanel;

PictureComponent[] pictures;

public static void main( String[] args ) {

new PictureDnd();

}

public PictureDnd() {

mainFrame = new JFrame();

mainPanel = new JPanel( new GridLayout( 2, 2 ) );

pictures = new PictureComponent[ 4 ];

pictures[ 0 ] = new PictureComponent( new ImageIcon( "Sunset.jpg" ).getImage() );

pictures[ 1 ] = new PictureComponent( new ImageIcon( "Winter.jpg" ).getImage() );

pictures[ 2 ] = new PictureComponent( null );

pictures[ 3 ] = new PictureComponent( null );

mainPanel.add( pictures[ 0 ] );

mainPanel.add( pictures[ 1 ] );

mainPanel.add( pictures[ 2 ] );

mainPanel.add( pictures[ 3 ] );

mainPanel.setBorder( BorderFactory.createEmptyBorder( 20, 20, 20, 20 ) );

mainFrame.getContentPane().add( mainPanel );

mainFrame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

mainFrame.setSize( 350, 400 );

mainFrame.setLocationRelativeTo( null );

mainFrame.setVisible( true );

}

PicrureComponent.java

package demo.gui;

import java.awt.Color;

import java.awt.Dimension;

import java.awt.Graphics;

import java.awt.Image;

import java.awt.event.FocusEvent;

import java.awt.event.FocusListener;

import java.awt.event.MouseEvent;

import java.awt.event.MouseListener;

import java.util.HashSet;

import javax.swing.JComponent;

public class PictureComponent extends JComponent

implements FocusListener, MouseListener {

Image image;

HashSet< PictureComponent > pcs = new HashSet< PictureComponent >();

public PictureComponent( Image image ) {

this.image = image;

setPreferredSize( new Dimension(125, 125 ) );

setFocusable( true );

setTransferHandler( new PictureTransferHandler() );

addFocusListener( this );

addMouseListener( this );

}

public HashSet< PictureComponent > getPcs() {

return this.pcs;

}

public void setPcs( HashSet< PictureComponent > pcs ) {

this.pcs = pcs;

}

public Image getImage() {

return this.image;

}

public void setImage( Image image ){

this.image = image;

repaint();

}

public void paintComponent( Graphics graphics ){

Graphics g = graphics.create();

g.setColor( Color.white );

g.fillRect( 0, 0, 125,125 );

if( image != null ) {

g.drawImage( image, 0, 0, 125, 125, Color.BLACK, this );

}

if( isFocusOwner() ) {

g.setColor( Color.red );

}

else {

g.setColor( Color.black );

}

g.drawRect( 0, 0, 125, 125 );

g.dispose();

}

public void focusGained( FocusEvent e ) {

repaint();

}

public void focusLost( FocusEvent e ) {

repaint();

}

public void mouseClicked( MouseEvent e ) {

requestFocusInWindow();

}

public void mouseEntered( MouseEvent e ) {}

public void mousePressed( MouseEvent e ) {}

public void mouseExited( MouseEvent e ) {}

public void mouseReleased( MouseEvent e ) {}

}

TransferablePicture:

package demo.gui;

import java.awt.Image;

import java.awt.datatransfer.DataFlavor;

import java.awt.datatransfer.Transferable;

/* Transferalbe */

public class TransferablePicture implements Transferable {

DataFlavor[] flavors = { DataFlavor.imageFlavor };

Image image;

public TransferablePicture( Image image ) {

this.image = image;

}

public DataFlavor[] getTransferDataFlavors() {

return flavors;

}

public Object getTransferData( DataFlavor flavor ) {

if( flavor.equals( DataFlavor.imageFlavor ) ) {

return image;

}

return null;

}

public boolean isDataFlavorSupported( DataFlavor flavor ) {

return flavor.equals( DataFlavor.imageFlavor );

}

PictureTransferHandler.java

package demo.gui;

import java.awt.Image;

import java.awt.datatransfer.DataFlavor;

import java.awt.datatransfer.Transferable;

import java.awt.datatransfer.UnsupportedFlavorException;

import java.io.IOException;

import javax.swing.Icon;

import javax.swing.ImageIcon;

import javax.swing.JComponent;

import javax.swing.TransferHandler;

import dt.TransferablePicture;

/* Transfer Handler */

class PictureTransferHandler extends TransferHandler {

public Transferable createTransferable( JComponent c ) {

PictureComponent pc = (PictureComponent)c;

return new TransferablePicture( pc.getImage() );

}

public boolean canImport( JComponent c, DataFlavor[] flavors ) {

for( DataFlavor flavor : flavors ) {

if( flavor.equals( DataFlavor.imageFlavor ) ) {

return true;

}

return false;

}

public boolean importData( JComponent c, Transferable t ) {

if( canImport(c, t.getTransferDataFlavors() ) ) {

PictureComponent pc = ( PictureComponent )c;

try {

Image image = (Image)t.getTransferData( DataFlavor.imageFlavor );

pc.setImage( image );

System.out.println( "它能接受" );

return true;

} catch( UnsupportedFlavorException e ) {

e.printStackTrace();

} catch( IOException e ) {

e.printStackTrace();

}

System.out.println( "它不能接受" );

return false;

}

public void exportDone( JComponent c, Transferable data, int action ) {

PictureComponent picture = ( PictureComponent )c;

if( action == MOVE ) {

picture.setImage( null );

}

public int getSourceActions( JComponent c ){

return COPY_OR_MOVE;

}

public Icon getVisualRepresentation( Transferable t ) {

Image image = null;

try {

System.out.println( "getVisualRepresentation" );

image = (Image)t.getTransferData( DataFlavor.imageFlavor );

} catch( Exception e ) {

e.printStackTrace();

}

return new ImageIcon( image );

}

效果如下:

2.高級D&D:利用javax.awt.dnd.*中的類實(shí)現(xiàn).
第二種實(shí)現(xiàn)方法和第一種的區(qū)別主要是在Drag Source和Drop Target上.而且這第二種實(shí)現(xiàn)方法支持所有Component及其子類上實(shí)現(xiàn)拖拽,而不止是JComponent.

Drag Target   一個(gè)對象那個(gè)如果想作為拖拽源的話，必須和五個(gè)對象建立聯(lián)系，這五個(gè)對象分別是：    * java.awt.dnd.DragSource    獲取DragSource的方法很簡單，直接調(diào)用DragSource.getDefaultDragSource()；就可以得到DragSource對象    * java.awt.dnd.DragGestureRecognizer    DragGestureRecognizer類中實(shí)現(xiàn)了一些與平臺(tái)無關(guān)的方法，我們?nèi)绻朐谧约旱慕M件上實(shí)現(xiàn)拖拽的話只要調(diào)用createDefaultDragGestureRecognizer()方法就可以了    該方法接收三個(gè)參數(shù)，建立組件和拖拽動(dòng)作之間的關(guān)系    * java.awt.dnd.DragGestureListener    當(dāng)建立了組件和拖拽動(dòng)作之間的聯(lián)系后，如果用戶執(zhí)行了拖拽操作，組件將發(fā)送一個(gè)消息給DragGestureListener監(jiān)聽器    DragGestureListener監(jiān)聽器接下來會(huì)發(fā)送一個(gè)startDrag()消息給拖拽源對象，告訴組件應(yīng)該執(zhí)行拖拽的初始化操作了    拖拽源會(huì)產(chǎn)生一個(gè)DragSourceContext對象來監(jiān)聽動(dòng)作的狀態(tài)，這個(gè)監(jiān)聽過程是通過監(jiān)聽本地方法DragSourceContextPeer來實(shí)現(xiàn)的    * java.awt.datatransfer.Transferable    * java.awt.dnd.DragSourceListener     DragSourceListener接口負(fù)責(zé)當(dāng)鼠標(biāo)拖拽對象經(jīng)過組件時(shí)的可視化處理， DragSourceListener接口的顯示結(jié)果只是暫時(shí)改變組件的外觀    同時(shí)他提供一個(gè)feedback，當(dāng)用戶的拖拽操作完成之后會(huì)收到一個(gè)dragDropEnd的消息，我們可以在這個(gè)函數(shù)中執(zhí)行相應(yīng)的操作    再來回顧一下拖拽源的建立過程 1.DragGestureRecognizer 確認(rèn)一個(gè)拖拽操作，同時(shí)告知 DragGestureListener. 2.假如actions and/or flavors are OK, DragGestureListener 讓 DragSource 調(diào)用 startDrag(). 3.DragSource建立一個(gè) DragSourceContext和一個(gè)DragSourceContextPeer. 4.DragSourceContext 把它自己作為一個(gè)DragSourceListener,偵聽DragSourceContextPeer.DragSourceContextPeer會(huì)從本地系統(tǒng)得到Coponent的狀態(tài)改變的通知(component entered/exited/is over), 并把他們代理給DragSourceContext.5.DragSourceContext通知 DragSourceListener,而DragSourceListener提供 drag over 的反饋(如果DropTargetListener接受這個(gè)動(dòng)作). 典型的反饋包括讓DrogSourceContext改變鼠標(biāo).
6.一旦drop完畢, DragSourceListener就得到一個(gè)dragDropEnd的通知消息.
Drop Source   創(chuàng)建一個(gè) droppable Component必須和下面兩個(gè)對象發(fā)生關(guān)聯(lián)       * java.awt.dnd.DropTarget    DropTarget構(gòu)造函數(shù)使DropTarget 和 DropTargetListener objects發(fā)生關(guān)聯(lián)    Droptarget對象提供 setComponent 和addDropTargetListener 兩個(gè)方法        * java.awt.dnd.DropTargetListener
    DropTargetListener需要與一個(gè)Component聯(lián)系, 以讓DropTargetListener在Component操作的時(shí)候能夠顯示”drag under”效果.
    下面的這個(gè)例子以第二種方式實(shí)現(xiàn)拖拽:
DragAndDrop.java

package dnd;

import java.awt.*;

import javax.swing.*;

import java.awt.dnd.*;

import java.awt.datatransfer.*;

import java.io.*;

import javax.swing.tree.*;

public class DragAndDrop extends JFrame {

JScrollPane jScrollPane1 = new JScrollPane();

JTextArea jTextArea1 = new JTextArea();

public DragAndDrop() {

this.getContentPane().setLayout( new BorderLayout() );

jScrollPane1.getViewport().setBackground( new Color( 105, 38, 125 ) );

jTextArea1.setBackground( Color.orange );

jTextArea1.setToolTipText( "" );

JTree jtr = new JTree();

jtr.setBackground( Color.BLUE );

jScrollPane1.getViewport().add( jtr );

this.getContentPane().add( jTextArea1, BorderLayout.PAGE_END );

this.getContentPane().add( jScrollPane1, BorderLayout.PAGE_START );

// Drag And Drop Relative.

DragSource dragSource = DragSource.getDefaultDragSource();

dragSource.createDefaultDragGestureRecognizer( jtr, DnDConstants.ACTION_COPY_OR_MOVE, new DragAndDropDragGestureListener() );

DropTarget dropTarget = new DropTarget( jTextArea1, new DragAndDropDropTargetListener() );

}

public static void main( String[] args ) {

DragAndDrop dad = new DragAndDrop();

dad.setTitle( "拖拽演示" );

dad.setSize( 400, 300 );

dad.setVisible( true );

}

DragAndDropDragGestureListener.java

package dnd;

import java.awt.dnd.DragGestureEvent;

import java.awt.dnd.DragGestureListener;

import java.awt.dnd.DragSource;

import javax.swing.JTree;

import javax.swing.tree.DefaultMutableTreeNode;

import javax.swing.tree.TreePath;

/* Drag Gesture Listener */

public class DragAndDropDragGestureListener implements DragGestureListener {

public void dragGestureRecognized( DragGestureEvent dge ) {

JTree tree = (JTree)dge.getComponent();

TreePath path = tree.getSelectionPath();

if( path != null ) {

DefaultMutableTreeNode selection = ( DefaultMutableTreeNode )path.getLastPathComponent();

DragAndDropTransferable dragAndDropTransferable = new DragAndDropTransferable( selection );

dge.startDrag( DragSource.DefaultCopyDrop, dragAndDropTransferable, new DragAndDropDragSourceListener() );

}

DragAndDropDragSourceListener.java

package dnd;

import java.awt.dnd.DnDConstants;

import java.awt.dnd.DragSource;

import java.awt.dnd.DragSourceContext;

import java.awt.dnd.DragSourceDragEvent;

import java.awt.dnd.DragSourceDropEvent;

import java.awt.dnd.DragSourceEvent;

import java.awt.dnd.DragSourceListener;

import javax.swing.JTree;

import javax.swing.tree.DefaultMutableTreeNode;

import javax.swing.tree.TreePath;

/* Drag Source Listener */

public class DragAndDropDragSourceListener implements DragSourceListener {

public void dragDropEnd( DragSourceDropEvent e ) {

if( e.getDropSuccess() ) {

int dropAction = e.getDropAction();

if( dropAction == DnDConstants.ACTION_MOVE ) {

//System.out.println( "MOVE: remove node" );

}

public void dragEnter( DragSourceDragEvent e ) {

DragSourceContext context = e.getDragSourceContext();

int dropAction = e.getDropAction();

if( ( dropAction & DnDConstants.ACTION_COPY ) != 0 ) {

context.setCursor( DragSource.DefaultCopyDrop );

} else if( ( dropAction & DnDConstants.ACTION_MOVE ) != 0 ) {

context.setCursor( DragSource.DefaultMoveDrop );

} else {

context.setCursor( DragSource.DefaultCopyNoDrop );

}

public void dragExit( DragSourceEvent e ) {}

public void dragOver( DragSourceDragEvent e ){}

public void dropActionChanged( DragSourceDragEvent e ){}

}

DragAndDropDropTargetListener.java

package dnd;

import java.awt.datatransfer.DataFlavor;

import java.awt.datatransfer.Transferable;

import java.awt.datatransfer.UnsupportedFlavorException;

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.io.IOException;

import javax.swing.JTextArea;

/* Drop Target Listener */

public class DragAndDropDropTargetListener implements DropTargetListener {

public void dragEnter( DropTargetDragEvent e ) {}

public void dragOver( DropTargetDragEvent e ) {}

public void dropActionChanged( DropTargetDragEvent e ) {}

public void dragExit( DropTargetEvent e ) {}

public void drop( DropTargetDropEvent e ) {

Transferable t = e.getTransferable();

String s = "";

try {

if( t.isDataFlavorSupported( DataFlavor.stringFlavor ) ) {

s = t.getTransferData( DataFlavor.stringFlavor ).toString();

}

} catch( IOException ioe ) {

ioe.printStackTrace();

} catch( UnsupportedFlavorException ufe ) {

ufe.printStackTrace();

}

System.out.println( s );

DropTarget dt = (DropTarget)e.getSource();

JTextArea d = ( JTextArea )dt.getComponent();

if( s != null && s.equals( "" ) == false ) {

d.append( s + " ");

}

DragAndDropTransferable.java

package dnd;

import java.awt.datatransfer.DataFlavor;

import java.awt.datatransfer.Transferable;

import java.awt.datatransfer.UnsupportedFlavorException;

import java.io.IOException;

import javax.swing.tree.DefaultMutableTreeNode;

/* Drop Transferable */

public class DragAndDropTransferable implements Transferable {

private DefaultMutableTreeNode treeNode;

public DragAndDropTransferable( DefaultMutableTreeNode treeNode ) {

this.treeNode = treeNode;

}

DataFlavor[] flavors = { DataFlavor.stringFlavor };

public DataFlavor[] getTransferDataFlavors() {

return flavors;

}

public boolean isDataFlavorSupported( DataFlavor flavor ) {

for( DataFlavor df : flavors ) {

if( df.equals( flavor ) ) {

return true;

}

return false;

}

public Object getTransferData( DataFlavor df ) throws UnsupportedFlavorException, IOException {

return treeNode;

}

效果如下:

posted on 2008-01-10 14:12 九寶閱讀(862) 評論(0) 編輯收藏所屬分類: Java

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Java中的Drag and Drop詳解與代碼示例 (轉(zhuǎn))