使用MouseDrag方法拖動圖像

Question

我試圖編寫使用mouseDragged方法可以拖動圖像的位置，但似乎無法用我當前的代碼成功執行此操作。我的目標是確保當我將小拖放到小程序中的每個圖像上時，它都會跟隨光標。

/* Using drag mouseEvent, all objects in the app can be dragged... 
*/ 
package finals_two; 
import java.applet.*; 
import java.awt.*; 
import java.awt.event.*; 
/* 10/16/2015 
* @author michael.pabilona 
*/ 
public class Finals_Two extends Applet implements MouseMotionListener 
{ 
    int hei, wid, xCoordinate, yCoordinate; 
    Image leftReceiver1, leftReceiver2, leftReceiver3; 
    Image rightReceiver1, rightReceiver2, rightReceiver3;  
    Image leftSpiker, rightSpiker, center, setter; 

    public void init() 
    { 
     hei = getSize().height; 
     wid = getSize().width; 
     xCoordinate = hei; 
     yCoordinate = wid; 
     addMouseMotionListener(this); 
    } 

    public void mouseDragged(MouseEvent e) 
    { 
     xCoordinate = e.getX(); 
     yCoordinate = e.getY(); 
     repaint(); 
    } 

    public void paint(Graphics gr) 
    { 
     setBackground(Color.white); 
     gr.setColor(Color.black); 
     //court bound top line 
     gr.drawLine(400, 130, 1200, 130); 
     //court bound bottom line 
     gr.drawLine(200, 530, 1000, 530); 
     //court bound left line 
     gr.drawLine(400, 130, 200, 530); 
     //court bound right line 
     gr.drawLine(1000, 530, 1200, 130); 
     //net 
     gr.drawLine(800, 130, 600, 530); 
     gr.drawLine(800, 130, 800, 0); 
     gr.drawLine(600, 530, 600, 400); 
     //net horizontal lines 
     gr.drawLine(800, 0, 600, 400); 
     gr.drawLine(800, 10, 600, 410); 
     gr.drawLine(800, 20, 600, 420); 
     gr.drawLine(800, 30, 600, 430); 
     gr.drawLine(800, 40, 600, 440); 
     gr.drawLine(800, 50, 600, 450); 
     gr.drawLine(800, 60, 600, 460); 
     gr.drawLine(800, 70, 600, 470); 
     gr.drawLine(800, 80, 600, 480); 
     //net vertical lines 
     gr.drawLine(795, 5, 795, 90); 
     gr.drawLine(790, 20, 790, 100); 
     gr.drawLine(785, 30, 785, 110); 
     gr.drawLine(780, 40, 780, 120); 
     gr.drawLine(775, 50, 775, 130); 
     gr.drawLine(770, 60, 770, 140); 
     gr.drawLine(765, 70, 765, 150); 
     gr.drawLine(760, 80, 760, 160); 
     gr.drawLine(755, 90, 755, 170); 
     gr.drawLine(750, 100, 750, 180); 
     gr.drawLine(745, 110, 745, 190); 
     gr.drawLine(740, 120, 740, 200); 
     gr.drawLine(735, 130, 735, 210); 
     gr.drawLine(730, 140, 730, 220); 
     gr.drawLine(725, 150, 725, 230); 
     gr.drawLine(720, 160, 720, 240); 
     gr.drawLine(715, 170, 715, 250); 
     gr.drawLine(710, 180, 710, 260); 
     gr.drawLine(705, 190, 705, 270); 
     gr.drawLine(700, 200, 700, 280); 
     gr.drawLine(695, 210, 695, 290); 
     gr.drawLine(690, 220, 690, 300); 
     gr.drawLine(685, 230, 685, 310); 
     gr.drawLine(680, 240, 680, 320); 
     gr.drawLine(675, 250, 675, 330); 
     gr.drawLine(670, 260, 670, 340); 
     gr.drawLine(665, 270, 665, 350); 
     gr.drawLine(660, 280, 660, 360); 
     gr.drawLine(655, 290, 655, 370); 
     gr.drawLine(650, 300, 650, 380); 
     gr.drawLine(645, 310, 645, 390); 
     gr.drawLine(640, 320, 640, 400); 
     gr.drawLine(635, 330, 635, 410); 
     gr.drawLine(630, 340, 630, 420); 
     gr.drawLine(625, 350, 625, 430); 
     gr.drawLine(620, 360, 620, 440); 
     gr.drawLine(615, 370, 615, 450); 
     gr.drawLine(610, 380, 610, 460); 
     gr.drawLine(605, 390, 605, 470); 
     gr.drawLine(600, 390, 600, 480); 
     //left mid line 
     gr.drawLine(625, 130, 425, 530); 
     //right mid line 
     gr.drawLine(975, 130, 775, 530); 
     //left backend receivers 
     leftReceiver1 = getImage(getDocumentBase(),"receiver.jpg"); 
     gr.drawImage(leftReceiver1, 400, 100, 90, 90, this); 
     leftReceiver2 = getImage(getDocumentBase(),"receiver.jpg"); 
     gr.drawImage(leftReceiver2, 325, 250, 90, 90, this); 
     leftReceiver3 = getImage(getDocumentBase(),"server1.jpg"); 
     gr.drawImage(leftReceiver3, 75, 375, 150, 150, this);  
     //right backend receivers 
     rightReceiver1 = getImage(getDocumentBase(),"receiver1.jpg"); 
     gr.drawImage(rightReceiver1, 1000, 100, 100, 100, this); 
     rightReceiver2 = getImage(getDocumentBase(),"receiver1.jpg"); 
     gr.drawImage(rightReceiver2, 950, 250, 100, 100, this); 
     rightReceiver3 = getImage(getDocumentBase(),"receiver1.jpg"); 
     gr.drawImage(rightReceiver3, 900, 400, 100, 100, this); 
     //left front liners 
     leftSpiker = getImage(getDocumentBase(),"spiker.jpg"); 
     gr.drawImage(leftSpiker, 650, 30, 100, 100, this); 
     center = getImage(getDocumentBase(),"spiker.jpg"); 
     gr.drawImage(center,600,150,100,100,this); 
     setter = getImage(getDocumentBase(),"setter.jpg"); 
     gr.drawImage(setter, 500, 300, 150, 150, this); 
     //right front liners 
     rightSpiker = getImage(getDocumentBase(),"spiker1.jpg"); 
     gr.drawImage(rightSpiker,650,350,130,130,this); 
     center = getImage(getDocumentBase(),"server.jpg"); 
     gr.drawImage(center,750,150,130,130,this);   
     setter = getImage(getDocumentBase(),"defense1.jpg"); 
     gr.drawImage(setter,850,90,110,110,this); 
    } 


    @Override 
    public void mouseMoved(MouseEvent e) { 
     throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates. 
    } 


} 

這是我現在的代碼。有人能指導我失去什麼或者我在這裏做錯了什麼嗎？

Answer 1

爲了拖動任何東西，你需要知道幾件事情。你需要知道他們在哪裏和佔據的空間。

一旦你知道，你可以監視mouseDragged事件並更新它們的位置。

import java.awt.Dimension; 
import java.awt.EventQueue; 
import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.Image; 
import java.awt.Point; 
import java.awt.Rectangle; 
import java.awt.event.MouseAdapter; 
import java.awt.event.MouseEvent; 
import java.io.IOException; 
import java.util.HashMap; 
import java.util.Map; 
import javax.imageio.ImageIO; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 
import javax.swing.UIManager; 
import javax.swing.UnsupportedLookAndFeelException; 

public class DragMe { 

    public static void main(String[] args) { 
     new DragMe(); 
    } 

    public DragMe() { 
     EventQueue.invokeLater(new Runnable() { 
      @Override 
      public void run() { 
       try { 
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); 
       } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) { 
        ex.printStackTrace(); 
       } 

       JFrame frame = new JFrame("Testing"); 
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
       frame.add(new TestPane()); 
       frame.pack(); 
       frame.setLocationRelativeTo(null); 
       frame.setVisible(true); 
      } 
     }); 
    } 

    public class TestPane extends JPanel { 

     private Map<Image, Point> locations; 

     public TestPane() { 
      locations = new HashMap<>(25); 
      try { 
       locations.put(ImageIO.read(getClass().getResource("/Pony.png")), new Point(0, 0)); 
      } catch (IOException ex) { 
       ex.printStackTrace(); 
      } 

      MouseAdapter ma = new MouseAdapter() { 

       private Image dragImage; 
       private Point clickOffset; 

       @Override 
       public void mousePressed(MouseEvent e) { 
        for (Map.Entry<Image, Point> entry : locations.entrySet()) { 
         Image image = entry.getKey(); 
         Point point = entry.getValue(); 
         Rectangle bounds = new Rectangle(
             point.x, point.y, 
             image.getWidth(TestPane.this), image.getHeight(TestPane.this)); 
         if (bounds.contains(e.getPoint())) { 
          dragImage = image; 
          clickOffset = new Point(point.x - e.getPoint().x, point.y - e.getPoint().y); 
          break; 
         } 
        } 
       } 

       @Override 
       public void mouseReleased(MouseEvent e) { 
        dragImage = null; 
        clickOffset = null; 
       } 

       @Override 
       public void mouseDragged(MouseEvent e) { 
        if (dragImage != null) { 
         Point dragPoint = new Point(e.getPoint()); 
         dragPoint.x += clickOffset.x; 
         dragPoint.y += clickOffset.y; 

         locations.put(dragImage, dragPoint); 
         repaint(); 
        } 
       } 

      }; 

      addMouseListener(ma); 
      addMouseMotionListener(ma); 
     } 

     @Override 
     public Dimension getPreferredSize() { 
      return new Dimension(400, 400); 
     } 

     protected void paintComponent(Graphics g) { 
      super.paintComponent(g); 
      Graphics2D g2d = (Graphics2D) g.create(); 
      for (Map.Entry<Image, Point> entry : locations.entrySet()) { 
       Point point = entry.getValue(); 
       g2d.drawImage(entry.getKey(), point.x, point.y, this); 
      } 
      g2d.dispose(); 
     } 

    } 

}