java - 优化拖动代码

Question

所以我找到了这个代码here ，它有效，只是在拖动图像时会导致图像中出现相当多的抖动(拖动速度越快，图像抖动越多)。 OP 说它没有优化，因为这是一个死帖子，我想我会看看这里是否有人可以提供帮助!我还尝试过 stack 中的代码，但我无法让它做任何事情。如果有人对此代码有任何建议或更好的解决方案，我很乐意听到!

请注意，我的 Jpanel 需要拖动(paintComponent 绘制的对象)位于滚动 Pane 内!

   //initial reference point  
   private Point mouseLocation;  
   public void mousePressed(MouseEvent evt){  
      mouseLocation = evt.getPoint();  
   }  
   public void mouseDragged(MouseEvent evt){  
      //current mouse location  
      Point newLoc = evt.getPoint();  
      //deltas  
      int deltaX = newLoc.x-mouseLocation.x;  
      int deltaY = newLoc.y-mouseLocation.y;  
      p.setLocation(p.getX()+deltaX,p.getY()+deltaY);  
      //move the reference point to the current location  
      this.mouseLocation = newLoc;  
   }  

Here是一个显示抖动的示例程序!

Answer 1

So I found this code here, it works, it just causes quite a lot of juddering

那么我会说它不起作用。如果你仔细阅读这篇文章，OP 也会指出它不起作用。

此外，该按钮并不严格跟随鼠标，所以在我看来这很糟糕。

现在，需要考虑两件事:

1. 您正在使用 evt.getPoint():该方法的值是相对于 JButton 的。当您移动 JButton 时，您无法将该方法的值与前一个方法的值进行比较(因为您的按钮正在移动)。一种简单的解决方案是将这些点相对于固定面板(例如不移动的父面板)进行转换。 Tadaam:现在工作顺利，按钮完美跟随您的鼠标。
2. 当您使用 LayoutManager 时，您不能调用 setLocation (也不能调用 setBounds 或 setSize())，因为这是 LayoutManager 的工作，一旦它们重新布局您的容器，按钮将被设置回其原始位置(我猜你不希望这样)。有多种方法可以解决此问题，但通常最简单的方法是使用绝对定位(即，将布局设置为 null)。最后，这意味着您必须自己执行 LayoutManager 之前所做的任何事情。

这是一个小演示(有缺陷，但演示了基本原理):

import java.awt.Component;
import java.awt.Point;

import javax.swing.SwingUtilities;

/**
 * 
 * @author Stuart.Bradley
 */
public class NewJFrame extends javax.swing.JFrame {
    private Point mouseLocation;

    /**
     * Creates new form NewJFrame
     */
    public NewJFrame() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form. WARNING: Do NOT modify this code. The content of this
     * method is always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {
        jButton1 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jButton1.setText("jButton1");
        jButton1.addMouseListener(new java.awt.event.MouseAdapter() {
            @Override
            public void mousePressed(java.awt.event.MouseEvent evt) {
                jButton1MousePressed(evt);
            }
        });
        jButton1.addMouseMotionListener(new java.awt.event.MouseMotionAdapter() {
            @Override
            public void mouseDragged(java.awt.event.MouseEvent evt) {
                jButton1MouseDragged(evt);
            }
        });
        setLayout(null);
        jButton1.setSize(jButton1.getPreferredSize());
        add(jButton1);
        setSize(300, 300);
    }// </editor-fold>

    private void jButton1MouseDragged(java.awt.event.MouseEvent evt) {
        // current mouse location
        Point newLoc = SwingUtilities.convertPoint(evt.getComponent(), evt.getPoint(), jButton1.getParent());
        // deltas
        int deltaX = newLoc.x - mouseLocation.x;
        int deltaY = newLoc.y - mouseLocation.y;
        jButton1.setLocation(jButton1.getX() + deltaX, jButton1.getY() + deltaY);
        // move the reference point to the current location
        this.mouseLocation = newLoc; // TODO add your handling code here:
    }

    private void jButton1MousePressed(java.awt.event.MouseEvent evt) {
        mouseLocation = SwingUtilities.convertPoint(evt.getComponent(), evt.getPoint(), jButton1.getParent()); // TODO add your
    }

    /**
     * @param args
     *            the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        // <editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /*
         * If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel. For details see
         * http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        // </editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new NewJFrame().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify
    private javax.swing.JButton jButton1;
    // End of variables declaration
}