如何在Java Swing中使用鼠标平移图像 [英] How to pan an image using your mouse in Java Swing

问题描述

我正在创建一个Java应用程序，允许用户使用鼠标查看图像和平移图像。为了实现图像的平移，我使用JViewports组合使用 mouseClicked 和 mouseDragged 事件。大部分代码都在mouseDragged方法中

I am creating a Java app that will allow users to view images and to pan the image using their mouse. To implement the panning of the image I use a combination of mouseClicked and mouseDragged events using JViewports. The bulk of the code is in the mouseDragged method

public void mouseDragged(MouseEvent e, WindowWrapper w) {
    final JViewport vp = someFieldViewPort;

    //Getting the point that the mouse is dragged to to
    Point cp = e.getPoint();
    final Point vPoint = vp.getViewPosition();

    //I found the image went off the content to show the white border so I included this 
    // Here pp is a field that I sent when the mouse is clicked in a separate method

    if(vPoint.getX()+pp.x-cp.x>=0 & vPoint.getY()+pp.y-cp.y>=0)
        vPoint.translate(pp.x-cp.x, pp.y-cp.y);
    else if(vPoint.getX()+pp.x-cp.x>=0 & vPoint.getY()+pp.y-cp.y<0)
        vPoint.translate(pp.x-cp.x, (int) -vPoint.getY());
    else if(vPoint.getX()+pp.x-cp.x<0 & vPoint.getY()+pp.y-cp.y>=0)
        vPoint.translate((int) -vPoint.getX(), pp.y-cp.y);

    //finally set the position of the viewport
    vp.setViewPosition(vPoint);
    vp.repaint();
}

虽然这有效但我觉得必须有一种更简单的方法来做所有的事情这个。如果不是全部，是否可以替换防止视口从图像到周围边界的代码？

While this works I feel that there must be an easier way to do all of this. If not all of it, could the code to prevent the viewport going off the image to the surrounding border be replaced?

推荐答案

尝试使用 scrollRectToVisible（...）方法代替 JViewport #setViewPosition（...）：

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;
public class HandScrollDemo {
  static class HandScrollListener extends MouseAdapter {
    private final Point pp = new Point();
    @Override public void mouseDragged(MouseEvent e) {
      JViewport vport = (JViewport)e.getSource();
      JComponent label = (JComponent)vport.getView();
      Point cp = e.getPoint();
      Point vp = vport.getViewPosition();
      vp.translate(pp.x-cp.x, pp.y-cp.y);
      label.scrollRectToVisible(new Rectangle(vp, vport.getSize()));
      //vport.setViewPosition(vp);
      pp.setLocation(cp);
    }
    @Override public void mousePressed(MouseEvent e) {
      pp.setLocation(e.getPoint());
    }
  }
  public JComponent makeUI() {
    JLabel label = new JLabel(new Icon() {
      TexturePaint TEXTURE = makeCheckerTexture();
      @Override public void paintIcon(Component c, Graphics g, int x, int y) {
        Graphics2D g2 = (Graphics2D)g.create();
        g2.setPaint(TEXTURE);
        g2.fillRect(x,y,c.getWidth(),c.getHeight());
        g2.dispose();
      }
      @Override public int getIconWidth()  { return 2000; }
      @Override public int getIconHeight() { return 2000; }
    });
    label.setBorder(BorderFactory.createLineBorder(Color.RED, 20));
    JScrollPane scroll = new JScrollPane(label);
    JViewport vport = scroll.getViewport();
    MouseAdapter ma = new HandScrollListener();
    vport.addMouseMotionListener(ma);
    vport.addMouseListener(ma);
    return scroll;
  }
  private static TexturePaint makeCheckerTexture() {
    int cs = 20;
    int sz = cs*cs;
    BufferedImage img = new BufferedImage(sz,sz,BufferedImage.TYPE_INT_ARGB);
    Graphics2D g2 = img.createGraphics();
    g2.setPaint(Color.GRAY);
    for(int i=0; i*cs<sz; i++) { for(int j=0; j*cs<sz; j++) {
      if((i+j)%2==0) { g2.fillRect(i*cs, j*cs, cs, cs); }
    }}
    g2.dispose();
    return new TexturePaint(img, new Rectangle(0,0,sz,sz));
  }
  public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
      @Override public void run() { createAndShowGUI(); }
    });
  }
  public static void createAndShowGUI() {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    f.getContentPane().add(new HandScrollDemo().makeUI());
    f.setSize(320, 320);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
  }
}

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