根据比例因子变换鼠标坐标 - java swing

Question

我的程序涉及绘制三角形，我点击它们。

有两个类，Ecad和Line类。 Ecad是主框架，Line类用于绘制线条。

import javax.swing.*; 
import java.awt.*; 
import java.awt.event.*; 
import java.util.*; 
public class Ecad extends JFrame implements MouseListener{ 
    ArrayList<Line2> lines=new ArrayList(); 
    public Ecad(){ 
     this.setVisible(true); 
     this.setSize(600,400); 
     this.addMouseListener(this); 
    } 
    public void mouseReleased(MouseEvent me){ 
     Point p1,p2,p3; 
     int X=me.getX(); 
     int Y=me.getY(); 
     p1=new Point(X,Y);              
     p2=new Point((int)(p1.getX()-100),(int)(p1.getY()+(1.732/2*200))); 
     p3=new Point((int)(p1.getX()+100),(int)(p1.getY()+(1.732/2*200)));           
     Line2 l1=new Line2(p2,p1); 
     Line2 l2=new Line2(p1,p3); 
     Line2 l3=new Line2(p2,p3); 
     lines.add(l1); 
     lines.add(l2); 
     lines.add(l3); 
     this.repaint(); 
    } 
    public void mouseClicked(MouseEvent me){ 

    } 
    public void mouseExited(MouseEvent me){ 

    } 
    public void mouseEntered(MouseEvent me){ 

    } 
    public void mousePressed(MouseEvent me){ 
    } 
    public void mouseMoved(MouseEvent me){ 

    } 
    public static void main(String args[]){ 
     new Ecad(); 
    } 
    public void paint(Graphics g){ 
     Graphics2D g2=(Graphics2D)g; 
     super.paintComponents(g2); 
     //g2.scale(0.5, 0.5); 
     for(final Line2 r:lines){ 
      r.paint((Graphics2D)g2); 
     } 
    } 
} 

这是行级

import java.awt.*; 
public class Line2 { 
    Point start,end; 
    public Line2(Point a,Point b){  
     start=a; 
     end=b; 
    } 
    public void paint(Graphics2D g){ 
     g.drawLine((int)start.getX(),(int)start.getY(),(int)end.getX(),(int)end.getY()); 
    } 

} 

在ECAD类的paint（）方法，如果我使用缩放选项来放大或缩小，鼠标坐标没有得到转化。所以在缩放之后，如果我点击某一点，三角形就会被放置在其他点上。有什么方法来改变鼠标坐标，以及当我缩放图形组件？

Answer 1

同样，你应该使用比例尺和一个固定点来转换你绘制的形状（这里似乎每个形状的固定点会是三角形的顶点，但它可能是中心应该你这样决定，翻译是基于简单的几何原则，将是fixedPoint.x *（1-scale）/ scale，并且y翻译也是一样的。

例如（并且这个使用JPanel作为你上面的例子应该）：

import javax.swing.*; 
import javax.swing.event.*; 
import java.awt.*; 
import java.awt.event.*; 
import java.awt.geom.*; 
import java.util.*; 
import java.util.List; 

class EcadB extends JPanel { 
    private static final int PREF_W = 800; 
    private static final int PREF_H = 600; 
    private List<MyShape> myShapes = new ArrayList<MyShape>(); 
    private double scale = 1.0; 
    private JSlider slider = new JSlider(0, 200, 100); 

    public EcadB() { 
     addMouseListener(new MyMouseAdapter()); 
     setLayout(new BorderLayout()); 

     slider.setOpaque(false); 
     slider.setMajorTickSpacing(20); 
     slider.setMinorTickSpacing(10); 
     slider.setPaintLabels(true); 
     slider.setPaintTicks(true); 
     slider.addChangeListener(new SliderChangeListener()); 
     add(slider, BorderLayout.SOUTH); 
    } 

    @Override 
    protected void paintComponent(Graphics g) { 
     super.paintComponent(g); 
     Graphics2D g2 = (Graphics2D) g; 
     g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, 
      RenderingHints.VALUE_ANTIALIAS_ON); 
     Graphics2D g2b = (Graphics2D)g2.create(); 
     g2b.scale(scale, scale); 
     for (MyShape myShape : myShapes) { 
     myShape.draw(g2b, scale); 
     } 
     g2b.dispose(); 
    } 

    public void setScale(double scale) { 
     this.scale = scale; 
     repaint(); 
    } 

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

    private class MyMouseAdapter extends MouseAdapter { 
     @Override 
     public void mousePressed(MouseEvent e) { 
     Point2D p1 = e.getPoint(); 
     Point2D p2 = new Point((int) (p1.getX() - 100), 
       (int) (p1.getY() + (1.732/2 * 200))); 
     Point2D p3 = new Point((int) (p1.getX() + 100), 
       (int) (p1.getY() + (1.732/2 * 200))); 
     Path2D path = new Path2D.Double(); 
     path.moveTo(p1.getX(), p1.getY()); 
     path.lineTo(p2.getX(), p2.getY()); 
     path.lineTo(p3.getX(), p3.getY()); 
     path.lineTo(p1.getX(), p1.getY()); 

     myShapes.add(new MyShape(path, p1)); 
     repaint(); 
     } 
    } 

    private class SliderChangeListener implements ChangeListener { 
     @Override 
     public void stateChanged(ChangeEvent arg0) { 
     double value = slider.getValue()/100.0; 
     setScale(value); 
     } 
    } 

    public static void main(String args[]) { 
     // new Ecad(); 
     SwingUtilities.invokeLater(new Runnable() { 
     public void run() { 
      EcadB ecadB = new EcadB(); 
      JFrame frame = new JFrame("Scale"); 
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
      frame.getContentPane().add(ecadB); 
      frame.pack(); 
      frame.setLocationRelativeTo(null); 
      frame.setVisible(true); 
     } 
     }); 
    } 
} 

class MyShape { 
    Shape shape; 
    Point2D fixedPoint; 

    public MyShape(Shape shape, Point2D fixedPoint) { 
     this.shape = shape; 
     this.fixedPoint = fixedPoint; 
    } 

    public void draw(Graphics2D g2, double scale) { 
     Graphics2D g2b = (Graphics2D) g2.create(); 
     double tx = fixedPoint.getX() * (1.0 - scale)/scale; 
     double ty = fixedPoint.getY() * (1.0 - scale)/scale; 
     g2b.translate(tx, ty); 
     g2b.draw(shape); 
     g2b.dispose(); 
    } 
} 

请注意，我转换它们之前，我的图形对象的副本，以便没有tra nsform影响可能由Graphic对象绘制的其他对象。例如，如果您摆脱了在JPanel的paintComponent(...)方法中使用的Graphics2D副本，则会发现JSlider会与其他所有内容一起缩放。