如何在 Java 的缩放面板中操作形状？答案

【问题标题】：How do I manipulate shapes within a zoomed panel in Java?如何在 Java 的缩放面板中操作形状？
【发布时间】：2020-08-30 15:23:33
【问题描述】：

我在互联网上找到了一些代码，可以让我控制 Java 中可滚动面板的缩放和平移，但我希望能够操纵该区域内的形状，并且无法将 x 和 y 坐标转换回原始（未缩放）尺寸..

我想对这些形状做一些事情，但首先，当鼠标在其中移动时，如何将两个实体矩形涂成红色？

这是我目前的代码：

import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;

import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;

public class CanvasPane extends JPanel {

    private static Canvas canvas;

    public CanvasPane(boolean isDoubleBuffered) {
        super(isDoubleBuffered);
        setLayout(new BorderLayout());
        canvas = new Canvas(1.0);
        JScrollPane pane = new JScrollPane(canvas);
        pane.getViewport().setBackground(Color.DARK_GRAY);
        add(pane, BorderLayout.CENTER);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Test Graphics");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new BorderLayout());
        frame.add(new CanvasPane(true), BorderLayout.CENTER);
        frame.pack();
  
        frame.setSize(800, 600);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

        //Initial scrolling of the canvas to its center
        Rectangle canvasRectangle = canvas.getBounds();
        Rectangle visibleRectangle = canvas.getVisibleRect();
        double tx = (canvasRectangle.getWidth() - visibleRectangle.getWidth())/2;
        double ty = (canvasRectangle.getHeight() - visibleRectangle.getHeight())/2;
        visibleRectangle.setBounds((int)tx, (int)ty, visibleRectangle.width, visibleRectangle.height);
        canvas.scrollRectToVisible(visibleRectangle);
    }
}

class Canvas extends JComponent implements MouseWheelListener, MouseMotionListener, MouseListener {

    private static final long serialVersionUID = 1L;
    private double zoom = 1.0;
    public static final double SCALE_STEP = 0.1d;
    private Dimension initialSize;
    private Point origin;
    private double previousZoom = zoom;
    private double scrollX = 0d;
    private double scrollY = 0d;
    private Rectangle2D workspace = new Rectangle2D.Double(0,0, 1024, 768);
    
    private Rectangle entity1 = new Rectangle(10, 10, 100, 100);
    private Rectangle entity2 = new Rectangle(300, 300, 100, 100);

    public Canvas(double zoom) {
        this.zoom = zoom;
        addMouseWheelListener(this);
        addMouseMotionListener(this);
        addMouseListener(this);
        setAutoscrolls(true);
        setPreferredSize(new Dimension((int)workspace.getWidth(), (int)workspace.getHeight()));
    }

    @Override public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;

        //Zoom graphics
        g2d.scale(zoom, zoom);

        //translate graphics to be always in center of the canvas
        Rectangle size = getBounds();
        double tx = ((size.getWidth() - workspace.getWidth() * zoom) / 2) / zoom;
        double ty = ((size.getHeight() - workspace.getHeight() * zoom) / 2) / zoom;
        g2d.translate(tx, ty);

        //Draw
        g2d.setColor(Color.LIGHT_GRAY);
        g2d.fill(workspace);
                       
        g2d.setColor(Color.DARK_GRAY);
        g2d.setStroke(new BasicStroke(5.0f));
        g2d.draw(workspace);
        
        g2d.draw(entity1);
        g2d.draw(entity2);        
    }

    @Override public void setSize(Dimension size) {
        super.setSize(size);
        if (initialSize == null) {
            this.initialSize = size;
        }
    }

    @Override public void setPreferredSize(Dimension preferredSize) {
        super.setPreferredSize(preferredSize);
        if (initialSize == null) {
            this.initialSize = preferredSize;
        }
    }

    public void mouseWheelMoved(MouseWheelEvent e) {
        double zoomFactor = -SCALE_STEP * e.getPreciseWheelRotation() * zoom;
        zoom = Math.abs(zoom + zoomFactor);
        
        //Here we calculate new size of canvas relative to zoom.
        Dimension d = new Dimension(
                (int)(initialSize.width * zoom),
                (int)(initialSize.height * zoom));
            setPreferredSize(d);
            setSize(d);
            validate();
        followMouseOrCenter(e.getPoint());
        previousZoom = zoom;
    }

    public void followMouseOrCenter(Point2D point) {
        Rectangle size = getBounds();
        Rectangle visibleRect = getVisibleRect();
        scrollX = size.getCenterX();
        scrollY = size.getCenterY();
        
        if (point != null) {
            scrollX = point.getX() / previousZoom * zoom - (point.getX() - visibleRect.getX());
            scrollY = point.getY() / previousZoom * zoom - (point.getY() - visibleRect.getY());
        }

        visibleRect.setRect(scrollX, scrollY, visibleRect.getWidth(), visibleRect.getHeight());
        scrollRectToVisible(visibleRect);
    }

    public void mouseDragged(MouseEvent e) {
        if (origin != null) {
            int deltaX = origin.x - e.getX();
            int deltaY = origin.y - e.getY();
            Rectangle view = getVisibleRect();
            view.x += deltaX;
            view.y += deltaY;
            scrollRectToVisible(view);
        }
    }

    public void mousePressed(MouseEvent e) {
        origin = new Point(e.getPoint());
    }
       
    public void mouseMoved(MouseEvent e) {


    }
    
    public void mouseClicked(MouseEvent e) {}
    public void mouseReleased(MouseEvent e) {}
    public void mouseEntered(MouseEvent e) {}
    public void mouseExited(MouseEvent e) {}
}

我尝试使用以下代码进行计算，但这不太正确

public void mouseMoved(MouseEvent e) {

    double x = e.getX() / zoom;
    double y = e.getY() / zoom;

    double x2 = getWidth() - workspace.getWidth() * zoom; 
    double y2 = getHeight() - workspace.getHeight() * zoom; 
    
    if(x2 > 0) x -= x2;
    if(y2 > 0) y -= y2;
    
    Point p = new Point((int)x, (int)y);
    
    if(entity1.contains(p)) {
        intersects = true;
    } 
    else {
        intersects = false;
    }       
    repaint();
}

【问题讨论】：

但是首先，当鼠标在其中移动时，如何将两个实体矩形涂成红色？ - 首先你需要稍微重构一下你的代码。 1）您需要保留要绘制的对象的 ArrayList。 2) ArrayList 中的对象需要有关要绘制的形状和要绘制的颜色的信息。然后您的 paintComponent() 方法将遍历 ArrayList 并绘制每个对象。参见Custom Painting Approaches 中的DrawOnComponent 示例。
一个被改变的。然后，您将能够使用 ArrayLIst 来确定鼠标何时移到某个形状上。首先，您需要通过缩放因子调整鼠标点，然后您将遍历 ArrayList 以找到包含鼠标点的 Shape。然后你改变颜色并重新绘制。
如果我不进行缩放，那就可以了……但是一旦我缩放，它就不再起作用了……我尝试使用缩放值进行多重处理，但这也不起作用……我猜我需要在 MouseMove 方法中做这个翻译，但不确定计算
我不敢相信您在 6 分钟内完成了所有这些建议的更改。在那 6 分钟内你做了什么调试？也许您需要除以缩放因子？查看您计算的值，看看它们是否有意义？
我放了一个“CLICK”打印语句，如下所示： public void mouseMoved(MouseEvent e) { if(entity1.contains(e.getPoint())) { System.out.println("CLICK" ); } else { System.out.println("MISS"); } } 我会尝试分割....

标签： java swing scroll graphics mouseover

【解决方案1】：

这似乎效果更好，但我不确定它是否是最干净的解决方案......

public void mouseMoved(MouseEvent e) {

    double x = e.getX() / zoom;
    double y = e.getY() / zoom;

//  double x2 = getWidth() - workspace.getWidth() * zoom; 
//  double y2 = getHeight() - workspace.getHeight() * zoom; 
        
    double x2 = ((getWidth() - workspace.getWidth() * zoom) / 2) / zoom;
    double y2 = ((getHeight() - workspace.getHeight() * zoom) / 2) / zoom;

    
    
    if(x2 > 0) x -= x2;
    if(y2 > 0) y -= y2;
    
    Point p = new Point((int)x, (int)y);
    
    if(entity1.contains(p)) {
        intersects = true;
    } 
    else {
        intersects = false;
    }       
    repaint();
}

【讨论】：