我正在尝试使用swing和java2D创建一个简单的绘图应用程序。 目的是实现平滑的缩放，始终相对于鼠标光标点。 该应用程序由两个类组成：CanvasPane和Canvas。
当矩形小于visibleRect时，画布大小等于visibleRect，我调用AffineTransform.translate跟随鼠标 （感谢this question）
当矩形变大然后画布时，画布大小也会增长并变得可滚动。然后我调用它上面的scrollRectToVisible跟随鼠标。
问题是： 如何将translate和scrollRectToVisible一起使用，以平滑缩放而无需图形跳转。可能有一些已知的决定？
我希望在YED Graph Editor中完全实现，但它的代码已关闭。 我尝试了很多例子，但只有缩放或滚动而没有复杂的使用。
完整代码如下。
Class CanvasPane：
import javax.swing.*;
import java.awt.*;
public class CanvasPane extends JPanel {
private 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.setSize(new Dimension(1000, 800));
frame.setVisible(true);
}
}
Class Canvas：
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.AffineTransform;
import java.awt.geom.NoninvertibleTransformException;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
public class Canvas extends JComponent implements MouseWheelListener, MouseMotionListener, MouseListener {
private double zoom = 1.0;
public static final double SCALE_STEP = 0.1d;
private Dimension initialSize;
private Point origin;
private double previousZoom = zoom;
AffineTransform tx = new AffineTransform();
private double scrollX = 0d;
private double scrollY = 0d;
private Rectangle2D rect = new Rectangle2D.Double(0,0, 800, 600);
public Canvas(double zoom) {
this.zoom = zoom;
addMouseWheelListener(this);
addMouseMotionListener(this);
addMouseListener(this);
setAutoscrolls(true);
}
public Dimension getInitialSize() {
return initialSize;
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
Graphics2D g2d = (Graphics2D) g.create();
g2d.clearRect(0, 0, getWidth(), getHeight());
g2d.transform(tx);
g2d.setColor(Color.DARK_GRAY);
g2d.fill(rect);
g2d.setColor(Color.GRAY);
g2d.setStroke(new BasicStroke(5.0f));
g2d.draw(rect);
g2d.dispose();
}
@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.
Rectangle realView = getVisibleRect();
Dimension d = new Dimension(
(int)(initialSize.width*zoom),
(int)(initialSize.height*zoom));
// if (d.getWidth() >= realView.getWidth() && d.getHeight() >= realView.getHeight()) {
setPreferredSize(d);
setSize(d);
validate();
followMouseOrCenter(e);
// }
//Here we calculate transform for the canvas graphics to scale relative to mouse
translate(e);
repaint();
previousZoom = zoom;
}
private void translate(MouseWheelEvent e) {
Rectangle realView = getVisibleRect();
Point2D p1 = e.getPoint();
Point2D p2 = null;
try {
p2 = tx.inverseTransform(p1, null);
} catch (NoninvertibleTransformException ex) {
ex.printStackTrace();
return;
}
Dimension d = getSize();
if (d.getWidth() <= realView.getWidth() && d.getHeight() <= realView.getHeight()) {
//Zooming and translating relative to the mouse position
tx.setToIdentity();
tx.translate(p1.getX(), p1.getY());
tx.scale(zoom, zoom);
tx.translate(-p2.getX(), -p2.getY());
} else {
//Only zooming, translate is not needed because scrollRectToVisible works;
tx.setToIdentity();
tx.scale(zoom, zoom);
}
// What to do next?
// The only translation works when rect is smaller then canvas size.
// Rect bigger then canvas must be scrollable, but relative to mouse position as before.
// But when the rect gets bigger than canvas, there is a terrible jump of a graphics.
//So there must be some combination of translation ans scroll to achieve a smooth scale.
//... brain explosion(((
}
public void followMouseOrCenter(MouseWheelEvent e) {
Point2D point = e.getPoint();
Rectangle visibleRect = getVisibleRect();
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();
Dimension size = getSize();
view.x += deltaX;
view.y += deltaY;
scrollRectToVisible(view);
}
}
public void mouseMoved(MouseEvent e) {
}
public void mouseClicked(MouseEvent e) {
}
public void mousePressed(MouseEvent e) {
origin = new Point(e.getPoint());
}
public void mouseReleased(MouseEvent e) {
}
public void mouseEntered(MouseEvent e) {
}
public void mouseExited(MouseEvent e) {
}
}
答案 0 :(得分：0)
我终于实现了启蒙=）
我们可以简单地使画布尺寸远大于绘图对象的尺寸，因此忘记计算任何难以理解的变换。
我最初使画布比绘制矩形大100倍。 然后我缩放Graphics2D并在绘画时将缩放的图形转换为画布的中心。接下来，我计算一个新的visibleRect来跟随鼠标点并滚动到它。
当canvas变得不可滚动时，跟随鼠标是不合理的，因为绘图对象太小（比初始尺寸小100倍），所以我只将它居中以便始终可见。 它完全按照我的需要工作。
因此，我们有一个工作示例，使用鼠标缩放鼠标并进行拖动。 代码如下。
CanvasPane类：
import javax.swing.*;
import java.awt.*;
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.setSize(new Dimension(1000, 800));
frame.pack();
frame.setVisible(true);
//Initial scrolling of the canvas to its center
Rectangle rect = canvas.getBounds();
Rectangle visibleRect = canvas.getVisibleRect();
double tx = (rect.getWidth() - visibleRect.getWidth())/2;
double ty = (rect.getHeight() - visibleRect.getHeight())/2;
visibleRect.setBounds((int)tx, (int)ty, visibleRect.width, visibleRect.height);
canvas.scrollRectToVisible(visibleRect);
}
}
Class Canvas：
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
public class Canvas extends JComponent implements MouseWheelListener, MouseMotionListener, MouseListener {
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 rect = new Rectangle2D.Double(0,0, 800, 600);
private float hexSize = 3f;
public Canvas(double zoom) {
this.zoom = zoom;
addMouseWheelListener(this);
addMouseMotionListener(this);
addMouseListener(this);
setAutoscrolls(true);
//Set preferred size to be 100x bigger then drawing object
//So the canvas will be scrollable until our drawing object gets 100x smaller then its natural size.
//When the drawing object became so small, it is unnecessary to follow mouse on it,
//and we only center it on the canvas
setPreferredSize(new Dimension((int)(rect.getWidth()*100), (int)(rect.getHeight()*100)));
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
//Obtain a copy of graphics object without any transforms
Graphics2D g2d = (Graphics2D) g.create();
g2d.clearRect(0, 0, getWidth(), getHeight());
//Zoom graphics
g2d.scale(zoom, zoom);
//translate graphics to be always in center of the canvas
Rectangle size = getBounds();
double tx = ((size.getWidth() - rect.getWidth() * zoom) / 2) / zoom;
double ty = ((size.getHeight() - rect.getHeight() * zoom) / 2) / zoom;
g2d.translate(tx, ty);
//Draw
g2d.setColor(Color.LIGHT_GRAY);
g2d.fill(rect);
g2d.setColor(Color.DARK_GRAY);
g2d.setStroke(new BasicStroke(5.0f));
g2d.draw(rect);
//Forget all transforms
g2d.dispose();
}
@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 mouseMoved(MouseEvent e) {
}
public void mouseClicked(MouseEvent e) {
}
public void mousePressed(MouseEvent e) {
origin = new Point(e.getPoint());
}
public void mouseReleased(MouseEvent e) {
}
public void mouseEntered(MouseEvent e) {
}
public void mouseExited(MouseEvent e) {
}
}