我有一个面板,其中一些2D对象正在移动。我已经根据需要重写了paintComponent()。现在我想能够缩放该区域。缩放时,将出现滚动条,可以通过滚动查看整个区域。在缩放时,2D对象应相应地增加或减小。哪种Swing组件或组件的组合可帮助实现此目标?
最简单的方法是修改您的面板并引入一个指示您缩放级别的双倍数。这个双倍数将指示您的比例尺,其中1为正常大小,更高的数字表示缩放。您可以在paintComponent
中使用该双倍数和Graphics2D
。
例如:
Graphics2D g2 = (Graphics2D) g;
int w = // real width of canvas
int h = // real height of canvas
// Translate used to make sure scale is centered
g2.translate(w/2, h/2);
g2.scale(scale, scale);
g2.translate(-w/2, -h/2);
为了进行滚动,将您的面板放入JScrollPane中,并结合一个使用缩放比例的getPreferredSize。JScrollPane使用放置在其中的组件的首选大小。如果首选大小超过自己的大小,它将显示滚动条。
如果更改面板的首选大小,使其返回的宽度和高度被缩放,那么您就可以了。基本上,您只需返回类似于以下内容的东西:
return new Dimension(w * scale, h * scale)
addMouseWheelListener(this);
为了实现缩放,我使用了一个布尔值zoomer
(用于指示用户何时使用鼠标滚轮),以及两个双精度浮点数zoomFactor
(用于保存对象大小乘以的当前因子)和prevZoomFactor
(用于前一次缩放因子)。
private double zoomFactor = 1;
private double prevZoomFactor = 1;
private boolean zoomer;
我还重写了JPanel的paint()
方法,在此方法中(在绘制任何内容之前),如果用户缩放(zoomer
=true), 我将图形按照zoomFactor
进行缩放。代码:
@Override
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2 = (Graphics2D) g;
if (zoomer) {
AffineTransform at = new AffineTransform();
at.scale(zoomFactor, zoomFactor);
prevZoomFactor = zoomFactor;
g2.transform(at);
zoomer = false;
}
// All drawings go here
}
最后,我重写了MouseWheelListener的mouseWheelMoved方法,在该方法中,如果用户向上滚动,则增加zoomFactor;如果用户向下滚动,则减少zoomFactor。 代码如下:
@Override
public void mouseWheelMoved(MouseWheelEvent e) {
zoomer = true;
//Zoom in
if (e.getWheelRotation() < 0) {
zoomFactor *= 1.1;
repaint();
}
//Zoom out
if (e.getWheelRotation() > 0) {
zoomFactor /= 1.1;
repaint();
}
}
如果你想要使用拖动功能,并且希望根据鼠标位置进行缩放,你可以使用以下类,在构造函数中传入一个BufferedImage参数以便在屏幕上显示内容。
我还在GitHub上上传了一个名为Zoomable-Java-Panel的项目,其中有一个可运行的示例,展示了我上述所说的内容,您可以测试并了解如何将其应用到项目中。
package zoomable.panel;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.MouseInfo;
import java.awt.Point;
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.AffineTransform;
import java.awt.image.BufferedImage;
import javax.swing.JPanel;
/**
*
* @author Thanasis1101
* @version 1.0
*/
public class MainPanel extends JPanel implements MouseWheelListener, MouseListener, MouseMotionListener {
private final BufferedImage image;
private double zoomFactor = 1;
private double prevZoomFactor = 1;
private boolean zoomer;
private boolean dragger;
private boolean released;
private double xOffset = 0;
private double yOffset = 0;
private int xDiff;
private int yDiff;
private Point startPoint;
public MainPanel(BufferedImage image) {
this.image = image;
initComponent();
}
private void initComponent() {
addMouseWheelListener(this);
addMouseMotionListener(this);
addMouseListener(this);
}
@Override
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2 = (Graphics2D) g;
if (zoomer) {
AffineTransform at = new AffineTransform();
double xRel = MouseInfo.getPointerInfo().getLocation().getX() - getLocationOnScreen().getX();
double yRel = MouseInfo.getPointerInfo().getLocation().getY() - getLocationOnScreen().getY();
double zoomDiv = zoomFactor / prevZoomFactor;
xOffset = (zoomDiv) * (xOffset) + (1 - zoomDiv) * xRel;
yOffset = (zoomDiv) * (yOffset) + (1 - zoomDiv) * yRel;
at.translate(xOffset, yOffset);
at.scale(zoomFactor, zoomFactor);
prevZoomFactor = zoomFactor;
g2.transform(at);
zoomer = false;
}
if (dragger) {
AffineTransform at = new AffineTransform();
at.translate(xOffset + xDiff, yOffset + yDiff);
at.scale(zoomFactor, zoomFactor);
g2.transform(at);
if (released) {
xOffset += xDiff;
yOffset += yDiff;
dragger = false;
}
}
// All drawings go here
g2.drawImage(image, 0, 0, this);
}
@Override
public void mouseWheelMoved(MouseWheelEvent e) {
zoomer = true;
//Zoom in
if (e.getWheelRotation() < 0) {
zoomFactor *= 1.1;
repaint();
}
//Zoom out
if (e.getWheelRotation() > 0) {
zoomFactor /= 1.1;
repaint();
}
}
@Override
public void mouseDragged(MouseEvent e) {
Point curPoint = e.getLocationOnScreen();
xDiff = curPoint.x - startPoint.x;
yDiff = curPoint.y - startPoint.y;
dragger = true;
repaint();
}
@Override
public void mouseMoved(MouseEvent e) {
}
@Override
public void mouseClicked(MouseEvent e) {
}
@Override
public void mousePressed(MouseEvent e) {
released = false;
startPoint = MouseInfo.getPointerInfo().getLocation();
}
@Override
public void mouseReleased(MouseEvent e) {
released = true;
repaint();
}
@Override
public void mouseEntered(MouseEvent e) {
}
@Override
public void mouseExited(MouseEvent e) {
}
}
paint()
方法。而是应该覆盖 paintComponent()
方法。在大多数情况下,效果是相同的。但当你有一个不透明的面板或向面板添加了小部件等其他情况时,会出现问题。 - Mark Jeronimus