Question

我这里的代码是使用MouseAdapter来监听用户在他们想要放大的图像区域周围“绘制”一个框，并计算框与图像的比例。然后它将图像调整为计算的比例。这部分有效。

我遇到的问题是，在调整图像大小后，JScrollPane视图看起来好像仍处于相同的左上角位置。我已经尝试了几种方法似乎已经接近我想要的结果但不完全正确。

这是侦听器，它找到比例并设置位置：

import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.Graphics;
import java.awt.Point;

import javax.swing.JScrollPane;
import javax.swing.JViewport;
import javax.swing.JComponent;

public class DynamicZoom extends MouseAdapter {

private Point start;
private Point end;
private double zoom = 1.0;
private JScrollPane pane;
private JViewport port;


public void mousePressed(MouseEvent e) {
    if(e.getButton() == MouseEvent.BUTTON1) {
        this.pane = (JScrollPane)e.getSource();
        this.port = pane.getViewport();
        start = e.getPoint();
    }
}

public void mouseReleased(MouseEvent e) {
    if(this.pane != null) {
        Point curr = this.port.getViewPosition();
        end = e.getPoint();

        ImageComponent canvas = (ImageComponent)this.port.getView();
        zoom = canvas.getScale();
        double factor = 0.0;
        double selectedWidth = Math.abs(end.getX() - start.getX());
        double selectedHeight = Math.abs(end.getY() - start.getY());
        if(selectedWidth > selectedHeight)
            factor = this.port.getWidth() / selectedWidth;
        else
            factor = this.port.getHeight() / selectedHeight;

        zoom *= factor;
        int x = (int)((start.x+curr.x)*zoom);
        int y = (int)((start.y+curr.y)*zoom);

        Point point = new Point(x, y);

        ((ImageComponent)(this.port.getView())).setScale(zoom);

        ResizeViewport.resize(pane);
        this.port.setViewPosition(point);
    }
}

public void mouseDragged(MouseEvent e) {
    if(this.pane != null) {
        Graphics g = this.port.getGraphics();
        int width = this.start.x - e.getX();
        int height = this.start.y - e.getY();

        int w = Math.abs( width );
        int h = Math.abs( height );
        int x = width < 0 ? this.start.x : e.getX();
        int y = height < 0 ? this.start.y : e.getY();
        g.drawRect(x, y, w, h);
        this.port.repaint();
    }
}

}

这是它调整大小并显示图像的ImageComponent：

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;

import javax.swing.JComponent;

public class ImageComponent extends JComponent {
private static final long serialVersionUID = 1975488835382044371L;
private BufferedImage img = null;

private double scale = 0.0;

public ImageComponent() {}

public ImageComponent(BufferedImage img) {
    this.displayPage(img);
}

@Override
public void paint(Graphics g) {
    Graphics2D g2 = ((Graphics2D)g);
    if(this.img != null) {
        int width = (int)(this.img.getWidth() * this.scale);
        int height = (int)(this.img.getHeight() * this.scale);
        this.setPreferredSize(new Dimension(width, height));
        g2.drawImage(this.img, 0, 0, width, height, null, null);
        g2.dispose();
    }
}

public void displayPage(BufferedImage pic) {
    if(img != null) {
        this.img = pic;
    }
}

public BufferedImage getPage() {
    return this.img;
}

public void setScale(double ratio) {
    if(ratio > .04) {
        this.scale = ratio;
        this.repaint();
    }
}

public double getScale() {
    return this.scale;
}
}

ResizeViewport强制视口在放大时显示整个ImageComponent，否则它将以之前的大小剪切图像：

import java.awt.Dimension;

import javax.swing.JScrollPane;
public class ResizeViewport {
public static void resize(JScrollPane scroll) {
    int vw = scroll.getWidth()-scroll.getVerticalScrollBar().getWidth();
    int vh = scroll.getHeight()-scroll.getHorizontalScrollBar().getHeight();
    scroll.getViewport().setViewSize(new Dimension(vw, vh));
}
}

Answer 1

事实证明，用于计算位置的数学或我设计代码的方式没有任何问题。问题是ImageComponent在计算位置时仍然在另一个Thread中绘制;因此返回getWidth（）和getHeight（）方法的“false”值。我使用以下代码解决了这个问题：

EventQueue.invokeLater(new Runnable() {
   public void run() {
      port.setViewPosition(new Point(x,y));
   }
});

这允许在尝试计算图像大小和在JScrollPane中设置位置之前完成绘画。问题解决了。我还是要感谢花时间至少审查这个问题的人们。

Answer 2

我遇到了类似的问题，但有时在调整大小后第一次出现错误，经过数小时试图找到解决方法之后，我找到了解决方案！

在滚动窗格中调整面板大小后，最好是通过设置为null来破坏视口，然后将面板添加回滚动窗格，这将重新创建一个新的视口，一切正常！

// Old viewport has to be replaced
scrollPane.setViewport(null);
scrollPane.setViewportView(zoomablePanel);

/安德斯

Answer 3

我遇到的问题是 JScrollPane视图看起来就像它一样仍处于同一左上角调整图像大小后。

抱歉，我不确定你在问什么。如果你澄清一点，我或许可以给出答案。

“缩放”后的JScrollPane setViewPosition

3 个答案: