我正在尝试在JScrollPane中编码可缩放图像.
当图像完全缩小时,它应该水平和垂直居中.当两个滚动条都出现时,变焦应该总是相对于鼠标坐标发生,即图像的相同点应该在缩放事件之前和之后的鼠标下面.
我几乎实现了我的目标.不幸的是,“scrollPane.getViewport().setViewPosition()”方法有时无法正确更新视图位置.在大多数情况下,调用该方法两次(黑客！)克服了这个问题,但视图仍然闪烁.
我没有解释为什么会这样.但是我相信这不是数学问题.
以下是MWE.要查看我的问题,您可以执行以下操作：
>放大直到你有一些滚动条(200％变焦左右)
>单击滚动条滚动到右下角
>将鼠标放在角落并放大两次.第二次你会看到滚动位置如何向中心跳跃.
如果有人能告诉我问题所在,我真的很感激.谢谢！
package com.vitco;
import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseWheelEvent;
import java.awt.image.BufferedImage;
import java.util.Random;
/**
* Zoom-able scroll panel test case
*/
public class ZoomScrollPanel {
// the size of our image
private final static int IMAGE_SIZE = 600;
// create an image to display
private BufferedImage getImage() {
BufferedImage image = new BufferedImage(IMAGE_SIZE,IMAGE_SIZE,BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
// draw the small pixel first
Random rand = new Random();
for (int x = 0; x < IMAGE_SIZE; x += 10) {
for (int y = 0; y < IMAGE_SIZE; y += 10) {
g.setColor(new Color(rand.nextInt(255),rand.nextInt(255),rand.nextInt(255)));
g.fillRect(x,y,10,10);
}
}
// draw the larger transparent pixel second
for (int x = 0; x < IMAGE_SIZE; x += 100) {
for (int y = 0; y < IMAGE_SIZE; y += 100) {
g.setColor(new Color(rand.nextInt(255),180));
g.fillRect(x,100,100);
}
}
return image;
}
// the image panel that resizes according to zoom level
private class ImagePanel extends JPanel {
private final BufferedImage image = getImage();
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g.create();
g2.scale(scale,scale);
g2.drawImage(image,null);
g2.dispose();
}
@Override
public Dimension getPreferredSize() {
return new Dimension((int)Math.round(IMAGE_SIZE * scale),(int)Math.round(IMAGE_SIZE * scale));
}
}
// the current zoom level (100 means the image is shown in original size)
private double zoom = 100;
// the current scale (scale = zoom/100)
private double scale = 1;
// the last seen scale
private double lastScale = 1;
public void alignViewPort(Point mousePosition) {
// if the scale didn't change there is nothing we should do
if (scale != lastScale) {
// compute the factor by that the image zoom has changed
double scaleChange = scale / lastScale;
// compute the scaled mouse position
Point scaledMousePosition = new Point(
(int)Math.round(mousePosition.x * scaleChange),(int)Math.round(mousePosition.y * scaleChange)
);
// retrieve the current viewport position
Point viewportPosition = scrollPane.getViewport().getViewPosition();
// compute the new viewport position
Point newViewportPosition = new Point(
viewportPosition.x + scaledMousePosition.x - mousePosition.x,viewportPosition.y + scaledMousePosition.y - mousePosition.y
);
// update the viewport position
// IMPORTANT: This call doesn't always update the viewport position. If the call is made twice
// it works correctly. However the screen still "flickers".
scrollPane.getViewport().setViewPosition(newViewportPosition);
// debug
if (!newViewportPosition.equals(scrollPane.getViewport().getViewPosition())) {
System.out.println("Error: " + newViewportPosition + " != " + scrollPane.getViewport().getViewPosition());
}
// remember the last scale
lastScale = scale;
}
}
// reference to the scroll pane container
private final JScrollPane scrollPane;
// constructor
public ZoomScrollPanel() {
// initialize the frame
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setSize(600,600);
// initialize the components
final ImagePanel imagePanel = new ImagePanel();
final JPanel centerPanel = new JPanel();
centerPanel.setLayout(new GridBagLayout());
centerPanel.add(imagePanel);
scrollPane = new JScrollPane(centerPanel);
scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);
frame.add(scrollPane);
// add mouse wheel listener
imagePanel.addMouseWheelListener(new MouseAdapter() {
@Override
public void mouseWheelMoved(MouseWheelEvent e) {
super.mouseWheelMoved(e);
// check the rotation of the mousewheel
int rotation = e.getWheelRotation();
boolean zoomed = false;
if (rotation > 0) {
// only zoom out until no scrollbars are visible
if (scrollPane.getHeight() < imagePanel.getPreferredSize().getHeight() ||
scrollPane.getWidth() < imagePanel.getPreferredSize().getWidth()) {
zoom = zoom / 1.3;
zoomed = true;
}
} else {
// zoom in until maximum zoom size is reached
double newCurrentZoom = zoom * 1.3;
if (newCurrentZoom < 1000) { // 1000 ~ 10 times zoom
zoom = newCurrentZoom;
zoomed = true;
}
}
// check if a zoom happened
if (zoomed) {
// compute the scale
scale = (float) (zoom / 100f);
// align our viewport
alignViewPort(e.getPoint());
// invalidate and repaint to update components
imagePanel.revalidate();
scrollPane.repaint();
}
}
});
// display our frame
frame.setVisible(true);
}
// the main method
public static void main(String[] args) {
new ZoomScrollPanel();
}
}
注意：我也在这里查看了JScrollPane setViewPosition After “Zoom”的问题,但不幸的是问题和解决方案略有不同,不适用.
编辑
我已经通过使用hack解决了这个问题,但是我仍然没有更接近理解底层问题是什么.发生的事情是,当调用setViewPosition时,某些内部状态更改会触发对setViewPosition的其他调用.这些额外的呼叫偶尔会发生.当我阻止它们时,一切都很完美.
为了解决这个问题,我简单介绍了一个新的布尔变量“blocked = false;”并替换了线
scrollPane = new JScrollPane(centerPanel);
和
scrollPane.getViewport().setViewPosition(newViewportPosition);
同
scrollPane = new JScrollPane();
scrollPane.setViewport(new JViewport() {
private boolean inCall = false;
@Override
public void setViewPosition(Point pos) {
if (!inCall || !blocked) {
inCall = true;
super.setViewPosition(pos);
inCall = false;
}
}
});
scrollPane.getViewport().add(centerPanel);
和
blocked = true;
scrollPane.getViewport().setViewPosition(newViewportPosition);
blocked = false;
如果有人能理解这一点,我仍然会非常感激！
为什么这个黑客工作？有没有更简洁的方法来实现相同的功能？
解决方法
这是完整的,功能齐全的代码.我仍然不明白为什么黑客是必要的,但至少它现在按预期工作：
import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseWheelEvent;
import java.awt.image.BufferedImage;
import java.util.Random;
/**
* Zoom-able scroll panel
*/
public class ZoomScrollPanel {
// the size of our image
private final static int IMAGE_SIZE = 600;
// create an image to display
private BufferedImage getImage() {
BufferedImage image = new BufferedImage(IMAGE_SIZE,(int)Math.round(IMAGE_SIZE * scale));
}
}
// the current zoom level (100 means the image is shown in original size)
private double zoom = 100;
// the current scale (scale = zoom/100)
private double scale = 1;
// the last seen scale
private double lastScale = 1;
// true if currently executing setViewPosition
private boolean blocked = false;
public void alignViewPort(Point mousePosition) {
// if the scale didn't change there is nothing we should do
if (scale != lastScale) {
// compute the factor by that the image zoom has changed
double scaleChange = scale / lastScale;
// compute the scaled mouse position
Point scaledMousePosition = new Point(
(int)Math.round(mousePosition.x * scaleChange),viewportPosition.y + scaledMousePosition.y - mousePosition.y
);
// update the viewport position
blocked = true;
scrollPane.getViewport().setViewPosition(newViewportPosition);
blocked = false;
// remember the last scale
lastScale = scale;
}
}
// reference to the scroll pane container
private final JScrollPane scrollPane;
// constructor
public ZoomScrollPanel() {
// initialize the frame
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setSize(600,600);
// initialize the components
final ImagePanel imagePanel = new ImagePanel();
final JPanel centerPanel = new JPanel();
centerPanel.setLayout(new GridBagLayout());
centerPanel.add(imagePanel);
scrollPane = new JScrollPane();
scrollPane.setViewport(new JViewport() {
private boolean inCall = false;
@Override
public void setViewPosition(Point pos) {
if (!inCall || !blocked) {
inCall = true;
super.setViewPosition(pos);
inCall = false;
}
}
});
scrollPane.getViewport().add(centerPanel);
scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);
frame.add(scrollPane);
// add mouse wheel listener
imagePanel.addMouseWheelListener(new MouseAdapter() {
@Override
public void mouseWheelMoved(MouseWheelEvent e) {
super.mouseWheelMoved(e);
// check the rotation of the mousewheel
int rotation = e.getWheelRotation();
boolean zoomed = false;
if (rotation > 0) {
// only zoom out until no scrollbars are visible
if (scrollPane.getHeight() < imagePanel.getPreferredSize().getHeight() ||
scrollPane.getWidth() < imagePanel.getPreferredSize().getWidth()) {
zoom = zoom / 1.3;
zoomed = true;
}
} else {
// zoom in until maximum zoom size is reached
double newCurrentZoom = zoom * 1.3;
if (newCurrentZoom < 1000) { // 1000 ~ 10 times zoom
zoom = newCurrentZoom;
zoomed = true;
}
}
// check if a zoom happened
if (zoomed) {
// compute the scale
scale = (float) (zoom / 100f);
// align our viewport
alignViewPort(e.getPoint());
// invalidate and repaint to update components
imagePanel.revalidate();
scrollPane.repaint();
}
}
});
// display our frame
frame.setVisible(true);
}
// the main method
public static void main(String[] args) {
new ZoomScrollPanel();
}
}
版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 dio@foxmail.com 举报，一经查实，本站将立刻删除。