如何解决如何从 JEditorPane 中获取 BufferedImage？
我需要将一个 URL 加载到 JEditorPane 中，然后从 JEditorPane 中获取一个 BufferedImge，我下面的代码将为我提供一个空白/黑色图像：
import java.awt.*;
import java.awt.image.*;
import javax.imageio.*;
import javax.swing.JEditorPane;
import javax.swing.JFrame;
import javax.swing.text.html.*;
import java.io.*;
public class Html_Browser
{
public static void main(String[] args)
{
Dimension screenSize=Toolkit.getDefaultToolkit().getScreenSize();
JEditorPane editorPane=new JEditorPane();
editorPane.setEditorKit(new HTMLEditorKit());
editorPane.setEditable(false);
try
{
editorPane.setPage("https://news.yahoo.com/");
Thread.sleep(3000);
BufferedImage saveimg=new BufferedImage((int)screenSize.getWidth(),(int)screenSize.getHeight()-36,BufferedImage.TYPE_INT_RGB);
Graphics2D g2=saveimg.createGraphics();
editorPane.paint(g2);
ImageIO.write(saveimg,"png",new File("test.png"));
}
catch (Exception e)
{
editorPane.setContentType("text/html");
editorPane.setText("<html>Connection issues!</html>");
}
JFrame frame=new JFrame();
frame.getContentPane().add(editorPane);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setBounds(0,(int)screenSize.getWidth(),(int)screenSize.getHeight()-36);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}
我添加了 3 秒的延迟，但没有用，正确的做法是什么？
解决方法
您试图在渲染 GUI（包括组件）之前绘制组件，但这是行不通的。建议包括：
- 使用
SwingUtilities.invokeLater()在 Swing 事件线程上加载 GUI - 使用 SwingWorker 在后台线程中加载任何网络数据。或者在创建 Swing GUI 之前在主线程中获取网页，然后将其传递到 Swing GUI。
- 仅在网页加载且 GUI 呈现（可见）后创建图像
- 摆脱所有
Thread.sleep调用。这些不是您的朋友，只会阻碍 Swing GUI 渲染。
例如：
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.*;
public class EditorStuff extends JPanel {
private static final String URL_PATH = "https://docs.oracle.com/javase/tutorial/index.html";
private JEditorPane editorPane;
public EditorStuff(URL url) throws IOException {
int w = 800;
int h = 650;
setPreferredSize(new Dimension(w,h));
editorPane = new JEditorPane(url);
// editorPane.setPage(url);
JScrollPane scrollPane = new JScrollPane(editorPane);
setLayout(new BorderLayout());
add(scrollPane);
}
public void captureImage() throws IOException {
int w = editorPane.getWidth();
int h = editorPane.getHeight();
BufferedImage img = new BufferedImage(w,h,BufferedImage.TYPE_INT_ARGB);
Graphics2D g2 = img.createGraphics();
editorPane.paint(g2);
ImageIO.write(img,"png",new File("test.png"));
g2.dispose();
}
public static void main(String[] args) {
try {
URL url = new URL(URL_PATH);
SwingUtilities.invokeLater(() -> createAndShowGui(url));
} catch (IOException ioEx) {
ioEx.printStackTrace();
}
}
private static void createAndShowGui(final URL url) {
try {
EditorStuff mainPanel = new EditorStuff(url);
JFrame frame = new JFrame("EditorStuff");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
mainPanel.captureImage(); // called *after* rendering
} catch (IOException ioEx) {
ioEx.printStackTrace();
}
}
}
您或许可以使用这种方法。
它修改了编辑器窗格以同步读取所有文件。然后在 I/O 完成时生成一个 PropertyChanngeEvent。
import java.awt.*;
import java.awt.event.*;
import java.beans.*;
import java.io.*;
import java.net.*;
import javax.swing.*;
import javax.swing.text.*;
import javax.swing.text.html.*;
import java.awt.image.*;
public class EditorPaneLoadSynchronously extends JFrame
implements ActionListener,PropertyChangeListener
{
private JEditorPane html;
private JTextField webURL;
public EditorPaneLoadSynchronously()
{
JPanel urlPanel = new JPanel();
getContentPane().add(urlPanel,BorderLayout.NORTH);
webURL = new JTextField("https://stackoverflow.com",15);
webURL.addActionListener(this);
urlPanel.add(webURL);
JButton gotoURL = new JButton("Goto URL");
gotoURL.addActionListener(this);
urlPanel.add(gotoURL);
HTMLEditorKit editorKit = new HTMLEditorKit()
{
private final ViewFactory factory = new HTMLFactory()
{
public View create(Element elem)
{
View v = super.create(elem);
if ((v != null) && (v instanceof ImageView))
{
((ImageView)v).setLoadsSynchronously( true );
}
return v;
}
};
public ViewFactory getViewFactory()
{
return factory;
}
};
html = new JEditorPane();
// html.setEditorKit( editorKit );
// html.setEditable( false );
html.addPropertyChangeListener("page",this);
JScrollPane scrollPane = new JScrollPane(html);
scrollPane.setPreferredSize( new Dimension(400,400) );
getContentPane().add(scrollPane);
}
public void actionPerformed(ActionEvent e)
{
try
{
// html.setDocument( new HTMLDocument() );
html.setPage( new URL(webURL.getText()) );
System.out.println("After setPage");
}
catch(Exception exc)
{
System.out.println(exc);
}
}
public void propertyChange(PropertyChangeEvent e)
{
try
{
System.out.println("Page Loaded");
// BufferedImage bi = ScreenImage.createImage(html);
// ScreenImage.writeImage(bi,"sync.jpg");
}
catch(Exception ee) {}
}
private static void createAndShowGUI()
{
EditorPaneLoadSynchronously frame = new EditorPaneLoadSynchronously();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationByPlatform( true );
frame.setVisible( true );
frame.actionPerformed(null);
}
public static void main(String[] args) throws Exception
{
java.awt.EventQueue.invokeLater( () -> createAndShowGUI() );
}
}
注意：上面的代码使用了 Screen Image 便利类。您可以将其替换为您创建和编写 BufferedImage 的唯一代码。
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