вторник, 21 апреля 2009 г.

Create hyperlink with browsing support.


Yesterday, one of my tasks was to display hyperlink to local file. When user clicks hyperlink, program have to open file in an associated application. Earlier I have been writing desktop applications on QT and I haven't had any problems. But it is not very simple in Java(Swing). First, I've created label and put html as text:



JLabel label = new JLabel("<html><a href=\"someurl.com\">link</a>");


When I launched an application, I turned to be very happy because I saw hyperlink. Furthermore, my delight was anticipatory :( Label was only looking like hyperlink :(



My colleagues told me to use jdic. This is a good library, but after some time I found the solution in JDK. JDK has the class java.awt.Desktop that was introduced in the version 1.6. The desktop has static method browse(URI uri). It opens the uri in a default browser on your system. Besides, you can use static method open(File f) to open file in an associated application.



When I solved trouble with URL browsing, I back to the problem with look'n'feel - label with html has underline text, always(but need underline only when cursor on hyperlink). Also, label returned text that was containing html tags which was not very good. I had some problems to underline the text in the label. I found solution on java.sun.com



When I've solved all problems I wrote two classes. One for the look'n'feel and the other(inherited from first) for browsing URLs.




public class HyperlinkView extends JLabel {
Font srcFont;

public HyperlinkView() {
this("");
}

public HyperlinkView(String text) {
super(text);
setForeground(Color.BLUE);
setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
srcFont = HyperlinkView.this.getFont();
addMouseListener(new MouseAdapter() {
@Override
public void mouseEntered(MouseEvent e) {
Font font = HyperlinkView.this.getFont();
Hashtable<TextAttribute, Object> attributes = new Hashtable<TextAttribute, Object>();
attributes.put(TextAttribute.UNDERLINE, TextAttribute.UNDERLINE_ON);
HyperlinkView.this.setFont(font.deriveFont(attributes));
}

@Override
public void mouseExited(MouseEvent e) {
HyperlinkView.this.setFont(srcFont);
}
});
}
}



public class HyperlinkLabel extends HyperlinkView {
private String url;

public HyperlinkLabel(String text, String url) {
super(text);
this.url = url;
addMouseListener(new MouseAdapter() {
@Override
public void mouseClicked(MouseEvent e) {
super.mouseClicked(e);
try {
Desktop.getDesktop().browse(URI.create(HyperlinkLabel.this.getUrl()));
} catch (IOException e1) {
JOptionPane.showMessageDialog(HyperlinkLabel.this, "Associated application not found", "Error", JOptionPane.ERROR_MESSAGE);
}
}
});
}

public HyperlinkLabel() {
this("", null);
}

public String getUrl() {
return url == null ? "" : url;
}

public void setUrl(String url) {
this.url = url;
}
}

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