Java ${Level Up}: апреля 2009

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;
}
}

воскресенье, 19 апреля 2009 г.

test syntax highlighter for blogger


public class SimpleClass {
  public SimpleClass() {
    System.out.println("I'm a simple class!!!");
  }
}

If you want the same highlighter in your blogger:
1.Install widget from here: http://fazibear.googlepages.com/blogger.html
2.Reading usage instruction(and do it:)) from here: http://code.google.com/p/syntaxhighlighter/wiki/Usage

Big thanks to developers of syntaxhighlighter.

воскресенье, 12 апреля 2009 г.

Using inner classes

Hi all! In this post I want to tell you about inner classes. Very often, we create static inner classes that contains information about main class. For example:


 public class Person { 
   private String name;
   private String occupation;
   public static class PersonInfo {
     private String info;
     public PersonInfo(String name, String occupation) {
       info = “His name is ” + name + “ . He is a ” + occupation;
   }
   public String getInfo() {
     return info;
   }
 }
 public Person(String name){
   this.name = name;
 }
 public void setOccupation(String occupation){
   this.occupation = occupation;
 }
 public String getOccupation() {
   return occupation;
 }
 public PersonInfo getInfo() {
   return new PersonInfo(name, occupation);
 }
 }

This is a good example of using inner class. It demonstrates one of the main OOP conception – encapsulation. But it has one problem. If we put this object in some model, model don't know anything about Person and if Person object will be change, model won't know about this. And now I want to show powerful feature of inner class in java – this.outer:

public class Person {

private String name;

private String occupation;

public class PersonInfo {

public PersonInfo() {}

public String getInfo() {

return “His name is ” + this.Person.name +

“ . He is a ” + this.Person.occupation;

}

public Person(String name){

this.name = name;

}

public void setOccupation(String occupation){

this.occupation = occupation;

}

public String getOccupation() {

return occupation;

}

public PersonInfo getInfo() {

return new PersonInfo();

}

Now, PersonInfo will return actually information about Person at anytime. And I shouldn't reload model that use it when Person object change. I can use feature this.superClass in anonymous class, too. Notice, that PersonInfo is not static. Actually, in first simple example PersonInfo is standalone class. In the second example, PersonInfo is in Person object.

Java ${Level Up}

вторник, 21 апреля 2009 г.

Create hyperlink with browsing support.

воскресенье, 19 апреля 2009 г.

test syntax highlighter for blogger

воскресенье, 12 апреля 2009 г.

Using inner classes

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вторник, 21 апреля 2009 г.

Create hyperlink with browsing support.

воскресенье, 19 апреля 2009 г.

test syntax highlighter for blogger

воскресенье, 12 апреля 2009 г.

Using inner classes

Most popular

Authors

вторник, 21 апреля 2009 г.

воскресенье, 19 апреля 2009 г.

воскресенье, 12 апреля 2009 г.