nakkayadotcom

Java & OS X Integration

19 Apr 2009

Apple provides an Application class that allows you to integrate your application with the OS X environment. It allows Java applications to behave more like native OS X applications.

Handling Quit

Following snippet will install an window listener and run your clean up code before the application is exited. However when user selects Quit instead of hitting the close button, clean up code will not run.

addWindowListener(new WindowAdapter(){
       public void windowClosing(WindowEvent we){

       //do something here
       System.exit(0);
    }});

In order to handle quit menu item. Apple's Application class class provides handlers, but these classes are Apple only, so you should not try loading them when you are not OS X. So wrap them in a class and load that class only when you are on OS X and use standard window listener on other operating systems.

import com.apple.eawt.*;
import com.apple.mrj.*;

 public class MacApplication extends Application {
     public MacApplication() {
         addApplicationListener( new ApplicationAdapter(){
                 public void handleReOpenApplication(ApplicationEvent event) {

                 }
                 public void handleQuit( ApplicationEvent event ) {
                     //do something here...
                     System.exit(0);
                 }
                 public void handleAbout(ApplicationEvent event){

                 }
             });
     }
 }

Now when Quit menu item is selected your application will run your clean up code.

Hiding your application

When you close a window on a Mac OS X, application is kept running and only the window is hidden. In order for our application to act more like a native application we should also implement this. Fortunately Application class provides a handler for that too.

public void handleReOpenApplication(ApplicationEvent event) {
    mainFrame.setVisible(true);
}

Now when the dock icon is clicked your application will be visible and when closed, it will be hidden. Don't forget to set your main frame's default close operation to hide.

Knowing your OS

If you are not on OS X, you shouldn't load MacApplication class. On Mac OS X mrj.version system property is always set you can check it's value to see if you are on OS X. If it's set create your application object.

    if(System.getProperty("mrj.version") == null){
        addWindowListener(new WindowAdapter(){
                public void windowClosing(WindowEvent we){
                    //not on a mac cleanup
                    System.exit(0);
                }});
    }else{      
        MacApplication macApplication = new MacApplication();
    }

Resources

• Application (Apple Java Extensions)

Intercepting Links in Firefox

19 Apr 2009

While working on a Firefox extension i needed to intercept links Firefox is about to open and stop it on certain conditions. While it seems like an easy task it took more time then i thought due to not much information was available online. I saw the question asked multiple times with no definitive answer. Correct recipe turns out to be using a observer and listen for an "http-on-examine-response".

Following script will listen all request and you will have a chance to stop the transmission based on your rules.

var observer = {
  observe: function(subject,topic,data){

    var httpChannel = 
    subject.QueryInterface(Components.interfaces.nsIHttpChannel);
    var contentType = httpChannel.getResponseHeader("Content-Type");

    var channel = subject.QueryInterface(Components.interfaces.nsIChannel);
    var url = channel.URI.spec;
    url = url.toString();

    if ( isDownloadable( url ) == true 
         &&  contentType.indexOf("html") == -1 ){

        window.getBrowser().stop();

        download( url );
        //alert("Wait a moment!\n"+ url );
    }

    //alert("Topic sent: " + topic);
  }
};

var observerService =
    Components.classes["@mozilla.org/observer-service;1"]
    .getService(Components.interfaces.nsIObserverService);
observerService.addObserver(observer,"http-on-examine-response",false);

I am no extension guru, so maybe it is not the best way to do it but it gets the job done.