Question

We are successfully runnning Apache Felix 4.0.3 on Android (2.1) and can deploy/remove Bundles at runtime. For dependeny management between OSGI Bundles we use the Felix DependenyManager.

Now we want to to send data from running OSGI Bundles to the Android GUI and display it.

How can we accomplish this task ? Is there some kind of callback we could use ?

Answer 1

Assuming that by ‘send data’, you mean interacting with the services that bundles provide, there is nothing special about this: just make sure you keep hold of the BundleContext instance that your Felix instance gives you, and use it to request services. The way you bind your data, is then totally up to you, just as it is in any other Java project.

Just showing data

As a rather contrived example, you can do something like

Map<String, Object> config = new HashMap<String, Object>();
/// make settings here, including providing the bundles to start
Felix felix = new Felix(config);

    felix.start();

BundleContext context = felix.getBundleContext();

// now get some service! Remember to do nullchecks.
ServiceReference<PackageAdmin> ref = context.getServiceReference(PackageAdmin.class);
PackageAdmin admin = context.getService(ref);
ExportedPackage[] exportedPackages = admin.getExportedPackages(felix);

// use the result to update your UI
TextView field = (TextView) findViewById(R.id.textfield);
field.setText(exportedPackages[0].getName());

to set up the framework, get some service, and put update the UI with some data.

Binding

There is no default callback you can use, but one trick I particularly like is to make UI elements aware of their OSGi environment; in that way, you can make them ‘listen’ to changes in your framework. Below is a simplified view of what I use, I prefer delegating the complicated stuff to the Apache Felix Dependency Manager.

For instance, say you have some listener interface.

public interface ClockListener {
    public void timeChanged(String newTime);
}

and you have some service that regularly calls all services that implement this interface with the current time. You can now create a TextField that updates itself every time this method is called. Something like,

public class ClockTextField extends TextView implements ClockListener {
    public ClockTextField(Context context) {
        super(context);
    }

    public void timeChanged(String newTime) {
        setText(newTime);
    }

    public void register(BundleContext bundleContext) {
        // remember to hold on to the service registration, so you can pull the service later.
        // Better yet, think about using a dependency management tool.
        bundleContext.registerService(ClockListener.class, this, null);
    }
}