GenericServiceConnection.java

package vandy.mooc.common;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import android.content.ComponentName;
import android.content.ServiceConnection;
import android.os.IBinder;
import android.util.Log;

/**
 * @class GenericServiceConnection
 *
 * @brief This class provides a generic framework for defining a
 *        ServiceConnection object to an AIDLInterface that resides in
 *        a Bound Service.  It uses Java reflection to factor out
 *        common behavior that is otherwise written in a tedious and
 *        error-prone way for each ServiceConnection object.
 *
 *        Thanks to Peter Koves for providing the reflection logic!
 */
public class GenericServiceConnection<AIDLInterface extends 
                                      android.os.IInterface> 
             implements ServiceConnection {
    /**
     * The following are dependent on code generated by the AIDL
     * compiler, so if that generated code were to change (which is
     * unlikely) we'd need to update this code.
     */
    private static final String STUB = "Stub";
    private static final String AS_INTERFACE = "asInterface";
    private static final Class<?>[] AI_PARAMS = {IBinder.class};

    /**
     * Reference to the AIDL interface object after the client has
     * finished binding to the Bound Service.
     */
    private AIDLInterface mInterface;

    /**
     * The stub class of the AIDL interface.
     */
    private final Class<?> mStub;
    
    /**
     * The reflective asInterface(IBinder service) method of the stub.
     */
    private final Method mAsInterface;

    /**
     * Accessor that returns the AIDL interface object.
     */
    public AIDLInterface getInterface() {
        return mInterface;
    }
    
    /**
     * Create a Generic ServiceConnection using the specified AIDL
     * interface.
     * @param aidl the AIDL Interface class object which must match
     * the generic parameter.
     */
    public GenericServiceConnection(final Class<AIDLInterface> aidl) {
        Class<?> stub = null;
        Method method = null;
        for (final Class<?> c : aidl.getDeclaredClasses()) {
            if (c.getSimpleName().equals(STUB)) {
                try {
                    stub = c;
                    method = stub.getMethod(AS_INTERFACE,
                                            AI_PARAMS);
                    break;
                } catch (final NoSuchMethodException e) { // Should not be possible
                    e.printStackTrace();
                }
            }
        }
        mStub = stub;
        mAsInterface = method;
    }

    /**
     * Hook method called back by the Android Service framework after
     * connection is established to a Bound Service.
     */
    @SuppressWarnings("unchecked")
    @Override
    public void onServiceConnected(ComponentName name,
                                   IBinder service) {
        Log.d("GenericServiceConnection", "Connected to ComponentName " + name);
        try {
            mInterface = (AIDLInterface)mAsInterface.invoke(mStub,
                                                            new Object[]{service});
        } catch (IllegalArgumentException e) { // Should not be possible
            e.printStackTrace();
        } catch (IllegalAccessException e) { // Should not be possible
            e.printStackTrace();
        } catch (InvocationTargetException e) { // Should not be possible
            e.printStackTrace();
        }
    }

    /**
     * Called if the Bound Service crashes and is no longer
     * available. The ServiceConnection will remain bound, but the
     * Service will not respond to any requests.
     */
    @Override
    public void onServiceDisconnected(ComponentName name) {
        mInterface = null;
    }
}