Question

First off – I’m rather novice at Java so if the question makes no sense do let me know.

Basically I’m making an Android app which communicates with my web service and so I’ve made a separate class to deal with the communication, which also includes the AsyncTask (I’ve removed a lot from the code here just for preview):

public class api {

private String caller = null;
Context that = null;

api(Context that) {

    this.that = that;
    this.caller = that.getClass().getSimpleName();

}

void call(String action) {

    /* .... */

    }

    new back().execute(param1, param2);

}

void callback(String action, String result){

    that.callback(action, result);

}



public class back extends AsyncTask<String, Void, String> {

    public String response = null;

    protected String doInBackground(String... params) {

        response = connection.executeRequest(params[1]);
        return response;

    }

    protected void onPostExecute(String result) {

        callback("a", "b");                 

    }

}    


}

And when I use the class from some part of the app (let’s say SomeClass.class), I do:

api WS = new api(this);
WS.call("....");

And it’s supposed to execute the function ‘callback’ which is in SomeClass.
But the key problem here is this line:

that.callback(action, result);

Eclipse makes me add the name of the “caller” class in the cast:

(SomeClass) that.callback(action, result);

But that doesn’t work for me, because I use the ‘api’ class from many different classes, so ideally I need to put a variable in the cast. I do get the name of the “caller” class here:

this.caller = that.getClass().getSimpleName();
//obviously this won't work:
(this.caller) that.callback(action, result);

Is there anyway to do that, or am I doing something fundamentally wrong?

Thank you.

Answer 1

Currently your api class accepts a Context object in its default constructor. It would make more sense to extend Context with a new class which contains a callback method which you can then override in subclasses such as SomeClass, that would negate the need for casting in your api class. e.g:

public class APIContext extends Context
{
    public void callback( String action, String result )
    {
        /* ... */
    }
}

public class SomeClass extends APIContext
{
    @Override
    public void callback( String action, String result )
    {
        /* ... */
    }
}

public class api
{
    private APIContext callerContext = null;

    public api( APIContext context )
    {
        this.callerContext = context;
    }

    public void callback( String action, String result )
    {
        callerContext.callback( action, result );
    }
}