Android : Android : Get current activity object

Bear with me since I am noob in android coding. I want to get the current activity object in order to get it's context in a plain class which is not an activity. Using ActivityManager we can get activity in form of ComponentName. But I want the actual activity object. Any idea how shall I achieve it? Thanks.

Update

Below is the function I've written to get current activity.

private static ComponentName getCurrentTopActivity() {
    ActivityManager mActivityManager = (ActivityManager)MediWatchReceptionistApplication.getAppContext().getSystemService(Context.ACTIVITY_SERVICE);
    List<ActivityManager.RunningTaskInfo> RunningTask = mActivityManager.getRunningTasks(1);
    ActivityManager.RunningTaskInfo ar = RunningTask.get(0);
    return ar.topActivity;
}

The class which contains above function looks like this:

public class MediWatchReceptionistWebApiWrapper {

    ..................
}