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Making a dynamic list of all classes in a package

Let's say I am making a list of possible items in the game. Every one of them is deriving from the class Item and all of them are placed in the specific package "com.name.app.items".
I want to make a list of them created dynamically, without adding any external information apart from the file containing the class.
I tried getting all files in a package and computing them accordingly but to no avail. Reflection simply refuses to cooperate. No matter what configuration I use, a scanner always returns an empty set.
My second thought was to to simply invoke a static method like ItemDatabase.add(this) but as far as I know it isn't possible without creating an instance of this object or calling a static method from outside.
Is there a go-to method for resolving this kind of issue? Or it is necessary to (apart from declaring the very class) notifying some registry of it's existence?

After many hours of research I finally found a suitable answer.
A simple Gradle task did the job for me as Reflections, ClassGraph etc. doesn't work very well on Android.
Bear in mind that if you would like to read what classes are available in a package on runtime - it will be a very difficult task so find another solution or prepare yourself for a long journey.

android: Changing values of constants/variables depending on the application using the activity

I am working on an AlertDialog Fragment which is supposed to pop up under certain circumstances, for example usage days of the app. I defined a constant for the current App and simply check if requirements are met before the onCreate is called like this:
if(statistics.getDays()>REQUIREMENT_VARIABLE)
{
onCreateTest=true;
}
Now I was planning to use this Activity with other applications/build variants (and change the values of the check variables for each individual app) however I was not sure how to go about checking which application is using it. Is a config xml where I define the packages in strings a good way to approach this? Thanks in advance.

I think you should define these variable in your app build.gradle specially for the build variant.
This post may help you.
Hope this helps.
Sorry for my english.

Create new java class along with your activity. Access and use that java class from another application to initialize check variables depends upon your business logic. And use those variables in the mentioned condition.

Is there anything wrong with using a public static Context? ( Regarding getResources() )

Recently I ran into a problem when trying to load an bitmap outside of my main class. I found that within my main class I could pass this as a Context to any given function allowing me to call getResources() from within that function. There are a couple of things about this which don't make sense to me.
The keyword "this" simply refers to the current object the function is running in, right? If so, how can I pass my main class as a Context by using "this"? It doesn't even have a Context in it. I am using "extends Activity", but Activity doesn't seem to contain any function called getResources() in it either.
I found a workaround which allows me to do what I want a bit easier which is to declare a public static Context appContext; within my main class. Then, within onCreate() I set appContext = this; Then, from elsewhere I can call MainActivity.appContext.getResources() whenever I need it. So, I really have a few questions here.
Why are MainActivity(my main class) and appContext not essentially the same thing when appContext is set to "this" from inside MainActivity (There is no such thing as MainActivity.getResources())
Is this unsafe to do? Could this cause any potential problems in my program?
Is there a way to load images without having to use getResources()?
What is the proper way to show my code in this website? The standard I am used to ([code][/code] tags) don't seem to work properly in the preview, so I am assuming it is handled differently here. The formatting help page says to simply use four spaces, but that doesn't seem to show any difference in the preview section either.
EDIT:
I just read in another thread somebody said
now everything depends on your main activity's onCreate method having been called.
That got me thinking. Under what circumstances would onCreate not be called? It seems like if it wasn't called the program would stop working properly in many ways not related to having a static variable initialized inside it(ie. setContentView would not be called).
So assuming that there is nothing wrong with doing it this way, the only drawback I can find, is that "MainActivity.appContext.getResources()" is a lot to type to call a function. Is there any way to create a sort of alias for this? I suppose I could create a function which simply calls that, but that just seems silly.

If you look here you see that activity is a subclass of Context.
You can format code with a backtic, or just use the {} buttons on the editor. See the markdown manual for more info.

Java API Question

I am trying to implement a custom Java widget using GWT.This requires me to copy a class from the GWT API and pasting it in my own new Class.(I am not sure if this is a right approach.Suggest me if its wrong to copy the API in my new class).The reason why i am doing this is i need to make modifications to the API,because the API does not provide me getter/setter's for a object.
But the problem with this is ,the API class uses many methods which have the protected access modifier.So when i paste this code in my package ,these methods are not recognized.I cannot even think of making my class a sub class (a workaround for protected access modifier) as the methods are from different classes and i cannot make my class a sub class of more than one class.
Can any one suggest me a work around for this scenario.I am trying to implement a widget whose functionality is similar to the browser's navigation widget(the place where we enter a website's url).Its similar to combining the functionality of ListBox+SuggestBox.
This is my previous question.That is what i am trying to implement.
Thanks

Derive a new widget by extending from Composite and then implement whatever functionality you need within that. e.g. If you need a ListBox to make suggestions then create one from inside your Composite and hook up whatever listeners you need to on the inner widget to drive suggestions.
A sample of a Composite widget is shown here.
There shouldn't be any reason to have to copy & paste existing source code. Indeed doing so is not going to get you far since most widgets in GWT are just wrappers HTML elements anyway with some plumbing to hook up to the event model.

It would really help if you provided some sample code, you should never have to copy and paste code from the API. What are you trying to extend and what variables within that class do you need access to and to do what? Usually there is a reason why variables are private and thats because messing with them will cause a break in functionality.

Alternatives to static variables in Android

I am using static Arrays and HashMaps to store some values in my AppWidgetProvider class. But they are becoming null when the process dies, so the widget does not work anymore. Are there any alternatives to using static members to store data for an AppWidgetProvider in Android?

The "correct" way to do what you're doing (I believe) would be SharedPreferences. The Android dev guide has a great page on the different methods of Data Storage in Android. Also, try not to use too many static values; perhaps what you're doing would be better accomplished with singleton classes, though, from the question, it's hard to tell what you're using them for.

Have you checked out Typed Array Resources?
Resource Types in the Android Dev Guide

You can write an object to a file .Define class and fill it with required values at run time use objectwriter to save it