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Android app with weak reference and singleton

I'm in the process of completely redesigning my Android app. Before, EVERYTHING was in the same class.
So I tried to redraw everything so that the code is clearer apart Admob than the doc advice to put in the Main thread, I separate the different part of my code in class. So I used two technique: I created a songleton that contains variables that I want to have access to constantly,and I call my classes via weak reference.
Here is what it looks like:
For example, the UIManager class that needs to update the game's IU have a weak reference looks like this:
private static SoftReference<UIManager> ManageUI;
static{ManageUI= new SoftReference<>(null);}
static UIManager get()
{
if(ManageUI.get()==null)
{
ManageUI= new SoftReference<>(new UIManager());
}
return ManageUI.get();
}
GameManager Manager=GameManager.getInstance();
to be able to use the findviewbyid for example I place in method argument the main class that is the mainthread
the singleton that contains all my variables that I want to have permanent access to looks like this:
private GameManager()
{}
/** Holder */
private static class Manager
{
/** Instance unique non préinitialisée */
private final static GameManager instance = new GameManager();
}
/** Point d'accès pour l'instance unique du singleton */
public static GameManager getInstance()
{
return Manager.instance;
}
To separate all in different class, I pass argument to my method so I can call au stuff belong to Activity like that:
(My main class is called GamePlay)
void OpenGlobalScene(GamePlay activity)
{
Manager.OnTitle=false;
if (!checkLayout(activity,R.id.globalscene)) {
LayoutInflater(activity,9, true);
LinearLayout GamePlan = (LinearLayout) activity.findViewById(R.id.globalscene);
GamePlan.setAlpha(Manager.AlphaBord);
}
}
For now, I have not noticed any problems except a few slownesses on old android phone 4.4.2.
Also compared to my old code were EVERYTHING was in the same class, it's much easier to change pieces of code (going to the inapp billing V3 was simpler since everything was in one class that I call like the others with weak referencre)
My questions are:
-What are the problems that such a structure might pose?
I had also chosen that structure to not load or leave in memory things that are not useful
-How are chance that Android will erase from memory an action in progress called with weak reference?
-As you can see I pass the activity has argument to the method, sometimes I pass it from a method to another. Is that fact can cause some trouble?
Thank you for your help.

Check Dagger2 is better than the clasic singleton https://developer.android.com/training/dependency-injection/dagger-android?hl=es-419

thanks for your answer and your tips. I'am gonna check this out.
Anyone else know something about consequences on memory when using weak references ?

strings.xml on MVPand clean architecture

I'm developing an android app implementing MVP and clean architecture. I have the following scenario:
One core module with presenters and view interfaces,...
One domain module with repositories, data sources,..
App module with the core implementation (so the Fragment/Activities).
Currently the strings.xml file is in the app module, but I'm thinking whether it should be in a commons module or not. The problem is that, sometimes, the presenter must set the text to the view, so the presenter should need to access to the strings.xml. I've thought in two possible solutions:
1) Create a TextHelper interface on core module that will be implemented on the app module and injected to the presenter, so the presenter will use this helper to get the strings it requires. (This is the solution I have implemented).
2) Move the strings.xml file to a common module so the file can be accessed from core module. But this solution would have a problem: the presenter doesn't have a context.
What do you think? What is the best approach?
Thanks in advance

If your view has nested if/elses related to strings, then they should probably be unit-tested. Therefore, that logic should stay in presenters or use-cases, where can be tested more quickly.
Your question is about how to retrieve the actual strings, given that they reside in the "outer layers" of the Clean Architecture scheme, i.e. in the Context object. IMHO your TextHelper is the right approach, as it allows to inject a mock when writing unit tests: you're interested in how the strings are processed, rather than how the strings actually look. I'm trying a very similar approach and calling it StringsRepository.
A point of uncertainty is how the the repository API should look like:
A single method like getString(#StringRes int stringResId, Object... formatArgs) that simply wraps Context.getString(): very simple to implement, but will make the presenters depend on your R.string class, which in turns requires strings.xml to be in the same module as your code under test;
One method per string with optional arguments, each one containing the reference to the appropriate string ID. This solution allows for best abstraction, but may become big (both the interface and the implementation...) and many domain classes may depend upon it. Handle with care.
Like (2), but with several classes, one per each part of your app. Each class may have a base class similar to (1) but with that method with protected visibility.
The best options for your case would be (2) or (3), but your mileage may vary.

You can use Application class to get the context any where from the app.
public class MVPApplication extends Application {
private static Context context;
public static Context getContext() {
return context;
}
#Override
public void onCreate() {
super.onCreate();
context = getApplicationContext();
}
}

What does 'this' mean as a parameter in Android SDK? [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
What is the meaning of “this” in Java?
I'm still very new to learning Android programming, and I noticed that "this" was used often in parameters for method calls in the language. I'm following The New Boston tutorials through YouTube, but he never really explains quite detailed enough what the 'this' statement means. Can somebody please explain it to me? Maybe dumb it down a bit?

this refers to the instance of the class you are currently coding within.
You cannot use it in a static context because in this situation you are not within any object context. Therefore this doesn't exist.
public class MyClass {
public void myMethod(){
this.otherMethod(); // Here you don't need to use 'this' but it shows the concept
}
private void otherMethod(){
}
public static void myStaticMethod(){
// here you cant use 'this' as static methods don't have an instance of a class to refer to
}
}

In android class.this is used to pass context around.
Formal definition of context: It allows access to application-specific resources and classes, as well as up-calls for application-level operations such as launching activities.
That means if you need to access resources (including R and user interface) you will have to use context.
In java this means the instance of the class that you are in. For example MainActivity.this points to the current instance of the MainActivity. So by using MainActivity.this.foo you are accessing the foo field of MainActivity class.

public class YourClass {
private int YourInt;
public setTheInt(int YourInt) {
this.YourInt = YourInt;
}
}
"this" is used to see whether an attribute or function belongs to the class we're working on, clearer.
Also, you see that setTheInt operation gets an integer named as the same as your attribute. In that function's namespace, YourInt is not this class's YourInt, but a reflection of the integer coming from setTheInt's calls. "this" helps here to divide the outer and the inner "YourInt"s.

Is it possible to get application's context in an Android Library Project?

I would like to get the context of application which has reference/hosted my library at run-time inside one class of my library project. Is it possible? If yes, how?
Thanks
Update
I don't want my user to pass context in parameter to my library project because it is possible that my library project will be called through JNI and I have no idea how I can get context in JNI and pass it to Java layer.

There is one more way, add application class in your library project:
/**
* Base class for those who need to maintain global application state.
*/
public class LibApp extends Application {
/** Instance of the current application. */
private static LibApp instance;
/**
* Constructor.
*/
public LibApp() {
instance = this;
}
/**
* Gets the application context.
*
* #return the application context
*/
public static Context getContext() {
return instance;
}
}
Then in your regular project make the real application class extend LibApp:
/**
* Base class for those who need to maintain global application state.
*/
public class App extends LibApp {
#Override
public void onCreate() {
super.onCreate();
}
}
Make sure that you have "Name" defined in AndroidManifest:
<application android:name="App" ...>
and that your App class is in the base package.
You can then use LibApp.getContext() your library project to get the application context of the application that is using the library.
This may not be good solution but it works for me.
I am sharing it because it might be useful to somebody else.

Is it possible?
Yes.
If yes, how?
Pass it in as a parameter.
I don't want my user to pass context in parameter to my library project because it is possible that my library project will be called through JNI and I have no idea how I can get context in JNI and pass it to Java layer.
Then figure out "how [you] can get context in JNI and pass it to Java layer". I would imagine that you would pass it like any other object. As #Blundell noted, you do not really have any other option.

There's another way to get context in jni, neither passing a parameter nor saving context by yourself, but by using android api.
I found that there's a class named:
android.app.AppGlobals
in the source code. And the static function
getInitialApplication
can return an Application object. But it must be called in main thread, and the class is hidden.
Anyway you can use it by reflecting in java. And you can just use FindClass() and FindStaticObjectMethod() to find out the method, and use it.
Hope that helps.

According to this post you can let the library auto-initialize itself with the application context by the aid of a ContentProvider.
Be careful anyway, as described in the post comments, there may be drawbacks concerning loading time and instant run, as well as crashes on multi-process apps.
HTH

I would pass it as a parameter or pass it a singleton in that library.
Having the main app application extend the library's application class is a bad idea coz in java you can only extend once from a class. If your application requires to pass to another library you will be in trouble.

How to use Android's getString() without violating basic OOD principles?

I need to use getString() from most of the modules in my application.
But for some strange reason, it is tied to Application or Context, so that means I need to pass to each and every class in my application, the Application reference as a parameter.
This clearly violates one of the most basic principles of object oriented design.
Is there a way around this?

The 'strange reason' is that since the string resources are tied to your application, there is no way to access them without some sort of handle to it (the Context). If most of your classes that are not activities need to access string resources, you might want to rethink your design a bit. A simple way to not depend on a Context is to load the strings and pass them to your classes in the constructor.

Yes, there is a workaround - if you happen to (or can) pass a View (any View-derived class) to the constructor, and you assign it to a data member, then you can access the string resources from anywhere in your class:
String str_via_res = yourView.getContext().getString(R.string.str_via_res);
Otherwise, you will have to pass a Context to every class that needs access to these string resources.

you can extend android.app.Application class to create a static method to pass on the context across all classes in your application.
Refer : PhoneApp.java