Static way to get 'Context' in Android?

Question

Is there a way to get the current Context instance inside a static method?

I\'m looking for that way because I hate saving the \'Context\' instance eac

Answer 1

It depends on what you are using the context for. I can think of at least one disadvantage to that method:

If you are trying to create an AlertDialog with AlertDialog.Builder, the Application context won't work. I believe you need the context for the current Activity...

Answer 2

If you for some reason want Application context in any class, not just those extending application/activity, maybe for some factory or helper classes. You can add the following singleton to your app.

public class GlobalAppContextSingleton {
    private static GlobalAppContextSingleton mInstance;
    private Context context;

    public static GlobalAppContextSingleton getInstance() {
        if (mInstance == null) mInstance = getSync();
        return mInstance;
    }

    private static synchronized GlobalAppContextSingleton getSync() {
        if (mInstance == null) mInstance = 
                new GlobalAppContextSingleton();
        return mInstance;
    }

    public void initialize(Context context) {
        this.context = context;
    }

    public Context getApplicationContext() {
        return context;
    }
}

then initialize it in your application class's onCreate with

GlobalAppContextSingleton.getInstance().initialize(this);

use it anywhere by calling

GlobalAppContextSingleton.getInstance().getApplicationContext()

I don't recommend this approach to anything but application context however. As it can cause memory leaks.

Answer 3

Do this:

In the Android Manifest file, declare the following.

<application android:name="com.xyz.MyApplication">

</application>

Then write the class:

public class MyApplication extends Application {

    private static Context context;

    public void onCreate() {
        super.onCreate();
        MyApplication.context = getApplicationContext();
    }

    public static Context getAppContext() {
        return MyApplication.context;
    }
}

Now everywhere call MyApplication.getAppContext() to get your application context statically.

Answer 4

The majority of apps that want a convenient method to get the application context create their own class which extends android.app.Application.

GUIDE

You can accomplish this by first creating a class in your project like the following:

import android.app.Application;
import android.content.Context;

public class App extends Application {

    private static Application sApplication;

    public static Application getApplication() {
        return sApplication;
    }

    public static Context getContext() {
        return getApplication().getApplicationContext();
    }

    @Override
    public void onCreate() {
        super.onCreate();
        sApplication = this;
    }
}

Then, in your AndroidManifest you should specify the name of your class in the AndroidManifest.xml’s tag:

<application 
    ...
    android:name="com.example.App" >
    ...
</application>

You can then retrieve the application context in any static method using the following:

public static void someMethod() {
    Context context = App.getContext();
}

---

WARNING

Before adding something like the above to your project you should consider what the documentation says:

There is normally no need to subclass Application. In most situation, static singletons can provide the same functionality in a more modular way. If your singleton needs a global context (for example to register broadcast receivers), the function to retrieve it can be given a Context which internally uses Context.getApplicationContext() when first constructing the singleton.

---

REFLECTION

There is also another way to get the application context using reflection. Reflection is often looked down upon in Android and I personally think this should not be used in production.

To retrieve the application context we must invoke a method on a hidden class (ActivityThread) which has been available since API 1:

public static Application getApplicationUsingReflection() throws Exception {
    return (Application) Class.forName("android.app.ActivityThread")
            .getMethod("currentApplication").invoke(null, (Object[]) null);
}

There is one more hidden class (AppGlobals) which provides a way to get the application context in a static way. It gets the context using ActivityThread so there really is no difference between the following method and the one posted above:

public static Application getApplicationUsingReflection() throws Exception {
    return (Application) Class.forName("android.app.AppGlobals")
            .getMethod("getInitialApplication").invoke(null, (Object[]) null);
} 

---

Happy coding!

Answer 5

According to this source you can obtain your own Context by extending ContextWrapper

public class SomeClass extends ContextWrapper {

    public SomeClass(Context base) {
      super(base);
    }

    public void someMethod() {
        // notice how I can use "this" for Context
        // this works because this class has it's own Context just like an Activity or Service
        startActivity(this, SomeRealActivity.class);

        //would require context too
        File cacheDir = getCacheDir();
    }
}

JavaDoc for ContextWrapper

Proxying implementation of Context that simply delegates all of its calls to another Context. Can be subclassed to modify behavior without changing the original Context.

Answer 6

No, I don't think there is. Unfortunately, you're stuck calling getApplicationContext() from Activity or one of the other subclasses of Context. Also, this question is somewhat related.