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 each time it changes

User · Answer

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

User · Answer

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

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I ve used this at some point   ActivityThread at   ActivityThread systemMain    Context context   at getSystemContext      This is a valid context I used at getting system services and worked   But  I used it only in framework base modifications and did not try it in Android applications   A warning that you must know  When registering for broadcast receivers with this context  it will not work and you will get      java lang SecurityException  Given caller package android is not running in process ProcessRecord

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I just released a jQuery-inspired framework for Android called Vapor API that aims to make app development simpler   The central   facade class maintains a WeakReference  link to awesome Java blog post about this by Ethan Nicholas  to the current Activity context which you can retrieve by calling     act     A WeakReference maintains a reference without preventing the garbage collection reclaiming the original object  so you shouldn t have a problem with memory leaks   The downside of course is that you run the risk that   act   could return null  I have not come across this scenario yet though  so it s perhaps just a minimal risk  worth mentioning   You can also set the context manually if you are not using VaporActivity as your Activity class     act Activity     Also  much of the Vapor API framework uses this stored context inherently which might mean you needn t store it yourself at all if you decide to use the framework  Check out the site for more information and samples   I hope that helps

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Kotlin way   Manifest    lt application android name  MyApplication  gt    lt  application gt    MyApplication kt  class MyApplication  Application          override fun onCreate             super onCreate           instance   this            companion object           lateinit var instance  MyApplication             private set           You can then access the property via MyApplication instance

User · Answer

Kotlin open class MyApp   Application         override fun onCreate             super onCreate           mInstance   this            companion object           lateinit var mInstance  MyApp         fun getContext    Context                return mInstance applicationContext                    and get Context like MyApp mInstance  or MyApp getContext

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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    lt application              android name  com example App   gt           lt  application gt    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

User · Answer

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

User · Answer

Do this   In the Android Manifest file  declare the following    lt application android name  com xyz MyApplication  gt    lt  application gt    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

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I use a variation of the Singleton design pattern to help me with this   import android app Activity  import android content Context   public class ApplicationContextSingleton       private static Activity gContext       public static void setContext  Activity activity            gContext   activity             public static Activity getActivity             return gContext             public static Context getContext             return gContext            I then call ApplicationContextSingleton setContext  this    in my activity onCreate   and ApplicationContextSingleton setContext  null    in onDestroy

User · Answer

Rohit s answer seems correct  However  be aware that AndroidStudio s  Instant Run  depends on not having static Context attributes in your code  as far as I know

User · Answer

I think you need a body for the getAppContext   method   public static Context getAppContext      return MyApplication context

User · Answer

Assuming we re talking about getting the Application Context  I implemented it as suggested by  Rohit Ghatol extending Application  What happened then  it s that there s no guarantee that the context retrieved in such a way will always be non-null  At the time you need it  it s usually because you want to initialize an helper  or get a resource  that you cannot delay in time  handling the null case will not help you  So I understood I was basically fighting against the Android architecture  as stated in the docs     Note  There is normally no need to subclass Application  In most situations  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   include Context getApplicationContext   as a Context argument when invoking your singleton s getInstance   method    and explained by Dianne Hackborn     The only reason Application exists as something you can derive from is because during the pre-1 0 development one of our application developers was continually bugging me about needing to have a top-level application object they can derive from so they could have a more  normal  to them application model  and I eventually gave in    I will forever regret giving in on that one       She is also suggesting the solution to this problem      If what you want is some global state that can be shared across different parts of your app  use a singleton        And this leads more naturally to how you should be managing these things -- initializing them on demand    so what I did was getting rid of extending Application  and pass the context directly to the singleton helper s getInstance    while saving a reference to the application context in the private constructor   private static MyHelper instance  private final Context mContext       private MyHelper  NonNull Context context        mContext   context getApplicationContext       public static MyHelper getInstance  NonNull Context context        synchronized MyHelper class            if  instance    null                instance   new MyHelper context                     return instance            the caller will then pass a local context to the helper   Helper getInstance myCtx  doSomething      So  to answer this question properly  there are ways to access the Application Context statically  but they all should be discouraged  and you should prefer passing a local context to the singleton s getInstance       For anyone interested  you can read a more detailed version at fwd blog

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If you re open to using RoboGuice  you can have the context injected into any class you want   Here s a small sample of how to do it with RoboGuice 2 0  beta 4 at time of this writing   import android content Context  import android os Build  import roboguice inject ContextSingleton   import javax inject Inject    ContextSingleton public class DataManager        Inject     public DataManager Context context                Properties properties   new Properties                properties load context getResources   getAssets   open  data properties               catch  IOException e

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Here is an undocumented way to get an Application  which is a Context  from anywhere in the UI thread  It relies on the hidden static method ActivityThread currentApplication    It should work at least on Android 4 x   try       final Class lt   gt  activityThreadClass               Class forName  android app ActivityThread        final Method method   activityThreadClass getMethod  currentApplication        return  Application  method invoke null   Object    null     catch  final ClassNotFoundException e           handle exception   catch  final NoSuchMethodException e           handle exception   catch  final IllegalArgumentException e           handle exception   catch  final IllegalAccessException e           handle exception   catch  final InvocationTargetException e           handle exception     Note that it is possible for this method to return null  e g  when you call the method outside of the UI thread  or the application is not bound to the thread   It is still better to use  RohitGhatol s solution if you can change the Application code

User · Answer

in Kotlin  putting Context App Context in companion object still produce warning Do not place Android context classes in static fields  this is a memory leak  and also breaks Instant Run    or if you use something like this       companion object           lateinit var instance  MyApp         It s simply fooling the lint to not discover the memory leak  the App instance still can produce memory leak  since Application class and its descendant is a Context   Alternatively  you can use functional interface or Functional properties to help you get your app context   Simply create an object class   object CoreHelper       lateinit var contextGetter     - gt  Context     or you could use it more safely using nullable type   object CoreHelper       var contextGetter      - gt  Context     null     and in your App class add this line    class MyApp  Application          override fun onCreate             super onCreate           CoreHelper contextGetter                 this                     and in your manifest declare the app name to   MyApp        lt application             android name   MyApp    When you wanna get the context simply call   CoreHelper contextGetter       or if you use the nullable version CoreHelper contextGetter  invoke     Hope it will help

User · Answer

You can use the following   MainActivity this getApplicationContext      MainActivity java       public class MainActivity           static MainActivity ma          public void onCreate Bundle b             super             ma this                 Any other class   public         public ANY METHOD               Context c   MainActivity ma getApplicationContext

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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

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If you don t want to modify the manifest file  you can manually store the context in a static variable in your initial activity   public class App       private static Context context       public static void setContext Context cntxt            context   cntxt             public static Context getContext             return context            And just set the context when your activity  or activities  start      MainActivity   Override public void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       setContentView R layout activity main           Set Context     App setContext getApplicationContext             Other stuff       Note  Like all other answers  this is a potential memory leak

[android] Static way to get 'Context' in Android?

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