Application extending class return null

Question

In my Android Application the class MyApp which extends Application base class like this :

public class MyApp extends Application {
   private static MyApp instance;

   public static MyApp getInstance() {
      return instance;
   }

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

declare in AndroidManifest.xml

<application android:name="com.mypackage.mypackage.MyApp">...</application>

While accessing like this from an activity class :

MyApp.getInstance()

Return null and causes Nullpointer Exception some times mostly in android version 7.0. I think this must probably due to application get killed. So how should I reinitiated the application class so that it getInstance() return non-null value.

IntelliJ Amiya · Answer 1 · 2018-04-23T08:01:32.703

1

NullPointerException is thrown when an application attempts to use an object reference that has the null value.

You should pass Current Activity Name.

 MyApp.getInstance(YourActivityName.this) // You should pass Context

For good approach use synchronized.

A synchronized block in Java is synchronized on some object. All synchronized blocks synchronized on the same object can only have one thread executing inside them at a time.

public static synchronized MyApp getInstance() {
        return instance ;
    }

edited Apr 23 '18 at 08:01

answered Apr 23 '18 at 07:54

IntelliJ Amiya

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Isn't define `private static MyApp instance' and accessing using function getInstance() causes memory leak problems? – Kapil Jindal Apr 23 '18 at 09:25
@KapilJindal Yeah! Kindly read https://stackoverflow.com/a/7026563/3395198 – IntelliJ Amiya Apr 23 '18 at 09:29

score 1 · Answer 2 · answered Apr 23 '18 at 07:55

1

Try this

public class MyApp extends Application {
public static MyApp instance;
static Context mContext;


public static MyApp getInstance() {
if (instance== null)
        instance= (MyApp) mContext;
  return instance;
}

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

answered Apr 23 '18 at 07:55

mehul chauhan

1,792
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Isn't this causes memory leak? – Kapil Jindal Apr 23 '18 at 09:02

score 0 · Answer 3 · answered Apr 23 '18 at 08:01

0

I hope this will work for you

public static synchronized MyApp getInstance() {
    return mInstance;
}

In Activity Access like this suppose for Toast (for Context)

Toast.makeText(MyApp.getInstance(), "hello",Toast.LENGTH_SHORT).show();

answered Apr 23 '18 at 08:01

GParekar

1,209
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Application extending class return null

3 Answers3