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Android

Posted by Aditya Pore
Aditya Pore
1,453 Points

refactor the Fun Facts app to use string resources

I was able to modify the string.xml under res folder. However while accessing the array in Java(FactBook.java) I am getting a null pointer exception.

Here is the code snippet;

import android.content.res.Resources; public class FactBook { Resources res = getResources();// cannot resolve getResources() method public String[] mFacts = res.getStringArray(R.array.app_facts); ................. }

When i tried to extend Factbook to Activity viz,

public class FactBook extends Activity {

} The IDE recognizes the getResources method. But I get a null pointer exception stating that getResources is trying to reference null object.

I tried it using Context Class also as follows: Context ctx; String []mFacts = ctx.getResources().getStringArray(R.array.app_facts);

This also did not work out ... same error Null Pointer exception.

I have declared a string array in strings.xml under res/values folder ..

Please help

2 Answers

Seth Kroger
Seth Kroger
56,416 Points

The problems with either approach is that the Activity/Context isn't properly initialized at that point for the getResouces call to work.

I can think of two different ways of doing this, both involve adding a constructor to FactBook. Either with a String array, or a Context and int id as arguments. You would then call that constructor in onCreate() instead of with the member declaration.

// Using the FactBook(String[]) version
Resources res = getResources();
mFactBook = new FactBook(res.getStringArray(R.array.app_facts));
Aditya Pore
Aditya Pore
1,453 Points

Thanks a lot it worked :)

Ben Deitch
STAFF
Ben Deitch
Treehouse Teacher
Ben Deitch
Ben Deitch
Treehouse Teacher

Hey Aditya! We can't just use any ol' Context when we want to call getResources(). We need to use our application's context which isn't available until we're creating our activity.

You'll need to add a constructor to your FactBook class that takes in a Context, and initialize your FactBook in the onCreate method of FunFactsActivity while passing in a Context (using either the 'this' keyword or 'getApplicationContext()').

Aditya Pore
Aditya Pore
1,453 Points

Thanks!