getFilesDir() android function is undefined if i dont extend my class with activity

If i have my class as

import java.io.File;

import java.io.FileOutputStream;

//Extends Activity

public class MyClass extends Activity
{

File fileDir = getFilesDir(); //no error

   . ....    
}

But if i don't extend MyClass , i get an error saying "getFilesDir()" undefined.

some thing like

   public class MyClass2
    {

    ....

    File fileDir = getFilesDir(); 开发者_运维问答//error

    }

---

That is the method of the Context class. You have to obtain an instance of the class to invoke it.

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http://developer.android.com/reference/android/content/ContextWrapper.html#getFilesDir()

getFilesDir is member of ContextWrapper. So if you don't extend ContextWrapper it's normal for the compiler to throw error undefined reference.