Application subclass class returns null pointer exception

Question

I am creating an application where i need to load the images for all the components like buttons, logo.. from the server. I am using three classes MemoryCache,FileCache and ImageLoder class from fedors Lazylist example https://github.com/thest1/LazyList/tree/master/src/com/fedorvlasov/lazylist where we can pass url and View to ImageLoader and load,cache the image etc.

so i want to initialize the ImageLoder class only once in the entire app and reused it in other Activities in order to do that i created a object for it in my MyGlobalClass extented with Application like this.

public class MyGlobalClass extends Application {
    private static Context context;
    private static MyGlobalClass singleton;
    private static ImageLoader imageLoder = new ImageLoader(getAppContext());
    private static String[] urls;

    public MyGlobalClass getInstance() {
        return singleton;
    }

    public void onCreate() {
        super.onCreate();
        singleton = this;
        MyGlobalClass .context = getApplicationContext();

        urls = getResources().getStringArray(R.array.urls);
    }

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

    public ImageLoader getImageLoader() {
        return imageLoder;
    }

    public String[] getUrls() {
        return urls;
    }
}

I created <appplication> field in AndroidManifest.xml as

<application
    android:name="com.xx.yy.MyGlobalClass"
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher">
</application>

But when I am using it in other activities like creating object of global class I am doing this:

MyGlobalClass myGClass = (MyGlobalClass)getApplicationContext(); // null pointer here

It's returning a null pointer exception.

I want to access ImageLoader in HomeActivity like this:

ImageButton homeBt = (ImageButton) findViewById(R.id.imageButton2);
ImageLoader imgLoader=(ImageLoader)myGClass.getImageLoader();
String[] urls=myGClass.getUrls();
imgLoader.DisplayImage(urls[1], cameraBt);

Can anybody see what is wrong with my code and suggest how to do it? I also created a singleton field but don't know why, and how to use it. Please provide some examples. I am actually adding the above exception line in activity class before onCreate(), so may be that is the problem..but when i am adding it in onCreate() in HomeActivity it gives me Class cast Exception..cannot cast to android.app.Application to com.xx.yy.MyGlobalClass

Answer 1

Actually iam creating Another "application" tag in the AndroidManifest.xml file unknowingly, the fact is --android:name="com.xx.yy.MyGlobalClass"-- should be added to same "application" tag which you created before if any, In Answers for the ClassCastException questions,every body mentioned we need to add tag with "android:name" property in the ManifestFile..but didn't specify it where..,i had to learn it the hardway wasting almost half of the day, hope it help to others..Thanks syed