NullPointerException happens in an Android code snippet

Question

Here\'s the code which deals with member registration.

public class RegisterActivity extends Activity {
    private static final String TAG = RegisterActivit         


        

Answer 1

As you can see, AppController is not added to your manifest:

<application
        android:name=".AppController" //this one
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme">

So onCreate never get called and mInstance is null.

Answer 2

the problem is you didn't declare your Subclass of Application to the AndroidManifest. Add android:name="path.to.AppController" to the Application tag, otherwise your subclass of Application is not instantiated and mInstance remains not initialized (null by default). And that explains the NPE

 <application
    android:name="path.to.AppController"
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >