calling startActivity() inside of a instance method - causing a NullPointerException

Heya - I'm trying to call startActivity开发者_运维问答() from a class that extends AsyncTask in the onPostExecute().

Here's the flow:

Class that extends AsyncTask:

protected void onPostExecute() {
    Login login = new Login();
    login.pushCreateNewOrChooseExistingFormActivity();
}

Class that extends Activity:

public void pushCreateNewOrChooseExistingFormActivity() {
    // start the CreateNewOrChooseExistingForm Activity
    Intent intent = new Intent(Intent.ACTION_VIEW);
    **ERROR_HERE*** intent.setClassName(this, CreateNewOrChooseExistingForm.class.getName());
    startActivity(intent);
}

And I get this error… every time:

03-17 16:04:29.579: ERROR/AndroidRuntime(1503): FATAL EXCEPTION: main
03-17 16:04:29.579: ERROR/AndroidRuntime(1503): java.lang.NullPointerException
03-17 16:04:29.579: ERROR/AndroidRuntime(1503): at android.content.ContextWrapper.getPackageName(ContextWrapper.java:120)
03-17 16:04:29.579: ERROR/AndroidRuntime(1503): at android.content.ComponentName.(ComponentName.java:62)
03-17 16:04:29.579: ERROR/AndroidRuntime(1503): at android.content.Intent.setClassName(Intent.java:4850)
03-17 16:04:29.579: ERROR/AndroidRuntime(1503): at com.att.AppName.Login.pushCreateNewOrChooseExistingFormActivity(Login.java:47)

For iOS developers - I'm just trying to push a new view controller on to a navigational controller's stack a la pushViewController:animated:. Which apparently - is hard to do on this platform.

Any ideas? Thanks in advance!

UPDATE - FIXED:

per @Falmarri advice, i managed to resolve this issue.

first of all, i'm no longer calling Login login = new Login(); to create a new login object. bad. bad. bad. no cookie.

instead, when preparing to call .execute(), this tutorial (appfulcrum.com/?p=126) suggests passing the applicationContext to the class the executes the AsyncTask, for my purposes, as shown below:

    CallWebServiceTask task = new CallWebServiceTask();
    // pass the login object to the task
    task.applicationContext = login;
    // execute the task in the background, passing the required params
    task.execute(login);

now, in onPostExecute(), i can get to my Login objects methods like so:

        ((Login) applicationContext).pushCreateNewOrChooseExistingFormActivity();
        ((Login) applicationContext).showLoginFailedAlert(result.get("httpResponseCode").toString());
        ...

hope this helps someone else out there! especially iOS developers transistioning over to Android...

---

If Login is a class that extends Activity, you should never, ever, ever, be creating a new Login object yourself such as

Login login = new Login();

This is very, very wrong and you should go back and go through some of the Android tutorials.