Why can one line of code work, but then the same line throws a null pointer exception later?

Question

I am creating an android app that involves creating a to-do list, when the onstart method is called I can call a context.findviewbyid() line succesfully but later that does not work, this only happens when the app has been rotated or reset in some way

onStart Method

@Override
public void onStart(){
super.onStart();
this.context = getActivity();
ViewGroup vg = (ViewGroup) context.findViewById(R.id.MainLayout);
databaseHandler = new DatabaseHandler(context, (ViewGroup)
context.findViewById(R.id.MainLayout));
vg.removeAllViews();
databaseHandler.reinstantiateAllWishes();
WishlistCounter = databaseHandler.getWishCount();
databaseHandler.close();
Log.v("onStart WishlistCounter: ", String.valueOf(WishlistCounter));
}

createNew Method

public void createNew(){
    Log.v("Creating new:","confirmed");
    //Get the message from the Edit Text
    EditText editText = (EditText) context.findViewById(R.id.WishListAddText);
    String message= editText.getText().toString();
    //If it is acceptable, continue
    if(!message.equals("") && WishlistCounter < SLOTS_LIMIT && !message.equals(null)){
        //Create new Wish
        Wish c = new Wish((ViewGroup) context.findViewById(R.id.MainLayout), getActivity(), this.databaseHandler);
        c.newBuilder(message);
        WishlistCounter++;
    //Explain unacceptability
    } else if(WishlistCounter >= SLOTS_LIMIT){
        Toast.makeText(context, "You cannot have over" +  String.valueOf(SLOTS_LIMIT) + "entries" ,Toast.LENGTH_SHORT).show();
    }
}

Error Log

FATAL EXCEPTION: main
java.lang.IllegalStateException: Could not execute method of the activity
at android.view.View$1.onClick(View.java:3039)
at android.view.View.performCLick(View.java:3480)
at android.view.View$PerformClick.run(View,java:13983)
at android.os.Handler.handleCallback(Handler.java:605)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.osLooper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4340)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
at com.android.intenal.os.ZygoteInit.main(ZygoteInit.java:551)
at dalvik.system.NativeStart.main(NativeMethod)
Caused by: java.lang.InvocationTargetException
at java.lang.reflect.Method.invokeNative(NativeMethod)
at java.lang.reflect.Method.invoke(Method.java:3034)
... 11 more
Caused by: java.lang.NullPointerException
at com.chesterbane.inspiriappaplpha.Frgmant4.createNew(Fragment4.java:61)
at com.chesterbane.inspiriappalpha.MainActivity.wishlistCreateNew(MainActivity.java:315)
... 14 more

It is the line EditText editText = (EditText) context.findViewById(R.id.WishListAddText); that is throwing the exception and I think that it is the context that is null. I dont understand what could be causing it to be null as it works fine in the onStart method. Any help would be greatly appreciated

"Why can one line of code work, but then the same line throws a null pointer exception later?" Basic object orientation. It's because on one line the object was proper initialized/referenced and on the other it wasn't. — Budius, Sep 01 '13 at 22:16
if you are calling the code from same activity, you may consider removing context. — Rachit Mishra, Sep 01 '13 at 22:47
Because WishListAddtext does not exist in the landscape layout? — Simon, Sep 01 '13 at 22:48
Because variables are variable? Otherwise it would be pointless to execute it twice? — user207421, Sep 01 '13 at 22:59

score 0 · Answer 1 · answered Sep 01 '13 at 22:08

0

On the third line of your onStart method you are setting the context to the activity. Try setting it to the context instead.

this.context = getActivity().getApplicationContext();

answered Sep 01 '13 at 22:08

Joel Dean

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Why can one line of code work, but then the same line throws a null pointer exception later?

1 Answers1