Null Object Reference in Android Application

Question

Hy Guys

So I am trying to get this below portion of the code for a shopping list application to run, however i am getting an error that is causing the application to crash.

Code:

public void setProduct(Context context, View shoppingListViewFragment, String userEmail, String userName, ListModel shoppingListModel, ItemModel productModel) {
    String listID = shoppingListModel.getListID();
    String listName = shoppingListModel.getListName();
    String itemID = productModel.getItemID();
    String itemName = productModel.getItemName();
    Boolean currentList = productModel.getCurrentList();
    productNameContainer.setText(itemName);

    FirebaseFirestore dbRef = FirebaseFirestore.getInstance();
    DocumentReference itemIdRef = dbRef.collection("products").document(listID)
            .collection("shoppingListProducts").document(itemID);

    itemView.setOnClickListener(view -> {
        Map<String, Object> map = new HashMap<>();
        if (currentList) {
            map.put("currentList", false);
        } else {
            map.put("currentList", true);
        }
        itemIdRef.update(map).addOnSuccessListener(aVoid -> {
            if (currentList) {
                dbRef.collection("shoppingLists").document(userEmail)
                        .collection("userShoppingLists").document(listID).get().addOnCompleteListener(task -> {
                            Map<String, Object> map1 = (Map<String, Object>) task.getResult().get("users");
                            String notificationMessage = userName + " has just bought " + itemName + " from " + listName + "'s list!";
                            UserNotificationsModel userNotificationsModel = new UserNotificationsModel(notificationMessage, userEmail);

                            for (Map.Entry<String, Object> entry : map1.entrySet()) {
                                String sharedUserEmail = entry.getKey();

                                if (!sharedUserEmail.equals(userEmail)) {
                                    dbRef.collection("notifications").document(sharedUserEmail)
                                            .collection("userNotifications").document()
                                            .set(userNotificationsModel);
                                }
                            }
                        });
            }
        });
    });

    itemView.setOnLongClickListener(view -> {
        AlertDialog.Builder builder = new AlertDialog.Builder(context);
        builder.setTitle("Edit / Delete Item");

        EditText editText = new EditText(context);
        editText.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_FLAG_CAP_WORDS);
        editText.setText(itemName);
        editText.setSelection(editText.getText().length());
        editText.setHint("Please type item name");
        editText.setHintTextColor(Color.GRAY);
        builder.setView(editText);

        builder.setPositiveButton("Update", (dialogInterface, i) -> {
            String newItemName = editText.getText().toString().trim();
            Map<String, Object> map = new HashMap<>();
            map.put("itemName", newItemName);
            itemIdRef.update(map);
        });

        builder.setNegativeButton("Delete", (dialogInterface, i) -> {
            itemIdRef.delete().addOnSuccessListener(aVoid -> Snackbar.make(shoppingListViewFragment, "Item deleted!", Snackbar.LENGTH_LONG).show());
        });

        AlertDialog alertDialog = builder.create();
        alertDialog.show();

        return true;
    });
}

When the application run, a fatal error occurs at line 61 which is at the for loop " for (Map.Entry entry : map1.entrySet())"

I am getting the below error from Android Studio IDE

E/AndroidRuntime: FATAL EXCEPTION: main Process: example.com.shoppinghelper, PID: 17150 java.lang.NullPointerException: Attempt to invoke interface method 'java.util.Set java.util.Map.entrySet()' on a null object reference at example.com.shoppinghelper.shopping_container.ProductContainer.lambda$null$0$ProductContainer(ProductContainer.java:61) at example.com.shoppinghelper.shopping_container.ProductContainer$$Lambda$6.onComplete(Unknown Source:0) at com.google.android.gms.tasks.zzf.run(Unknown Source:23) at android.os.Handler.handleCallback(Handler.java:789) at android.os.Handler.dispatchMessage(Handler.java:98) at android.os.Looper.loop(Looper.java:164) at android.app.ActivityThread.main(ActivityThread.java:6940) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)

Basically, the code is trying to data to a notifications collection provided the certain list was shared by someone. However, if if there is no one i shared the particular shopping list with, then i am getting the above stated error.

Video Tutorial which i am following is : https://www.youtube.com/watch?v=6RzB4HXzQyA&list=PLn2n4GESV0AmXOWOam729bC47v0d0Ohee&index=16

Please help. :)

Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Joseph Sible-Reinstate Monica, Oct 06 '18 at 03:49

score 0 · Accepted Answer · answered Oct 06 '18 at 03:55

Your map1 object is given the value of getResult() , but you’ll find that getResult() will be returning null

Map<String, Object> map1 = (Map<String, Object>) task.getResult().get("users");

Causing this for statement

for (Map.Entry<String, Object> entry : map1.entrySet()){}

To cause your null pointer exception, you should add a check before for it map1 != null

Null Object Reference in Android Application

1 Answers1