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Android

Posted by dlpuxdzztg
dlpuxdzztg
8,243 Points

DataSource Unable to Create Item After Insterting 'For' Loop in 'create()' Method

What I'm trying to accomplish

I'm saving an array of objects (ListItem) that have their own ArrayList parameter of custom objects (TaskItem). The approach I'm taking to saving both is by looping through the list of ListItem objects and retrieving each object's ArrayList parameter. I'm doing this in my DataSource:

public void create(ListItem item) {
    SQLiteDatabase database = open();
    database.beginTransaction();

    ContentValues contentValues = new ContentValues();
    contentValues.put(EasyListSQLiteHelper.LISTS_NAME, item.getListName());
    contentValues.put(EasyListSQLiteHelper.LISTS_CHECKED, item.getImportant());
    long listId = database.insert(EasyListSQLiteHelper.LISTS_TABLE, null, contentValues);

    for (TaskItem taskItem : item.getListsList()) {
        ContentValues taskValues = new ContentValues();
        taskValues.put(EasyListSQLiteHelper.TASK_NAME, taskItem.getTaskName());
        taskValues.put(EasyListSQLiteHelper.TASK_CHECKED, taskItem.getChecked());
        taskValues.put(EasyListSQLiteHelper.FOREIGN_KEY_LIST, listId);

        database.insert(EasyListSQLiteHelper.TASKS_TABLE, null, taskValues);
    }

    database.setTransactionSuccessful();
    database.endTransaction();
    close(database);
}

Then I create an 'addTask' function and call it in 'read' function:

public void addTask(ArrayList<ListItem> listItems) {
    SQLiteDatabase database = open();

    for (ListItem item : listItems) {
        ArrayList<TaskItem> taskItems = new ArrayList<>();
        Cursor cursor = database.rawQuery(
                "SELECT * FROM " + EasyListSQLiteHelper.TASKS_TABLE + " WHERE LIST_ID = " + item.getId(),
                null);

        if (cursor.moveToFirst()) {
            do {
                TaskItem taskItem = new TaskItem(getIntFromColumnName(cursor, BaseColumns._ID),
                        getStringFromColumnName(cursor, EasyListSQLiteHelper.TASK_NAME),
                        getIntFromColumnName(cursor, EasyListSQLiteHelper.TASK_CHECKED));
                taskItems.add(taskItem);
            } while(cursor.moveToNext());
        }
        item.setListsList(taskItems);
        cursor.close();
    }
    database.close();
}

read():

public ArrayList<ListItem> read() {
    ArrayList<ListItem> listItems = readList();
    addTask(listItems);
    return listItems;
}

What I'm dealing with:

When I add an item to my array of ListItems, I get this error:

04-21 12:04:45.729 13316-13316/com.example.x.x E/AndroidRuntime: FATAL EXCEPTION: main
                                                                        Process: com.example.x.x, PID: 13316
                                                                        java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.Iterator java.util.ArrayList.iterator()' on a null object reference
                                                                            at com.example.x.x.EasyListDataSource.create(EasyListDataSource.java:134)
                                                                            at com.example.x.x.Activitys.ListsActivity.saveList(ListsActivity.java:310)
                                                                            at com.example.x.x.Activitys.ListsActivity.createListClickListener(ListsActivity.java:205)
                                                                            at com.example.x.x.Fragments.NewListDialogFragment$1.onClick(NewListDialogFragment.java:92)
                                                                            at android.view.View.performClick(View.java:5217)
                                                                            at android.view.View$PerformClick.run(View.java:21349)
                                                                            at android.os.Handler.handleCallback(Handler.java:739)
                                                                            at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                            at android.os.Looper.loop(Looper.java:148)
                                                                            at android.app.ActivityThread.main(ActivityThread.java:5585)
                                                                            at java.lang.reflect.Method.invoke(Native Method)
                                                                            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730)
                                                                            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)

And I think I know whats going on: When I create a ListItem object, the object does get created. But the 'for' loop won't work because the ListItem's ArrayList parameter is not populated. With that being said, the 'for' loop wont work. So, how should I fix this?