I have a seperate DatabaseHandler("db") Class which extends SQLiteOpenHelper BUT NOT ACTIVITY which means this is a seperate class file which is not related to any activity. If you ask why i have such a class not in activity because i like keeping my files organized.
So i have listview in a fragment and i have a "DatabaseHandler.getAllRows()" function in that class which returns a "List" Object. Then i want to use this list to populate my listview.
So when this class is a seperate class which is not related to any activity, i can't use simplecursorAdapter since it wants a context in paramteres part when creating with new(i tried to send parameter as context but didnt work) so i need to use something else....
I can change return type, i can use another thing instead of listview.. just give me a good advice for how to populate listview or show table rows NICELY.
If you want a real simple solution, you can store your rows as an array, and use ArrayAdapter to display them. You can override the getView to display the results in your preferred way.
If this solution is not good enough, I think you will have to implement your own Adapter, which might be a good idea anyway.
Related
So, I am running up against a limitation of the Parse SDK here, and I don't know how to proceed.
I have a ListView that I am setting the adapter to from a subclass of the ParseQueryAdapter, which itself extends the BaseAdapter class.
Normally with an adapter, I pass the list along to the Adapter constructor in order to get access to the list I am dealing with, so that I can call getCount, getItem, etc. by accessing the size/index of that ArrayList.
I can't do that with the ParseQueryAdapter because it takes a ParseQueryFactory as part of the constructor, and it doesn't resolve it's items until they are fetched from the Parse app online...
Now the ParseQueryAdapter does have a List of Objects, which is exactly what I need, expect that it is Private... so even though the getItem() and getCount() methods exist, there is no way - AFAIK - to use them, as I have no access to the dataset that is fuelling my adapter...
Further to this, I would normally use getView(), which returns a position alongside my View, and everything would be snappy. Except Parse overrides that and provides a getItemView() method which resolves the Parse Object that is fetched from the cloud and passes it instead of the integer for position...
So, two questions here:
1) Is there another way in which I can access the list that is feeding an adapter ? I can hack a way to pass the resolved query into a list and pass that into the adapter later, by listening to addOnQueryLoadListener(), but that seems bad design and might take a while, handcuffing my UI.
2) Am I being naive in my understanding of how to use get getItem() and getCount() methods ?
I'm starting learning Android and I want to know if there is some option in Android that let you modify each item or view (I don't know how it's named exactly, I mean each of the items from an ArrayList that you show in a ListView).
Well, I made a ListView that is going to show some books that were located in an ArrayList named "books".
I made a custom adapter that I associate to the ListView to show each item with the corresponding layout in the application. I also have a class "book" for each item that is going to be shown in the ListView.
Further, I made an Intent that I call from MainActivity with startForActivityResult(), that I process in Book class and that I return to MainActivity with all data of a book with the method setResult and got the information with onActivityResult() and the requestCode.
So I don't have any problem to add items to the ListView, just I have the problems if I want to modify some of the items (or views) that are located in the ListView (for example if I have title and author of a book, if I put some wrong information, I want have the option to change it).
I have that, in the same moment that you click on some of the items of the ListView, a new layout will be show to modify the information that it's wrong so I use the method setOnItemClickListener with onItemClick event on the custom adapter that I created before. Here it's where I call the new Intent to modify the wrong information with the method startActivityForResult().
I made the same as before to add a new item but, instead of add a new item with custom_adapter.addBook(title,author) I want to know if there is some option to made something like this: custom_adapter.modify(title,author) or custom_adapter.update(title,author), I mean, when you have modify all the items that were wrong of a book (for example an EditText that were "title") and you have all the information in the MainActivity class (because you returned it with setResult), how to put it again in the same item updating it in the custom_adapter and also in the ArrayList.
I searched it on the Internet but I didn't find anything.
I'm sorry if I have a poor English, but I expect that it can be understand.
Thank you very much!
If I am understanding your problem correctly - you could simply modify the ArrayList of type Book that is backing your ArrayAdapter.
So if you know what Book object you want to modify then you can simply make your changes to the Book object itself. As long as this Book is a reference to the same object that you originally added to the ArrayList you instantiated your ArrayAdapter with then you can then call custom_adapter.notifyDataSetChanged() to tell the adapter to redraw its childviews with the new data.
There are some good code samples on the Internet but you have to understand the code for your purposes. So...here is a start, look at Using an ArrayAdapter with ListView. The code shows the use of ArrayAdapter with getView() method. And I hope it shows how to define the listeners, which you need.
How about that for a start? Have fun...
Thank you very much for all help you gave to me. I'm very pleased with you. :)
Finally, I just send the info with a Bundle when I started the Intent, also with the position. And after, I just used this position to set the new info to my items (in my case, books).
Again, thank you very much ;)
I am looking at this ListView Tutorial:
ListView Tutorial
and I was wondering how much better is to create my own ArrayAdapter, rather than just using and ArrayAdapter.
In the Tutorial it defines a "StableArrayAdapter", what exactly does this means? If I use a regular ArrayAdapter, could it be dangerous for some reason?
The two previous answers are absolutely right, but just to address more directly your question and in case someone else has the same doubt than you; a regular ArrayAdapter is not dangerous at all, the only "problem" is that it might not fulfill your needs, in which case you will have to create your own adapter, as the author of the tutorial did by creating what he called StableArrayAdapter in the end of the ListViewExampleActivity class.
Don't get lost by the name, which I guess comes from the fact that the overwritten method "hasStableIds" always returns true, it doesn't mean that the regular ArrayAdapter creates problems.
ArrayAdapter: It is merely a way to provide data to a ListView. It is also a BaseAdapter that is backed by an array of objects.
CustomAdapter: If if your ListView is a normal and simple ListView (wherein you are having one TextView per item in the list), then the use of ArrayAdapter would be apt.
But it is recommended you to create your own CustomAdapter which extends an ArrayAdapter that you can use for providing data to your ListView. This way you can easily extend your ListView to include more that one TextView or even ImageView (to show images).
CursorAdapter: Cursor Adapter is used when you have Data in a Cursor (typically when you are retrieving data from a database. The Cursor must include a column named "_id" or this class will not work.
If you are using a simple ListView, like merely a TextView per item, then just use the standard ArrayAdapter, on the other hand, if you want a custom item in the list, as in a combinations of views within each item in the ListView, then extend the ArrayAdapter and implement it to your needs.
StableArrayAdapter is merely an extended version of ArrayAdapter, but in StableArrayAdapter they have overridden the method hasStableIds() of BaseAdapter to return true.
You can check this in the following links:
StableArrayAdapter -
Override hasStableIds to return true
ArrayAdapter -
Has not Override hasStableIds but extended BaseAdapter
BaseAdapter -
Has hasStableIds but returning false
Now Question is What is the use of StableIds
This Indicates whether the item ids are stable across changes to the underlying data. If True then same id always refers to the same object. for more info
So here is my problem. I'm using a dialog fragment to display some info. In that fragment, i have a spinner view that is filled up by the Array list. Normally I create that adapter in my fragment like this:
ArrayAdapter<String> teamsAdapter = new ArrayAdapter<String>(getActivity(),
android.R.layout.simple_spinner_item, Variables.teamNames);
teamsAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
Variables.spinner.setAdapter(teamsAdapter);
Variables is my user-defined class where I keep all variables.
Now here is my question. I have around 10 DialogFragments and almost all of them have spinner. I would like to define that Adapter in my Variables class and whenever i need it, i would just call it from my variables class. Unfortunately to do that, i need getActivity() in my adapter constructor. I cannot go around it.
BTW, is it a good idea or I should use interface?
It would be awesome if somebody could actually tell me why would I use java interface in android?
Your fragment would still need to call some Variables method to retrieve the spinner and to add it to your layout, right? So when you do that call, you can pass the Activity as Context, something like this:
ArrayAdapter<String> teamsAdapter = Variables.getAdapterForTeams(getActivity());
The question about the Interface isn't an Android but a Java question. If it makes sense to use an Interface in Java it will make sense to use it in Android. There's plenty of literature and online resources about Java that will explain the why and when Interfaces should be used. I'm sure if you search online you'll find plenty of resources about it.
I am new to Android and am trying to get my header round the SimpleCursorAdapter and CursorLoader classes. From my understanding, all of the examples that I have seen use these two classes to load data into a ListView in a background thread (to not block the UI).
I am OK with this and have used this general approach with my own list of items, however I now want to be able to click on an item in the list and get the full information for the item. Is it usual practice to use SimpleCursorAdapter and CursorLoader to retrieve the details for a single item? or are they just meant for lists?.
Thanks.
They are not meant for lists only. You can - and should - use them in detail views (activities) as well.
I've sketched a possible way to do so on my blog:
http://www.grokkingandroid.com/using-loaders-in-android/
Think of Adapters as a layer of abstraction between your data (Cursor) and whatever you attach that Adapter to (ListView for example). This way, you have a common interface between your data (Cursor, ArrayList, whatever) and the View you display that data on (ListView, TableView, etc.), this is helpful because if you later find that you want to access your data through an ArrayList rather than a Cursor, then you simply swap out the adapter with a different one and you're ready.
Now considering your question, Adapters give an abstract access to information, therefore you can "ask" it for what information is stored and where. You could attach an OnItemClickListener to your ListView and then access your data from there.