I am new to making android apps and was trying to find out if there is a way for a user to add their own custom selections to a Spinner.
For example I want to make a database for keeping track of car maintenance.
So I want the user to be able to add/remove their own cars/trucks as needed to it.
If there is a better way to do this I am open to any suggestions.
I am using eclipse.
Thanks for any help in this matter.
So two ways to do this,
First off since you are using a database I would look at using a SimpleCursorAdapter or a Loader to manage the connection and updates to the db, so you don't manually have to refresh the query, and use a SimpleCursorAdapter to power the spinner like this answer https://stackoverflow.com/a/11216746/418505
Or, you could programmatically query the database and then use some UI event hook, like a button click to submit the new car/truck to then update whatever Adapter you have bound to the spinner (make sure you call notifyDataSetChanged)
Related
I'm learning Android, and I'm building an activity that will receive users that are using different devices, and I would like to show all these users nicknames together, in a Listview.
So, I was thinking about how could I do that, and had the idea to use a Handler to update my listview every second, and to display the list of users in real time, for all users that are connected to the activity.
I created a Database using Phpmyadmin, and I'm using Json to print all the informations from the database, so I can use Java to get all the data.
My questions are:
Is there any better way of doing what I'm trying to do?
Will my App crash?
Does the handlers have a huge effect on the users battery?
Thank you.
Yes there is another way you can do it. You can look for RecyclerView . And notifyDataSetChanged() method. Also you can use notifyItemRemoved()bla bla ..
In RecyclerView you have an adapter and you give list of items to that adapter. When your item list changed , if you notify it to your adapter your recyclerview should change.
Android Recyclerview : RecyclerView
Also you can follow guides like in this blog : Creating lists with recyclerview
Assume we have an Activity with n TextViews that represent one line notes. These notes are stored somewhere (local database, network etc), and each time onResume() being called, the proper number of TextViews are drawn according to that stored data.
Now, lets say the user want to delete a note, what would be the best way the resolve the specific TextView, back to its storage entity?
At the moment, the only way I know is by using View.Tag, and having some manager to translate it to data entity, but it look rather messy.
Are there any other options?
In Android, the Adapter acts a bridge between the view and the data model. You could display the n TextViews in either a ListView or a GridView, and when the user adds or deletes a note, the local or server database is first updated. Upon completion of the web service call and/or the local database update, the new data is added to the underlying Adapter. The View is then refreshed by calling adapter.notifyDataSetChanged(). This would be the way to do it.
Approaches:
If updating the local SQLite database, you could consider using a
CursorAdpater
to hold the data for the View, as it directly maps the entries in
the local database to the View.
If making use of a ContentProvider, it is even possible to combine
a CursorAdapter with a
LoaderManager
and a
CursorLoader:
these plug into the Activity / Fragment life-cycle and monitor
the underlying ContentProvider for changes that are published
automatically to the View on a separate thread.
It is also possible to use a
Filter
in conjunction with the Adapter to define a dynamic mechanism that
sorts the data entries on-the-fly. The filtering is performed by the
Filter on a separate thread, as per a query entered by the user,
possibly in an
AutoCompleteTextView.
References:
See the Retrieving a List of
Contacts
tutorial. The example here retrieves a set of contacts from the
contacts ContentProvider based on a dynamic, alphabetical search by
the user. It makes use of CursorAdapter, CursorLoader and
LoaderManager to monitor and update the data, and it displays the
search results in a ListView.
See also the Android Realtime (Instant) Search with Filter Class example, which shows how a Filter is to be used.
Android AutoCompleteTextView with Custom Adapter filtering.
Android AutocompleteTextView using ArrayAdapter and Filter.
I am new to Android App development, working on an android app which populate a list of numbers, in a listview dynamically, depending on the choice of the user, but, the moment user closes the App, the items in the listview are lost. How can I maintain the state of the listview?
Examples with code would be highly appreciated.
When I open Activity A, it allows users to add friends, and this friend list is shown in the form of items of listview in the same Activity, however, when I move to Activity B, and then come back to Activity A, this friend list disappears. I need to make sure that this friend list should not be lost while moving between activities. Please help.
I think that for your purpose there are 3 main methods, i'll explain them from the easier to the most difficult (in my opinion).
Text File
A way to do this is to create two methods in a class:
one has to create the text file in the storage if it isn't created before and read that, the other has to append a String to a StringBuilder and write it on the previous text file.
For this method you need the uses-permission of reading and writing to storage.
This link can help you: http://developer.android.com/training/basics/data-storage/files.html
JSON (also XML)
With JSON file you can create a list of objects with your data that you can serialize when you update the list and deserialize when you want to read it. For this purpose you have to study JavaScript syntax or, at least, JSON one.
SQLite Database
Android SDK incorporate a class named SQLiteOpenHelper that you can extend to create a database inside your app.
This link can help you: http://developer.android.com/training/basics/data-storage/databases.html
There are also references saving methods but i think that aren't right for your purpose, they work betters to save something like preferences or single data like last login informations.
I went through your comment. I would personally suggest using SQLiteOpenHelper
You might need to understand the use of SQLite, hence the tutorial
Simple Flow. On your Activity 1 where person Add Friends save it to DB
Then refresh the List from the DB. So when you move to Activity 2 and come back again to Activity 1 your List will refresh from DB. Hence no loss of data as you want.
EDIT
As user wanted to know how to use the ListView with DB.
Following are my suggestion
Sai Geetha
Youtube
I'm working on an Android project I need to finish very fast.
One of the app's features is loading a SQLite database content and listing it in a ListView inside a ListActivity.
The database contains a few tables, among which 2 are very large.
Each item in the database has many columns, out of which I need to display at least 2 (Name, Price), although preferably is 3.
This might seem a pretty easy task, as all I need to do in this part of the app is read a database and list it. I did this without any problems, testing the app versus a small sample database.
In my FIRST version, I used a Cursor to get the query, then an ArrayAdapter as the list's adapter, and after the query I simply loop the cursor from start to end, and for each position I add the Cursor's content to the adapter.
The onItemClickListener queries the database again versus other parameters (basically I open categories) so it clears the adapter, then loops the Cursor and adds its content to the adapter all over again.
The app worked like a charm, but when I used a real-life, big database (>300MB) I suddenly got my app taking very long to display the contents, and sometimes even blocking.
So I did some research and started using a SimpleCursorAdapter that automatically links the contents of a Cursor to the ListView using the usual parameters (String[] from, int[] to etc., where I used android.R.layout.simple_list_item_2 and android.R.id.text1 and text2).
Problem is, is doesn't change much the time to load.
I've came across some suggested solutions on different web sites and tutorials, most of them using, in one way or another, the AsyncTask class. I tried implementing this manually myself but it's hard to keep track of multiple threads and I failed.
Tutorials keep telling how to do this with content providers, but I found nothing clear bout my specific situation: very big SQLite database -> read to ListView.
Now my head is filled in with notions like LoaderManager, LoaderAdapter etc, all mixed up and confused in my head.
Can anybody please provide me a complete, nice, clean solution to do this "simple" task?
Again: I want to read a BIG SQLiteDatabase and display it in a ListView. I want the app NOT to block.
I need a class that has a member function that takes as parameter a query and the ListActivity's context and takes itself care of displaying the result of the query in the view.
Please don't provide me abstract answers. I'm running out of time and I'm very confused right now and I need a clean complete solution.
You're my only hope.
If you query such large database it will take tym, you need to find a smart way,
Like limit you database query to get first 10 or 30 items and then maintain,once last item is reached query rest 30 items and bind them
Refer this tutorial, it will teach you how to add data dynamically in a list view
http://p-xr.com/android-tutorial-dynamicaly-load-more-items-to-the-listview-never-ending-list/
The above list has expired chk this
http://mobile.dzone.com/news/android-tutorial-dynamicaly
If you query large database it will take time to fetch data and show it on List View. So it is better to populate data at run time. You can use Lazy Adapter concept to load data . This link1 may be useful for You.
Thanks
you can also use :
public class TodosOverviewActivity extends ListActivity implements
LoaderManager.LoaderCallbacks<Cursor>
check this link for more details.
I have some trouble when using CursorLoader... I want to download data from inet API page by page, however;
I also want to make pagination of the listview. It means that data should be downloaded page by page when the end of listview is reached.
I also want to filter my listview inputing constraint-text in AutocompleteTextView.
Each of these features works properly when I use them separately, but when I want use them together it works not pretty well. I want to implement such a scenario: if I entered filter-text in AutocompleteTextView my listview was invalidated (that works fine) and downloading process would start until listview size reach the end of screen.
The problem is I don't know how to organize the cursor update through CursorLoader, when I should restart loader and when should't I? Should I restart loader only when I set filter (setFilterQueryProvider, method runQuery(CharSequence constraint)) or should I do it when give new portion of data from inet?
Now when process was started I found out that callback onLoadFinished wasn't called and listview wasn't updated...
Maybe anybody give me some working example...
You could change your CursorLoader for an AsyncTaskLoader to fetch new information when no records found according to the filter criteria. With the AsyncTaskLoader you could handle DB and UI operations to manage the Activity's state when it is downloading data or querying it locally.
Hope it helps.