I had read the documentation of ContentProvider and quite good number of tutorials\questions but seems there's gap in my head about how could I use the ContentProvider project; the first project which is the ContentProvider from TutorialPoint and it's working fine, I added to my demo project the following statement android:sharedUserId="com.example.mycontentprovider to my AndroidManifest.XML to access the shared DB I had there. Now I want to use the CRUD functions and I'm not sure how to do this, I found one of solutions here is to do such statement Context friendContext = this.createPackageContext("com.example.mycontentprovider",Context.CONTEXT_IGNORE_SECURITY);
Another solution been found is to initialize Intent and start activity and I did as the following:
Intent openMyContentProvider = new Intent("com.example.mycontentprovider",MainActivity.this);
and it gives me error for the arguments and though not sure how to proceed after starting new Activity; Any further requirements or codes will be provided and thanks in advance for your response.
You can use a CursorLoader to read data from the content provider, with the advantage of getting updates when the data in the database changes.
Use ContentResolver for read, insert, update and delete operations. And there is AsyncQueryHandler to help make handling asynchronous ContentResolver queries easier, you can use its on*Complete() callbacks to let the user know the operation was successful. Using AsyncQueryHandler
Related
I'm looking for a way to suspend notifications on a given ContentProvider's Uri. The use case is:
An Activity is bound to a CursorAdapter through a CursorLoader.
A Service may do a lot of batch, single-row updates on a ContentProvider.
The CursorLoader will reload its content on every row update, as the ContentProvider notifies listeners by ContentResolver#notifyChange.
Since I cannot edit the ContentProvider, and I have no control over the batch queries execution, is there a way to suspend notifications on a Uri (in the executing Service) until all of the ContentProvider-managed queries have been executed? I need this in order to avoid the flickering caused by the continuous requerying of the CursorLoader.
You cannot disable this mechanism in your Service. But you should try to batch them by using ContentProviderOperations.
I've written an introductory post about ContentProviderOperations and two additional posts covering the methods withYieldAllowed() and withBackReference() respectively.
Especially the latter one should be of interest for what you've described here.
With ContentProviderOperations you can batch multiple updates and inserts. If you then call applyBatch() on your ContentResolver object the ContentProvider executes them all at once.
Now I've never used Nicolas Klein's generator but since he is a very, very proficient Android developer and works at Google, I bet that the generated code makes use of transactions and calls notifyChange() only once for the complete batch at the end.
Exactly what you need.
Can you substitute your own ContentResolver?
You may try extends ContentResolver with your own class then and you will may override method notifyChange and realize your logic there.
In your Content provider class, inside query() method before returning the cursor, just comment the code which looks something like this
cursor.setNotificationUri(getContext().getContentResolver(), uri);
I know this has been discussed yet I wanted to ask about the current state of the matter. Do i have to create a ContentProvider to use CursorLoader in connection with a sqlite database?
I found
CursorLoader usage without ContentProvider
Looks exactly what I was hoping for yet as Emmby commented
Users should be aware of one limitation, which is that it has no mechanism to refresh on data changes (as Loaders are supposed to do)
So another solution is mentioned
https://github.com/commonsguy/cwac-loaderex
yet again some drawback is pointed out
However, to make use of the automatic re-querying, you need to use the same loader for the UI as well as for the updates, limiting its usability for background services.
Of course when using LoaderManager we want to get all the benefits for which it was introduced. So my question is if there is a way to use LoaderManager in connection with a sqlite database without having to implement a content provider yet have all the benefits of it.
Thanks
The two implementations you mention in your post both offer all of the benefits of the CursorLoader except the ability to receive notifications when the underlying content changes.
I've been looking into this a lot recently and I can confidently tell you that the Android API currently does not provide a means of doing this with only a raw SQLiteDatabase (it only provides the ContentResolver#notifyChange() and Cursor#setNotificationUri() methods, which are used to notify all Cursors registered under a certain notification Uri).
That said, your options right now are to:
Implement an observer yourself that is capable of receiving notifications from the SQLiteDatabase when the content changes, and is somehow able to relay these notifications to all existing Loaders in your application. I wrote a pretty extensive blog post on how to implement Loaders that might come in handy if you wish to take on this challenge. Or...
Use Mark Murphy's LoaderEx library and only make database modifications using the AsyncTask operations his library provides. Note that the reason why his tasks refresh the Loader is because they call onContentChanged on the Loader immediately after the insertion/update/delete is performed, effectively telling the Loader that the content has changed and that it should refresh its data.
Just use a ContentProvider with a CursorLoader and you can use the ContentResolver#notifyChange() method to notify the CursorLoader that a content change has occurred.
I'm trying to figure out a better solution, and I'll report back in the future if I ever find/implement one, but for now these will have to do.
Here is my solution, in my onCreateLoader
{
Uri u = Uri.parse("content://what_string_you_want");
return new CursorLoader(this, yourURI, projection, null, null, null) {
private final ForceLoadContentObserver mObserver = new ForceLoadContentObserver();
#Override
public Cursor loadInBackground() {
Cursor c = YOUR_DATABASE.doYourQuery(...);
if (c != null) {
// Ensure the cursor window is filled
c.getCount();
c.registerContentObserver(mObserver);
}
c.setNotificationUri(getContext().getContentResolver(), getUri());
return c;
}
};
}
After the code that will change DB, add
getContentResolver().notifyChange(
Uri.parse("content://same_with_first_string"), null);
how about having a boolean in shared preferences as false .. updating the content when that boolean is true....
and when any of the operations which changes the underlying database .. that boolean will be set to true and as shared preferences you a changelistener you can recieve changes live directly after the relevant methods are called
I am trying to implement Content Providers and Cursor Loaders to get away from cursors as recommended by Android/Google. However, I'm having a terrible time of it. I'm using the tutorials at http://mobile.tutsplus.com/tutorials/android/android-sdk_content-providers/ as my guide and the simplest thing just isn't working. At the beginning of my Activity, I'm doing the following:
SQLData entry = new SQLData(getApplicationContext());
I've also tried
SQLData entry = new SQLData(this);
SQLData is the name of my database class. What I'd like to do after this line of code is create and populate the database using the methods from the content provider class I've created. However, when I try to move past this line in the debugger, a ClassLoader.class window opens, with the message "source not found". I've reloaded and refreshed and cleaned my package, but this doesn't help. I'm happy to provide all the code for my database and content provider classes, but I'm not sure that's what's needed here. Does anyone know how to approach this issue?
Thanks very much!
In android, or any java dev; you may find it more useful to write JUnit tests and put lots of
Log.v(TAG, "message about " + variable);
in your code instead of using the debugger...
I write Java code as my job and use the debug option maybe twice a year as a last resort...
the JUnit tests get my errors out and save me TONS of time, stepping through code in the debugger can be a very time consuming thing...
just a tip, and it may just be my personal pref...
I am implementing an app related to database.
So many times I am calling open and close database connection to insert, update and delete.
It is working fine.
But some times I am getting a database not opened exception in different situations.
How to solve these issues?
Well unless you put proper exception handling you would never know what causes this.
However a good idea is to adopt good ORM mapper for SQL Light with Android and this will improve your database interactions and exception handling and opening and closing it efficiently.
You can opt for SUGAR or ORMLight if you wish; In my opinion this should help you to fix your problem.
Based on the information you provided I can assume that the problem is in your business logic and nobody but you should be able to tell you the root cause.
Without your code here, we won't be able to point you to exact place.
One of the possible reasons can be that by your business logic you are trying to do some operation (insert, update whatever) on closed database.
You can do some workaround to try to ensure that your DB is always open when it is needed. If you implement database getter method with so called lazy initialization approach it will guarantee at least, that the DB is open when you need to access it.
Here is what I am talking about:
1. make a public method which supposed to return DB object:
public SQLiteDatabase getDB() {
if ((mDataBase == null) || (!mDataBase.isOpen())) {
// create or open your database using an OpenHelper
mDataBase = SQLiteOpenHelper.getWritableDatabase();
}
return mDataBase;
}
Now, everywhere in your code use this method to access the DB instead of directly accessing a variable mDataBase.
Note that the code is just to give you an idea and not actually compilable.
Still, I would recommend you to fix your business logic instead of using this workaround.
I am new to android development and I've hit a hurdle when trying to load SQLite data to populate a ListFragment. In previous versions of android one made a new instance of the cursor class, made an SQLite query to place the cursor in the appropriate position, called startManagingCursor, made a new SimpleCursorAdapter and finally called setListAdapter. Pretty darn simple (too bad about the UI thread)!
Now almost all of these methods are deprecated and I have no idea how to populate my poor ListView. The documentation says I should use CursorLoader but here on StackOverflow people advise against using it for SQLite queries. How do I tell my cursor to populate the ListView?
Thanks a lot in advance!
You need to convert you DbAdapter into a Content Provider if you want to use CursorLoaders. and put android:exported= false as a property of your content provider so that it is private. Android team is favoring this approach as they say Content Provider is better suited to handle logic. That is why they are bent on deprecating our old ways( was hard on me too). But I have changed my dbadapters to content providers and now gleefully using cursor loaders( they are too cool not to be used). Try it, generally you will do fine with some more boilerplate code of Content Providers in adition to that of DBadapter and sqliteHelper. GO for it!