Android :: SQLiteOpenHelper Per Activity?
Jul 21, 2010
Do I need an instance of my SQLiteOpenHelper class for each Activity I have? I have 1 currently that all activities access, but started getting an exception
"illegal state exception SQLiteDatabase created and never closed "
on simple a simple query and I can't seem to figure out why this is happening. I read online about this, and wanted to try to understand why the SQLiteOpenHelper was dependent on an Activity.
Is there a way to just have open SQLiteDatabase object without the Helper and have it just exist within all activities?
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Sep 10, 2009
I get a SQLiteException if I try to issue an alter statement in the onUpgrade method of SQLiteOpenHelper subclass:
Can't upgrade read-only database from version X to Y: /path/to/db
That makes no sense at all! Where did I go wrong?
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Feb 11, 2010
I would like to know if it is possible to have several DbOpenHelper in the same app Android but to use them to write and read in the same database? because I'm trying to create tables from 2 different OpenHelper (with different names) and only the first one seems to create. when I try to run the 2nd one, i get an error...
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Jun 9, 2010
I have a SQLite database, and several tables within that datbase. I am developing a DBAdapter for each table within the database. (reference Reto Meier's Professional Android 2 Application Development, Listing 7.1).
I am using the adb shell to interface with the database from the command line and see that the database is being populated as I expect. Occasionally, I want to drop a table so that I can ensure it's being built properly, from scratch.
The problem is that SQLiteOpenHelper only checks to see if the database exists. Is there a typical solution to writing a helper to also see that the table(s) exists? Basically once I drop a table, the helper checks to see that the database exists and assumes all is well.
Also, the CREATE_DATABASE string used in the reference above only creates the one table. Should I consider using the DBAdapter for an adapter to ALL of my tables? That doesn't seem as clean to me.
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Aug 17, 2010
I am doing my first app with a database and I am having a little trouble understanding the onUpgrade function. My database has a table with an items and a favorite column so that the user can favorite an item. Most implementations I see simply drop the table and reconstruct it but I don't want to do this. I want to be able to add more items to the table.
When the app is upgraded through the android marketplace does the database know its version number? So could I increment the version number in the code and then export it to the marketplace and when the user boots up the upgraded version for the first time then onUpgrade will be called?
If this is the case my onUpgrade would simply pull from a file and add the database items in. Is this a standard way of doing things or is there a better way of handling this in Android. I am trying to stay as standard as possible.
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Jul 9, 2010
The documentation does not make the interation between onUpgrade() and onCreate() clear.
When implementing onCreate() should this create the database at version 1, assuming that onUpgrade will apply all of the patches to bring it up to version x (lets say version 5 for example)? Or should onCreate build the latest version of the database, and onUpgrade is only used to upgrade legacy clients.
I kind of prefer the first, because it effectively means that the same SQL is executed for everybody. Whereas the second options means that there is a potential for onCreate to build something slightly different to the succession of patches built by onUpgrade.
I can always make onCreate call into onUpgrade, however, this is the kind of implementation detail that should go into the javadocs...
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May 21, 2010
If you extend SQLiteOpenHelper, for the Constructor you have to use a Context. I am wondering if there is a way to leave this out, and be able to work with database tables without a Context.
Or at least be least restrictive, I mean a way of project/class structure that will make history the several context passings I have to do now.
As it is my application has several level of classes, chained in each other, and there are a few that connects to the database, but have no whatsoever influence on the interface, so they don't actually need the Context.
Are you creating your classes in the way that you pass each time a Context to them?
If not, how you do, how you reuse a Context in a short class?
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Jun 11, 2010
The documentation describes the class as a helper object to create, open, and/or manage a database. Having that in mind wouldn't you say that the name is a little misleading?
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Sep 13, 2010
Every time i increase my database version and push the upgraded app to the users, something weird happens.. For some it works perfectly fine, and some report crashes (including through the Market's reporting system) caused by the lack of table columns i just added in onUpgrade.
If you want to see the method:
http://code.google.com/p/tag-todo-list/source/browse/trunk/Donut/src/com/android/todo/data/ToDoDB.java#136
I can't spot any exceptions that appear in onUpgrade. What i'm currently doing to bypass these problems is intercepting the exceptions where the new fields are invoked for the first time and then calling onUpgrade 'manually', which is kind of dirty.
Also, the app sometimes generates a 'no such table' SQLiteException when accessing the main table (again, only for some users) which is incredibly strange... Does someone know why these things happen? Or can you spot something wrong in my code?
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Jun 9, 2010
I have an existing SQLite database file from another project.
Where do I include the database file into my Eclipse project to have it deploy with the app.
Do I need to indicate that the database file is writable? (In the iPhone world you need to copy the database file from the app's bundle to a writable folder on the iPhone proper before first use.)
Once I have the database file on the phone, how do I tell SQLiteOpenHelper to use it? (I extend SQLiteOpenHelper in a custom class.
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Oct 17, 2010
How can I emulate an onUpgrade call for my SQLiteOpenHelper class? I have tried changing the version number in my SQLiteOpenHelper class and versionCode in manifest but onUpgrade is not called. Any idea? I need to check my onUpgrade code before upload it to the market, I don't want my app's users get a buggy upgrade.
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Aug 24, 2010
I'm trying to implement a database in my application. I'm following a tutorial about writing my own ContentProvider, but I'm confused about SQLiteOpenHelper::getType. We're supposed to write it and, essentially, write a switch that returns the MIME type corresponding to the type of data we're dealing with.
I don't fully understand it. I'm not sure, even though I have an example, what is precisely supposed to be conveyed here. How do I determine the MIME type of my different tables of data?
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Feb 27, 2010
I have two classes, one MainClass and one DataBaseHelper class, which extends SQLiteOpenHelper.
From my MainClass I call a method in the DataBaseHelper class to open a data base. Before opening the data base I want to check the users data base version (this is important as soon as I want to update the data base and push it to the Android market). So from the DataBaseHelper class I call the following method, which is in the MainClass.
CODE:..........
I call the checkCurrentDbVersion() method from the DataBaseHelper class like so:
CODE:.....................
As soon as the debugger runs the following line, it stops.
CODE:...........
I have no constructor defined. Could that be the failure?
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Nov 16, 2009
I've had fine luck using SQLite with straight, direct SQL in Android, but this is the first time I'm wrapping a DB in a ContentProvider. I keep getting a null pointer exception when calling getWritableDatabase() or getReadableDatabase().
Is this just a stupid mistake I've made with initializations in my code or is there a bigger issue?
CODE:.........
But here's LogCat showing the exception:
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Nov 20, 2010
My app uses two databases (separate files). To handle these databases I have created two Helper classes which extend SQLiteOpenHelper, one for each database.
I am now going to add a third database and wonder whether I need to create yet another Helper class (and if I used a 4th and a 5th database would I need even more Helper classes), or can I use the same Helper class for multiple databases?
The problem that I see with trying to use just one Helper class is that I can't see how to pass the name of the individual database files to the Helper. At present the name of the database is hard-coded as a Static field of each of the Helper classes, but if I had only one Helper class I would need to be able to pass the different names in to the Constructor when creating the separate Helper objects; the problem is that the SQLiteOpenHelper Constructor seems to be called by Android with just one parameter: the Context.
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Aug 2, 2010
Whenever the memory needs to be reclaimed, the process is being killed by Activity Manager Service in killPidsForProcess. I have a back button in my activity window on right corner of the title bar.
I want to kill the activity completely on clicking the close button. Can I reuse the same function and will it have any major effect? Please help me out in this.
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Jan 20, 2009
I want to be able to show the Battery Info activity in my app, which shows things such as the exact level, battery health, etc.I'm not sure how I can get it, though a few applications such as Power Manager, Any Cut, etc. show this screen as well. I found in the source code of Settings this intent in a file called testing_settings.xml,But I don't know how to use it. I would guess from the fact that Any Cut has a list of activities, that a list of said activities exists somewhere, and therefore an easy way to access them exists, but I haven't found it.
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Aug 27, 2010
My app is comprised of a set of reusable Activities that other apps can reuse. For various reasons, I would like my Activities to be launched in context of the invoking Activity's process, instead of always being launched in my Activity's process (default behavior on Android). How can I achieve this?
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Mar 3, 2010
So I have an app with Activity A. The layout on the activity is dynamic genearted. So it's possible that on Activity A a user hits a button that goes to "A" and the new page looks different, then a user clicks another button to go to "A" again. Now I have 2 Activities in the history stack. A, A, and currently on A. Is it possible that if a user clicks a button that the whole Activity stack is cleared in a scenario such as this?
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Apr 27, 2010
How to finish any previous activity in application stack (at any level , I mean not immediate parent) , from current activity like on some particular event I want to invalidate this previous activity?
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Jul 26, 2010
How can I make sure I only retain one copy of an activity on the stack when called from non-activity? When called from an activity I can just add the FLAG_ACTIVITY_REORDER_TO_FRONT flag to the Intent, but how can I do this from e.g. a widget or a notification?
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Aug 21, 2009
I have a problem to start/create Activity in landscape mode. My Activity need to start in landscape mode and be used in landscape mode by users. So far, I used setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE) to force screen orientation of my Activity to landscape mode in onCreate() method.
In addition to this screen mode requirement, my application need to start another background thread in onResume() method, and this thread takes some seconds in order to finish an initialization process, and it is not desirable to to stop/restart this thread's service during the initialization process.
However setRequestedOrientation (ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE) forces my Activity restart in a very little while (means onCreate->onResume->onPause->onStop are executed twice at the first place). As a result, my background thread be stopped/restarted during the initialization process, and this makes me a mess at this moment.
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Nov 5, 2010
The default behavior from my observation is if current activity force closes Android tries to go to previous activity on stack How can I control this behavior? I want force close to close all activities
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Jul 19, 2010
Im writing a program that offers a quick reply dialog upon receipt of an SMS.
However, I am getting an unexpected result. When I receieve an SMS, the appropriate dialog activity comes up displaying the correct phone number and message, however there is a second activity behind it that is the 'default' activity in my program (it is what opens when i launch my application)
I do not want this second activity to come up. The quick reply activity should come up by itself over top of whatever the user was doing before.
The 'floating' activity:
CODE:.........
The call to the activity inside an onReceive()
CODE:..............
The Manifest:
CODE:.................
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May 16, 2010
I'm writing an application that starts with a loading activity. In the loading activity the app requests html from web and parses the html, then it sends the parsing result to the main activity. The main activity has several tabs, and contents of these tabs are based on the result of parsing.For example, the result of parsing is a list of strings ["apple", "banana", "orange"], and I need to pass this list to main activity, so that the main activity can create three tabs named after three fruits.I would like to know if there is any way to pass a list of strings among activities, BTW, is it the common way of do this?
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Mar 3, 2010
example scenario is: from login screen - main screen - then when i clicked a hide button inside the mainscreen, the app will need to go in the home screen, and when im going to click the app again the main screen would be called and not the login screen
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Feb 18, 2010
have an activity which launches another activity, via a button click. By default, on newer OS versions of android, the OS will animate the new activity sliding in from right to left.Is there a way to disable this animation? I just want the new activity to appear without any sort of animation.
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Aug 12, 2010
I'm working on an app that launches the browser activity to perform a Twitter OAuth authorization. This process uses a callback url which will re-launch the activity that started the browser activity in the first place.My problem is that the browser pages remain in the history stack and when the user then clicks back from the preferences activity that launched the browser in the first place, they don't go back to the app's main activity, but instead are brought back to the browser. I've tried adding flags to the launching intent to prevent history and reset on clear, but it doesn't seem to work when running on my phone, only on the emulators.
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Jan 26, 2009
I have an application with contains multiple activities. The main activity will start the others ( use startActivity() ) depends on user event, when an activity close, it calls finish() and return back to main activity. It appears to behavior like that.
However, the "problem" I see is main activity's onCreate function is called every time. I think the the main activity should be placed in the activity stack and simply push to front when others exit, therefore only onResume, onStart are called. Is there some flag I need to set or I misunderstand the activity behaviro?
In child activity, besides calling finish() or startActivity for main activity, what is other way to move main activity to front?
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Jan 10, 2010
I created an application which enables the user to set whether he wants to receive notification while the application runs in background mode. If the notifications are enabled an activity should be started (the dialog should appear on the screen).
I tried to enabled it the following way:
CODE:...........
This is the method from main activity. When onPause() is executed isRunningInBackground is set true.
When I tried to debug it when the main application was running in the background the line
startActivity(intent) had no effect (the activity didn't appear).
Does anyone know how to midify the logic in order to start an activity from the main activity when the main activity is running in the background (after onPause() is called)?
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