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Bender  
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 More options Jul 15 2010, 9:51 am
From: Bender <abende...@googlemail.com>
Date: Thu, 15 Jul 2010 06:51:37 -0700 (PDT)
Local: Thurs, Jul 15 2010 9:51 am
Subject: Database handling - when do you open and close
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Hi,

I'm writing an app which has 2 activities and gets his data from a
database. Unfortunately I'm not sure when I have to open and close the
database properly. In both activities I'm opening the database so the
activities can access its data. When I do the following:

 * Start the app
 * Open activity 1
 * Open activity 2 (via button in activity 1)
 * Hit the back button (back to activity 1)
 * Again back button (back to home screen)
 * Start the app

I'm receiving such an leak error:

07-15 14:34:19.504: ERROR/Database(234): Leak found
07-15 14:34:19.504: ERROR/Database(234):
java.lang.IllegalStateException: mPrograms size 1
07-15 14:34:19.504: ERROR/Database(234):     at
android.database.sqlite.SQLiteDatabase.finalize(SQLiteDatabase.java:
1669)
07-15 14:34:19.504: ERROR/Database(234):     at
dalvik.system.NativeStart.run(Native Method)
07-15 14:34:19.504: ERROR/Database(234): Caused by:
java.lang.IllegalStateException: /data/data/de.anote/databases/
anote.db SQLiteDatabase created and never closed

.... more stuff .....

I guess it is because I'm not closing the database so implemented the
following:

 * db.open() in both onCreate() and both onResume() methods by the 2
activities
 * db.close() in both onPause() methods.

But now I'm receiving another error:

07-15 15:27:18.472: ERROR/AndroidRuntime(266): Uncaught handler:
thread main exiting due to uncaught exception
07-15 15:27:18.508: ERROR/AndroidRuntime(266):
java.lang.RuntimeException: Unable to resume activity {de.anote/
de.anote.gui.CategoryView}: java.lang.IllegalStateException: mQuery
SELECT _id, note_name, value, date, category, priority, reminderbool,
reminder, todo FROM t_note WHERE category=? ORDER BY date 1
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.app.ActivityThread.performResumeActivity(ActivityThread.java:
2950)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.app.ActivityThread.handleResumeActivity(ActivityThread.java:
2965)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1889)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.os.Handler.dispatchMessage(Handler.java:99)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.os.Looper.loop(Looper.java:123)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.app.ActivityThread.main(ActivityThread.java:4363)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
java.lang.reflect.Method.invokeNative(Native Method)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
java.lang.reflect.Method.invoke(Method.java:521)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
com.android.internal.os.ZygoteInit
$MethodAndArgsCaller.run(ZygoteInit.java:860)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
dalvik.system.NativeStart.main(Native Method)
07-15 15:27:18.508: ERROR/AndroidRuntime(266): Caused by:
java.lang.IllegalStateException: mQuery SELECT _id, note_name, value,
date, category, priority, reminderbool, reminder, todo FROM t_note
WHERE category=? ORDER BY date 1
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.database.sqlite.SQLiteQuery.requery(SQLiteQuery.java:162)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.database.sqlite.SQLiteCursor.requery(SQLiteCursor.java:536)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.app.Activity.performRestart(Activity.java:3736)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.app.Activity.performResume(Activity.java:3756)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.app.ActivityThread.performResumeActivity(ActivityThread.java:
2937)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     ... 10 more
07-15 15:27:18.508: ERROR/AndroidRuntime(266): Caused by:
android.database.sqlite.SQLiteMisuseException: library routine called
out of sequence: handle 0x0
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.database.sqlite.SQLiteProgram.native_bind_string(Native
Method)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.database.sqlite.SQLiteProgram.bindString(SQLiteProgram.java:
178)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     at
android.database.sqlite.SQLiteQuery.requery(SQLiteQuery.java:153)
07-15 15:27:18.508: ERROR/AndroidRuntime(266):     ... 14 more

Unfortunately I can't read which line in my code causes this exception
but I guess it is because there is some point where is a database
access and the db is still closed.

So my question is, at which places should I open and close my
database? It is right to open it in the onCreate(), onResume() methods
and close it in onPause()?


 
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YuviDroid  
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 More options Jul 15 2010, 10:07 am
From: YuviDroid <yuvidr...@gmail.com>
Date: Thu, 15 Jul 2010 16:07:14 +0200
Local: Thurs, Jul 15 2010 10:07 am
Subject: Re: [android-beginners] Database handling - when do you open and close
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Probably by opening the db both in onCreate() and onResume() in some
circustances (e.g. first execution of your app) the db will be opened twice,
which for sure is not good.
If you open the db only in onResume() it should be fine (although I didn't
try it by myself). Usually, when I need data from the db, I call db.open(),
fetch my data, and db.close(). In this way I'm pretty sure there won't be
any such leak. Still I don't know if that's "the best way" to do it.

YuviDroid

--
YuviDroid
http://android.yuvalsharon.net

 
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Bender  
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 More options Jul 15 2010, 10:49 am
From: Bender <abende...@googlemail.com>
Date: Thu, 15 Jul 2010 07:49:29 -0700 (PDT)
Local: Thurs, Jul 15 2010 10:49 am
Subject: Re: Database handling - when do you open and close
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Thanks for your reply. I tried to open the db only in onResume() but
that doesn't work since there are db accesses in the onCreate() method
which is called before onResume() as far as I know. I think opening
and closing the db after every access would slow the app down a lot
because i'm using the db in almost every method. I hope there is
another solution for it..

On 15 Jul., 16:07, YuviDroid <yuvidr...@gmail.com> wrote:


 
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YuviDroid  
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 More options Jul 15 2010, 11:03 am
From: YuviDroid <yuvidr...@gmail.com>
Date: Thu, 15 Jul 2010 17:03:20 +0200
Local: Thurs, Jul 15 2010 11:03 am
Subject: Re: [android-beginners] Re: Database handling - when do you open and close
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Then you could open the db in onCreate(), while in onResume() you open it
only if it's not already opened (by using SQLiteDatabase.isOpen()).

Just some ideas...;)

Hope it works!
Yuvi

--
YuviDroid
http://android.yuvalsharon.net

 
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Discussion subject changed to "Database handling - when do you open and close" by Kostya Vasilyev
Kostya Vasilyev  
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 More options Jul 15 2010, 11:03 am
From: Kostya Vasilyev <kmans...@gmail.com>
Date: Thu, 15 Jul 2010 19:03:58 +0400
Local: Thurs, Jul 15 2010 11:03 am
Subject: Re: [android-beginners] Re: Database handling - when do you open and close
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onResume / onPause are called when another activity pops in front, but
your activity stays on the screen. So this is probably a bit much.

You could try onStart / onStop, and move the code that populates views
with database data from onCreate to onStart.

-- Kostya

15.07.2010 18:49, Bender пишет:

--
Kostya Vasilev -- WiFi Manager + pretty widget -- http://kmansoft.wordpress.com

 
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Discussion subject changed to "Database handling - when do you open and close" by Bender
Bender  
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 More options Jul 15 2010, 12:36 pm
From: Bender <abende...@googlemail.com>
Date: Thu, 15 Jul 2010 09:36:58 -0700 (PDT)
Local: Thurs, Jul 15 2010 12:36 pm
Subject: Re: Database handling - when do you open and close
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@YuviDroid

I'm trying the following at the moment: the open() only gets called in
both onCreate() methods with:

        mDb = new DbAdapter(this);
        if(mDb.getDatabase() == null || !mDb.getDatabase().isOpen()) {
          mDb.open();
        }

The problem I'm having with this is, that there is always a new
DbAdapter created which is fine when the activity is created the first
time. But this way "mDb.getDatabase() == null" will be always true
because its a new mDb.

So I either need to find a way to check if the database is opened
without "mDb" or need to remember mDb even if the activity is stopped.

@Kostya Vasilyev

I tried that, but then my app crashes while switching between
activities. When I was searching for the error I put logs in the
open() and close() methods by my DbAdapter and I could see the
following:

 * open()  (app, activity1 started)
 * open()  (i hit a button in activity1, activity2 is starting and
open is called within onStart)
 * close()  (activity1 is stopped, in onStop close is called)

When I go back to activity1 it throws an exception because the
database is closed. -.-


 
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YuviDroid  
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 More options Jul 16 2010, 3:10 am
From: YuviDroid <yuvidr...@gmail.com>
Date: Fri, 16 Jul 2010 09:10:10 +0200
Local: Fri, Jul 16 2010 3:10 am
Subject: Re: [android-beginners] Re: Database handling - when do you open and close
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mmm I'm not really sure what you are trying to achieve. Exactly, at what
times do you want to open/close the db? The db should stay open while your
application is running? So, even when you switch among activities (yours
activities)?

--
YuviDroid
http://android.yuvalsharon.net

 
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Bender  
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 More options Jul 18 2010, 9:39 am
From: Bender <abende...@googlemail.com>
Date: Sun, 18 Jul 2010 06:39:13 -0700 (PDT)
Local: Sun, Jul 18 2010 9:39 am
Subject: Re: Database handling - when do you open and close
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I want to get rid of the error which is telling me that there is a
leak in my app because my db gets opened twice. The db doesn't need to
be open the whole time but it is accessed quite often so I don't think
it would be very performant to open and close it for every access.

On 16 Jul., 09:10, YuviDroid <yuvidr...@gmail.com> wrote:


 
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brucko  
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 More options Jul 18 2010, 6:30 pm
From: brucko <geoff.bruck...@gmail.com>
Date: Sun, 18 Jul 2010 15:30:09 -0700 (PDT)
Local: Sun, Jul 18 2010 6:30 pm
Subject: Re: Database handling - when do you open and close
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Bender,

put your db in a local Service. Open the db in onCreate() close it in
onDestroy(). Your Activities can bind and unbind to the Service as
many times as you like. The system will keep the service running as
long as  you have an activity in the foreground process bound to it or
otherwise until it needs to reclaim the resources.

Take a look at :

http://developer.android.com/resources/samples/ApiDemos/src/com/examp...

but DONT have your binder as a non-static inner class as in the
example - or you will create a memory leak and leak your Service.
Instead, pass the binder a reference to your service in onCreate and
get the binder to null the reference out in onDestroy


 
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Bender  
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 More options Aug 5 2010, 4:48 pm
From: Bender <abende...@googlemail.com>
Date: Thu, 5 Aug 2010 13:48:56 -0700 (PDT)
Local: Thurs, Aug 5 2010 4:48 pm
Subject: Re: Database handling - when do you open and close
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Thanks for your reply, and sorry for my late answer. :-)

I tried to get it running as a service but I don't really get how I
have to use services, binders and service connections. I'm reading a
book with an example for services but can't adopt it to my problem.
What I tried is the following:

I created one class for the service, which holds the variable for my
database:
__________________

public class DatabaseService extends Service {

        public DbAdapter mDbAdapter;
        private DatabaseBinder mDatabaseBinder = new DatabaseBinder();

        @Override
        public IBinder onBind(Intent intent) {
                return mDatabaseBinder;
        }

        @Override
        public void onCreate() {
                super.onCreate();
                mDatabaseBinder.mDatabaseService = this;
                mDbAdapter = new DbAdapter(getApplicationContext());
                mDbAdapter.open();
        }

        @Override
        public void onDestroy() {
                super.onDestroy();
                mDatabaseBinder.mDatabaseService = null;
                mDbAdapter.close();
        }

}

This is my database binder:
__________________

public class DatabaseBinder extends Binder {

        public DatabaseService mDatabaseService;

        public DbAdapter getDbAdapter() {
                return mDatabaseService.mDbAdapter;
        }

}

And this my service connection:
__________________

public class DbServiceConnection implements ServiceConnection {

        DatabaseBinder mBinder;

        public DbServiceConnection(DatabaseBinder binder) {
                mBinder = binder;
        }

        @Override
        public void onServiceConnected(ComponentName className, IBinder
binder) {
                mBinder = (DatabaseBinder) binder;
        }

        @Override
        public void onServiceDisconnected(ComponentName arg0) {
        }

}

If I want to use this in my activity with this:

        private DatabaseBinder mDatabaseBinder;
        private DbServiceConnection mServiceConnection = new
DbServiceConnection(mDatabaseBinder);

        final Intent databaseServiceIntent = new Intent(this,
DatabaseService.class);
        this.bindService(databaseServiceIntent, mServiceConnection,
Context.BIND_AUTO_CREATE);

        mDb = mDatabaseBinder.getDbAdapter();

I'm getting a nullpointer exception at the last line. I don't know if
I'm using it right (I guess not :D ), I haven't used services before.
Do you know why it is throwing a Nullpointer exception? Is this the
right way to use a service and bind it in the activity or should I do
it somehow different?

On 19 Jul., 00:30, brucko <geoff.bruck...@gmail.com> wrote:


 
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Kostya Vasilyev  
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 More options Aug 5 2010, 4:54 pm
From: Kostya Vasilyev <kmans...@gmail.com>
Date: Fri, 6 Aug 2010 00:54:50 +0400
Local: Thurs, Aug 5 2010 4:54 pm
Subject: Re: [android-beginners] Re: Database handling - when do you open and close
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Starting / binding to a service is asynchronous. You can't call bindService
and expect it to be already started and bound by the next line.

Call bindService and return control to Android by returning from onCreate or
whatever. Your service connection callback will be invoked a little later,
once the service is started.

--
Kostya Vasilyev -- http://kmansoft.wordpress.com

06.08.2010 0:49 пользователь "Bender" <abende...@googlemail.com> написал:

Thanks for your reply, and sorry for my late answer. :-)

I tried to get it running as a service but I don't really get how I
have to use services, binders and service connections. I'm reading a
book with an example for services but can't adopt it to my problem.
What I tried is the following:

I created one class for the service, which holds the variable for my
database:
__________________

public class DatabaseService extends Service {

       public DbAdapter mDbAdapter;
       private DatabaseBinder mDatabaseBinder = new DatabaseBinder();

       @Override
       public IBinder onBind(Intent intent) {
               return mDatabaseBinder;
       }

       @Override
       public void onCreate() {
               super.onCreate();
               mDatabaseBinder.mDatabaseService = this;
               mDbAdapter = new DbAdapter(getApplicationContext());
               mDbAdapter.open();
       }

       @Override
       public void onDestroy() {
               super.onDestroy();
               mDatabaseBinder.mDatabaseService = null;
               mDbAdapter.close();
       }

}

This is my database binder:
__________________

public class DatabaseBinder extends Binder {

       public DatabaseService mDatabaseService;

       public DbAdapter getDbAdapter() {
               return mDatabaseService.mDbAdapter;
       }

}

And this my service connection:
__________________

public class DbServiceConnection implements ServiceConnection {

       DatabaseBinder mBinder;

       public DbServiceConnection(DatabaseBinder binder) {
               mBinder = binder;
       }

       @Override
       public void onServiceConnected(ComponentName className, IBinder
binder) {
               mBinder = (DatabaseBinder) binder;
       }

       @Override
       public void onServiceDisconnected(ComponentName arg0) {
       }

}

If I want to use this in my activity with this:

       private DatabaseBinder mDatabaseBinder;
       private DbServiceConnection mServiceConnection = new
DbServiceConnection(mDatabaseBinder);

       final Intent databaseServiceIntent = new Intent(this,
DatabaseService.class);
       this.bindService(databaseServiceIntent, mServiceConnection,
Context.BIND_AUTO_CREATE);

       mDb = mDatabaseBinder.getDbAdapter();

I'm getting a nullpointer exception at the last line. I don't know if
I'm using it right (I guess not :D ), I haven't used services before.
Do you know why it is throwing a Nullpointer exception? Is this the
right way to use a service and bind it in the activity or should I do
it somehow different?

On 19 Jul., 00:30, brucko <geoff.bruck...@gmail.com> wrote:

> Bender,

> put your db in a local Se...
> http://developer.android.com/resources/samples/ApiDemos/src/com/examp...

> but DONT have your binder as a non-static inner class as in the
> example - or you will create a...

ATTENTION: Android-Beginners will be permanently disabled on August 9 2010.
For more information about this change, please read [http://goo.gl/xkfl] or
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Bender  
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 More options Aug 6 2010, 4:08 am
From: Bender <abende...@googlemail.com>
Date: Fri, 6 Aug 2010 01:08:09 -0700 (PDT)
Local: Fri, Aug 6 2010 4:08 am
Subject: Re: Database handling - when do you open and close
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Ok I tried to find out at which point the service is started and when
I can access its database variable. The logs I used showed that the
services onCreate() is called after the onResume() method by my
activity. That is a bit late because I need access to the database
before onResume() to fill the views with data. Is there a way to tell
the activity to wait until the service is started?

On 5 Aug., 22:54, Kostya Vasilyev <kmans...@gmail.com> wrote:


 
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Kostya Vasilyev  
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 More options Aug 6 2010, 4:26 am
From: Kostya Vasilyev <kmans...@gmail.com>
Date: Fri, 6 Aug 2010 12:26:40 +0400
Local: Fri, Aug 6 2010 4:26 am
Subject: Re: [android-beginners] Re: Database handling - when do you open and close
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Sure. The service connection callback you seem to already have in your code.

--
Kostya Vasilyev -- http://kmansoft.wordpress.com

06.08.2010 12:10 пользователь "Bender" <abende...@googlemail.com> написал:

Ok I tried to find out at which point the service is started and when
I can access its database variable. The logs I used showed that the
services onCreate() is called after the onResume() method by my
activity. That is a bit late because I need access to the database
before onResume() to fill the views with data. Is there a way to tell
the activity to wait until the service is started?

On 5 Aug., 22:54, Kostya Vasilyev <kmans...@gmail.com> wrote:

> Starting / binding to a service is ...
> 06.08.2010 0:49 пользователь "Bender" <abende...@googlemail.com> написал:

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Bender  
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 More options Aug 6 2010, 4:52 am
From: Bender <abende...@googlemail.com>
Date: Fri, 6 Aug 2010 01:52:23 -0700 (PDT)
Local: Fri, Aug 6 2010 4:52 am
Subject: Re: Database handling - when do you open and close
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I tried the following in my activity:

        mServiceConnection =  new
DbServiceConnection(mDatabaseBinder);
        final Intent databaseServiceIntent = new Intent(this,
DatabaseService.class);
        this.bindService(databaseServiceIntent, mServiceConnection,
Context.BIND_AUTO_CREATE);

        while(mDatabaseBinder == null) {
                try {
                                Thread.sleep(100);
                        } catch (InterruptedException e) {
                                // catch...
                        }
        }

Did you mean that? Now it should wait until the mDatabaseBinder is set
which should be in the onServiceConnected() method but that code
results in an endless loop, mDatabaseBinder stays null. Maybe I got it
wrong how the components work together. As far as I understood it, you
have a service running in the background, which returns a binder in
onBind(). The service connection "fills" the binder
onServiceConnected() so it can be used in the activity to access the
services variables. Is that wrong?

On 6 Aug., 10:26, Kostya Vasilyev <kmans...@gmail.com> wrote:


 
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Discussion subject changed to "Database handling - when do you open and close" by Kostya Vasilyev
Kostya Vasilyev  
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 More options Aug 6 2010, 6:52 am
From: Kostya Vasilyev <kmans...@gmail.com>
Date: Fri, 06 Aug 2010 14:52:48 +0400
Local: Fri, Aug 6 2010 6:52 am
Subject: Re: [android-beginners] Re: Database handling - when do you open and close
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No, calling Thread.sleep() won't work.

Android framework is largely single-threaded, event-driven.

This means that your application and the framework run on the same
thread, passing control to each other, doing work in small pieces. This
thread is called the UI thread, and blocking it by calling sleep() can
do only one thing - cause the "Application Not Responding" dialog to appear.

The right thing to do is call bindService, and return from onResume.

You've done your piece of work (responded to onResume, and requested
that Android bind a service). Now you need to give Android a chance to
do its piece of work - by returning from onResume into Android framework
code, which will start the service (if necessary) and bind it, notifying
your callback.

Then it's your turn again - once in the ServiceConnection callback, you
know the service has been bound, and you can talk to the service and
ultimately populate the UI.

So that's basically the scheme with services.

You might also want to look at ContentProviders. They have a few
advantages over Services for this case - their lifecycle is managed by
Android, access is synchronous (using ContentResolver), and they handle
propagating data changes to existing queries / cursors (so if you have a
ListView, its data will be "live").

-- Kostya

06.08.2010 12:52, Bender пишет:

--
Kostya Vasilev -- WiFi Manager + pretty widget -- http://kmansoft.wordpress.com

 
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