hi,
Im starting with android and have few questions about database access.
1. Every tutorial I ve read (ie Notepad) that uses sqlite creates and
opens connection via SQLiteOpenHelper in onCreate callback. but I
really have never seen that the connection is closed (androids throws
exceptions that there is a leak as connection is never closed). So I
assume that onSaveInstanceState is the best bet to close as onCreate
opens the connection. but maybe it should be sooner - something like
onResume (for open) and onPause (for close). or maybe those tutorials
are too trivial and I should create another layer for accessing data
in services, so that data could be shared between activities and
wouldn't suffer from activity life cycle.
the only thing is that the exception is thrown after a while - not
immediately after destroying activity
D/MyMainActivity :( 305): on Pause.
D/MyMainActivity :( 305): on Stop.
D/MyMainActivity :( 305): on Destroy.
D/dalvikvm( 101): GC freed 408 objects / 18416 bytes in 78ms
I/ActivityManager( 55): Starting activity: Intent
{ act=android.intent.action.MAIN
cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=info.kami
D/MyMainActivity :( 305): on create.
D/MyMainActivity :( 305): on Start.
D/MyMainActivity :( 305): on Resume.
I/ActivityManager( 55): Displayed activity
my.app.android/.MainActivity: 664 ms (total 664 ms)
I/ActivityManager( 55): Starting activity: Intent
{ act=android.intent.action.MAIN cat=[android.intent.category.HOME]
flg=0x10200000 cmp=com.android.l
D/MyMainActivity :( 305): on Pause.
D/MyMainActivity :( 305): on Stop.
I/ActivityManager( 55): Starting activity: Intent
{ act=android.intent.action.MAIN
cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=info.kami
D/MyMainActivity :( 305): on Restar.
D/MyMainActivity :( 305): on Start.
D/MyMainActivity :( 305): on Resume.
D/dalvikvm( 305): GC freed 5465 objects / 347528 bytes in 95ms
E/Database( 305): Leak found
E/Database( 305): java.lang.IllegalStateException: mPrograms size 1
E/Database( 305): at
android.database.sqlite.SQLiteDatabase.finalize(SQLiteDatabase.java:
1668)
E/Database( 305): at dalvik.system.NativeStart.run(Native
Method)
E/Database( 305): Caused by: java.lang.IllegalStateException: /data/
data/my.app.android/databases/data SQLiteDatabase created and never
closed
E/Database( 305): at
android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:
1694)
E/Database( 305): at
android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:
738)
E/Database( 305): at
android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:
760)
E/Database( 305): at
android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:
753)
E/Database( 305): at
android.app.ApplicationContext.openOrCreateDatabase(ApplicationContext.java:
473)
E/Database( 305): at
android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:
193)
E/Database( 305): at
android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:
98)
E/Database( 305): at
my.app.android.dao.SQLiteTemplate.openToReadWrite(SQLiteTemplate.java:
60)
E/Database( 305): at
my.app.android.dao.SQLiteCallDao.open(SQLiteCallDao.java:54)
E/Database( 305): at
my.app.android.MainActivity.getDao(MainActivity.java:102)
E/Database( 305): at
my.app.android.MainActivity.onCreate(MainActivity.java:53)
E/Database( 305): at
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:
1047)
E/Database( 305): at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:
2459)
E/Database( 305): at
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:
2512)
E/Database( 305): at android.app.ActivityThread.access
$2200(ActivityThread.java:119)
E/Database( 305): at android.app.ActivityThread
$H.handleMessage(ActivityThread.java:1863)
E/Database( 305): at
android.os.Handler.dispatchMessage(Handler.java:99)
E/Database( 305): at android.os.Looper.loop(Looper.java:123)
E/Database( 305): at
android.app.ActivityThread.main(ActivityThread.java:4363)
E/Database( 305): at
java.lang.reflect.Method.invokeNative(Native Method)
E/Database( 305): at java.lang.reflect.Method.invoke(Method.java:
521)
E/Database( 305): at com.android.internal.os.ZygoteInit
$MethodAndArgsCaller.run(ZygoteInit.java:860)
E/Database( 305): at
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
E/Database( 305): at dalvik.system.NativeStart.main(Native
Method)
E/Database( 305): Leak found
2. Is it really that important (from performance point of view) to use
cursor when possible? usually I map each row in cursor to some type
and work on a List of that type.
3. how to avoid fetching (even that db is local) all data from some
table when my ListView can show only few results at a time. does api
support kind of data scrolling - that I missed reading tutorials?? Or
should I take care of such situation by myself and fetch-replace data
in the view when user drag the scroll bar.
4. I would love to AndroidManifest.xml act as IoC bean descriptor so
in code you could annotate field to have your data-service injected.
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