Android SQLite数据库已被锁定

Question

I have a bound service running multiple threads that read and write to an SQLite database. I create an instance of my database helper and get a connection to the database in the onCreate of my service, which should execute on the main thread. As it's a bound service there should only ever be one instance of the service in memory. However i still get exceptions occasionally when the service tries to open the database or when one of the threads tries to execute a statement.

Service code:

@Override
    public void onCreate() {
        super.onCreate();

        MyDatabaseHelper helper = new MyDatabaseHelper(this);
        database = helper.getWritableDatabase();
}

Exceptions:

java.lang.RuntimeException: Unable to create service uk.co.example.service.MyService: 
   android.database.sqlite.SQLiteException: unable to open database file
at android.app.ActivityThread.handleCreateService(ActivityThread.java:1959)
at android.app.ActivityThread.access$2500(ActivityThread.java:117)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:989)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:3691)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605)
at dalvik.system.NativeStart.main(Native Method)
Caused by: android.database.sqlite.SQLiteException: unable to open database file
at android.database.sqlite.SQLiteDatabase.dbopen(Native Method)
at android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1960)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:887)
at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:965)
at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:958)
at android.app.ContextImpl.openOrCreateDatabase(ContextImpl.java:585)
at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:203)
at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:118)
at uk.co.example.service.MyService.onCreate(MyService.java:69)
at android.app.ActivityThread.handleCreateService(ActivityThread.java:1949)
... 10 more

android.database.sqlite.SQLiteException: error code 5: database is locked
at android.database.sqlite.SQLiteStatement.native_execute(Native Method)
at android.database.sqlite.SQLiteStatement.execute(SQLiteStatement.java:61)
at uk.co.example.a.a.a.a(MyTable.java:147)
at uk.co.example.service.b.a.m.run(MySaveTask.java:84)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
at java.lang.Thread.run(Thread.java:1019)

Any ideas what could be causing this?

Thanks

David

Answer 1

Sqlite now supports a new journal mode called Writing-Ahead Logging, which is suitable for concurrent access to sqlite. you may want to take a look at http://www.sqlite.org/wal.html .