android - SQLite exception: Database is locked issue

Question

I'm having an issue with my SQLite database inside an Android app. It seems to happen every so often and I cannot reproduce it, but this is the report the Android Market gives.

Basically I have first a splash screen activity that starts by checking if all the needed data is in the database. If not, it will install the data in a asynchronous thread and close the db connection.

Then and only then can the main activity be started, which also opens and reads/writes the database.

This code is executed from the onCreate method of the splash screen activity:

dbWord = new WordDBAdapter(this, myUI);
dbWord.open();
if (dbWord.isDataInstalled()) {
    dbWord.close();
    databaseInstalled = true;
    clickToStartView.setText(myUI.PRESS_TO_START);
    clickToStartView.startAnimation(myBlinkAnim);
} else {
    // If not, try to install in asynchronous thread
    progressDialog = new ProgressDialog(this);
    progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
    progressDialog.setMessage(myUI.INSTALLING_DB);
    progressDialog.setCancelable(false);
    new InstallDBData().execute("");
}

The code for the asynchronous thread is:

private class InstallDBData extends AsyncTask<String, Integer, Integer> {

    @Override
    protected Integer doInBackground(String... arg0) {
        progressDialog.setProgress(0);
        dbWord.installData(0, getApplicationContext());
        progressDialog.setProgress(20);
        dbWord.installData(1, getApplicationContext());
        progressDialog.setProgress(40);
        dbWord.installData(2, getApplicationContext());
        progressDialog.setProgress(60);
        dbWord.installData(3, getApplicationContext());
        progressDialog.setProgress(80);
        dbWord.installData(4, getApplicationContext());
        progressDialog.setProgress(100);
        return 1;
    }

    protected void onPreExecute() {
        progressDialog.show();
    }

    protected void onPostExecute(Integer x) {
        dbWord.close();
        progressDialog.hide();
        databaseInstalled = true;
        clickToStartView.setText(myUI.PRESS_TO_START);
        clickToStartView.startAnimation(myBlinkAnim);
    }
}

These are important parts of the WordDBAdapter class, which is also used by the main activity:

public class WordDBAdapter {
    private DatabaseHelper mDbHelper;
    private SQLiteDatabase mDb;

    public WordDBAdapter open() throws android.database.SQLException {
        mDbHelper = new DatabaseHelper(mCtx);
        mDb = mDbHelper.getWritableDatabase();
        return this;
    }

    public void close() {
        mDbHelper.close();
    }
    ...
}

I'm getting the following exceptions, which are similar but have a different message:

First type of error message:

java.lang.RuntimeException: Unable to start activity 
  ComponentInfo{example.flashcards.medical/com.example.flashcards.common.SplashWindow}: 
  android.database.sqlite.SQLiteException: database is locked: BEGIN EXCLUSIVE;
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1830)
....
Caused by: android.database.sqlite.SQLiteException: database is locked: BEGIN EXCLUSIVE;
at android.database.sqlite.SQLiteDatabase.native_execSQL(Native Method)
at android.database.sqlite.SQLiteDatabase.execSQL(SQLiteDatabase.java:1870)
at android.database.sqlite.SQLiteDatabase.beginTransactionWithListener(SQLiteDatabase.java:602)

Second type of error message:

java.lang.RuntimeException: Unable to start activity 
  ComponentInfo{example.flashcards.medical/com.example.flashcards.common.SplashWindow}: 
  android.database.sqlite.SQLiteException: database is locked
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1768)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1784)
....
Caused by: android.database.sqlite.SQLiteException: database is locked
at android.database.sqlite.SQLiteDatabase.native_setLocale(Native Method)
at android.database.sqlite.SQLiteDatabase.setLocale(SQLiteDatabase.java:1987)
at android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1855)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:820)
at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:854)

I would really like to not have to create a ContentProvider, because I believe its overkill if a simpler solution is available. Also, only this application has access to the database.

Any suggestions on how this can be fixed?

Answer 1

After doing some effort I did it (My app was working on perfect till android 2.3 but got db lock error when I used to run it on HoneyComb tablet).
I did using Semaphores (using lock in critical sections).

Example 1

public class DbExp extends SQLiteOpenHelper{
    public static String Lock = "dblock";
    private static final String DATABASE_NAME = "db.db";
    private static final String TABLE_NAME = "table_name";

    public void delete(Context mContext){
        synchronized(Lock) {
            SQLiteDatabase db  = getWritableDatabase();
            db.delete(TABLE_NAME, null, null);
            db.close();
        }
    }

    public void insert(){
        synchronized(Lock) {
            SQLiteDatabase db  = getWritableDatabase();
            db.insert(TABLE_NAME, ..., ...);
            db.close();
        }
    }

}

Example 2

public class DB {
    public static String Lock = "dblock";
    private static final String DATABASE_NAME = "db.db";
    private static final String TABLE_NAME = "table_name";

    public void delete(Context mContext){
        synchronized(Lock) {
            SQLiteDatabase db  = mContext.openOrCreateDatabase(DATABASE_NAME, Context.MODE_PRIVATE, null);
            db.delete(TABLE_NAME, null, null);
            db.close();
        }
    }

    public void insert(Context mContext){
        synchronized(Lock) {
            SQLiteDatabase db  = mContext.openOrCreateDatabase(DATABASE_NAME, Context.MODE_PRIVATE, null);
            db.insert(TABLE_NAME, ..., ...);
            db.close();
        }
    }


}

Hope this would help Anyone in future :)