Android - Asynctask and Android Database web server database fetch issues

Android - Asynctask and Android Database web server database fetch issues

I have an application that fetches a zipped sqlite database dump file and
uses that database. I used this tutorial as a guide on how to fetch the
database. However, for my purpose, I instead pulled a database hosted on
my localhost (192.168.1.4).
The link above also contains the full project which I downloaded for
reference purposes but I had to tweak the code in such a way that it used
an AsyncTask to fetch the database, otherwise I would get a
NetworkOnMainThreadException. I managed to make the AsyncTask work
properly, my AsyncTask looks like this:
private class Connection extends AsyncTask {
@Override
protected Object doInBackground(Object... arg0) {
//connect();
myDroidSQLDatabase = new MyDroidSQLDatabase(MyDBAppActivity.this);
myDroidSQLDatabase.open();
return null;
}
}
And it is called in my main activity as follows:
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
new Connection().execute();
}
And the problem seems to be in the onResume() since logcat shows the error
Unable to resume activity:
@Override
protected void onResume() {
myDroidSQLDatabase.open();
super.onResume();
}
I am not quite sure why the onResume() triggered when I first installed
the application on my device. I think the issue is that after onCreate(),
onResume() is called and since the database is still open, it's trying to
open already open db.
However, the original example from the website deploys a packaged dump
file in the application and it executes properly. Since this method did
not require db fetch and execute in an AsyncTask, the onResume did not act
up. So my guess right now is that I have to wait for the AsyncTask to
finish so that onResume() won't give me problems.
Sorry but I'm totally new to Threads and Async Tasks so I have no idea how
to handle the thread when the job is done. I think the issues is that
onResume tries to run (as part of the activity life cycle) and since the
Async Task isn't done yet, the open() call acts up.
Any ideas?
Also, here are three more classes, it might help. MyDroidSQLDatabase
public class MyDroidSQLDatabase {
private SQLiteOpenHelper sqlLiteOpenHelper;
private SQLiteDatabase sqlLiteDatabase;
public MyDroidSQLDatabase(Context context) {
sqlLiteOpenHelper = new MyDroidSQLiteOpenHelper(context);
}
public void open() {
sqlLiteDatabase = sqlLiteOpenHelper.getWritableDatabase();
}
public void close() {
sqlLiteDatabase.close();
}
public SQLiteDatabase getSqlLiteDatabase() {
return sqlLiteDatabase;
}
}
MyDroidSQLiteOpenHelper
public class MyDroidSQLiteOpenHelper extends SQLiteOpenHelper {
private Context context;
private static final String __DB_NAME = "mydbapp.db";
private static final int __DB_VERSION = 1;
public MyDroidSQLiteOpenHelper(Context context) {
super(context, __DB_NAME, null, __DB_VERSION);
this.context=context;
}
@Override
public void onCreate(SQLiteDatabase sqlLiteDb) {
try {
//SQLiteDBDeploy.deploy(sqlLiteDb, this.context,
"northwind.zip");
// if you like to download file from remote site comment above
line and uncomment below line.
SQLiteDBDeploy.deploy(sqlLiteDb,
//"http://ingenious-camel.googlecode.com/svn/trunk/SQLiteDBDeployer/assets/northwind.zip");
"http://192.168.1.4/dbtest/android.zip");
} catch (IOException e) {
Log.e(MyDBAppActivity.TAG,e.getMessage(),e);
throw new Error(e.getMessage());
}
}
@Override
public void onUpgrade(SQLiteDatabase sqlLiteDb, int oldVersion, int
newVersion) {
}
}
SQLiteDBDeploy
public class SQLiteDBDeploy {
private static final String TAG = "SQLiteDBDeploy";
private static List<String> ignoreSQLs;
static {
ignoreSQLs = new LinkedList<String>();
ignoreSQLs.add("--");
ignoreSQLs.add("begin transaction;");
ignoreSQLs.add("commit;");
ignoreSQLs.add("create table android_metadata (locale text);");
ignoreSQLs.add("create table \"android_metadata\" (locale text);");
ignoreSQLs.add("insert into android_metadata values('en_us');");
ignoreSQLs.add("insert into \"android_metadata\" values('en_us');");
}
/**
* Deploys given zip file in SQLiteDatabase
*
* @param sqlLiteDb
* the database
* @param context
* to use to open or create the database
* @param dbName
* dump zip file
* @throws IOException
*/
public static void deploy(SQLiteDatabase sqlLiteDb, Context context,
String dbName) throws IOException {
Log.i(TAG, "reading zip file: " + dbName);
InputStream dbStream = context.getAssets().open(dbName);
deploy(sqlLiteDb, dbStream);
dbStream.close();
}
/**
* Deploys given zip file url in SQLiteDatabase
*
* @param sqlLiteDb
* the database
* @param dbUrl
* dump zip file url
* @throws IOException
*/
public static void deploy(SQLiteDatabase sqlLiteDb, String dbUrl)
throws IOException {
Log.i(TAG, "reading url: " + dbUrl);
HttpURLConnection c = (HttpURLConnection) new
URL(dbUrl).openConnection();
c.setRequestMethod("GET");
c.setDoOutput(true);
c.connect();
InputStream dbStream = c.getInputStream();
deploy(sqlLiteDb, dbStream);
dbStream.close();
c.disconnect();
}
/**
* Deploys given dump file stream in SQLiteDatabase
*
* @param sqlLiteDb the database
* @param dbStream stream to read dump data
* @throws IOException
*/
private static void deploy(SQLiteDatabase sqlLiteDb, InputStream
dbStream) throws IOException {
ZipInputStream zis = new ZipInputStream(new
BufferedInputStream(dbStream));
ZipEntry entry = null;
while ((entry = zis.getNextEntry()) != null) {
Log.i(TAG, "deploying zip entry: " + entry);
InputStreamReader dbReader = new InputStreamReader(zis);
deploy(sqlLiteDb, dbReader);
}
}
/**
* Deploys given stream in SQLiteDatabase
*
* @param sqlLiteDb
* the database
* @param dbReader
* stream to read dump SQL statements
* @throws IOException
* @throws SQLException
*/
private static void deploy(SQLiteDatabase sqlLiteDb, InputStreamReader
dbReader) throws IOException {
String sqlLine = null;
StringBuffer sqlBuffer = new StringBuffer();
BufferedReader bufferedReader = new BufferedReader(dbReader);
sqlLiteDb.beginTransaction();
try {
while ((sqlLine = bufferedReader.readLine()) != null) {
String sql = sqlLine.trim();
if (!isIgnoreSQL(sql)) {
if (sql.endsWith(";")) {
sqlBuffer.append(sql);
String execSQL = sqlBuffer.toString();
Log.d(TAG, "running sql=>" + execSQL);
sqlLiteDb.execSQL(execSQL);
sqlBuffer.delete(0, sqlBuffer.length());
} else {
if (sqlBuffer.length() > 0) {
sqlBuffer.append(' ');
}
sqlBuffer.append(sql);
}
}
}
sqlLiteDb.setTransactionSuccessful();
} finally {
sqlLiteDb.endTransaction();
}
}
/**
* Returns true if the given SQL statement is to be ignored
* @param sql SQL statement
* @return
*/
private static boolean isIgnoreSQL(String sql) {
if (sql.length() == 0) {
return true;
}
String lowerSQL = sql.toLowerCase();
for (String ignoreSQL : ignoreSQLs) {
if (lowerSQL.startsWith(ignoreSQL)) {
return true;
}
}
return false;
}
}