Using applicationComplete and initialize together in flex? - apache-flex

Question

<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" applicationComplete="init();" initialize="initializeHandler(event)">
<fx:Script>
<![CDATA[
import mx.collections.ArrayCollection;
import mx.events.FlexEvent;
import sandacreative.sqlite.events.StatementSuccessEvent;
import sandacreative.sqlite.SQLiteManager;
private var database:SQLiteManager = SQLiteManager.getInstance();
protected function initializeHandler(event:FlexEvent):void
{ trace("inside initializehandler");
database.start("Users.db", "Users", "CREATE TABLE Users(UserId VARCHAR(150) PRIMARY KEY, UserName VARCHAR(150))");
database.addEventListener(SQLiteManager.COMMAND_EXEC_SUCCESSFULLY, onSelectResult);
database.addEventListener(SQLiteManager.COMMAND_EXEC_FAILED, function():void {
trace("fail!");
});
readEntries();
}
private function insertEntry():void
{
var sql:String = "INSERT INTO Users VALUES('"+nameField.text+"');";
database.executeCustomCommand(sql);
}
// SQLite Ends Here*/
import flash.media.Camera;
import sandacreative.WebCam;
import sandacreative.Base64;
import mx.core.UIComponent;
import mx.graphics.codec.JPEGEncoder;
private var webCam:WebCam;
private function init():void {
webCam = new WebCam(160, 120);
var ref:UIComponent = new UIComponent();
preview.removeAllChildren();
preview.addChild(ref);
ref.addChild(webCam);
}
</fx:Script>
<mx:Panel width="180" height="160" id="preview" title="Snapshotr" x="158" y="343"/>
<mx:Button label="Save" id="submit" x="280" y="521" width="100" enabled="true" click="insertEntry();"/>
init() initiates a cam and that works properly .. while initiliseHandler() creates a sqlite table. But the table is not created and when i try to save it shows the error
Error: Error #3104: A SQLConnection must be open to perform this operation.
at Error$/throwError()
at flash.data::SQLStatement/checkAllowed()
at flash.data::SQLStatement/checkReady()
at flash.data::SQLStatement/execute()
at sandacreative.sqlite::SQLiteManager/executeCustomCommand()[C:\Documents and Settings\sujith\My Documents\Visitrac1\src\sandacreative\sqlite\SQLiteManager.as:238]
at sandacreative::Main/insertEntry()[C:\Documents and Settings\sujith\My Documents\Visitrac1\src\sandacreative\Main.mxml:34]
at sandacreative::Main/__submit_click()[C:\Documents and Settings\sujith\My Documents\Visitrac1\src\sandacreative\Main.mxml:153]
SQLiteManager.as
package sandacreative.sqlite
{
import sandacreative.sqlite.events.StatementSuccessEvent;
import flash.data.SQLConnection;
import flash.data.SQLStatement;
import flash.errors.SQLError;
import flash.events.Event;
import flash.events.EventDispatcher;
import flash.events.SQLErrorEvent;
import flash.events.SQLEvent;
import flash.filesystem.File;
public class SQLiteManager extends EventDispatcher implements ISQLiteManager
{
/**
* Database file name and extension
*/
public var dbFullFileName:String;
/**
* Database Name
*/
public var tableName:String;
/**
* SQL command to create the database
*/
public var createDbStatement:String;
// datsbase apis instances
protected var connection:SQLConnection;
protected var statement:SQLStatement;
protected var sqlFile:File;
// repeated sql command
protected var repeateFailCallBack:Function;
protected var repeateCallBack:Function;
protected var repeateSqlCommand:String = "";
// events strings
public static var COMMAND_EXEC_SUCCESSFULLY:String = "commandExecSuccesfully";
public static var DATABASE_CONNECTED_SUCCESSFULLY:String = "databaseConnectedSuccessfully";
public static var COMMAND_EXEC_FAILED:String = "commandExecFailed";
public static var DATABASE_READY:String = "databaseReady";
// Singleton instance.
protected static var instance:SQLiteManager;
/**
* Enforce singleton design pattern.
*
* #param enforcer
*
*/
public function SQLiteManager(enforcer:AccessRestriction)
{
if (enforcer == null)
throw new Error("Error enforcer input param is undefined" );
}
/**
* Opens a database connection.
*
* #param dbFullFileName the database file name for instance: Users.sql
* #param tableName holds the database name, for instance: Users
* #param createTableStatement holds the create database statment for instance: CREATE TABLE Users(userId VARCHAR(150) PRIMARY KEY, UserName VARCHAR(150))
*
*/
public function start(dbFullFileName:String, tableName:String, createTableStatement:String):void
{
this.dbFullFileName = dbFullFileName;
this.tableName = tableName;
this.createDbStatement = createTableStatement;
connection = new SQLConnection();
sqlFile = File.applicationStorageDirectory.resolvePath(dbFullFileName);
try
{
connection.open(sqlFile);
this.dispatchEvent(new Event(DATABASE_CONNECTED_SUCCESSFULLY));
}
catch (error:SQLError)
{
trace("Error message:", error.message);
trace("Details:", error.details);
fail();
}
}
/**
* Close connection
*
*/
public function close():void
{
connection.close();
}
/**
* Test the table to ensure it exists. Sends a fail call back function to create the table if
* it doesn't exists.
*
*/
public function testTableExists():void
{
var sql:String = "SELECT * FROM "+tableName+" LIMIT 1;";
executeCustomCommand(sql, this.onDatabaseReady, this.createTable );
}
/**
* Method to create the database table.
*
*/
private function createTable():void
{
statement = new SQLStatement();
statement.sqlConnection = connection;
statement.text = createDbStatement;
statement.execute();
statement.addEventListener(SQLEvent.RESULT, onDatabaseReady);
}
/**
* Common sql command: select all entries in database
*
* #param callback
* #param failCallback
*
*/
public function executeSelectAllCommand(callback:Function=null, failCallback:Function=null):void
{
var sql:String = "SELECT * FROM "+tableName+";";
executeCustomCommand(sql, callback, failCallback);
}
/**
* Common sql command: delete all entries in database
*
* #param callback
*
*/
public function executeDeleteAllCommand(callback:Function=null):void
{
var sql:String = "DELETE * FROM "+tableName+";";
executeCustomCommand(sql, callback);
}
/**
* Method to execute a SQL command
*
* #param sql SQL command string
* #param callback success call back function to impliment if necessery
* #param failCallBack fail call back function to impliment if necessery
*
*/
public function executeCustomCommand(sql:String, callBack:Function=null, failCallBack:Function=null):void
{
statement = new SQLStatement();
statement.sqlConnection = connection;
statement.text = sql;
if (callBack!=null)
{
statement.addEventListener(SQLEvent.RESULT, callBack);
}
else
{
statement.addEventListener(SQLEvent.RESULT, onStatementSuccess);
}
statement.addEventListener(SQLErrorEvent.ERROR, function():void {
fail();
});
try
{
statement.execute();
}
catch (error:SQLError)
{
this.handleErrors(error, sql, callBack, failCallBack);
}
}
/**
* Utility method to clean bad characters that can break SQL commands
*
* #param str
* #return
*
*/
public static function removeBadCharacters(str:String):String
{
var retVal:String = str.split("'").join("’’");
return retVal;
}
// ------------------------------HANDLERS----------------------------
/**
* Method to handle SQL command that create the dataabase.
* If the method was created due to a fail SQL command method checks if need to repeate any SQL command.
*
* #param event
*
*/
private function onDatabaseReady(event:Event=null):void
{
var evt:Event = new Event(DATABASE_READY);
this.dispatchEvent(evt);
if (repeateSqlCommand != "")
{
this.executeCustomCommand(repeateSqlCommand, repeateCallBack, repeateFailCallBack);
repeateSqlCommand = "";
repeateFailCallBack = null;
repeateCallBack = null;
}
}
/**
* Handle successful calls
* #param event
*
*/
private function onStatementSuccess(event:SQLEvent):void
{
var results:Object = statement.getResult();
var evt:StatementSuccessEvent = new StatementSuccessEvent(COMMAND_EXEC_SUCCESSFULLY, results);
this.dispatchEvent(evt);
}
/**
* Error handler
*
* #param error
* #param sql
* #param callBack
* #param failCallBack
*
*/
private function handleErrors(error:SQLError, sql:String, callBack:Function, failCallBack:Function):void
{
trace("Error message:", error.message);
trace("Details:", error.details);
if (error.details == "no such table: '"+tableName+"'")
{
repeateSqlCommand = sql;
repeateFailCallBack = failCallBack;
repeateCallBack = callBack;
createTable();
}
else
{
if (failCallBack != null)
{
failCallBack();
}
else
{
fail();
}
}
}
/**
* Handler for fail calls
*
* #param event
*
*/
private function fail(event:Event=null):void
{
var evt:Event = new Event(COMMAND_EXEC_FAILED);
this.dispatchEvent(evt);
close();
}
/**
* Method function to retrieve instance of the class
*
* #return The same instance of the class
*
*/
public static function getInstance():SQLiteManager
{
if( instance == null )
instance = new SQLiteManager(new AccessRestriction());
return instance;
}
}
}
class AccessRestriction {} // can this happen ?
ISQLiteManager.as
package sandacreative.sqlite
{
/**
* Describes the contract for Objects that serve as a central point to access SQLite database.
*
* #author Elad Elrom
*
*/
public interface ISQLiteManager
{
function start(dbFullFileName:String, tableName:String, createTableStatement:String):void
function close():void
}
}
StatementSucessEvent.as
package sandacreative.sqlite.events
{
import flash.events.Event;
public class StatementSuccessEvent extends Event
{
/**
* Holds the event string name
*/
public static var COMMAND_EXEC_SUCCESSFULLY:String = "command_exec_succesfully";
/**
* Holds results object
*/
public var results:Object;
/**
* Default constructor
*
* #param type event name
* #param videoList video list collection
*
*/
public function StatementSuccessEvent(type:String, results:Object)
{
super(type);
this.results = results;
}
}
}
I took this code from Elad Elrom
Is that because i used both applicationComplete and Initilize together ? Please help

Answer 1

The error is kind of obvious. Your database hasn't been created/connected yet before your button is pressed. Also, the createTable function is never called because you never keep state on your connection property.
Before any statement is executed, you should always check that the DB is connected. For all you know, the connection failed.
And thirdly (and probably most important), you are doing a synchronous execution because you used connection.open. For this to work, you need to do connection.begin() before executing any statements and finish with connection.commit(). I think the better way for you to go here is to use connection.openAsync instead to create an asynchronous execution which is easier to manage and probably what you wanted to do. Only use synchronous if the order of the statements are important (like in a transaction or if one statement is dependent on another).