我想让它包含城市左视图，并详细了解我市在右视图列表的应用程序使用SplitViewNavigator容器，在右侧视图中有一个文本输入，通过我得到城市和商店的名称在SQLite数据库，这个名字应该加上从SQLite数据库左视图我开始在Main.mxml流code列出：

I want to make an App using SplitViewNavigator container which contains List of cities in left view and Detail about the city in right view, In right view there is a text input through I get Name of city and store in a SQLite Database, and that name should be added to list in left view from SQLite Database I got started with flowing code in Main.mxml:

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
                        xmlns:s="library://ns.adobe.com/flex/spark" 
                        applicationDPI="160"
                        initialize="application1_initializeHandler(event)">
<fx:Script>
    <![CDATA[
        import model.DataModel;

        import mx.events.FlexEvent;
        import valueobject.CityValueObject;
        import utillities.CityUtils;

        public var sqlConnection:SQLConnection;
        protected var statement:SQLStatement;
        protected function application1_initializeHandler(event:FlexEvent):void
        {
            sqlConnection = new SQLConnection();
            sqlConnection.open(File.applicationStorageDirectory.resolvePath("cityDB.db"), SQLMode.CREATE);
            statement.sqlConnection = sqlConnection; // Here error occurs saying that Error #1009: Cannot access a property or method of a null object reference.
            statement.text = "CREATE TABLE IF NOT EXISTS CITYNAME (" +
                "id INTEGER PRIMARY KEY AUTOINCREMENT, " +
                "nameofcity TEXT)";
            statement.execute();
            DataModel.getInstance().connection = sqlConnection;

            CityUtils.getAllCities();
        }

    ]]>
</fx:Script>
<fx:Declarations>
    <!-- Place non-visual elements (e.g., services, value objects) here -->
</fx:Declarations>
<s:SplitViewNavigator id="svn" width="100%" height="100%">
    <s:ViewNavigator width="30%" height="100%" id="list_of_cities" firstView="views.ListOfCities"/>
    <s:ViewNavigator width="70%" height="100%" id="display_contents" firstView="views.DisplayContents"/>
</s:SplitViewNavigator>

我的model.DataModel是动作脚本类：

My model.DataModel is an action script class:

    package model
    {
    import flash.data.SQLConnection;

    import mx.collections.ArrayCollection;

    [Bindable]
    public class DataModel
    {
        public var connection:SQLConnection;
        public var cityList:ArrayCollection = new ArrayCollection();
        public var logs:String="Application Logs........\n";

        public static var _instance:DataModel;

        public function DataModel()
        {

        }

        public static function getInstance():DataModel
        {
            if(_instance == null)
            {
                _instance = new DataModel();
            }
            return _instance;
        }
    }
}

我的valueobject.CityValueObject类是：

My valueobject.CityValueObject class is:

package valueobject
{
[Bindable]
public class CityValueObject
{
    public var id:uint;
    public var nameofcity:String;
}}

和我的uttillities.CityUtils类::

And My uttillities.CityUtils class is ::

package utillities
{
import flash.data.SQLResult;
import flash.data.SQLStatement;
import flash.display.Loader;
import flash.display.LoaderInfo;
import flash.events.Event;
import flash.net.URLRequest;
import flash.utils.ByteArray;

import model.DataModel;

import mx.collections.Sort;
import mx.collections.SortField;

import valueobject.CityValueObject;


public class CityUtils
{
    public static function getAllCities():void
    {
        var contactListStatement:SQLStatement = new SQLStatement();
        contactListStatement.sqlConnection = DataModel.getInstance().connection;
        contactListStatement.text = "SELECT * FROM CITYNAME";
        contactListStatement.execute();
        var result:SQLResult = contactListStatement.getResult();
        if( result.data!=null)
        {
            DataModel.getInstance().cityList.removeAll();

            for(var count:uint=0;count<result.data.length;count++)
            {
                var cityVO:CityValueObject = new CityValueObject();
                cityVO.id = result.data[count].id;
                cityVO.nameofcity = result.data[count].city;                    
                DataModel.getInstance().cityList.addItem(cityVO);
            }
        }
        sortData();     
    }

    public static function sortData():void
    {
        var dataSortField:SortField = new SortField();
        dataSortField.name = "cityName";
        dataSortField.numeric = false;

        /* Create the Sort object and add the SortField object created earlier to the array of fields to sort on. */
        var numericDataSort:Sort = new Sort();
        numericDataSort.fields = [dataSortField];

        /* Set the ArrayCollection object's sort property to our custom sort, and refresh the ArrayCollection. */
        DataModel.getInstance().cityList.sort = numericDataSort;
        DataModel.getInstance().cityList.refresh();
    }

    public static function updateLog(newLog:String):void
    {
        DataModel.getInstance().logs += new Date().time+" :-> "+newLog+"\n";
    }
}

}

我包含城市列表左边是：

My left containing list of cities is :

<?xml version="1.0" encoding="utf-8"?>
<s:View xmlns:fx="http://ns.adobe.com/mxml/2009" 
    xmlns:s="library://ns.adobe.com/flex/spark" title="Cities"
    >
<fx:Declarations>
    <!-- Place non-visual elements (e.g., services, value objects) here -->
</fx:Declarations>

<fx:Script>
    <![CDATA[
        import model.DataModel;

        import mx.collections.ArrayCollection;
        import mx.events.FlexEvent;
        import mx.events.IndexChangedEvent;

        import spark.components.SplitViewNavigator;
        import spark.components.ViewNavigator;
        import spark.transitions.ViewTransitionBase;
        protected function myList_changeHandler():void {
            // Create a reference to the SplitViewNavigator.
            var splitNavigator:SplitViewNavigator = navigator.parentNavigator as SplitViewNavigator;

            // Create a reference to the ViewNavigator for the Detail frame.
            var detailNavigator:ViewNavigator = splitNavigator.getViewNavigatorAt(1) as ViewNavigator;

            detailNavigator.transitionsEnabled = false;

            // Change the view of the Detail frame based on the selected List item.
            detailNavigator.pushView(DisplayContents, list_of_cities.selectedItem);             
        }           
    ]]>
</fx:Script>
<s:VGroup width="100%" height="100%">
    <s:List id="list_of_cities" height="100%" width="100%" change="myList_changeHandler();" 
            dataProvider="{DataModel.getInstance().cityList}" labelField="nameofcity">

    </s:List>       
</s:VGroup>

和去年我的显示细节的城市仅仅是这样的：

and in last my Display Detail about city is simply like this :

<?xml version="1.0" encoding="utf-8"?>
<s:View xmlns:fx="http://ns.adobe.com/mxml/2009" 
    xmlns:s="library://ns.adobe.com/flex/spark" title="Detail About City"
    >
<fx:Declarations>
    <!-- Place non-visual elements (e.g., services, value objects) here -->

</fx:Declarations>
<s:actionContent>
    <s:CalloutButton id="add_call_out_button" label="Add City" verticalPosition="after" 
                     icon="@Embed('assets/add.png')" calloutDestructionPolicy="never">
        <!-- layout the callout content here -->
        <s:calloutLayout>
            <s:VerticalLayout paddingTop="10" paddingBottom="10" paddingLeft="10" paddingRight="10" horizontalAlign="center" gap="5"/>
        </s:calloutLayout>
        <s:calloutContent>              
            <s:TextInput id="city_name_input" prompt="Enter City Name" text="Sydney"/>
            <s:HGroup gap="40">
                <s:Button id="add_city_name" label="Add City" width="150" height="40" click="add_city_name_clickHandler()"/>
                <s:CheckBox id="preferred_cbox" label="Preferred" height="40" />
            </s:HGroup>

        </s:calloutContent>
    </s:CalloutButton>
    <s:Button id="remove_city_name" label="Remove" width="120" height="40"
              click="remove_city_name_clickHandler()" icon="@Embed('assets/delete.png')"/>

</s:actionContent>

<s:Label id="nameSomeThing" text="{data.Description}"/>

<fx:Script>
    <![CDATA[
        import model.DataModel;

        import spark.components.SplitViewNavigator;
        import spark.components.ViewNavigator; 

        protected function add_city_name_clickHandler():void
        {
            var sqlStatement:SQLStatement = new SQLStatement();
            sqlStatement.sqlConnection = DataModel.getInstance().connection;
            sqlStatement.text = "INSERT INTO CITYNAME (nameofcity)" +
                                "VALUES(:nameofcity)";
            sqlStatement.parameters[":nameofcity"] = city_name_input.text;
            sqlStatement.execute();

            var splitNavigator:SplitViewNavigator = navigator.parentNavigator as SplitViewNavigator;

            // Create a reference to the ViewNavigator for the Detail frame.
            var detailNavigator:ViewNavigator = splitNavigator.getViewNavigatorAt(1) as ViewNavigator;

            detailNavigator.transitionsEnabled = false;

            // Change the view of the Detail frame based on the selected List item.
            detailNavigator.popToFirstView();
        }

        protected function remove_city_name_clickHandler():void
        {
            // TODO Auto-generated method stub

        }

    ]]>
</fx:Script>

以上观点（显示详细信息）仍处于开发阶段，但在这个阶段，我试图增加城市名称的城市，列出通过得到的名字从城市的名称输入文本输入，但在：

the above view(Display Detail) is still in development but at this stage I was Trying to add City Name to list of cities by getting name from city name input text input but at:

statement.sqlConnection = sqlConnection; // Here error occurs saying that Error #1009: Cannot access a property or method of a null object reference.

的iget的错误，无法继续前进。

Iget that error and not be able to go ahead.

任何一个可以请给我以我的code givien解决我的这个问题上面，或给我建议的其他办法通过这个应用程序在此先感谢...

Can any one please give me the way to solve my this problem by my code givien above or suggest me an other way to meet my needs by this App Thanks in Advance...

推荐答案

随着错误消息指出，语句为空。

As the error message says, statement is null.

我没有看到任何code，将其初始化。 您需要：

I don't see any code that would initialize it. You need:

statement = new SQLStament();

（我看不出有任何理由为什么这个变量将需要在 application1_initializeHandler 函数外。）