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左側の都市のリストと右側の都市の詳細を含むSplitViewNavigatorコンテナを使用してアプリを作成したいのですが、右側のビューでは、都市の名前を取得してSQLiteデータベースに保存することでテキストを入力できます。 SQLiteデータベースの左側のビューのリストに追加する必要があります。Main.mxmlのフローコードを開始しました。

<?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>

私のmodel.DataModelは、アクションスクリプトクラスです。

    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;
        }
    }
}

私のvalueobject.CityValueObjectクラスは次のとおりです。

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

そして私のuttillities.CityUtilsクラスは::

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";
    }
}

}

私の左の都市リストは次のとおりです。

<?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>

そして最後に、都市に関する私の表示の詳細は次のようになります。

<?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>

上記のビュー（詳細の表示）はまだ開発中ですが、この段階では、都市名の入力テキスト入力から名前を取得して、都市のリストに都市名を追加しようとしていましたが、次の場所にあります。

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

そのエラーを取得し、先に進むことができません。

上記のコードgivienでこの問題を解決する方法を教えてもらえますか、またはこのアプリで私のニーズを満たす別の方法を提案してください。

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1 に答える 1

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エラーメッセージにあるように、statementはnullです。

初期化するコードはありません。必要なもの：

statement = new SQLStament();

（そして、この変数が関数の外にある必要がある理由はわかりませんapplication1_initializeHandler。）

于 2012-10-24T17:12:47.453 に答える