AccessibleObject.GetChildCount メソッド

.NET Framework クラス ライブラリ リファレンス

AccessibleObject.GetChildCount メソッド

ユーザー補助オブジェトに属する子の数を取得します。

名前空間: System.Windows.Forms
アセンブリ: System.Windows.Forms (system.windows.forms.dll 内)
構文

Visual Basic (宣言)

Public Overridable Function
 GetChildCount As Integer

Visual Basic (使用法)

Dim instance As AccessibleObject
Dim returnValue As Integer

returnValue = instance.GetChildCount

C#

public virtual int GetChildCount ()

C++

public:
virtual int GetChildCount ()

J#

public int GetChildCount ()

JScript

public function GetChildCount () : int

戻り値
ユーザー補助オブジェトに属する子の数。

解説

継承時の注意 すべてのオブジェクトがこのプロパティをサポートする必要があります。既定の実装は、-1 を返します。ユーザー補助オブジェクトで独自の子ユーザー補助オブジェクトを提供する必要がある場合は、このメソッドをオーバーライドします。このメソッドをオーバーライドする場合は、GetChild もオーバーライドする必要があります。

使用例

ユーザー補助情報を公開する AccessibleObject クラスおよび Control.ControlAccessibleObject クラスを使用して、ユーザー補助対応のチャート コントロールを作成する方法の例を次に示します。コントロールは、凡例に沿って 2 つの曲線をプロットします。ControlAccessibleObject から派生された ChartControlAccessibleObject クラスは、チャート コントロールの独自のユーザー補助情報を提供することを目的として、CreateAccessibilityInstance メソッドで使用します。チャートの凡例は実際の Control ベースのコントロールではなく、チャート コントロールによって描画されるため、組み込みのユーザー補助情報は含まれていません。このため、ChartControlAccessibleObject クラスは、GetChild メソッドをオーバーライドして、凡例の各部分のユーザー補助情報を表す CurveLegendAccessibleObject を返します。ユーザー補助対応のアプリケーションでこのコントロールが使用された場合、このコントロールは必要なユーザー補助情報を提供できます。

GetChildCount メソッドをオーバーライドする例を次に示します。コード例全体については、AccessibleObject クラスの概要を参照してください。

Visual Basic

' Inner Class ChartControlAccessibleObject represents accessible information
 
' associated with the ChartControl.
' The ChartControlAccessibleObject is returned in the         ' ChartControl.CreateAccessibilityInstance
 override.
Public Class ChartControlAccessibleObject
    Inherits Control.ControlAccessibleObject

    Private chartControl As ChartControl
    
    Public Sub New(ctrl
 As ChartControl)
        MyBase.New(ctrl)
        chartControl = ctrl
    End Sub 'New
    
    ' Get the role for the Chart. This is used by accessibility programs.
            
    Public Overrides ReadOnly
 Property Role() As AccessibleRole
        Get
            Return System.Windows.Forms.AccessibleRole.Chart
        End Get
    End Property
    
    ' Get the state for the Chart. This is used by accessibility programs.
            
    Public Overrides ReadOnly
 Property State() As AccessibleStates
        Get
            Return AccessibleStates.ReadOnly
        End Get
    End Property                        
    
    ' The CurveLegend objects are "child" controls in terms
 of accessibility so 
    ' return the number of ChartLengend objects.            
    Public Overrides Function
 GetChildCount() As Integer
        Return chartControl.Legends.Length
    End Function 
    
    ' Get the Accessibility object of the child CurveLegend idetified
 by index.
    Public Overrides Function
 GetChild(index As Integer) As
 AccessibleObject
        If index >= 0 And index < chartControl.Legends.Length
 Then
            Return chartControl.Legends(index).AccessibilityObject
        End If
        Return Nothing
    End Function 
    
    ' Helper function that is used by the CurveLegend's accessibility
 object
    ' to navigate between sibiling controls. Specifically, this function
 is used in
    ' the CurveLegend.CurveLegendAccessibleObject.Navigate function.
    Friend Function NavigateFromChild(child
 As CurveLegend.CurveLegendAccessibleObject, _
                                    navdir As AccessibleNavigation)
 As AccessibleObject
        Select Case navdir
            Case AccessibleNavigation.Down, AccessibleNavigation.Next
                    Return GetChild(child.ID + 1)
            
            Case AccessibleNavigation.Up, AccessibleNavigation.Previous
                    Return GetChild(child.ID - 1)
        End Select
        Return Nothing
    End Function            

    ' Helper function that is used by the CurveLegend's accessibility
 object
    ' to select a specific CurveLegend control. Specifically, this function
 is used 
    ' in the CurveLegend.CurveLegendAccessibleObject.Select function.
            
    Friend Sub SelectChild(child As
 CurveLegend.CurveLegendAccessibleObject, selection As AccessibleSelection)
        Dim childID As Integer
 = child.ID
        
        ' Determine which selection action should occur, based on the
        ' AccessibleSelection value.
        If (selection And AccessibleSelection.TakeSelection)
 <> 0 Then
            Dim i As Integer
            For i = 0 To chartControl.Legends.Length
 - 1
                If i = childID Then
                    chartControl.Legends(i).Selected = True
                Else
                    chartControl.Legends(i).Selected = False
                End If
            Next i
            
            ' AccessibleSelection.AddSelection means that the CurveLegend
 will be selected.
            If (selection And AccessibleSelection.AddSelection)
 <> 0 Then
                chartControl.Legends(childID).Selected = True
            End If

            ' AccessibleSelection.AddSelection means that the CurveLegend
 will be unselected.                    
            If (selection And AccessibleSelection.RemoveSelection)
 <> 0 Then
                chartControl.Legends(childID).Selected = False
            End If
        End If
    End Sub 'SelectChild
End Class 'ChartControlAccessibleObject

C#

// Inner class ChartControlAccessibleObject represents accessible information
 associated with the ChartControl.
// The ChartControlAccessibleObject is returned in the ChartControl.CreateAccessibilityInstance
 override.
public class ChartControlAccessibleObject :
 ControlAccessibleObject
{
    ChartControl chartControl;

    public ChartControlAccessibleObject(ChartControl ctrl) : base(ctrl)
 
    {
        chartControl = ctrl;
    }

    // Gets the role for the Chart. This is used by accessibility programs.
    public override AccessibleRole Role
    {  
        get {
            return AccessibleRole.Chart;
        }
    }

    // Gets the state for the Chart. This is used by accessibility programs.
    public override AccessibleStates State
    {  
        get {                    
            return AccessibleStates.ReadOnly;
        }
    }

    // The CurveLegend objects are "child" controls in terms
 of accessibility so 
    // return the number of ChartLengend objects.
    public override int GetChildCount()
    {  
        return chartControl.Legends.Length;
    }

    // Gets the Accessibility object of the child CurveLegend idetified
 by index.
    public override AccessibleObject GetChild(int
 index)
    {  
        if (index >= 0 && index < chartControl.Legends.Length)
 {
            return chartControl.Legends[index].AccessibilityObject;
        }                
        return null;
    }

    // Helper function that is used by the CurveLegend's accessibility
 object
    // to navigate between sibiling controls. Specifically, this function
 is used in
    // the CurveLegend.CurveLegendAccessibleObject.Navigate function.
    internal AccessibleObject NavigateFromChild(CurveLegend.CurveLegendAccessibleObject
 child, 
                                                AccessibleNavigation navdir) 
    {  
        switch(navdir) {
            case AccessibleNavigation.Down:
            case AccessibleNavigation.Next:
                return GetChild(child.ID + 1);
                
            case AccessibleNavigation.Up:
            case AccessibleNavigation.Previous:
                return GetChild(child.ID - 1);               
         
        }
        return null;
    }

    // Helper function that is used by the CurveLegend's accessibility
 object
    // to select a specific CurveLegend control. Specifically, this
 function is used
    // in the CurveLegend.CurveLegendAccessibleObject.Select function.
    internal void SelectChild(CurveLegend.CurveLegendAccessibleObject
 child, AccessibleSelection selection) 
    {   
        int childID = child.ID;

        // Determine which selection action should occur, based on the
        // AccessibleSelection value.
        if ((selection & AccessibleSelection.TakeSelection)
 != 0) {
            for(int i = 0; i < chartControl.Legends.Length;
 i++) {
                if (i == childID) {
                    chartControl.Legends[i].Selected = true; 
                       
                } else {
                    chartControl.Legends[i].Selected = false;
                }
            }

            // AccessibleSelection.AddSelection means that the CurveLegend
 will be selected.
            if ((selection & AccessibleSelection.AddSelection)
 != 0) {
                chartControl.Legends[childID].Selected = true;
                        
            }

            // AccessibleSelection.AddSelection means that the CurveLegend
 will be unselected.
            if ((selection & AccessibleSelection.RemoveSelection)
 != 0) {
                chartControl.Legends[childID].Selected = false;
                        
            }
        }            
    }
}

C++

// Inner class ChartControlAccessibleObject represents accessible information
 associated with the ChartControl.
// The ChartControlAccessibleObject is returned in the ChartControl::CreateAccessibilityInstance
 .
ref class ChartControlAccessibleObject: public
 ControlAccessibleObject
{
private:
   ChartControl^ chartControl;

public:
   ChartControlAccessibleObject( ChartControl^ ctrl )
      : ControlAccessibleObject( ctrl )
   {
      chartControl = ctrl;
   }


   property System::Windows::Forms::AccessibleRole Role 
   {

      // Gets the role for the Chart. This is used by accessibility
 programs.
      virtual System::Windows::Forms::AccessibleRole get() override
      {
         return ::AccessibleRole::Chart;
      }

   }

   property AccessibleStates State 
   {

      // Gets the state for the Chart. This is used by accessibility
 programs.
      virtual AccessibleStates get() override
      {
         return AccessibleStates::ReadOnly;
      }

   }

   // The CurveLegend objects are "child" controls in terms
 of accessibility so
   // return the number of ChartLengend objects.
   virtual int GetChildCount() override
   {
      return chartControl->Legends->Length;
   }


   // Gets the Accessibility object of the child CurveLegend idetified
 by index.
   virtual AccessibleObject^ GetChild( int index ) override
   {
      if ( index >= 0 && index < chartControl->Legends->Length
 )
      {
         return chartControl->Legends[ index ]->AccessibilityObject;
      }

      return nullptr;
   }


internal:

   // Helper function that is used by the CurveLegend's accessibility
 object
   // to navigate between sibiling controls. Specifically, this function
 is used in
   // the CurveLegend::CurveLegendAccessibleObject.Navigate function.
   AccessibleObject^ NavigateFromChild( CurveLegend::CurveLegendAccessibleObject^
 child, AccessibleNavigation navdir )
   {
      switch ( navdir )
      {
         case AccessibleNavigation::Down:
         case AccessibleNavigation::Next:
            return GetChild( child->ID + 1 );

         case AccessibleNavigation::Up:
         case AccessibleNavigation::Previous:
            return GetChild( child->ID - 1 );
      }
      return nullptr;
   }


   // Helper function that is used by the CurveLegend's accessibility
 object
   // to select a specific CurveLegend control. Specifically, this function
 is used
   // in the CurveLegend::CurveLegendAccessibleObject.Select function.
   void SelectChild( CurveLegend::CurveLegendAccessibleObject^
 child, AccessibleSelection selection )
   {
      int childID = child->ID;
      
      // Determine which selection action should occur, based on the
      // AccessibleSelection value.
      if ( (selection & AccessibleSelection::TakeSelection)
 != (AccessibleSelection)0 )
      {
         for ( int i = 0; i < chartControl->Legends->Length;
 i++ )
         {
            if ( i == childID )
            {
               chartControl->Legends[ i ]->Selected = true;
            }
            else
            {
               chartControl->Legends[ i ]->Selected = false;
            }

         }
         
         // AccessibleSelection->AddSelection means that the CurveLegend
 will be selected.
         if ( (selection & AccessibleSelection::AddSelection)
 != (AccessibleSelection)0 )
         {
            chartControl->Legends[ childID ]->Selected = true;
         }
         
         // AccessibleSelection->AddSelection means that the CurveLegend
 will be unselected.
         if ( (selection & AccessibleSelection::RemoveSelection)
 != (AccessibleSelection)0 )
         {
            chartControl->Legends[ childID ]->Selected = false;
         }
      }
   }

};

// class ChartControlAccessibleObject

J#

// Inner class ChartControlAccessibleObject represents accessible 
// information associated with the ChartControl.
// The ChartControlAccessibleObject is returned in the 
// ChartControl.CreateAccessibilityInstance override.
public static class ChartControlAccessibleObject
 
    extends ControlAccessibleObject
{
    private ChartControl chartControl;

    public ChartControlAccessibleObject(ChartControl ctrl)
    {
        super(ctrl);
        chartControl = ctrl;
    } //ChartControlAccessibleObject

    // Gets the role for the Chart. This is used by accessibility programs.
    /** @property 
     */
    public AccessibleRole get_Role()
    {
        return AccessibleRole.Chart;
    } //get_Role

    // Gets the state for the Chart. This is used by accessibility programs.
    /** @property 
     */
    public AccessibleStates get_State()
    {
        return AccessibleStates.ReadOnly;
    } //get_State

    // The CurveLegend objects are "child" controls in terms
 of  
    // accessibility so return the number of ChartLengend objects.
    public int GetChildCount()
    {
        return chartControl.get_Legends().get_Length();
    } //GetChildCount

    // Gets the Accessibility object of the child CurveLegend 
    // idetified by index.
    public AccessibleObject GetChild(int index)
    {
        if (index >= 0 && index < chartControl.get_Legends().get_Length())
 {
            return chartControl.get_Legends()[index].
                get_AccessibilityObject();
        }
        return null;
    } //GetChild

    // Helper function that is used by the CurveLegend's accessibility
 
    // object to navigate between sibiling controls.  
    // Specifically, this function is used in
    // the CurveLegend.CurveLegendAccessibleObject.Navigate function.
    AccessibleObject NavigateFromChild(
        CurveLegend.CurveLegendAccessibleObject child, 
        AccessibleNavigation navDir)
    {
        if (navDir.Equals(AccessibleNavigation.Down) 
            || navDir.Equals(AccessibleNavigation.Next)) {
            return GetChild(child.get_ID() + 1);
        }
        else {
            if (navDir.Equals(AccessibleNavigation.Up) 
                || navDir.Equals(AccessibleNavigation.Previous)) {
                return GetChild(child.get_ID() - 1);
            }
        }
        return null;
    } //NavigateFromChild

    // Helper function that is used by the CurveLegend's accessibility
    // object to select a specific CurveLegend control. 
    // Specifically, this function is used
    // in the CurveLegend.CurveLegendAccessibleObject.Select function.
    public void SelectChild(CurveLegend.CurveLegendAccessibleObject
 child, 
        AccessibleSelection selection)
    {
        int childID = child.get_ID();

        // Determine which selection action should occur, based on the
        // AccessibleSelection value.
        if (Convert.ToInt32(selection & AccessibleSelection.TakeSelection)
            != 0) {
            for (int i = 0; i < chartControl.get_Legends().get_Length();
 
                i++) {
                if (i == childID) {
                    ((CurveLegend)chartControl.get_Legends().get_Item(i)).
                        set_Selected(true);
                }
                else {
                    ((CurveLegend)chartControl.get_Legends().get_Item(i)).
                        set_Selected(false);
                }
            }

            // AccessibleSelection.AddSelection means that the CurveLegend
 
            // will be selected.
            if (Convert.ToInt32(selection & AccessibleSelection.AddSelection)
                != 0) {
                ((CurveLegend)chartControl.get_Legends().get_Item(childID)).
                    set_Selected(true);
            }

            // AccessibleSelection.AddSelection means that the CurveLegend
 
            // will be unselected.
            if (Convert.ToInt32(selection & 
                AccessibleSelection.RemoveSelection) != 0) {
                ((CurveLegend)chartControl.get_Legends().get_Item(childID)).
                    set_Selected(false);
            }
        }
    } //SelectChild
} //ChartControlAccessibleObject

プラットフォーム

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

開発プラットフォームの中には、.NET Framework によってサポートされていないバージョンがあります。サポートされているバージョンについては、「システム要件」を参照してください。

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0

参照

関連項目
AccessibleObject クラス
AccessibleObject メンバ
System.Windows.Forms 名前空間