Procedura: Distinguere tra clic e doppio clic

Articolo
10/19/2023

In genere, un singolo clic avvia un'azione dell'interfaccia utente e un doppio clic estende l'azione. Ad esempio, un solo clic consente in genere di scegliere un elemento e un doppio clic consente di modificare l'elemento selezionato. Gli eventi Click in Windows Form, tuttavia, non si adattano facilmente a uno scenario in cui un clic e un doppio clic eseguono azioni incompatibili, perché un'azione associata all'evento Click o MouseClick viene eseguito prima dell'azione collegata all'evento DoubleClick o MouseDoubleClick. Questo argomento illustra due soluzioni a questo problema. Una soluzione consiste nel gestire l'evento di doppio clic e ripristinare le azioni nella gestione dell'evento Click. In rare situazioni potrebbe essere necessario simulare un comportamento di clic e doppio clic gestendo l'evento MouseDown e usando le proprietà DoubleClickTime e DoubleClickSize della classe SystemInformation. A questo punto, si misura l'intervallo trascorso tra un clic e l'altro e, se viene eseguito un secondo clic prima che venga raggiunto il valore di DoubleClickTime all'interno di un rettangolo definito da DoubleClickSize, eseguire l'azione di doppio clic; in caso contrario, eseguire l'azione di clic.

Per eseguire il rollback di un'azione di clic

Assicurarsi che il controllo con cui si lavora disponga del comportamento standard di doppio clic. In caso contrario, abilitare il controllo con il metodo SetStyle. Gestire l'evento di doppio clic ed eseguire il rollback dell'azione di clic, nonché dell'azione di doppio clic. L'esempio di codice seguente illustra come creare un pulsante personalizzato con doppio clic abilitato, nonché come eseguire il rollback dell'azione di clic nel codice di gestione dell'evento di doppio clic.

using System;
using System.ComponentModel;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace MouseRollBackSingleClick
{
    public class Form1 : Form
    {
        private DoubleClickButton button1;
        private FormBorderStyle initialStyle;

        public Form1()
        {
            initialStyle = this.FormBorderStyle;
            this.ClientSize = new System.Drawing.Size(292, 266);
            button1 = new DoubleClickButton();
            button1.Location = new Point (40,40);
            button1.Click += new EventHandler(button1_Click);
            button1.AutoSize = true;
            this.AllowDrop = true;
            button1.Text = "Click or Double Click";
            button1.DoubleClick += new EventHandler(button1_DoubleClick);
            this.Controls.Add(button1);
        }

        // Handle the double click event.
        void button1_DoubleClick(object sender, EventArgs e)
        {
            // Change the border style back to the initial style.
            this.FormBorderStyle = initialStyle;
            MessageBox.Show("Rolled back single click change.");
        }

        // Handle the click event.
        void button1_Click(object sender, EventArgs e)
        {
            this.FormBorderStyle = FormBorderStyle.FixedToolWindow;
        }

        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.Run(new Form1());
        }
    }
    public class DoubleClickButton : Button
    {
        public DoubleClickButton() : base()
        {
            // Set the style so a double click event occurs.
            SetStyle(ControlStyles.StandardClick |
                ControlStyles.StandardDoubleClick, true);
        }
    }
}

Imports System.ComponentModel
Imports System.Drawing
Imports System.Text
Imports System.Windows.Forms



Public Class Form1
    Inherits Form
    Private WithEvents button1 As DoubleClickButton
    Private initialStyle As FormBorderStyle
    
    Public Sub New() 
        Me.SuspendLayout()
        initialStyle = Me.FormBorderStyle
        Me.ClientSize = New System.Drawing.Size(292, 266)
        button1 = New DoubleClickButton()
        button1.Location = New Point(40, 40)
        button1.AutoSize = True
        button1.Text = "Click or Double Click"
        Me.Controls.Add(button1)
        Me.Name = "Form1"
        Me.ResumeLayout(False)
        Me.PerformLayout()
    
    End Sub
    
    
    ' Handle the double click event.
    Private Sub button1_DoubleClick(ByVal sender As Object, ByVal e As EventArgs) _
        Handles button1.DoubleClick

        ' Change the border style back to the initial style.
        Me.FormBorderStyle = initialStyle
        MessageBox.Show("Rolled back single click change.")

    End Sub
    
    
    ' Handle the click event.
    Private Sub button1_Click(ByVal sender As Object, ByVal e As EventArgs) _
         Handles button1.Click

        Me.FormBorderStyle = FormBorderStyle.FixedToolWindow

    End Sub


    <STAThread()> _
    Shared Sub Main()
        Application.EnableVisualStyles()
        Application.Run(New Form1())

    End Sub
End Class

Public Class DoubleClickButton
    Inherits Button
    
    Public Sub New() 
        ' Set the style so a double click event occurs.
        SetStyle(ControlStyles.StandardClick Or ControlStyles.StandardDoubleClick, True)
    
    End Sub
End Class

Per distinguere tra clic nell'evento MouseDown

Gestire l'evento MouseDown e determinare la posizione e l'intervallo tra i clic usando le proprietà SystemInformation appropriate e un componente Timer. Eseguire l'azione appropriata a seconda che venga eseguito un clic o un doppio clic. Nell'esempio di codice seguente viene illustrato come procedere.

#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>
#using <System.dll>

using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;

namespace SingleVersusDoubleClick
{
    public ref class Form1 : public Form
    {
    private:
        Rectangle hitTestRectangle;
    private:
        Rectangle doubleClickRectangle;
    private:
        TextBox^ outputBox;
    private:
        Timer^ doubleClickTimer;
    private:
        ProgressBar^ doubleClickBar;
    private:
        Label^ hitTestLabel;
    private:
        Label^ timerLabel;
    private:
        bool isFirstClick;
    private:
        bool isDoubleClick;
    private:
        int milliseconds;

    public:
        Form1()
        {
            hitTestRectangle = Rectangle();
            hitTestRectangle.Location = Point(30, 20);
            hitTestRectangle.Size = System::Drawing::Size(100, 40);

            doubleClickRectangle = Rectangle();

            outputBox = gcnew TextBox();
            outputBox->Location = Point(30, 120);
            outputBox->Size = System::Drawing::Size(200, 100);
            outputBox->AutoSize = false;
            outputBox->Multiline = true;

            doubleClickTimer = gcnew Timer();
            doubleClickTimer->Interval = 100;
            doubleClickTimer->Tick +=
                gcnew EventHandler(this, &Form1::doubleClickTimer_Tick);

            doubleClickBar = gcnew ProgressBar();
            doubleClickBar->Location = Point(30, 85);
            doubleClickBar->Minimum = 0;
            doubleClickBar->Maximum = SystemInformation::DoubleClickTime;

            hitTestLabel = gcnew Label();
            hitTestLabel->Location = Point(30, 5);
            hitTestLabel->Size = System::Drawing::Size(100, 15);
            hitTestLabel->Text = "Hit test rectangle:";

            timerLabel = gcnew Label();
            timerLabel->Location = Point(30, 70);
            timerLabel->Size = System::Drawing::Size(100, 15);
            timerLabel->Text = "Double click timer:";

            isFirstClick = true;

            this->Paint += gcnew PaintEventHandler(this, &Form1::Form1_Paint);
            this->MouseDown += 
                gcnew MouseEventHandler(this, &Form1::Form1_MouseDown);
            this->Controls->
                AddRange(gcnew array<Control^> { doubleClickBar, outputBox,
                hitTestLabel, timerLabel });
        }

        // Detect a valid single click or double click.
    private:
        void Form1_MouseDown(Object^ sender, MouseEventArgs^ e)
        {
            // Verify that the mouse click is in the main hit
            // test rectangle.
            if (!hitTestRectangle.Contains(e->Location))
            {
                return;
            }

            // This is the first mouse click.
            if (isFirstClick)
            {
                isFirstClick = false;

                // Determine the location and size of the double click
                // rectangle area to draw around the cursor point.
                doubleClickRectangle = Rectangle(
                    e->X - (SystemInformation::DoubleClickSize.Width / 2),                    
                    e->Y - (SystemInformation::DoubleClickSize.Height / 2),                    
                    SystemInformation::DoubleClickSize.Width,                    
                    SystemInformation::DoubleClickSize.Height);
                Invalidate();

                // Start the double click timer.
                doubleClickTimer->Start();
            }

            // This is the second mouse click.
            else
            {
                // Verify that the mouse click is within the double click
                // rectangle and is within the system-defined double
                // click period.
                if (doubleClickRectangle.Contains(e->Location) &&
                    milliseconds < SystemInformation::DoubleClickTime)
                {
                    isDoubleClick = true;
                }
            }
        }

    private:
        void doubleClickTimer_Tick(Object^ sender, EventArgs^ e)
        {
            milliseconds += 100;
            doubleClickBar->Increment(100);

            // The timer has reached the double click time limit.
            if (milliseconds >= SystemInformation::DoubleClickTime)
            {
                doubleClickTimer->Stop();

                if (isDoubleClick)
                {
                    outputBox->AppendText("Perform double click action");
                    outputBox->AppendText(Environment::NewLine);
                }
                else
                {
                    outputBox->AppendText("Perform single click action");
                    outputBox->AppendText(Environment::NewLine);
                }

                // Allow the MouseDown event handler to process clicks again.
                isFirstClick = true;
                isDoubleClick = false;
                milliseconds = 0;
                doubleClickBar->Value = 0;
            }
        }

        // Paint the hit test and double click rectangles.
    private:
        void Form1_Paint(Object^ sender, PaintEventArgs^ e)
        {
            // Draw the border of the main hit test rectangle.
            e->Graphics->DrawRectangle(Pens::Black, hitTestRectangle);

            // Fill in the double click rectangle.
            e->Graphics->FillRectangle(Brushes::Blue, doubleClickRectangle);
        }
    };
}


[STAThread]
int main()
{
    Application::EnableVisualStyles();
    Application::Run(gcnew SingleVersusDoubleClick::Form1);
}

using System;
using System.Drawing;
using System.Windows.Forms;

namespace SingleVersusDoubleClick
{
    class Form1 : Form
    {
        private Rectangle hitTestRectangle = new Rectangle();
        private Rectangle doubleClickRectangle = new Rectangle();
        private TextBox textBox1 = new TextBox();
        private Timer doubleClickTimer = new Timer();
        private ProgressBar doubleClickBar = new ProgressBar();
        private Label label1 = new Label();
        private Label label2 = new Label();
        private bool isFirstClick = true;
        private bool isDoubleClick = false;
        private int milliseconds = 0;

        [STAThread]
        public static void Main()
        {
            Application.EnableVisualStyles();
            Application.Run(new Form1());
        }

        public Form1()
        {
            label1.Location = new Point(30, 5);
            label1.Size = new Size(100, 15);
            label1.Text = "Hit test rectangle:";

            label2.Location = new Point(30, 70);
            label2.Size = new Size(100, 15);
            label2.Text = "Double click timer:";

            hitTestRectangle.Location = new Point(30, 20);
            hitTestRectangle.Size = new Size(100, 40);

            doubleClickTimer.Interval = 100;
            doubleClickTimer.Tick +=
                new EventHandler(doubleClickTimer_Tick);

            doubleClickBar.Location = new Point(30, 85);
            doubleClickBar.Minimum = 0;
            doubleClickBar.Maximum = SystemInformation.DoubleClickTime;

            textBox1.Location = new Point(30, 120);
            textBox1.Size = new Size(200, 100);
            textBox1.AutoSize = false;
            textBox1.Multiline = true;

            this.Paint += new PaintEventHandler(Form1_Paint);
            this.MouseDown += new MouseEventHandler(Form1_MouseDown);
            this.Controls.AddRange(new Control[] { doubleClickBar, textBox1,
                label1, label2 });
        }

        // Detect a valid single click or double click.
        void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            // Verify that the mouse click is in the main hit
            // test rectangle.
            if (!hitTestRectangle.Contains(e.Location))
            {
                return;
            }

            // This is the first mouse click.
            if (isFirstClick)
            {
                isFirstClick = false;

                // Determine the location and size of the double click
                // rectangle area to draw around the cursor point.
                doubleClickRectangle = new Rectangle(
                    e.X - (SystemInformation.DoubleClickSize.Width / 2),
                    e.Y - (SystemInformation.DoubleClickSize.Height / 2),
                    SystemInformation.DoubleClickSize.Width,
                    SystemInformation.DoubleClickSize.Height);
                Invalidate();

                // Start the double click timer.
                doubleClickTimer.Start();
            }

            // This is the second mouse click.
            else
            {
                // Verify that the mouse click is within the double click
                // rectangle and is within the system-defined double
                // click period.
                if (doubleClickRectangle.Contains(e.Location) &&
                    milliseconds < SystemInformation.DoubleClickTime)
                {
                    isDoubleClick = true;
                }
            }
        }

        void doubleClickTimer_Tick(object sender, EventArgs e)
        {
            milliseconds += 100;
            doubleClickBar.Increment(100);

            // The timer has reached the double click time limit.
            if (milliseconds >= SystemInformation.DoubleClickTime)
            {
                doubleClickTimer.Stop();

                if (isDoubleClick)
                {
                    textBox1.AppendText("Perform double click action");
                    textBox1.AppendText(Environment.NewLine);
                }
                else
                {
                    textBox1.AppendText("Perform single click action");
                    textBox1.AppendText(Environment.NewLine);
                }

                // Allow the MouseDown event handler to process clicks again.
                isFirstClick = true;
                isDoubleClick = false;
                milliseconds = 0;
                doubleClickBar.Value = 0;
            }
        }

        // Paint the hit test and double click rectangles.
        void Form1_Paint(object sender, PaintEventArgs e)
        {
            // Draw the border of the main hit test rectangle.
            e.Graphics.DrawRectangle(Pens.Black, hitTestRectangle);

            // Fill in the double click rectangle.
            e.Graphics.FillRectangle(Brushes.Blue, doubleClickRectangle);
        }
    }
}

Imports System.Drawing
Imports System.Windows.Forms

Namespace SingleVersusDoubleClick

    Class Form1
        Inherits Form
        Private hitTestRectangle As New Rectangle()
        Private doubleClickRectangle As New Rectangle()
        Private textBox1 As New TextBox()
        Private WithEvents doubleClickTimer As New Timer()
        Private doubleClickBar As New ProgressBar()
        Private label1 As New Label()
        Private label2 As New Label()
        Private isFirstClick As Boolean = True
        Private isDoubleClick As Boolean = False
        Private milliseconds As Integer = 0

        <STAThread()> _
        Public Shared Sub Main()
            Application.EnableVisualStyles()
            Application.Run(New Form1())
        End Sub

        Public Sub New()
            label1.Location = New Point(30, 5)
            label1.Size = New Size(100, 15)
            label1.Text = "Hit test rectangle:"

            label2.Location = New Point(30, 70)
            label2.Size = New Size(100, 15)
            label2.Text = "Double click timer:"

            hitTestRectangle.Location = New Point(30, 20)
            hitTestRectangle.Size = New Size(100, 40)
            doubleClickTimer.Interval = 100

            doubleClickBar.Location = New Point(30, 85)
            doubleClickBar.Minimum = 0
            doubleClickBar.Maximum = SystemInformation.DoubleClickTime

            textBox1.Location = New Point(30, 120)
            textBox1.Size = New Size(200, 100)
            textBox1.AutoSize = False
            textBox1.Multiline = True

            Me.Controls.Add(doubleClickBar)
            Me.Controls.Add(textBox1)
            Me.Controls.Add(label1)
            Me.Controls.Add(label2)
        End Sub

        ' Detect a valid single click or double click.
        Sub Form1_MouseDown(ByVal sender As Object, _
            ByVal e As MouseEventArgs) Handles Me.MouseDown

            ' Verify that the mouse click is in the main hit
            ' test rectangle.
            If Not hitTestRectangle.Contains(e.Location) Then
                Return
            End If

            ' This is the first mouse click.
            If isFirstClick = True Then
                isFirstClick = False

                ' Determine the location and size of the double click 
                ' rectangle to draw around the cursor point.
                doubleClickRectangle = New Rectangle( _
                    e.X - (SystemInformation.DoubleClickSize.Width / 2), _
                    e.Y - (SystemInformation.DoubleClickSize.Height / 2), _
                    SystemInformation.DoubleClickSize.Width, _
                    SystemInformation.DoubleClickSize.Height)
                Invalidate()

                ' Start the double click timer.
                doubleClickTimer.Start()

            ' This is the second mouse click.
            Else
                ' Verify that the mouse click is within the double click
                ' rectangle and is within the system-defined double 
                ' click period.
                If doubleClickRectangle.Contains(e.Location) And _
                    milliseconds < SystemInformation.DoubleClickTime Then
                    isDoubleClick = True
                End If
            End If
        End Sub

        Sub doubleClickTimer_Tick(ByVal sender As Object, _
            ByVal e As EventArgs) Handles doubleClickTimer.Tick

            milliseconds += 100
            doubleClickBar.Increment(100)

            ' The timer has reached the double click time limit.
            If milliseconds >= SystemInformation.DoubleClickTime Then
                doubleClickTimer.Stop()

                If isDoubleClick Then
                    textBox1.AppendText("Perform double click action")
                    textBox1.AppendText(Environment.NewLine)
                Else
                    textBox1.AppendText("Perform single click action")
                    textBox1.AppendText(Environment.NewLine)
                End If

                ' Allow the MouseDown event handler to process clicks again.
                isFirstClick = True
                isDoubleClick = False
                milliseconds = 0
                doubleClickBar.Value = 0
            End If
        End Sub

        ' Paint the hit test and double click rectangles.
        Sub Form1_Paint(ByVal sender As Object, _
            ByVal e As PaintEventArgs) Handles Me.Paint

            ' Draw the border of the main hit test rectangle.
            e.Graphics.DrawRectangle(Pens.Black, hitTestRectangle)

            ' Fill in the double click rectangle.
            e.Graphics.FillRectangle(Brushes.Blue, doubleClickRectangle)
        End Sub
    End Class
End Namespace

Compilazione del codice

Gli esempi presentano i requisiti seguenti:

Riferimenti agli assembly System, System.Drawing e System.Windows.Forms.

Vedi anche

Input del mouse in un'applicazione Windows Forms

Procedura: Distinguere tra clic e doppio clic

Per eseguire il rollback di un'azione di clic

Per distinguere tra clic nell'evento MouseDown

Compilazione del codice

Vedi anche

Commenti e suggerimenti

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