Procedura: distinguere tra clic e doppio clic
In genere un solo clic avvia un'azione dell'interfaccia utente (UI, User Interface) mentre un doppio clic la estende. Un clic, ad esempio, consente di selezionare un elemento e un doppio clic consente di modificarlo. Gli eventi click in Windows Form, tuttavia, non si adattano facilmente a situazioni in cui un clic e un doppio clic eseguono azioni incompatibili, perché un'azione collegata all'evento Click o MouseClick viene eseguita prima dell'azione collegata all'evento DoubleClick o MouseDoubleClick. In questo argomento vengono spiegate due soluzioni al problema. Una soluzione consiste nel gestire l'evento generato dal doppio clic e ripristinare le azioni nella gestione dell'evento generato dal clic. In alcune rare situazioni potrebbe essere necessario simulare l'effetto del clic e del doppio clic gestendo l'evento MouseDown e utilizzando le proprietà DoubleClickTime e DoubleClickSize della classe SystemInformation. Si misura il tempo intercorrente tra i clic e se un secondo clic si verifica prima che venga raggiunto il valore della proprietà DoubleClickTime e rientra nel rettangolo definito dalla proprietà DoubleClickSize, si esegue l'azione generata dal doppio clic, altrimenti si esegue l'azione generata dal clic singolo.
Per ripristinare l'azione generata da un clic
Assicurarsi che il controllo utilizzato disponga di un comportamento standard in risposta a un doppio clic. In caso contrario, attivare il controllo con il metodo SetStyle. Gestire l'evento generato dal doppio clic e ripristinare l'azione avviata dal clic nonché quella avviata dal doppio clic. Nell'esempio di codice riportato di seguito vengono illustrati la creazione di un pulsante personalizzato in cui è attivato il doppio clic e il ripristino dell'azione generata dal clic nel codice per la gestione dell'evento generato dal doppio clic.
Imports System 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 'New ' 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 'New End Class 'DoubleClickButtonusing 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); } } }
Per distinguere tra clic nell'evento MouseDown
Gestire l'evento MouseDown e determinare la posizione e l'intervallo tra i clic servendosi delle proprietà corrette della classe SystemInformation e di un componente Timer. Eseguire l'azione corretta a seconda che si verifichi un clic o un doppio clic. Nell'esempio di codice riportato di seguito viene illustrata tale operazione.
Imports System 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 Namespaceusing 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); } } }#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); }
Compilazione del codice
Requisiti:
- Riferimenti agli assembly System, System.Drawing e System.Windows.Forms.
Per informazioni sulla compilazione di questi esempi dalla riga di comando per Visual Basic o Visual C#, vedere Building from the Command Line (Visual Basic) o Compilazione dalla riga di comando con csc.exe. È anche possibile compilare questi esempi in Visual Studio incollando il codice in nuovi progetti. Per ulteriori informazioni, vedere Procedura: compilare ed eseguire un esempio di codice Windows Form completo tramite Visual Studio e Procedura: compilare ed eseguire un esempio di codice Windows Form completo tramite Visual Studio e Procedura: compilare ed eseguire un esempio di codice Windows Form completo tramite Visual Studio e Procedura: compilare ed eseguire un esempio di codice Windows Form completo tramite Visual Studio e Procedura: compilare ed eseguire un esempio di codice Windows Form completo tramite Visual Studio.