Procedura: Caricare in modo asincrono un suono in un Windows Form

  • Articolo

Nell'esempio di codice seguente viene caricato un suono in modo asincrono da un URL e quindi viene riprodotto in un nuovo thread.

Esempio

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Media;
using System.Windows.Forms;

namespace SoundPlayerLoadAsyncExample
{
    public class Form1 : Form
    {
        private SoundPlayer Player = new SoundPlayer();

        public Form1()
        {
            InitializeComponent();

            this.Player.LoadCompleted += new AsyncCompletedEventHandler(Player_LoadCompleted);
        }

        private void playSoundButton_Click(object sender, EventArgs e)
        {
            this.LoadAsyncSound();
        }

        public void LoadAsyncSound()
        {
            try
            {
                // Replace this file name with a valid file name.
                this.Player.SoundLocation = "http://www.tailspintoys.com/sounds/stop.wav";
                this.Player.LoadAsync();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "Error loading sound");
            }
        }

        // This is the event handler for the LoadCompleted event.
        void Player_LoadCompleted(object sender, AsyncCompletedEventArgs e)
        {
            if (Player.IsLoadCompleted)
            {
                try
                {
                    this.Player.Play();
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message, "Error playing sound");
                }
            }
        }

        private Button playSoundButton;

        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.playSoundButton = new System.Windows.Forms.Button();
            this.SuspendLayout();
            //
            // playSoundButton
            //
            this.playSoundButton.Location = new System.Drawing.Point(106, 112);
            this.playSoundButton.Name = "playSoundButton";
            this.playSoundButton.Size = new System.Drawing.Size(75, 23);
            this.playSoundButton.TabIndex = 0;
            this.playSoundButton.Text = "Play Sound";
            this.playSoundButton.Click += new System.EventHandler(this.playSoundButton_Click);
            //
            // Form1
            //
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(292, 273);
            this.Controls.Add(this.playSoundButton);
            this.Name = "Form1";
            this.Text = "Form1";
            this.ResumeLayout(false);
        }

        #endregion

    }

    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.Run(new Form1());
        }
    }
}

Imports System.Media
Imports System.Windows.Forms

Public Class Form1
    Inherits System.Windows.Forms.Form

    Friend WithEvents playSoundButton As System.Windows.Forms.Button
    Private WithEvents Player As New SoundPlayer

    Sub New()

        Me.InitializeComponent()

    End Sub

    Private Sub playSoundButton_Click( _
        ByVal sender As System.Object, _
        ByVal e As System.EventArgs) _
        Handles playSoundButton.Click

        ' Replace this file name with a valid file name.
        Me.Player.SoundLocation = "http://www.tailspintoys.com/sounds/stop.wav"
        Me.Player.LoadAsync()

    End Sub

    Private Sub Player_LoadCompleted( _
        ByVal sender As Object, _
        ByVal e As _
        System.ComponentModel.AsyncCompletedEventArgs) _
        Handles Player.LoadCompleted

        If Me.Player.IsLoadCompleted Then
            Me.Player.Play()
        End If

    End Sub

    'Form overrides dispose to clean up the component list.
    <System.Diagnostics.DebuggerNonUserCode()> _
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing AndAlso components IsNot Nothing Then
            components.Dispose()
        End If
        MyBase.Dispose(disposing)
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> _
    Private Sub InitializeComponent()
        Me.playSoundButton = New System.Windows.Forms.Button
        Me.SuspendLayout()
        '
        'playSoundButton
        '
        Me.playSoundButton.Location = New System.Drawing.Point(105, 107)
        Me.playSoundButton.Name = "playSoundButton"
        Me.playSoundButton.Size = New System.Drawing.Size(75, 23)
        Me.playSoundButton.TabIndex = 0
        Me.playSoundButton.Text = "Play Sound"
        Me.playSoundButton.UseVisualStyleBackColor = True
        '
        'Form1
        '
        Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
        Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
        Me.ClientSize = New System.Drawing.Size(292, 273)
        Me.Controls.Add(Me.playSoundButton)
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)

    End Sub

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

End Class

Compilazione del codice

L'esempio presenta i requisiti seguenti:

  • Riferimenti agli assembly System e System.Windows.Forms.

  • Sostituzione del nome del file "http://www.tailspintoys.com/sounds/stop.wav" con un nome file valido.

Programmazione efficiente

Le operazioni sui file devono essere racchiuse tra blocchi di gestione delle eccezioni appropriati.

Le seguenti condizioni possono generare un'eccezione:

Sicurezza di .NET Framework

Non basarsi sul nome del file per prendere decisioni in merito al relativo contenuto. È possibile ad esempio che il file Form1.vb non sia un file di origine di Visual Basic. Prima di usare i dati nell'applicazione verificare tutti gli input.

Vedi anche