如何停止System.Timers.Timer

Question

我正在使用Windows Forms启动一个System.Timers.Timer，每隔3秒触发一个事件。当我关闭表单时，进程会继续触发，这很好。当我重新打开窗体以在单击按钮btnSendOff_Click时停止计时器时，就会出现问题。

    System.Timers.Timer sendTimer = new System.Timers.Timer();
    sendTimer.Elapsed += new ElapsedEventHandler(sendProcessTimerEvent);
    sendTimer.Interval = 3000;

    private void sendProcessTimerEvent(object sender, EventArgs e)
    {
        MessageBox.Show("Send 3 sec");
    }

    private void btnSendOn_Click(object sender, EventArgs e)
    {
        sendTimer.Start();
    }

    private void btnSendOff_Click(object sender, EventArgs e)
    {
        sendTimer.Stop();
    }

在此窗体上将有更多的异步计时器。如何在重新打开表单时停止此计时器？

Answer 1

如果窗体需要在窗体关闭后继续运行，则窗体不应该在每次创建窗体的新实例时都创建新的计时器。按照您声明计时器的方式，每次创建表单时，它都会创建另一个计时器。您应该将计时器放在不同的窗体上，或者在某个全局模块中声明它，并且只使窗体激活或停用计时器。如果在窗体关闭时计时器需要继续运行，则窗体不应该是拥有或创建计时器的窗体。如果在窗体关闭时计时器不需要继续运行，那么您应该使用Forms.Timer而不是System.Timer。

编辑:添加示例代码

static class Program
{
    public static System.Timers.Timer sendTimer;
    public static System.Text.StringBuilder accumulatedText;

    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        sendTimer = new System.Timers.Timer();
        accumulatedText = new System.Text.StringBuilder("Started at " + DateTime.Now.ToLongTimeString() + Environment.NewLine);
        sendTimer.Interval = 3000;
        sendTimer.Elapsed += new System.Timers.ElapsedEventHandler(sendProcessTimerEvent);
        Application.Run(new MainForm());
    }

    static void sendProcessTimerEvent(object sender, System.Timers.ElapsedEventArgs e)
    {
        accumulatedText.AppendLine("Pinged at " + DateTime.Now.ToLongTimeString());
    }
}

class MainForm : Form
{
    ToolStrip mainToolStrip = new ToolStrip();
    public MainForm()
    {
        mainToolStrip.Items.Add("Log Control").Click += new EventHandler(MainForm_Click);
        Controls.Add(mainToolStrip);
    }

    void MainForm_Click(object sender, EventArgs e)
    {
        Form1 frm = new Form1();
        frm.ShowDialog();
    }
}

class Form1 : Form
{
    private Button button1 = new Button();
    private TextBox text1 = new TextBox();
    public Form1()
    {
        button1.Dock = DockStyle.Bottom;
        button1.Text = Program.sendTimer.Enabled ? "Stop": "Start";
        button1.Click += new EventHandler(button1_Click);
        text1 = new TextBox();
        text1.Dock = DockStyle.Fill;
        text1.Multiline= true;
        text1.ScrollBars = ScrollBars.Vertical;
        text1.Text = Program.accumulatedText.ToString();
        Controls.AddRange(new Control[] {button1, text1});
    }

    void button1_Click(object sender, EventArgs e)
    {
        Program.sendTimer.Enabled = !Program.sendTimer.Enabled;
        button1.Text = Program.sendTimer.Enabled ? "Stop" : "Start";
    }
}