3

在下面的代码中是否有可能在 myForm_FormClosing 之后调用 timer_Tick 。

如果有机会：是否足以在 myForm_FormClosing 中调用 timer.Stop() 以避免在 myForm_FormClosing 之后调用 timer_Tick？

using System;
using System.Windows.Forms;
using System.ComponentModel;

namespace Test
{
    static class Program
    {
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new MyForm());
        }
    }

    class MyForm : Form
    {
        private IContainer components;
        private Timer timer;

        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        public MyForm()
        {
            components = new Container();
            timer = new Timer(components);

            timer.Interval = 50;
            timer.Tick += timer_Tick;
            timer.Enabled = true;

            FormClosing += myForm_FormClosing;
        }

        private void timer_Tick(object sender, EventArgs e)
        {
        }

        private void myForm_FormClosing(object sender, FormClosingEventArgs e)
        {
        }
    }
}

更新：收到一些提示（感谢您的帮助）后，我基本上选择了以下代码来实现我想要的。请不要在调用 myForm_FormClosing 之后仍然可以调用 timer1_Tick！这个解决方案只是引入了一个标志（我称之为 doWork），它停止 timer1_Tick 内的代码在调用 myForm_FormClosing 之后执行。

using System;
using System.Windows.Forms;
using System.ComponentModel;

namespace Test
{
    static class Program
    {
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new MyForm());
        }
    }

    class MyForm : Form
    {
        private IContainer components;
        private Timer timer;
        private bool  doWork = true;

        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        public MyForm()
        {
            components = new Container();
            timer = new Timer(components);

            timer.Interval = 50;
            timer.Tick += timer_Tick;
            timer.Enabled = true;

            FormClosing += myForm_FormClosing;
        }

        private void timer_Tick(object sender, EventArgs e)
        {
            if (doWork)
            {
                //do the work
            }
        }

        private void myForm_FormClosing(object sender, FormClosingEventArgs e)
        {
            doWork = false;
        }
    }
}
4

3 回答 3

2

对的，这是可能的。根据文档...

在窗体关闭之前发生。

当表单关闭时，它会被释放，释放与表单相关的所有资源。

在 FormClosing 事件之后，计时器才会被释放。这是一个非常人为的例子，说明它是如何发生的。在调用 FormClosing 之后，您将看到在 Timer 滴答声上点击了调试器断点。 

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Diagnostics;
using System.Threading.Tasks;
using System.Threading;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        private System.Windows.Forms.Timer _time = new System.Windows.Forms.Timer();
        private Task _t1 = null;
        private Task _t2 = null;
        private bool _closingFlag = false;
        public Form1()
        {
            InitializeComponent();

            _time.Interval = 50;
            _time.Tick += (s, e) => { 
                textBox1.Text = DateTime.Now.ToString();
                if (_closingFlag) Debugger.Break();
            };

            _time.Start();
        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            _closingFlag = true;

            _t1 = Task.Factory.StartNew(() => { Thread.Sleep(1000); });
            _t2 = Task.Factory.StartNew(() => { Thread.Sleep(1000); });

            Task.WaitAll(_t1, _t2);
        }
    }
}
于 2012-08-14T17:46:50.317 回答
1

如果您使用计时器System.Windows.Forms.Timer，则 UI 线程必须处于空闲状态才能处理来自计时器的滴答声，因此根据我的理解，这是不可能的。

如果您将计时器与自己的线程一起使用，则可能会发生这种情况System.Timers.Timer。在这种情况下，我们可以通过实现以下内容来避免您提到的内容：

class MyForm : Form
{
    private System.Timers.Timer timer;

    private Object justForLocking = new Object();
    private Boolean safeToProceed = true;

    [...]

    public MyForm()
    {
        components = new Container();
        timer = new System.Timers.Timer();

        timer.Interval = 50;
        timer.Elapsed += new System.Timers.ElapsedEventHandler(timer_Elapsed);
        timer.Start();

        FormClosing += myForm_FormClosing;
    }

    void timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
    {
         // In case that this code is being executed after
         // the method myForm_FormClosing has adquired the 
         // exclusive lock over our dummy resource,
         // the timer thread will wait until the resource if released.
         // Once is released, our control flag will be set to false
         // and the timer should just return and never execute again.
         lock(justForLocking)
         {
             if (safeToProceed)
             {
                 // Do whatever you want to do at this point
             }
         }
    }

    private void myForm_FormClosing(object sender, FormClosingEventArgs e)
    {
         lock(justForLocking)
         {
             safeToProceed = false;
         }
         timer.Stop();

         // Do something else
    }

    [...]
}

This other SO question有相关信息。

编辑：System.Timers.Timer上面的代码仅在使用 a 而不是 System.Windows.Forms.Timer时才有效

于 2012-08-14T18:20:09.213 回答
0

我不这么认为，但无论如何最好还是调用 timer.stop() 。如果您需要它，尽管您应该在 program.cs 中创建计时器对象

于 2012-08-14T17:24:08.753 回答