Question

我想创建一个时钟类，它使用委托在本地时间将其值更改一秒时通知潜在订阅者。当我运行程序时。它没有给我这样的输出。输出看起来像这样，取决于运行程序的时间：

Current Time: 14:53:56
Logging to file: 14:53:56
Current Time: 14:53:57
Logging to file: 14:53:57
Current Time: 14:53:58
Logging to file: 14:53:58

任何人都可以帮我解决这个问题吗？这是代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace Clock_Events_Delegates
{
    // EventArgs is the base class for all event data. It inherits all its methods from Object.
    // EventArgs class is an empty bucket that you can use to supply any information you want
    // about the event. a class to hold the information about the event
    public class TimeInfoEventArgs : EventArgs
    {
        public int hour;
        public int minute;
        public int second;

        public TimeInfoEventArgs(int hour, int minute, int second)
        {
            this.hour = hour;
            this.minute = minute;
            this.second = second;
        }
    }
    // The publisher: the class that other classes will observe. This publishes one delegate:
    // SecondChangHandler
    public class Clock
    {
        private int hour;
        private int minute;
        private int second;

        // the delegate the subscribers must implement
        public delegate void SecondChangeHandler(object clock,TimeInfoEventArgs timeInformation);

        // an instance of the delegate
        public SecondChangeHandler SecondChanged;

        // Set the clock running
        // It will raise an event for each new second
        public void Run()
        {
            // an infinite loop
            for (; ; )

           // Sleep for a second
            Thread.Sleep(100);

            // get the current time
            System.DateTime dt = System.DateTime.Now;

            // if the second has changed
            // notify the subscribers
            if(dt.Second != second)
            {
                // create the TimeInfoEventArgs object
                // to pass to the subscriber
                TimeInfoEventArgs timeInformation = new TimeInfoEventArgs(dt.Hour, dt.Minute, dt.Second);

                // if anyone has subsribed notify them
                if(SecondChanged != null)
                {
                    SecondChanged(this, timeInformation);
                }
            }
            // update the state
            this.second = dt.Second;
            this.minute = dt.Minute;
            this.hour = dt.Hour;
        }
    }
    // A subscriber: DisplayClock subscibes to the clock's events. The job of  the Display Clock is
    // to display the currentTime
    public class DisplayClock
    {
        // given a clock, subscribe to its SecondChangedHandler event
        public void Subscribe(Clock theClock)
        {
            theClock.SecondChanged += new Clock.SecondChangeHandler(TimeHasChanged);
        }

        // method that implements delegated functionality
        public void TimeHasChanged(object theClock, TimeInfoEventArgs ti)
        {
            Console.WriteLine("Current Time: {0}:{1}:{2}",
                ti.hour.ToString(), ti.minute.ToString(), ti.second.ToString());
        }
    }
    // a second subscriber whose job is to write to a file
    public class LogCurrentTime
    {
        public void Subscribe(Clock theClock)
        {
            theClock.SecondChanged += new Clock.SecondChangeHandler(WriteLogEntry);   
        }

        public void WriteLogEntry(object theClock, TimeInfoEventArgs ti)
        {
            Console.WriteLine("Logging to file: {0}:{1}:{2}",
                ti.hour.ToString(), ti.minute.ToString(), ti.second.ToString());
        }
    }
    public class Tester
    {
        public void Run()
        {
            // Create a new clock
            Clock theClock = new Clock();

            // create the display and tell it subscribe to the clock just created
            DisplayClock dc = new DisplayClock();
            dc.Subscribe(theClock);

            // create the log object and tell it to subscribe to the clock
            LogCurrentTime lct = new LogCurrentTime();
            lct.Subscribe(theClock);

            theClock.Run();
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            Tester t = new Tester();
            t.Run();
        }
    }
}

Answer 1

看看这段代码：

// an infinite loop
for (; ; )

// Sleep for a second
Thread.Sleep(100);

// get the current time
System.DateTime dt = System.DateTime.Now;

以下行永远不会执行：

System.DateTime dt = System.DateTime.Now;

因为实际的循环是：

for (; ; ){
    Thread.Sleep(100);
}

所以只需使用支撑声明正确的循环体。

当我运行程序它没有在控制台窗口给我一个预期的输出

1 个答案: