一、前言

最近在搞C#的winform窗体应用，需要监听Console日志写入本地日志，类似Unity的Application.logMessageReceviedThreaded。

二、具体实现

1、原理

Console提供了一个SetOut接口，传入一个TextWriter，即可通过TextWriter重写Write和WriteLine接口，将日志写入我们的日志文件了。

public static void SetOut(TextWriter newOut);

2、具体实现

自己创建一个类，比如LoggerTextWriter，它继承TextWriter，重写Write和WriteLine接口，写入日志到本地。

LoggerTextWriter logSW = new LoggerTextWriter("./");
logSW.Init();
Console.SetOut(logSW);

Console.WriteLine("Hello Wrold");

其中LoggerTextWriter代码如下

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

public class LoggerTextWriter : TextWriter
{
    private string m_outputLogPath;

    public LoggerTextWriter (string launcherDir) : base()
    {
        m_outputLogPath = Path.Combine(launcherDir, "output.log");
    }

    public override Encoding Encoding { get { return Encoding.UTF8; } }

    public override void Write(string value)
    {
        WriteLog(value);
    }
    public override void WriteLine(string value)
    {
        WriteLog(value);
    }
    public override void Close()
    {
        base.Close();
    }

    public void Init()
    {
        if (File.Exists(m_outputLogPath))
        {
            File.Delete(m_outputLogPath);
        }
    }

    public void WriteLog(string msg)
    {
        try
        {
            FileStream fs;
            StreamWriter sw;
            StringBuilder sbr = new StringBuilder(16);

            if (!File.Exists(m_outputLogPath))
            {
                fs = new FileStream(m_outputLogPath, FileMode.CreateNew, FileAccess.Write, FileShare.ReadWrite);
                sw = new StreamWriter(fs, Encoding.UTF8);
                sbr.Append("日志开始");
                sbr.AppendLine();
            }
            else
            {
                fs = new FileStream(m_outputLogPath, FileMode.Append, FileAccess.Write, FileShare.ReadWrite);
                sw = new StreamWriter(fs, Encoding.UTF8);
            }
            sbr.Append("[");
            sbr.Append(DateTime.Now.ToString("yyyy/MM/dd HH:mm:ss.fff"));
            sbr.Append("]: ");
            sbr.Append(msg);
            sw.WriteLine(sbr.ToString());

            sw.Flush();
            sw.Close();
            fs.Close();
            sbr.Clear();
        }
        catch (Exception)
        {
            throw;
        }
    }
}