如何在MvvmCross中使用IMvxTrace

Question

最近开始研究Xamarin，今天打开了MvvmCross上写的大项目，里面要加新功能。这很难，因为我通常使用 Java 和 Android Studio，但现在我必须深入研究 C# 和 Visual Studio。

首先我想了解这个项目的流程，为此我想在不同的 .cs 中插入日志类并在浏览应用程序时查看它们。

在Setup.cs中：

protected override IMvxTrace CreateDebugTrace()
    {
        return new NLogTrace();
    }

NLogTrace.cs:

public class NLogTrace : IMvxTrace
{
    private readonly ILogger _logger;

    public NLogTrace()
    {
        InitializeNLog();

        _logger = LogManager.GetLogger("MvvmCross");
    }

    public static string LogFileName => Path.Combine(GetCacheFolder(), "logFile.txt");

    private static void InitializeNLog()
    {
        // Step 1. Create configuration object 
        var config = new LoggingConfiguration();

        // Step 2. Create targets and add them to the configuration 
        var consoleTarget = new ConsoleTarget();
        config.AddTarget("console", consoleTarget);

        var logFolderPath = GetCacheFolder();
        var fileTarget = new FileTarget
        {
            FileName = Path.Combine(logFolderPath, "logFile.txt"),
            ArchiveFileName = Path.Combine(logFolderPath, "log.{#}.txt"),
            ArchiveEvery = FileArchivePeriod.Day,
            ArchiveNumbering = ArchiveNumberingMode.Date,
            MaxArchiveFiles = 7
        };
        config.AddTarget("file", fileTarget);

        // Step 3. Set target properties 
        consoleTarget.Layout = @"${longdate}|${level:uppercase=true}|${logger}|${message}"; //
        fileTarget.Layout = "${longdate}|${level:uppercase=true}|${logger}|${message}";

        // Step 4. Define rules
        var rule1 = new LoggingRule("*", LogLevel.Trace, consoleTarget);
        config.LoggingRules.Add(rule1);

        #if DEBUG
        var rule2 = new LoggingRule("*", LogLevel.Debug, fileTarget);
        config.LoggingRules.Add(rule2);
        #else
        var rule2 = new LoggingRule("*", LogLevel.Info, fileTarget);
        config.LoggingRules.Add(rule2);
        #endif

        LogManager.Configuration = config;
    }

    private static string GetCacheFolder()
    {
        var documents = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
        var relativeCacheFolderPath = Path.Combine(documents, "Storage", "Logs");

        var directory = new DirectoryInfo(relativeCacheFolderPath);
        var resolvedCacheFolderPath = directory.FullName;
        return resolvedCacheFolderPath;
    }

    public void Trace(MvxTraceLevel level, string tag, string message)
    {
        switch (level)
        {
            case MvxTraceLevel.Diagnostic:
                _logger.Debug(message);
                break;
            case MvxTraceLevel.Warning:
                _logger.Warn(message);
                break;
            case MvxTraceLevel.Error:
                _logger.Error(message);
                break;
        }
    }

    public void Trace(MvxTraceLevel level, string tag, Func<string> message)
    {
        switch (level)
        {
            case MvxTraceLevel.Diagnostic:
                _logger.Debug(message());
                break;
            case MvxTraceLevel.Warning:
                _logger.Warn(message());
                break;
            case MvxTraceLevel.Error:
                _logger.Error(message());
                break;
        }
    }

    public void Trace(MvxTraceLevel level, string tag, string message, params object[] args)
    {
        switch (level)
        {
            case MvxTraceLevel.Diagnostic:
                _logger.Debug(message, args);
                break;
            case MvxTraceLevel.Warning:
                _logger.Warn(message, args);
                break;
            case MvxTraceLevel.Error:
                _logger.Error(message, args);
                break;
        }
    }
}

所以，我看到了一些记录器，但我不知道如何在某些 .cs 文件中使用它。你能提供一些如何使用的片段

Trace(MvxTraceLevel level, string tag, string message)

在 .Core 或 .Droid 项目中任意选择的 .cs 文件中？

Answer 1

你必须使用依赖注入。如需完整文档 see docs。简而言之，您在视图 model/service 构造函数中添加一个 IMvxLog 参数：

public MyViewModel( IMvxLog logger )
{
   this._logger = logger;
}

然后在 _logger 上调用适当的方法:

_log.Trace("Some message");

如果你想在无法设置依赖注入的class中使用IMvxLog，你可以使用Mvx解决它：

var logger = Mvx.Resolve<IMvxLog>();

如何在MvvmCross中使用IMvxTrace

How to use IMvxTrace in MvvmCross

c#

logging

mvvmcross

xamarin