错误或在android.util.Log？ - Log.isLoggable（调试）= FALSE，但Log.d（）不是禁用 [英] Bug or feature in android.util.Log? - Log.isLoggable(DEBUG) = false but Log.d() is not disabled

问题描述

更新：新配方的问题和头：

Update: Reformulated the question and header:

我一直以为问如果日志被激活像这样昂贵的Andr​​oid日志记录方法可以优化

I always thought that expensive android Logging methods can be optimized by asking if logging is active like this

    import android.util.Log;

    if (Log.isLoggable("MyContext", Log.DEBUG))
    {
        Log.d("MyContext", "my logging: " + callExpensiveCalculation());
    }

不过了Android 2.2的模拟器尝试这种时候，我Log.d（）永远不会被调用。

However when trying this with the android 2.2 emulator my Log.d() is never called.

所以，我想这code

So i tried this code

    Log.v(MY_CONTEXT, "VERBOSE logging is active: " + Log.isLoggable(MY_CONTEXT, Log.VERBOSE));
    Log.d(MY_CONTEXT, "DEBUG logging is active: " + Log.isLoggable(MY_CONTEXT, Log.DEBUG));
    Log.i(MY_CONTEXT, "INFO logging is active: " + Log.isLoggable(MY_CONTEXT, Log.INFO));
    Log.w(MY_CONTEXT, "WARN logging is active: " + Log.isLoggable(MY_CONTEXT, Log.WARN));
    Log.e(MY_CONTEXT, "ERROR logging is active: " + Log.isLoggable(MY_CONTEXT, Log.ERROR));

和出乎我的意料，我得到

and to my surprise i got

02-27 19:05:43.015: V/MyContext(334): VERBOSE logging is active: false
02-27 19:05:43.015: D/MyContext(334): DEBUG logging is active: false
02-27 19:05:43.015: I/MyContext(334): INFO logging is active: true
02-27 19:05:43.015: W/MyContext(334): WARN logging is active: true
02-27 19:05:43.015: E/MyContext(334): ERROR logging is active: true

因此​​，如果日志被禁用日志记录也可使用。
这是Android还是在我的测试 - code错误？

so logging works even if logging is disabled. Is this a bug in android or in my test-code?

是否有其他的方式，以找出是否调试（或其他记录等级的一种）有效与否？

Is there an other way to find out if debugging (or one of the other loglevels) is active or not?

我用eclipse的logcat视图与日志级别冗长和运行在Android应用开始从日食测试

I use eclipse logcat-view with log-level verbose and started the test from eclipse with run as android-app

推荐答案

isLoggable 真的只是一个机制，为您提供方便某些标签提供一个标志。它实际上并没有做任何事情来禁用日志记录。您code的第一个块是正确的：

isLoggable is really just a mechanism to provide a flag for certain tags for your convenience. It doesn't actually do anything to disable logging. Your first block of code is correct:

if (Log.isLoggable("MyContext", Log.DEBUG))
{
    Log.d("MyContext", "my logging: " + callExpensiveCalculation());
}

这将记录或取决于如果 isLoggable 收益真正或假无法登录。但是，当你这样做（而不检查 isLoggable ）

This will log or not log depending on if isLoggable returns true or false. However, when you do this (without checking isLoggable):

Log.d(MY_CONTEXT, "DEBUG logging is active: " + Log.isLoggable(MY_CONTEXT, Log.DEBUG));

它会不管是什么 isLoggable 将返回已调用它记录。总之，你的需要以做检查无处不在，如果你想根据该标志启用/禁用日志记录您登录。在如果语句，可以让你跳过不必要的日志中的一部分。如果如果子句假中，code里面永远不会运行。

It will log regardless of what isLoggable would have returned had you called it. In short, you need to do that check everywhere that you log if you want to enable/disable logging based on that flag. The if statement is the part that lets you skip unnecessary logs. If the if clause is false, the code inside is never run.

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