什么是isLoggable？

isLoggable是android.util.Log提供的方法，用于检查指定Log的TAG的level是否满足打印条件，如满足则返回true反之则返回false。

源码中关于isLoggable的注释

isLoggable在源码中的注释如下：

/**     
* Checks to see whether or not a log for the specified tag is loggable at the specified level.     
*     
*  The default level of any tag is set to INFO. This means that any level above and including     
*  INFO will be logged. Before you make any calls to a logging method you should check to see     
*  if your tag should be logged. You can change the default level by setting a system property:     
*      'setprop log.tag.<YOUR_LOG_TAG> <LEVEL>'     
*  Where level is either VERBOSE, DEBUG, INFO, WARN, ERROR, ASSERT, or SUPPRESS. SUPPRESS will     
*  turn off all logging for your tag. You can also create a local.prop file that with the     
*  following in it:     
*      'log.tag.<YOUR_LOG_TAG>=<LEVEL>'     
*  and place that in /data/local.prop.     
*     
* @param tag The tag to check.     
* @param level The level to check.     
* @return Whether or not that this is allowed to be logged.     
* @throws IllegalArgumentException is thrown if the tag.length() > 23.     
*/    
public static native boolean isLoggable(String tag, int level);

使用注意

1. isLoggable默认level为android.util.Log.INFO；

2. 只有 level >= INFO才能输出，即level >= INFO时isLoggable返回true，反之则返回false；