framework中的Log如何打印出来

打印出来"/>

framework中的Log如何打印出来

在从事framework开发的过程中，经常会看到如下代码

public class AudioService extends IAudioService.Stubimplements AccessibilityManager.TouchExplorationStateChangeListener,AccessibilityManager.AccessibilityServicesStateChangeListener {private static final String TAG = "AudioService";/** Debug audio mode */protected static final boolean DEBUG_MODE = Log.isLoggable(TAG + ".MOD", Log.DEBUG);/** Debug audio policy feature */protected static final boolean DEBUG_AP = Log.isLoggable(TAG + ".AP", Log.DEBUG);/** Debug volumes */protected static final boolean DEBUG_VOL = Log.isLoggable(TAG + ".VOL", Log.DEBUG);/** debug calls to devices APIs */protected static final boolean DEBUG_DEVICES = Log.isLoggable(TAG + ".DEVICES", Log.DEBUG);
}

这些Log默认都是关闭的，想要打开其实也很容易

    /*** 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.&lt;YOUR_LOG_TAG> &lt;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.&lt;YOUR_LOG_TAG>=&lt;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*         for Nougat (7.0) releases (API <= 23) and prior, there is no*         tag limit of concern after this API level.*/public static native boolean isLoggable(String tag, int level);

第一种方法：

setprop log.tag.AudioService.VOL D
stop
start

第二种方法：

这种方法重启以后他的系统属性也会保留，因为重启以后打开还是会打开

setprop persist.log.tag.AudioService.VOL D