Android Log.isLoggable

Log.isLoggable

API中關于此方法的說明：

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. ’ 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.=’ and place that in /data/local.prop.

Log.isLoggable()的預設log級别是INFO，像級别低一些的DEBUG和VERBOSE的log就直接被過濾掉了。使用此API，我們可以實作按需求控制log列印：

在正式版本中，像一些DEBUG和VERBOSE的log不會被列印出來，減少了系統列印的log數量

在我們平時調試的時候，可以手動設定log輸出級别，

所有應用都采用同樣的過濾方式，比設定boolean變量控制友善

final String TAG = "Test";
Log.v(TAG, "verbose is active: " + Log.isLoggable(TAG, Log.VERBOSE));
Log.d(TAG, "debug is active: " + Log.isLoggable(TAG, Log.DEBUG));
Log.i(TAG, "info is active: " + Log.isLoggable(TAG, Log.INFO));
Log.w(TAG, "warn is active: " + Log.isLoggable(TAG, Log.WARN));
Log.e(TAG, "error is active: " + Log.isLoggable(TAG, Log.ERROR));
           

輸出

VERBOSE/Test(): verbose is active: false
DEBUG/Test(): debug is active: false
INFO/Test(): info is active: true
WARN/Test(): warn is active: true
ERROR/Test(): error is active: true
           

法的資訊可以看出，有2種方式可以修改log過濾級别

• setprop

adb root

adb shell setprop log.tag.TAG VERBOSE

//在我們的開發闆子上面，直接在序列槽下面輸入setprop log.tag.TAG VERBOSE,注意，TAG是我們自己定義的TAG名稱
           

但大多數log都不適用，因為它們是在boot時就決定是否要印出log，而此property性質在重開機後就消失

• 利用local.prop

在linux上，vim local.prop，並寫入 log.tag.TAG=VERBOSE (TAG為依據framework上所設定的TAG， = 要加)

adb root
adb remount
adb push local.prop /data/local.prop
adb shell chmod  /data/local.prop
adb shell chown root.root /data/local.prop
adb reboot
//在開發版上面，直接cp檔案到/data
cp XXX/local.prop /data
chmod  /data/local.prop
chown root.root /data/local.prop
reboot
           

參考如下：

http://www.dotblogs.com.tw/kent2480/archive/2014/03/21/144467.aspx

http://stackoverflow.com/questions/7948204/does-log-isloggable-returns-wrong-values