An explanation of the log mechanism in Android

There are several types of log output in Android:

LOG.V (string tag, string msg); VERBOSE
LOG.D (string tag, string msg); DEBUG
LOG.I (string tag, string msg); INFO
LOG.W (string tag, string msg); WARN
LOG.E (string tag, string msg); ERROR

The above log level in turn, VERBOSE debug information should only exist in the development, info,warn,error these three kinds of log will appear in the release version.

For Java classes, you can declare a string constant Tag,logcat can distinguish between different logs based on him, for example in a class of Windowsmanagerservice.java, as defined below:
Static final Sting TAG = "WindowManager"
Where you need to hit log.
LOG.V (TAG, "figuring out where to add App window" + client.asbinder () + "(token=" + token + ")");

Logcat use the following method:

logcat [Options] [Filterspecs]
Option "-S" is used to set the filter, the format is such <tag>[:p riority]
Where <tag> means log component, tag (or use * for all), the priority is as follows:
V Verbose
D Debug
I Info
W Warn
E Error
F Fatal
S Silent

Cases:
Logcat-s *:s don't hit any log
Logcat-s windowmnager:v <--Printing Verbose information in Windowmanagerservice
If you view the Android log output in Eclipse, which is LogCat information, you can choose Windows > Show View > Other ... > Android > LogCat.

Report
Logcat parameter Description:
usage:logcat [Options] [Filterspecs]
Options include:
-S Set default filter to silent.
Like specifying Filterspec ' *:s '
-F <filename> Log to file. Default to stdout
-R [<kbytes>] Rotate log every kbytes. (if unspecified). Requires-f
-N <count> sets max number of rotated logs to <count>, default 4
-V <format> sets the log print format, where <format> is one of:

Brief process Tag thread raw time long

-C Clear (flush) the entire log and exit
-D Dump the log and then exit (Don ' t block)
-G get the size of the log ' s ring buffer and exit
-B <buffer> Request alternate ring buffer, defaults to ' main '
Filterspecs is a series of
<tag>[:p Riority]

Where <tag> is a log component tag (or * for all) and the IS:
V Verbose
D Debug
I Info
W Warn
E Error
F Fatal
S Silent (supress all output)

' * ' means ' *:d ' and <tag> by itself means <tag>:v

If not specified on the commandline, Filterspec are set from Android_log_tag
If no filterspec is found, filter defaults to ' *:i '

If not specified WITH-V, format was set from Android_printf_log
or defaults to "brief"