本文主要是介绍Android的logcat日志详解,希望对大家解决编程问题提供一定的参考价值,需要的开发者们随着小编来一起学习吧!
Android log系统
logcat介绍
logcat是android中的一个命令行工具,可以用于得到程序的log信息。下面介绍 adb logcat中的详细参数命令以及如何才能高效的打印日志,或把日志保存到我们指定的位置。
可以输入 adb logcat --help
,查看一下一些简单的数据格式:
adb logcat --help
输出结果:
Usage: logcat [options] [filterspecs]General options:-b, --buffer=<buffer> Request alternate ring buffer(s):main system radio events crash default allAdditionally, 'kernel' for userdebug and eng builds, and'security' for Device Owner installations.Multiple -b parameters or comma separated list of buffers areallowed. Buffers are interleaved.Default -b main,system,crash,kernel.-L, --last Dump logs from prior to last reboot from pstore.-c, --clear Clear (flush) the entire log and exit.if -f is specified, clear the specified file and its related rotatedlog files instead.if -L is specified, clear pstore log instead.-d Dump the log and then exit (don't block).--pid=<pid> Only print logs from the given pid.--wrap Sleep for 2 hours or when buffer about to wrap whichevercomes first. Improves efficiency of polling by providingan about-to-wrap wakeup.Formatting:-v, --format=<format> Sets log print format verb and adverbs, where <format> is one of:brief help long process raw tag thread threadtime timeModifying adverbs can be added:color descriptive epoch monotonic printable uid usec UTC year zoneMultiple -v parameters or comma separated list of format and formatmodifiers are allowed.-D, --dividers Print dividers between each log buffer.-B, --binary Output the log in binary.Outfile files:-f, --file=<file> Log to file instead of stdout.-r, --rotate-kbytes=<n> Rotate log every <n> kbytes. Requires -f option.-n, --rotate-count=<count> Sets max number of rotated logs to <count>, default 4.--id=<id> If the signature <id> for logging to file changes, then clear theassociated files and continue.Logd control:These options send a control message to the logd daemon on device, print its return message ifapplicable, then exit. They are incompatible with -L, as these attributes do not apply to pstore.-g, --buffer-size Get the size of the ring buffers within logd.-G, --buffer-size=<size> Set size of a ring buffer in logd. May suffix with K or M.This can individually control each buffer's size with -b.-S, --statistics Output statistics.--pid can be used to provide pid specific stats.-p, --prune Print prune rules. Each rule is specified as UID, UID/PID or /PID. A'~' prefix indicates that elements matching the rule should be prunedwith higher priority otherwise they're pruned with lower priority. Allother pruning activity is oldest first. Special case ~! represents anautomatic pruning for the noisiest UID as determined by the currentstatistics. Special case ~1000/! represents pruning of the worst PIDwithin AID_SYSTEM when AID_SYSTEM is the noisiest UID.-P, --prune='<list> ...' Set prune rules, using same format as listed above. Must be quoted.Filtering:-s Set default filter to silent. Equivalent to filterspec '*:S'-e, --regex=<expr> Only print lines where the log message matches <expr> where <expr> isan ECMAScript regular expression.-m, --max-count=<count> Quit after printing <count> lines. This is meant to be paired with--regex, but will work on its own.--print This option is only applicable when --regex is set and only useful if--max-count is also provided.With --print, logcat will print all messages even if they do notmatch the regex. Logcat will quit after printing the max-count numberof lines that match the regex.-t <count> Print only the most recent <count> lines (implies -d).-t '<time>' Print the lines since specified time (implies -d).-T <count> Print only the most recent <count> lines (does not imply -d).-T '<time>' Print the lines since specified time (not imply -d).count is pure numerical, time is 'MM-DD hh:mm:ss.mmm...''YYYY-MM-DD hh:mm:ss.mmm...' or 'sssss.mmm...' format.--uid=<uids> Only display log messages from UIDs present in the comma separate list<uids>. No name look-up is performed, so UIDs must be provided asnumeric values. This option is only useful for the 'root', 'log', and'system' users since only those users can view logs from other users.filterspecs are a series of<tag>[:priority]where <tag> is a log component tag (or * for all) and priority is:V Verbose (default for <tag>)D Debug (default for '*')I InfoW WarnE ErrorF FatalS Silent (suppress all output)'*' by itself means '*:D' and <tag> by itself means <tag>:V.
If no '*' filterspec or -s on command line, all filter defaults to '*:V'.
eg: '*:S <tag>' prints only <tag>, '<tag>:S' suppresses all <tag> log messages.If not specified on the command line, filterspec is set from ANDROID_LOG_TAGS.If not specified with -v on command line, format is set from ANDROID_PRINTF_LOG
or defaults to "threadtime"
log类是一个日志类,可以在代码中使用logcat打印出消息。常见的日志记录方法包括。
方法 | 描述 |
v(String,String) (vervbose) | 显示全部信息 |
d(String,String)(debug) | 显示调试信息 |
i(String,String)(information) | 显示⼀般信息 |
w(String,String)(waning) | 显示警告信息 |
e(String,String)(error) | 显示错误信息 |
例如:
// 开发过程中获取 log
Log.i("MyActivity","MyClass.getView() - get item number"+position);
//adb 获取 log
adb logcat
adb logcat 输出的⽇志格式如下:
I/ActivityManager( 1754): Waited long enough for: ServiceRecord{2b24178c u0
com.google.android.gms/.checkin.CheckinService}
logcat命令格式
语法格式:
[adb] logcat [] … [ ] …
PC 端使⽤: adb logcat
shell 模式下使⽤: logcat
logcat缓冲区
缓冲区介绍
Android 日志系统为日志消息保留了多个环形缓冲区,但并非多有的日志消息都会发送到默认的环形缓冲区。这里可以采用 logcat -b 命令查看设备的其他缓冲区:
缓冲区 | 描述 | 举例 |
radio | 输出通信系统的日志,包含无线装置/电话相关消息 | logcat -b radio |
events | 输出event模块的日志 | logcat -b events |
main | 主日志缓冲区(默认),不包含系统和崩溃日志消息 | logcat -b main |
system | 输出系统日志 | logcat -b system |
crash | 输出崩溃日志 | logcat -b crash |
all | 输出所有缓冲区日志 | logcat -b all |
default | 输出main、system、crash缓冲区日志 | logcat -b default |
缓冲区模型
logcat命令参数
参数 | 含义 | 举例 |
-b | 加载⼀个可使⽤的⽇志缓冲区供查看,⽐如 event和 radio 。默认值是 main | logcat -b system |
-B | 以二进制文件形式输出日志 | |
-c | 清除缓冲区中的全部⽇志并退出(清除完后可以使⽤ -g 查看缓冲区)默认清除 | logcat -c;logcat -b all -c |
-d | 将缓冲区的 log 转存到屏幕中然后退出 | logcat -d > log.txt |
-f <file> | 将 log 输出到指定的⽂件中 < ⽂件名 >. 默认为标准输出( stdout ) | logcat -f sdcard/log.txt |
-g | 打印⽇志缓冲区的大小并退出 | logcat -g |
-G | 设置日志环形缓冲区的大小,可以在结尾处添加 | logcat -G 2M |
-n <count> | 设置⽇志的最⼤数⽬,默认值是 4 ,需要和 -r 选项⼀起使⽤ | |
-r <kbytes> | 每时输出⽇志,默认值是 16 ,需要和 -f 选项⼀起使⽤ | logcat -f sdcard/log.txt -r 1 |
-s | 输出指定 tag 的日志,相当于过滤器表达式 *:S | logcat -s tag |
-S | 在输出中包含统计信息,以识别和定位日志垃圾信息发送者 | |
-v <format> | 设置输出格式的⽇志消息。默认是短暂的格式。⽀持的格式列表 | logcat -v threadtime |
-m <count> | 输出 行后退出 | logcat -m 5 |
-D | 输出各个日志缓冲区之间的分隔线 | logcat -D … |
-e <expr> | 输出正则匹配的日志消息 | logcat -e [匹配数据] -m 5 |
-t <count> | 仅输出最新的行数,此选项包括 -d 功能 | logcat -t 5 |
-t '<time>' | 输出自指定时间以来的最新行,此选项包括 -d 功能 | logcat -t ‘01-26 20:52:41.820’ |
--pid=<pid> | 仅输出来自给定 PID 的日志 | logcat --pid=4321 |
⼀般⻓时间输出 log 的话建议 -f , -n , -r 三个参数连⽤,这样当⼀个⽂件⽇志输出满了之后可以⻢上在另⼀个中进⾏输出。
Android
日志系统为日志消息保留了多个环形缓冲区,但并非多有的日志消息都会发送到默认的环形缓冲区。
logcat -b
是logcat
命令的一个选项,用于指定查看日志缓冲区。你可以用它来查看不同类型的日志缓冲区。下面是基本用法:
logcat -b events|grep -E "am_proc_start|input_focus.*entering"
基本命令格式:
shCopy Code
adb logcat -b <buffer>
选项说明:
main
: 默认缓冲区,包含大多数应用程序和系统日志。
system
: 系统日志缓冲区,包含系统服务和硬件相关日志。
events
: 事件日志缓冲区,记录系统事件和调试信息。
crash
: 崩溃日志缓冲区,记录应用崩溃的信息。
示例用法:
-
查看主缓冲区日志:
shCopy Code
adb logcat -b main
-
查看系统缓冲区日志:
shCopy Code
adb logcat -b system
-
查看事件缓冲区日志:
shCopy Code
adb logcat -b events
-
查看崩溃缓冲区日志:
shCopy Code
adb logcat -b crash
这些选项帮助你根据需要过滤和查看不同类型的日志数据。
logcat格式化输出
参数说明
⽇志消息包含⼀个元数据字段,除了标签和优先级,您可以修改输出显示⼀个特定的元数据字段格式的消息。为此,您使⽤-v 选项来指定⼀个⽀持的输出格式。⼀下为⽀持的格式:
格式 | 含义 |
brief | 显示优先级 / 标记和过程的 PID 发出的消息(默认格式) |
process | 只显示PID |
tag | 只显示优先级/标记 |
raw | 显示原始的⽇志消息,没有其他元数据字段 |
time | 调⽤显示⽇期、时间、优先级 / 标签和过程的 PID 发出消息 |
thread | 旧版格式,显示优先级、PID 以及发出消息的线程的 TID |
threadtime | 调⽤显示⽇期、时间、优先级、标签遗迹 PID TID线程发出的消息 |
long | 显示所有元数据字段与空⽩⾏和单独的消息 |
color | 使用不同的颜色来显示每个优先级 |
descriptive | 显示日志缓冲区事件说明。此修饰符仅影响事件日志缓冲区消息,不会对其他非二进制文件缓冲区产生任何影响 |
epoch | 显示自 1970 年 1 月 1 日以来的时间(以秒为单位) |
uid | 如果访问控制允许,则显示 UID 或记录的进程的 Android ID |
usec | 显示精确到微秒的时间 |
UTC | 显示 UTC 时间 |
year | 将年份添加到显示的时间 |
zone | 将本地时区添加到显示的时间 |
当 logcat 开始,指定想要输出格式 -v 选项:
[adb] logcat [-v ]
adb logcat –v thread
只能指定⼀个输出格式 -v。
logcat优先级
按日志级别过滤日志:
adb logcat <tag>[:priority]
tag
表示标签;priority
表示输出级别;
日志默认级别是 V
,如果错误日志我们选择 E
就可以,Android
的日志分为如下几个优先级(priority):
选项 | 描述 | 举例 |
V | –Verbose(最低优先级) | adb logcat *:V |
D | – Debug | adb logcat *:D |
I | – Info | adb logcat *:I |
W | – Warning | adb logcat *:W |
E | – Error | adb logcat *:E |
F | – Fatal | adb logcat *:F |
S | – Silent | adb logcat *:S |
*
可以是某个tag
,如果没有指明,就表示所有。
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