can not write to the file that under the android getExternalFilesDir()

[whatisjava]

Describe the bug

i want record the log to android's context.getExternalFilesDir("logs")?.absolutePath?: context.filesDir?.absolutePath, the log path is: /storage/emulated/0/Android/data/cn.newup.elecdetonator/files/logs/app-log , the file is created, but not write anything in it, but the logcat has print same log content, why it's this? ,

Reproduction

in application clalss 's onCreate method call LogConfig.configureLogbackDirectly(this)

Logs

10:04:30.771 logdir D /storage/emulated/0/Android/data/cn.newup.elecdetonator/files/logs
10:04:30.912 System.out I 10:04:30,447 |-INFO in ch.qos.logback.classic.LoggerContext[default] - Could NOT find resource [assets/logback.xml]
10:04:30.912 System.out I 10:04:30,824 |-INFO in c.q.l.core.rolling.SizeAndTimeBasedRollingPolicy@218310893 - setting totalSizeCap to 5 GB
10:04:30.912 System.out I 10:04:30,827 |-INFO in c.q.l.core.rolling.SizeAndTimeBasedRollingPolicy@218310893 - Archive files will be limited to [1 MB] each.
10:04:30.912 System.out I 10:04:30,834 |-INFO in c.q.l.core.rolling.SizeAndTimeBasedRollingPolicy@218310893 - No compression will be used
10:04:30.912 System.out I 10:04:30,840 |-INFO in c.q.l.core.rolling.SizeAndTimeBasedRollingPolicy@218310893 - Will use the pattern /storage/emulated/0/Android/data/cn.newup.elecdetonator/files/logs/%d{yyyy-MM-dd}/app-%i.log for the active file
10:04:30.912 System.out I 10:04:30,843 |-INFO in ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP@51ed322 - The date pattern is 'yyyy-MM-dd' from file name pattern '/storage/emulated/0/Android/data/cn.newup.elecdetonator/files/logs/%d{yyyy-MM-dd}/app-%i.log'.
10:04:30.912 System.out I 10:04:30,843 |-INFO in ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP@51ed322 - Roll-over at midnight.
10:04:30.912 System.out I 10:04:30,878 |-INFO in ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP@51ed322 - Setting initial period to Tue Apr 16 08:56:06 GMT+08:00 2024
10:04:30.912 System.out I 10:04:30,894 |-INFO in ch.qos.logback.core.rolling.RollingFileAppender[null] - Active log file name: /storage/emulated/0/Android/data/cn.newup.elecdetonator/files/logs/app.log
10:04:30.912 System.out I 10:04:30,895 |-INFO in ch.qos.logback.core.rolling.RollingFileAppender[null] - File property is set to [/storage/emulated/0/Android/data/cn.newup.elecdetonator/files/logs/app.log]
10:04:30.912 System.out I 10:04:30,899 |-INFO in ch.qos.logback.classic.AsyncAppender[null] - Attaching appender named [null] to AsyncAppender.

logback-android version

logbackAndroid = "3.0.0"

OS Version

Android 9.0

What logback configuration are you using? (logback.xml or Java/Kotlin code)

fun configureLogbackDirectly(context: android.content.Context){
        val loggerContext = LoggerFactory.getILoggerFactory() as LoggerContext
        loggerContext.stop()

        val logDir = context.getExternalFilesDir("logs")?.absolutePath?: context.filesDir?.absolutePath
        Timber.tag("logdir").d(logDir)

        // setup RollingFileAppender
        val rollingFileAppender = RollingFileAppender<ILoggingEvent>()
        rollingFileAppender.context = loggerContext
        rollingFileAppender.isAppend = true

        val patternLayoutEncoder = PatternLayoutEncoder()
        patternLayoutEncoder.context = loggerContext
        patternLayoutEncoder.pattern = """ [%date{yyyy-MM-dd HH:mm:ss.SSS}] %-5level %logger{0}.%M\(%F:%L\): - %msg%n """
        patternLayoutEncoder.charset = Charset.forName("UTF-8")
        patternLayoutEncoder.start()
        rollingFileAppender.encoder = patternLayoutEncoder

        rollingFileAppender.file = "${logDir}/app.log"

        val sizeAndTimeBasedRollingPolicy = SizeAndTimeBasedRollingPolicy<ILoggingEvent>()
        sizeAndTimeBasedRollingPolicy.context = loggerContext
        sizeAndTimeBasedRollingPolicy.fileNamePattern = "${logDir}/%d{yyyy-MM-dd}/app-%i.log"
        sizeAndTimeBasedRollingPolicy.maxHistory = 300
        sizeAndTimeBasedRollingPolicy.setParent(rollingFileAppender)
        sizeAndTimeBasedRollingPolicy.setMaxFileSize(FileSize.valueOf("1 mb"))
        sizeAndTimeBasedRollingPolicy.setTotalSizeCap(FileSize.valueOf("5 gb"))
        sizeAndTimeBasedRollingPolicy.isCleanHistoryOnStart = false
        sizeAndTimeBasedRollingPolicy.start()

        rollingFileAppender.rollingPolicy = sizeAndTimeBasedRollingPolicy

        rollingFileAppender.start()

        val asyncAppender = AsyncAppender()
        asyncAppender.context = loggerContext
        asyncAppender.name = "ASYNC"
        asyncAppender.addAppender(rollingFileAppender)

        // setup LogcatAppender
        val logcatTagEncoder = PatternLayoutEncoder()
        logcatTagEncoder.context = loggerContext
        logcatTagEncoder.pattern = "%logger{0}"
        logcatTagEncoder.start()

        val logcatAppender = LogcatAppender()
        logcatAppender.context = loggerContext
        logcatAppender.encoder = patternLayoutEncoder
        logcatAppender.tagEncoder = logcatTagEncoder
        logcatAppender.start()

        // add the newly created appenders to the root logger;
        // qualify Logger to disambiguate from org.slf4j.Logger
        val rootLogger = LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME) as Logger
        rootLogger.level = Level.TRACE
        rootLogger.addAppender(asyncAppender)
        rootLogger.addAppender(logcatAppender)

        // print any status messages (warnings, etc) encountered in logback config
        StatusPrinter.print(loggerContext)
    }

Validations

• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A, please open a GitHub Discussion instead.
• The provided reproduction is a minimal reproducible of the bug.

[tony19]

Writing to getExternalFilesDir(...) is fully supported (it's app-specific storage, no permissions needed even with scoped storage), so the path itself isn't the problem — and your status log confirms the policy started. The posted log cuts off right after the SizeAndTimeBasedFNATP line, and the interesting part is what comes after: whether the RollingFileAppender itself reports an error when opening the active file.

Two common causes for "file created but empty":

1. Active file vs. archive pattern mismatch — your active file is .../logs/app-log but the pattern is .../logs/%d{yyyy-MM-dd}/app-%i.log, i.e. archives go into a dated subdirectory. If rollover triggers immediately (e.g. the active file predates the current period), content can land in logs/<date>/app-0.log while the freshly recreated app-log stays empty. Check whether the dated subdirectory has your logs.
2. Appender not attached / level filtering — if logcat shows the messages but the file appender gets nothing, verify the appender-ref is attached to the logger you're actually logging to.

Could you post the complete status output (add <statusListener class="ch.qos.logback.core.status.OnConsoleStatusListener"/> or OnConsoleStatusListener.addNewInstanceToContext(context)) and your full configureLogbackDirectly code? That will show exactly what the appender did after startup.

---

Generated by Claude Code