logger on file

Logger.kt

import org.jetbrains.annotations.NonNls
import timber.log.Timber
import java.io.File

class Logger {

    private lateinit var cacheDir: File

    companion object {

        private fun initializeTimber(logFile: File) {
            Timber.plant(TimberFileTree(logFile))
        }

        fun v(@NonNls message: String) = Timber.v(message)
        fun d(@NonNls message: String) = Timber.d(message)
        fun i(@NonNls message: String) = Timber.i(message)
        fun w(@NonNls message: String) = Timber.w(message)
        fun e(@NonNls message: String) = Timber.e(message)
        fun wtf(@NonNls message: String) = Timber.wtf(message)
    }

    fun onCreate(cacheDir: File) {
        this.cacheDir = cacheDir
        cleanLogFile()
        initializeTimber(getLogFile())
    }

    fun onClearCache() {
        cleanLogFile()
    }

    fun onDestroy() {
        deleteLogFile()
    }

    private fun getLogFile(): File {
        return File(cacheDir.absolutePath + "/log.txt")
    }

    private fun cleanLogFile() {
        // force clean previous log
        getLogFile().writeText("")
    }

    private fun deleteLogFile() {
        getLogFile().delete()
    }
}

TimberFileTree.kt

import android.util.Log
import timber.log.Timber
import java.io.File

class TimberFileTree(private val log: File) : Timber.Tree() {

    override fun log(priority: Int, tag: String?, message: String, t: Throwable?) {
        when (priority) {
            Log.VERBOSE -> log.appendText("V: ")
            Log.DEBUG -> log.appendText("D: ")
            Log.INFO -> log.appendText("I: ")
            Log.WARN -> log.appendText("W: ")
            Log.ERROR -> log.appendText("E: ")
            Log.ASSERT -> log.appendText("A: ")
        }
        log.appendText(message + "\n")
    }
}