我尝试将文件夹添加到zip文件，但总是得到ZipException，表明zip文件小于预期大小。

val file = File.createTempFile("export_", ".zip")
val zipfile = ZipFile(file)

val tmpFolder = context.cacheDir.absolutePath + "/test"
File(tmpFolder).mkdir()
File(tmpFolder + "/test1.txt").createNewFile()
File(tmpFolder + "/test2.txt").createNewFile()

zipfile.addFolder(File(tmpFolder))

在最后一行，ZipException被引发

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: xxxx, PID: 20023
    java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:612)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130)
     Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130) 
     Caused by: net.lingala.zip4j.exception.ZipException: Zip file size less than minimum expected zip file size. Probably not a zip file or a corrupted zip file
        at net.lingala.zip4j.headers.HeaderReader.readAllHeaders(HeaderReader.java:69)
        at net.lingala.zip4j.ZipFile.readZipInfo(ZipFile.java:1142)
        at net.lingala.zip4j.ZipFile.addFolder(ZipFile.java:378)
        at net.lingala.zip4j.ZipFile.addFolder(ZipFile.java:365)
        at net.lingala.zip4j.ZipFile.addFolder(ZipFile.java:331)
        at android.view.View.performClick(View.java:8160)
        at android.widget.TextView.performClick(TextView.java:16222)
        at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:1119)
        at android.view.View.performClickInternal(View.java:8137)
        at android.view.View.access$3700(View.java:888)
        at android.view.View$PerformClick.run(View.java:30236)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:246)

文件和文件夹都存在，为什么会有例外？