Build Fail: Can't build Android .apk on Unity

Question

Whenever I try to build & run my Unity application for android I receive the following error:

Build Failure: Unable to list target platforms. please make sure the 
android sdk path is correct. See the Console for details.

The thing is that the path is set correctly and I am also able to build Apps with Android Studio. In Unity I set the path correctly to

'/Users/MYUSERNAME/Library/Android/sdk'

Unity even opens a prompt and tells me that a Android SDK has been found when I click on Browse in Preferences -> External Tools.

In the Unity-Log I also receive the following Error Message:

CommandInvokationFailure: Unable to list target platforms. Please make sure the android sdk path is correct. 
/Users/MYUSERNAME/Library/Android/sdk/tools/bin/avdmanager list target -c

stderr[
Exception in thread "main" java.lang.NoClassDefFoundError: javax/xml/bind/annotation/XmlSchema
    at com.android.repository.api.SchemaModule$SchemaModuleVersion.<init>(SchemaModule.java:156)
    at com.android.repository.api.SchemaModule.<init>(SchemaModule.java:75)
    at com.android.sdklib.repository.AndroidSdkHandler.<clinit>(AndroidSdkHandler.java:81)
    at com.android.sdklib.tool.AvdManagerCli.run(AvdManagerCli.java:213)
    at com.android.sdklib.tool.AvdManagerCli.main(AvdManagerCli.java:200)
Caused by: java.lang.ClassNotFoundException: javax.xml.bind.annotation.XmlSchema
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:582)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:190)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:499)
    ... 5 more
]
stdout[

]
exit code: 1
UnityEditor.Android.Command.WaitForProgramToRun (UnityEditor.Utils.Program p, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
UnityEditor.Android.Command.Run (System.Diagnostics.ProcessStartInfo psi, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
UnityEditor.Android.AndroidSDKTools.RunAndroidSdkTool (System.String toolName, System.String arguments, Boolean updateCommand, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
UnityEditor.Android.AndroidSDKTools.ListTargetPlatforms (UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit)
UnityEditor.Android.AndroidSDKTools.GetTopAndroidPlatformAvailable (UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit)
UnityEditor.Android.PostProcessor.Tasks.CheckAndroidSDK+SDKPlatformDetector.GetVersion (UnityEditor.Android.AndroidSDKTools sdkTools)
UnityEditor.Android.PostProcessor.Tasks.CheckAndroidSDK+SDKComponentDetector.Detect (UnityEditor.Android.AndroidSDKTools sdkTools, System.Version minVersion, UnityEditor.Android.PostProcessor.ProgressHandler onProgress)
UnityEditor.Android.PostProcessor.Tasks.CheckAndroidSDK.EnsureSDKComponentVersion (System.Version minVersion, UnityEditor.Android.PostProcessor.Tasks.SDKComponentDetector detector)
UnityEditor.Android.PostProcessor.Tasks.CheckAndroidSDK.EnsureSDKComponentVersion (Int32 minVersion, UnityEditor.Android.PostProcessor.Tasks.SDKComponentDetector detector)
UnityEditor.Android.PostProcessor.Tasks.CheckAndroidSDK.Execute (UnityEditor.Android.PostProcessor.PostProcessorContext context)
UnityEditor.Android.PostProcessor.PostProcessRunner.RunAllTasks (UnityEditor.Android.PostProcessor.PostProcessorContext context)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

Answer 1

You need v25.5.5 of the Android SDK.

If you haven't downgraded it, here are the steps:

1- Delete Android SDK "tools" folder : [Your Android SDK root]/tools -> tools.

2- Download SDK Tools: http://dl-ssl.google.com/android/repository/tools_r25.2.5-windows.zip .

3- Extract that to the Android SDK root.

Source of the instructions

If you have done it already, then let me know.

Answer 2

I solved the problem by myself. I don't know why it was the problem, but after I downgraded my JDK to 1.8 I was able to build the .apk.