Android DownloadManager illegalstateexception unable to create directory

What can I do?

If you read the documentation for setDestinationInExternalPublicDir(), you will see that the first parameter is "the directory type to pass to getExternalStoragePublicDirectory(String)". That needs to be one of the constants defined on the Environment class, like Environment.DIRECTORY_DOWNLOADS. You are passing something else, which is not supported.

Make sure you have

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

in your manifest.xml

Also if you are using an emulator, make sure you created it with SD card storage. It's NOT created by default.