Adb backup does not work

Question

I need help from you guys, because I don't know what I did wrong with adb backup.

I want to backup my Samsung Galaxy S3 LTE (GT-I9305) without root. I googled it and found Full Android Backup with SDK Manager. I installed all i need for this like Java Development Kit 8 version 66 (JDK 8u66 x64) and Android Studio which contains SDK Manager. Then they sad i should download the Google USB Driver. I downloaded it but nothing happened. I thought it should work now and then I went to C:\Users\MYNAME\AppData\Local\Android\sdk\platform-tools and left-clicked adb whilst holding Shift. Then I clicked "Open command window here". After this I typed in "adb devices" and it said:

List of devices attached

3204cfaaf8611199 device

Then I typed in:

adb backup -apk -shared -all -f C:\Users\NAME\backup.ab 

It said

Now unlock your device and confirm the backup operation.

I did this and my Smartphone opened "Full Backup" and then I was able to set a password for the backup. I don`t need a password and I just clicked "Back up my data" Then it went back to my homescreen and said "Starting backup..." as a toast message and immediately after this it said "Backup finished" and created a backup file with 40 bytes. I don't know what I should do now.

Answer 1

Rather than trying to find an old version of adb, it's easier to add quotes to the arguments to adb backup :

adb backup "-apk -shared -all -f C:\Users\NAME\backup.ab"