Implementing Facebook into your App: invalid key with keytool

I recently had an annoying error. I wanted to implement some "Post to Facebook" functionality to my application and i got an error saying that my key vas invalid...

Facebook unique hash error

To implement this I just followed the official implementation of the SDK and after a quick search it seems that its is a problem that more developers run into.

I found the answer to my problem on StackOverflow. Mr. Omsn just makes the key that the Facebook API wants from within your application.

Here is a quick code snippet:

try {
   PackageInfo info = getPackageManager().getPackageInfo("**YOURPACKAGENAME**", PackageManager.GET_SIGNATURES);
   for (Signature signature : info.signatures) {
        MessageDigest md = MessageDigest.getInstance("SHA");
        md.update(signature.toByteArray());
        Log.i("PXR", Base64.encodeBytes(md.digest()));
   }
}
catch (NameNotFoundException e) {}
catch (NoSuchAlgorithmException e) {}

Only thing you need is 1 extra class (Base64) to get this working. I used this one.

one other thing i changed is the application type to "Native App" in the Facebook application registry.

I made a simple Eclipse project that prints the key to the LogCat window. I hope this helps you guys, whenever you run into this problem.

• Eclipse source project

Edit: this appears to be a Windows problem. You can also install Cygwin and run the keytool command in the Cygwyn shell