Step 2: Create a new Signed APK, transfer to your device and install. If it is already installed, naturally, it will prompt.
Step 3: With your DDMS (Logcat) running and your device connected to the computer, run the application and keep looking for a key mismatch warning. That warning has the actual Hash Key. Copy that key, go to your Facebook Developer page and add the new key to the list.
I have already hash key in my FB dashboard.
I try these steps but I haven't get any key in log cat it's simple key mismatch.