How to Get Key Hashes for Android App Facebook Integration.
Create MainActivity class in project.

import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.content.pm.Signature;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Base64;
import android.util.Log;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        try {
            PackageInfo info = getPackageManager().getPackageInfo(
                    "laptop.example.com.haskkeygenerate",
                    PackageManager.GET_SIGNATURES);
            for (Signature signature : info.signatures) {
                MessageDigest md = MessageDigest.getInstance("SHA");
                md.update(signature.toByteArray());
                Log.d("KeyHash::::", Base64.encodeToString(md.digest(), Base64.DEFAULT));
            }
        } catch (PackageManager.NameNotFoundException e) {
        } catch (NoSuchAlgorithmException e) {
        }
    }
}


OutPut:-