Android Facebook integration with invalid key hash

Question

In one of my apps I need to get data from Facebook... I am doing this:

I have created app ID. It logs in successfully, but after logging out, I log in, and then it gives me:

What is wrong I am doing? I am using the Facebook SDK... I have installed Facebook on my phone... It is running well within an emulator, but that does not have the inbuilt Facebook application installed.

This is my code:

if (FB_APP_ID == null) {
    Builder alertBuilder = new Builder(this);
    alertBuilder.setTitle("Warning");
    alertBuilder.setMessage("A Facebook Applicaton ID must be " +
                            "specified before running this example: see App.java");
    alertBuilder.create().show();
}

// Initialize the dispatcher
Dispatcher dispatcher = new Dispatcher(this);
dispatcher.addHandler("login", LoginHandler.class);
dispatcher.addHandler("stream", StreamHandler.class);
dispatcher.addHandler("logout", LogoutHandler.class);

// If a session already exists, render the stream page
// immediately. Otherwise, render the login page.
Session session = Session.restore(this);
if (session != null) {
    dispatcher.runHandler("stream");
}
else {
    dispatcher.runHandler("login");
}

Answer 1

The generated hash key is wrong. You may get the hash key using two steps.

One is through a command prompt. Another one is through coding. The hash key through a command prompt is working on the first time only. I don't know the reason. I have also got the same problem. So I tried it through programmatically.

Follow these steps:

Paste the following code in oncreate().

try {
    PackageInfo info = getPackageManager().getPackageInfo(
                           "com.example.packagename",
                           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 (NameNotFoundException e) {
}
catch (NoSuchAlgorithmException e) {
}

Modify "com.example.packagename" with your package name in the above coding without fail (you may find your package name in the Android manifest file).

Run your application. Go to the activity where you pasted the above code. In the LogCat file, search for "KeyHash". You may find a key hash. Copy the key hash and go to Facebook application dashboard page. Go to settings and enter the details like in the below image.

Once you finished the above step, relaunch the app again. You may now log into Facebook. For more details about key hash, check the link.

If you add wrong information in the settings page, it means it will give some error. So use the correct information there. And also if the public (other than you) need to use your application means you need to enable the permission (change "yes" in the "Status & Review" next to the setting).