Android Facebook SDK Login exception - authentication

Question

I am following the tutorial of the official android SDK,and try to write a simple log in program.
So what I did is..
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.logintutorial"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="20" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<meta-data
android:name="com.facebook.sdk.ApplicationId"
android:value="#string/app_id"/>
</manifest>
The MainActivity simply uses fragment transaction.
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;
public class MainActivity extends FragmentActivity {
private MainFragment mainFragment;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState == null) {
// Add the fragment on initial activity setup
mainFragment = new MainFragment();
getSupportFragmentManager()
.beginTransaction()
.add(android.R.id.content, mainFragment)
.commit();
} else {
// Or set the fragment from restored state info
mainFragment = (MainFragment) getSupportFragmentManager()
.findFragmentById(android.R.id.content);
}
}
}
The MainFragment class is used for the Session Management with the help of the UiLifecyleHelper and the Session.StatusCallBack class.
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.facebook.Session;
import com.facebook.SessionState;
import com.facebook.UiLifecycleHelper;
import com.facebook.widget.LoginButton;
public class MainFragment extends Fragment {
private static final String TAG = "MainFragment";
private UiLifecycleHelper uiHelper;
private Session.StatusCallback callback = new Session.StatusCallback() {
#Override
public void call(final Session session, final SessionState state, final Exception exception)
{
onSessionStateChange(session, state, exception);
}
};
#Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.activity_main, container, false);
LoginButton authButton = (LoginButton) view.findViewById(R.id.authButton);
authButton.setFragment(this);
//authButton.setReadPermissions(Arrays.asList("user_likes", "user_status"));
return view;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
uiHelper = new UiLifecycleHelper(getActivity(), callback);
uiHelper.onCreate(savedInstanceState);
}
#Override
public void onResume() {
super.onResume();
// For scenarios where the main activity is launched and user
// session is not null, the session state change notification
// may not be triggered. Trigger it if it's open/closed.
Session session = Session.getActiveSession();
if (session != null &&
(session.isOpened() || session.isClosed()) ) {
onSessionStateChange(session, session.getState(), null);
}
uiHelper.onResume();
}
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
uiHelper.onActivityResult(requestCode, resultCode, data);
}
#Override
public void onPause() {
super.onPause();
uiHelper.onPause();
}
#Override
public void onDestroy() {
super.onDestroy();
uiHelper.onDestroy();
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
uiHelper.onSaveInstanceState(outState);
}
private void onSessionStateChange(Session session, SessionState state, Exception exception) {
if (state.isOpened()) {
Log.i(TAG, "Logged in...");
} else if (state.isClosed()) {
Log.i(TAG, "Logged out...");
}
}
}
Also the main activity's xml file...
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<com.facebook.widget.LoginButton
android:id="#+id/authButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginTop="30dp"
/>
</LinearLayout>
and finally I put the app id in the string.xml file as
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">Login Tutorial</string>
<string name="hello_world">Hello world!</string>
<string name="action_settings">Settings</string>
<string name="app_id">XXX6999249XXXXX</string>
</resources>
When I run it, I get the following exception.
11-10 13:01:46.784: E/AndroidRuntime(31157): FATAL EXCEPTION: main
11-10 13:01:46.784: E/AndroidRuntime(31157): java.lang.RuntimeException:
Unable to start activity
ComponentInfo{com.example.logintutorial/com.example.logintutorial.MainActivity}:
java.lang.NullPointerException: Argument 'applicationId' cannot be null

Answer 1

The metadata tag has to be inside the application tag and not outside!. Change manifest to:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.logintutorial"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="20" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<meta-data
android:name="com.facebook.sdk.ApplicationId"
android:value="#string/app_id"/>
</application>
</manifest>