The following classes could not be instantiated: - com.facebook.widget.LoginButton

Question

I have been working on getting the facebook practice apps working and I cannot for the life of me figure out why I cannot reference the LoginButton found in the Facebook SDK

Answer 1

//write this first

FacebookSdk.sdkInitialize(getApplicationContext());

//then set contentview

    setContentView(R.layout.activity_main);

Answer 2

If you are use android studio then its clear documentation here,

Use facebook with fragment Tutorial

User facebook without fragment

Step 1 :Create java file MyApplication.java inside your package.

Tutorial

and copu myApplicatyon.java

Step 2 :setup androidmenufest.xml

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/Theme.Myapptheme"
    android:name=".MyApplication"
     >
    <meta-data android:name="com.facebook.sdk.ApplicationId" android:value="@string/app_id" />
    <activity android:name="com.facebook.FacebookActivity"
        android:configChanges=
            "keyboard|keyboardHidden|screenLayout|screenSize|orientation"
        android:theme="@android:style/Theme.Translucent.NoTitleBar"
        android:label="@string/app_name" />

Step 3 : Init inside activity where you are looking for init Login Button

    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    callbackManager = CallbackManager.Factory.create();
    FacebookSdk.sdkInitialize(getApplicationContext());
    setContentView(R.layout.activity_auth_login);

    //Init Elements
    etEmail = (EditText) findViewById(R.id.etEmail);
    etPassword = (EditText) findViewById(R.id.etPassword);

    validator = new Validator(this);
    validator.setValidationListener(this);

    serverConnection = new ServerConnection();

    //Faceboo login init
    loginButton = (LoginButton) findViewById(R.id.btnFbLogin);
    loginButton.setReadPermissions(Arrays.asList("public_profile","email","user_photos"));



    // Other app specific specialization
    // Callback registration
    loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
        @Override
        public void onSuccess(LoginResult loginResult) {
            // App code

            Profile profile = Profile.getCurrentProfile();

            Log.v("profile.getName:",profile.getName());
        }

        @Override
        public void onCancel() {
            // App code
        }

        @Override
        public void onError(FacebookException exception) {
            // App code
        }
    });

}

Answer 3

OPTION #1:

Sometimes, when a new resource is added, Eclipse doesn't compile correctly the new code (maybe a caching issue), causing this error.

Normally, simply restarting Eclipse is enough to fix the problem.

OPTION #2:

Sometimes, rendering custom views causes this exception. The only workaround I know is checking View.isInEditMode every time you try to use the getResources().

An example could be:

if (isInEditMode()) {
    //do something else, as getResources() is not valid.
} else {
    //you can use getResources()
    String mystring = getResources().getString(R.string.mystring);
}