Any Example showing how to login using Facebook SDK 4.0 in Android either by using own button or Facebook Button?

This might help you

// Custom buttonprivate Button fbbutton;// Creating Facebook CallbackManager Valuepublic static CallbackManager callbackmanager;@Overrideprotected void onCreate(final Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    // Initialize SDK before setContentView(Layout ID)    FacebookSdk.sdkInitialize(getApplicationContext());    setContentView(R.layout.activity_main);    // Initialize layout button    fbbutton = (Button) findViewById(R.id.button2);    fbbutton.setOnClickListener(new OnClickListener() {        @Override        public void onClick(View v) {            // Call private method            onFblogin();        }    });}// Private method to handle Facebook login and callbackprivate void onFblogin(){    callbackmanager = CallbackManager.Factory.create();    // Set permissions     LoginManager.getInstance().logInWithReadPermissions(this, Arrays.asList("email","user_photos","public_profile"));    LoginManager.getInstance().registerCallback(callbackmanager,            new FacebookCallback<LoginResult>() {                @Override                public void onSuccess(LoginResult loginResult) {                    System.out.println("Success");                    GraphRequest.newMeRequest(                            loginResult.getAccessToken(), new GraphRequest.GraphJSONObjectCallback() {                                @Override                                public void onCompleted(JSONObject json, GraphResponse response) {                                    if (response.getError() != null) {                                        // handle error                                        System.out.println("ERROR");                                    } else {                                        System.out.println("Success");                                        try {                                            String jsonresult = String.valueOf(json);                                            System.out.println("JSON Result"+jsonresult);                                            String str_email = json.getString("email");                                            String str_id = json.getString("id");                                            String str_firstname = json.getString("first_name");                                            String str_lastname = json.getString("last_name");                                        } catch (JSONException e) {                                            e.printStackTrace();                                        }                                    }                                }                            }).executeAsync();                }                @Override                public void onCancel() {                    Log.d(TAG_CANCEL,"On cancel");                }                @Override                public void onError(FacebookException error) {                     Log.d(TAG_ERROR,error.toString());                }    });}@Overridepublic void onActivityResult(int requestCode, int resultCode, Intent data) {    super.onActivityResult(requestCode, resultCode, data);    callbackmanager.onActivityResult(requestCode, resultCode, data);}

In manifest add following,

<application    android:allowBackup="true"    android:icon="@drawable/app_icon"    android:label="@string/app_name"    android:theme="@style/AppTheme" >    .    .     <!-- [START Facebook] -->    <activity        android:name="com.facebook.FacebookActivity"        android:configChanges="keyboard|keyboardHidden|screenLayout|screenSize|orientation"        android:label="@string/app_name"        android:theme="@android:style/Theme.Translucent.NoTitleBar" />    <meta-data        android:name="com.facebook.sdk.ApplicationId"        android:value="@string/facebook_app_id" />    <!-- [END Facebook] -->    .    .</application>

The best solution is to log in by using LoginManager. Here is how I managed this ( on click is made with ButterKnife ):

 @Overridepublic void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);            mCallbackManager = CallbackManager.Factory.create();}@Overridepublic void onViewCreated(View view, @Nullable Bundle savedInstanceState) {    super.onViewCreated(view, savedInstanceState);    LoginManager.getInstance().registerCallback(mCallbackManager, this);}@OnClick(R.id.facebook_login_button)@SuppressWarnings("unused")public void loginWithFacebookAccount() {    LoginManager.getInstance().logInWithReadPermissions(this, Arrays.asList("public_profile", "email"));}@Overridepublic void onSuccess(LoginResult loginResult) {    Bundle parameters = new Bundle();    parameters.putString("fields", "id,name,last_name,link,email,picture");    GraphRequest request = GraphRequest.newMeRequest(loginResult.getAccessToken(), (jsonObject, graphResponse) -> {        String id = null;        if (jsonObject != null) {            try {                id = jsonObject.getString("id");            } catch (JSONException e) {                e.printStackTrace();            }                        }    });    request.setParameters(parameters);    request.executeAsync();}@Overridepublic void onCancel() {}@Overridepublic void onError(FacebookException e) {}@Overridepublic void onActivityResult(int requestCode, int resultCode, Intent data) {    super.onActivityResult(requestCode, resultCode, data);    if (resultCode == Activity.RESULT_OK) {        mCallbackManager.onActivityResult(requestCode, resultCode, data);               }}

So this is how I've made it. Feel free to ask ;)

public class AuthWFacebookSDKFour extends Activity implements View.OnClickListener,FacebookCallback<LoginResult>   {    List<String> permissionNeeds=Arrays.asList("user_photos","friends_photos", "email", "user_birthday", "user_friends");    //facebook callbacks manager    private CallbackManager cm;    private LoginButton mFbLoginButton;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //init facebook sdk and         FacebookSdk.sdkInitialize(getApplicationContext());        //instantiate callbacks manager        mCallbackManager = CallbackManager.Factory.create();        mFbLoginButton=(LoginButton)findViewById(R.id.FBBUTTONID);        //set permissions mFbLoginButton.setReadPermissions(ApplicationContext.facebookPermissions);        // register callback        //means hey facebook after login call onActivityResult of **this**          mFbLoginButton.registerCallback(mCallbackManager, this);    }    @Override    protected void onActivityResult(int requestCode, int resultCode, Intent data) {        super.onActivityResult(requestCode, resultCode, data);        //manage login result        mCallbackManager.onActivityResult(requestCode, resultCode, data);    }    @Override    public void onSuccess(LoginResult loginResults) {        //login ok  get access token         AccessToken.getActiveAccessToken();       }    @Override    public void onCancel() {        Log.e(TAG(),"facebook login canceled");    }    @Override    public void onError(FacebookException e) {        Log.e(TAG(),"facebook login failed error");    }}

remember to insert in manifest

<activity android:name="com.facebook.FacebookActivity" android:label="@string/app_name" android:theme="@android:style/Theme.Translucent.NoTitleBar"                />