问Facebook SDK 4.0.1不带登录按钮的登录

EN

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.hema.testfcaebooksdk" >

    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

        <meta-data android:name="com.facebook.sdk.ApplicationId" android:value="@string/facebook_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" />

        <provider android:authorities="com.facebook.app.FacebookContentProvider****************"
            android:name="com.facebook.FacebookContentProvider"
            android:exported="true" />

        <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>

</manifest>

public class MainActivity extends ActionBarActivity {

    CallbackManager callbackManager;
    LoginManager loginManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        FacebookSdk.sdkInitialize(getApplicationContext());

        callbackManager = CallbackManager.Factory.create();

        loginManager = LoginManager.getInstance();

        loginManager.registerCallback(callbackManager,
                new FacebookCallback<LoginResult>() {
                    @Override
                    public void onSuccess(LoginResult loginResult) {
                        // App code
                        Toast.makeText(getApplicationContext(), loginResult.getAccessToken().toString(), Toast.LENGTH_SHORT).show();

                    }

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

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

        Collection<String> permissions = Arrays.asList("public_profile", "user_friends");

        loginManager.logInWithReadPermissions(this, permissions); // Null Pointer Exception here
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        callbackManager.onActivityResult(requestCode, resultCode, data);
    }
}

04-14 20:03:46.840    8075-8075/com.example.hema.testfacebooksdk E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.hema.testfacebooksdk, PID: 8075
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.hema.testfacebooksdk/com.example.hema.testfacebooksdk.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2413)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2471)
            at android.app.ActivityThread.access$900(ActivityThread.java:175)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:146)
            at android.app.ActivityThread.main(ActivityThread.java:5602)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.facebook.login.LoginManager.getLogger(LoginManager.java:391)
            at com.facebook.login.LoginManager.logCompleteLogin(LoginManager.java:414)
            at com.facebook.login.LoginManager.startLogin(LoginManager.java:384)
            at com.facebook.login.LoginManager.logInWithReadPermissions(LoginManager.java:262)
            at com.example.hema.testfacebooksdk.MainActivity.onCreate(MainActivity.java:59)
            at android.app.Activity.performCreate(Activity.java:5451)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2377)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2471)
            at android.app.ActivityThread.access$900(ActivityThread.java:175)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:146)
            at android.app.ActivityThread.main(ActivityThread.java:5602)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
            at dalvik.system.NativeStart.main(Native Method)