问题
I have implemented a facebook login for my app. After the successful login, the onSuccess() callback is called. However, When I logout from facebook, the onCancel() callback is not called though the logout is successful. In the logs I see the following line after I click the logout:
01-24 17:22:07.801 952-952/? W/SurfaceFlinger: couldn't log to binary event log: overflow
I am using the API 23. Tried it on the Emulator with Android 6.0 and Facebook SDK 4.6.0 The following is my code:
package com.example.ankur.pollutionandweathermonitor;
import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;
import com.facebook.AccessToken;
import com.facebook.CallbackManager;
import com.facebook.FacebookCallback;
import com.facebook.FacebookException;
import com.facebook.FacebookSdk;
import com.facebook.Profile;
import com.facebook.login.LoginResult;
import com.facebook.login.widget.LoginButton;
public class MainActivity extends AppCompatActivity {
//LoginButton and callbackManager are for facebook login
private LoginButton loginButton;
CallbackManager callbackManager;
/*firstName is to store the firstname of the logged in facebook user*/
private String firstName;
/*profile and accessToken are for to get the current session tokens of the logged in users*/
private Profile profile;
private AccessToken accessToken;
/*permissionStatus is to store the ACCESS_FINE_LOCATION permission of the user*/
private boolean permissionStatus;
/*EXTRA_MESSAGE_FIRSTNAME is to send the firstname of the logged in facebook user in the intent*/
public final static String EXTRA_MESSAGE_FIRSTNAME = "USERNAME";
/*EXTRA_MESSAGE_LOCATION_PERMISSION is to send the ACCESS_FINE_LOCATION permission value in the intent*/
public final static String EXTRA_MESSAGE_LOCATION_PERMISSION = "PERMISSION";
/*Logs generated in this class are accessed through the Tag LOGTAG*/
private String LOGTAG = MainActivity.class.getSimpleName();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Initialize the facebook SDK for login
FacebookSdk.sdkInitialize(getApplicationContext());
callbackManager = CallbackManager.Factory.create();
setContentView(R.layout.activity_main);
//Call the CheckFacebookToken() function to see if there is a logged in user already.
//The function returns the firstname if there is a logged in user, else returns null
firstName = CheckFacebookToken();
if(firstName != null) {
//If there is an active current Session, then check if the user has granted the
// ACCESS_FINE_LOCATION permission. This check is only for Android >= 6.0
//For Android <6, the permission can be put in the AndroidMenifestFile
CheckLocationPermission();
}
//create the facebook login Button
loginButton = (LoginButton) findViewById(R.id.login_button);
try{
loginButton.setReadPermissions("user_friends");
loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
@Override
public void onSuccess(LoginResult loginResult) {
Log.v(LOGTAG, "successfully connected to facebook");
//After the login is successful, get the firstname of the logged in user
firstName = CheckFacebookToken();
//If there is an active current Session, then check if the user has granted the
// ACCESS_FINE_LOCATION permission. This check is only for Android >= 6.0
//For Android <6, the permission can be put in the AndroidMenifestFile
CheckLocationPermission();
}
@Override
public void onCancel() {
someCallback();
Log.v(LOGTAG, " connection to facebook cancelled");
}
@Override
public void onError(FacebookException exception) {
Toast.makeText(getApplicationContext(), "Fb Login Error", Toast.LENGTH_LONG);
Log.v(LOGTAG, "Error on connection to facebook");
}
});
}catch (Exception e){
Log.v(LOGTAG, "Error in the loginButton facebook");
e.printStackTrace();
}
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
}
//check if the user has granted the ACCESS_FINE_LOCATION permission.
// This check is only for Android >= 6.0. For Android <6, the permission can be put in the AndroidMenifestFile
protected void CheckLocationPermission(){
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 100);
}
else{
//Redirects the user to the Activity DisplayInformation
RedirectToDisplayInformation();
}
}
protected void someCallback(){
Log.v(LOGTAG, "logged out from facebook");
}
//The function CheckFacebookToken returns the firstname of the logged in facebook user, else returns null
protected String CheckFacebookToken(){
//Check if there is an active facebook session
String fName = null;
try{
accessToken = AccessToken.getCurrentAccessToken();
Log.v(LOGTAG, accessToken.getToken());
} catch (Exception e){
e.printStackTrace();
}
//If there is an Active facebook session, get the firstname and redirect user to the
//DisplayInformation Activity, send the username through the intent
if(accessToken != null) {
try {
profile = Profile.getCurrentProfile();
if(profile != null) {
fName = profile.getFirstName();
Log.v(LOGTAG, "There is an active session. The logged in user is " + fName);
}
}catch (Exception e){
e.printStackTrace();
}
}
else {
Log.v(LOGTAG, "No Active sessions found");
}
return fName;
}
//The function RedirectToDisplayInformation redirects the user to the Activity DisplayInformation
//The intent also sends the firstname of the logged in facebook user
protected void RedirectToDisplayInformation(){
Log.v(LOGTAG, "successfully called the function RedirectToDisplayInformation");
Intent intent = new Intent(this, DisplayInformation.class);
intent.putExtra(EXTRA_MESSAGE_LOCATION_PERMISSION, String.valueOf(permissionStatus));
intent.putExtra(EXTRA_MESSAGE_FIRSTNAME,firstName );
//startActivity(intent);
}
//This function is to call the callback functions of facebook after the login attempt
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
callbackManager.onActivityResult(requestCode, resultCode, data);
}
@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);
}
//The function onRequestPermissionResult is a callback to promt the user to either allow or deny the
//permissions. This function is significant only for Android >6
@Override
public void onRequestPermissionsResult(int requestCode,String permissions[], int[] grantResults) {
Log.v(LOGTAG, "onRequestPermissionResult");
switch (requestCode) {
case 100: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
permissionStatus = true;
Log.v(LOGTAG, "Permission Granted. Status is: " + String.valueOf(permissionStatus));
}
else {
permissionStatus = false;
Log.v(LOGTAG, "Permission Denied. Status is: " + String.valueOf(permissionStatus));
}
RedirectToDisplayInformation();
return;
}
}
}
}
回答1:
FacebookCallback onCancel() will be called only when you dismiss the login dialog without continuing log in.
When you logout, Profile and AccessToken would become null but onCancel will not be called.
Hope this helps :)
来源：https://stackoverflow.com/questions/34978263/facebook-sdk-android-onsuccess-called-but-oncancel-not-called