Google+退出方法返回nullpointer異常

Question

我正在使用Google登錄名登錄用戶。 我在另一個活動中處理登錄，並且在另一個活動中有一個退出按鈕。

    private void signOut() {
if(mGoogleApiClient.isConnected()){
    Auth.GoogleSignInApi.signOut(mGoogleApiClient).setResultCallback(
            new ResultCallback<Status>() {
                @Override
                public void onResult(@NonNull Status status) {
                    loadloginActivity();
                }
            });

    }
    }

在上面的方法中，我要注銷用戶並執行將用戶定向到登錄活動的功能。 但是，當我按退出按鈕時，出現以下空指針錯誤。

    09-22 16:42:29.660 4459-4459/com.myapplication.tester E/AndroidRuntime: FATAL EXCEPTION: main
                                                                       Process: com.myapplication.tester, PID: 4459


java.lang.NullPointerException: Attempt to invoke virtual method 'boolean com.google.android.gms.common.api.GoogleApiClient.isConnected()' on a null object reference
                                                                           at com.myapplication.tester.BaseActivity.signOut(BaseActivity.java:190)
                                                                           at com.myapplication.tester.BaseActivity.onOptionsItemSelected(BaseActivity.java:180)
                                                                           at android.app.Activity.onMenuItemSelected(Activity.java:2948)
                                                                           at android.support.v4.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:406)
                                                                           at android.support.v7.app.AppCompatActivity.onMenuItemSelected(AppCompatActivity.java:195)
                                                                           at android.support.v7.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:103)
                                                                           at android.support.v7.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:103)
                                                                           at android.support.v7.app.ToolbarActionBar$2.onMenuItemClick(ToolbarActionBar.java:69)
                                                                           at android.support.v7.widget.Toolbar$1.onMenuItemClick(Toolbar.java:203)
                                                                           at android.support.v7.widget.ActionMenuView$MenuBuilderCallback.onMenuItemSelected(ActionMenuView.java:759)
                                                                           at android.support.v7.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:810)
                                                                           at android.support.v7.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:152)
                                                                           at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:957)
                                                                           at android.support.v7.view.menu.MenuPopup.onItemClick(MenuPopup.java:127)
                                                                           at android.widget.AdapterView.performItemClick(AdapterView.java:310)

如果有人可以幫助我解決此問題，我將非常高興。

編輯-我也嘗試了不檢查GoogleApiClient連接，但仍然出現nullpointer錯誤

public abstract class BaseActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {

    private Toolbar mActionBarToolbar;
    private DrawerLayout mDrawerLayout;
    protected NavigationView mNavigationView;
    private ActionBarDrawerToggle mToggle;
    //Initialized mGoogleApiClient
    GoogleApiClient mGoogleApiClient;

    private GoogleApiClient client;

    protected boolean useToolbar() {
        return true;
    }

    protected boolean useDrawerToggle() {
        return true;
    }

    @Override
    public void setContentView(int layoutResID) {
        super.setContentView(layoutResID);
        getActionBarToolbar();
        setupNavDrawer();
    }//end setContentView

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
    }
              private void signOut() {   

            Auth.GoogleSignInApi.signOut(mGoogleApiClient).setResultCallback(
                    new ResultCallback<Status>() {
                        @Override
                        public void onResult(@NonNull Status status) {
                            loadloginActivity();
                        }
                    });


            }
        }

Answer 1

在您的應用程序類中聲明mGoogleApiClient。 如果您沒有應用程序類，則將其創建為

public class MyApplication extends Application {
      public static GoogleApiClient mGoogleApiClient;
      @Override
      public void onCreate() {
           super.onCreate(); 
      }
}

並在“登錄活動”中實例化它。 如

MyApplcation.mGoogleApiClient= new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(Plus.API, Plus.PlusOptions.builder().build())
                .addScope(Plus.SCOPE_PLUS_LOGIN);

然后，您可以使用相同的參考注銷。 即，喜歡

 if (MyApplication.mGoogleApiClient.isConnected()) {
      //Your Logout Logic
       MyApplication.mGoogleApiClient.disconnect();
       MyApplication.mGoogleApiClient=null;
 }