Google+登出方法返回空指針異常

我正在使用Google登錄來登錄用戶。我在另一個活動中處理登錄，並且在另一個活動中有一個登出按鈕。Google+登出方法返回空指針異常

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，我註銷用戶並執行一個函數來指導用戶登錄活動。但是當我按下登出按鈕時，我收到以下空指針錯誤。

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)

如果有人能幫我解決這個問題，我會很高興。

編輯 - 我還沒有嘗試過檢查GoogleApiClient連接，但我仍然得到空指針錯誤

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(); 
         } 
        }); 


      } 
     }

來源

2016-09-22 Aksh

你在哪裏初始化'mGoogleApiClient'？ – Egor

在onCreate方法之前，我在類的開始處初始化了它。在代碼中添加了該代碼。謝謝。 – Aksh

這不是「初始化」。它只是聲明，默認值爲null。 – shmosel

聲明mGoogleApiClient在你的應用程序類。如果您沒有應用程序類，請將其創建爲

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

並在登錄活動中將其實例化。 as

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

然後您可以使用相同的引用來註銷。即，像

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

來源

2016-09-23 05:01:58 Tchinmai

它被聲明，它不是一個字符串。 – shmosel

對不起。我將重新解釋我的答案。 – Tchinmai

Google+登出方法返回空指針異常

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