无法访问getPreferences方法

问题描述：

我无法访问我的方法中的sharedPreferences接口的getPreferences方法。我在我的方法logintofophot中使用了getpreferences方法，但它给了我PRIVATE_MODE错误，我该如何解决此问题。无法访问getPreferences方法

这是我编辑的代码。

public class FacebookUtils { 

private static final DialogListener DEFAULT_AUTH_ACTIVITY_CODE = null; 

private static String APP_ID = "783826255024540"; 
public Facebook facebook = new Facebook(APP_ID); 
private AsyncFacebookRunner mAsyncRunner; 
String FILENAME = "AndroidSSO_data"; 
private SharedPreferences mPrefs; 
Button btnFbLogin; 
Button btnFbGetProfile; 
Context mcontext; 

public FacebookUtils() { 
    // TODO Auto-generated constructor stub 

} 
public void authorize(Activity activity, String[] permissions, 
     final DialogListener listener) { 
    authorize(activity, permissions, DEFAULT_AUTH_ACTIVITY_CODE); 
} 
public FacebookUtils(Context context) { 

} 


@SuppressWarnings("unused") 
public void loginToFacebook() { 

    SharedPreferences sharedPreferences=mcontext.getSharedPreferences("", Context.MODE_PRIVATE); 
    String access_token = mPrefs.getString("access_token", null); 
    long expires = mPrefs.getLong("access_expires", 0); 

    if (access_token != null) { 
     facebook.setAccessToken(access_token); 
     btnFbLogin.setVisibility(View.INVISIBLE); 
     btnFbGetProfile.setVisibility(View.VISIBLE); 
     Log.d("FB Sessions", "" + facebook.isSessionValid()); 
    } 
    if (expires != 0) { 
     facebook.setAccessExpires(expires); 
    } 
    if (!facebook.isSessionValid()) { 
     facebook.authorize((Activity) mcontext, 
       new String[] { "email", "publish_stream" }, 
       new DialogListener() { 
        @Override 
        public void onCancel() { 
        } 
        @Override 
        public void onComplete(Bundle values) { 

         SharedPreferences sharedPreferences=mcontext.getSharedPreferences("", Context.MODE_PRIVATE); 
         Editor editor=sharedPreferences.edit(); 
         editor.putString("access_token",facebook.getAccessToken()); 
         editor.putLong("access_expires",facebook.getAccessExpires()); 
         editor.commit(); 
         btnFbLogin.setVisibility(View.INVISIBLE); 
         btnFbGetProfile.setVisibility(View.VISIBLE); 
        } 
        @Override 
        public void onError(DialogError error) { 
         // Function to handle error 
        } 
        @Override 
        public void onFacebookError(FacebookError fberror) { 
        } 

       }); 
     } 


} 



public void getprofileinformation() 
{ 

    mAsyncRunner.request("me", new RequestListener() { 

     @Override 
     public void onMalformedURLException(MalformedURLException e, Object state) { 
      // TODO Auto-generated method stub 

     } 

     @Override 
     public void onIOException(IOException e, Object state) { 
      // TODO Auto-generated method stub 

     } 

     @Override 
     public void onFileNotFoundException(FileNotFoundException e, Object state) { 
      // TODO Auto-generated method stub 

     } 

     @Override 
     public void onFacebookError(FacebookError e, Object state) { 
      // TODO Auto-generated method stub 

     } 

     @Override 
     public void onComplete(String response, Object state) { 
      // TODO Auto-generated method stub 
      Log.d("Profile", response); 
      String json = response; 
      try { 
       JSONObject profile = new JSONObject(json); 
       final String name = profile.getString("name"); 
       final String email = profile.getString("email"); 
       runOnUiThread(new Runnable() { 
        @Override 
        public void run() { 
         Toast.makeText(mcontext, "Name: " + name + "\nEmail: " + email, Toast.LENGTH_LONG).show(); 
        } 
       }); 
      } catch (JSONException e) { 
       e.printStackTrace(); 
      } 
     } 
    }); 

} 
protected void runOnUiThread(Runnable runnable) { 
    // TODO Auto-generated method stub 
} 
}

这是logcat错误。

12-02 13:31:36.648: E/AndroidRuntime(2524): FATAL EXCEPTION: main 
12-02 13:31:36.648: E/AndroidRuntime(2524): Process: com.facebook.androidhive, PID: 2524 
12-02 13:31:36.648: E/AndroidRuntime(2524): java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences(java.lang.String, int)' on a null object reference 
12-02 13:31:36.648: E/AndroidRuntime(2524):  at com.facebook.demo.FacebookUtils.loginToFacebook(FacebookUtils.java:56) 
12-02 13:31:36.648: E/AndroidRuntime(2524):  at com.facebook.demo.AndroidFacebookConnectActivity$1.onClick(AndroidFacebookConnectActivity.java:51) 
12-02 13:31:36.648: E/AndroidRuntime(2524):  at android.view.View.performClick(View.java:4756) 
12-02 13:31:36.648: E/AndroidRuntime(2524):  at android.view.View$PerformClick.run(View.java:19749) 
12-02 13:31:36.648: E/AndroidRuntime(2524):  at android.os.Handler.handleCallback(Handler.java:739) 
12-02 13:31:36.648: E/AndroidRuntime(2524):  at android.os.Handler.dispatchMessage(Handler.java:95) 
12-02 13:31:36.648: E/AndroidRuntime(2524):  at android.os.Looper.loop(Looper.java:135) 
12-02 13:31:36.648: E/AndroidRuntime(2524):  at android.app.ActivityThread.main(ActivityThread.java:5221) 
12-02 13:31:36.648: E/AndroidRuntime(2524):  at java.lang.reflect.Method.invoke(Native Method) 
12-02 13:31:36.648: E/AndroidRuntime(2524):  at java.lang.reflect.Method.invoke(Method.java:372) 
12-02 13:31:36.648: E/AndroidRuntime(2524):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) 
12-02 13:31:36.648: E/AndroidRuntime(2524):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)`

这是我第二次参加这个班。

public class AndroidFacebookConnectActivity extends Activity { 
    private static String APP_ID = "783826255024540"; 
    private Facebook facebook = new Facebook(APP_ID); 
    private AsyncFacebookRunner mAsyncRunner; 
    String FILENAME = "AndroidSSO_data"; 
    private SharedPreferences mPrefs; 
    Button btnFbLogin; 
    Button btnFbGetProfile; 
    @SuppressWarnings("unused") 
    private FacebookUtils utils; 
    Context mContext; 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 
     btnFbLogin = (Button) findViewById(R.id.btn_fblogin); 
     btnFbGetProfile = (Button) findViewById(R.id.btn_get_profile); 
     mAsyncRunner = new AsyncFacebookRunner(facebook); 
     utils = new FacebookUtils(); 
     btnFbLogin.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       Log.d("Image Button", "button Clicked"); 
       utils.loginToFacebook(mContext); 
      } 
     }); 
     btnFbGetProfile.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       utils.getprofileinformation(); 
      } 
     }); 
    }

错误与此活动有关吗？我在这一行中得到了null异常。 String access_token = mPrefs.getString（“access_token”，null）;

请从logcat粘贴错误 – BzH 2014-12-02 07:38:12

我没有运行应用程序，因为我收到错误MODE_PRIVATE无法解析为变量错误。 – user3354610 2014-12-02 07:41:08

可能你需要调用mPrefs = getPreferences（MODE_PRIVATE）;与context.getPreferences（MODE_PRIVATE）; – 2014-12-02 08:02:17

答

这将是您轻松： -

把值

SharedPreferences sharedPreferences=mContext.getSharedPreferences("", Context.MODE_PRIVATE); 
Editor editor=sharedPreferences.edit(); 
editor.putString("access_token",facebook.getAccessToken()); 
editor.putLong("access_expires",facebook.getAccessExpires()); 
editor.commit();

获取值

SharedPreferences sharedPreferences=mContext.getSharedPreferences("", Context.MODE_PRIVATE); 
String access_token = sharedPreferences.getString("access_token", null); 
long expires = sharedPreferences.getLong("access_expires", 0);

检查构造一次。可能是mContext为null。试试这个： -

public FacebookUtils(Context context) { 
    mContext=context; 
}

尝试上下文传递给loginToFacebook（）： -

public void loginToFacebook(Context mContext) { 
}

它给了我错误创建方法getSharedPreferences行SharedPreferences sharedPreferences = getSharedPreferences（“”，Context.MODE_PRIVATE）; – user3354610 2014-12-02 07:44:21

我已编辑答案。使用'SharedPreferences sharedPreferences = mContext.getSharedPreferences（“”，Context.MODE_PRIVATE）;' – 2014-12-02 07:46:13

仍然收到错误：12-02 13：18：22.562：E/AndroidRuntime（2420）：java.lang.NullPointerException：试图调用虚拟方法'空的对象引用 – user3354610 2014-12-02 07:49:13

答

您还没有初始化的变量mPrefs。因此错误，因为当你试图做mPrefs.getString("access_token", null);它的null;

截至目前你只用语句声明它，

private SharedPreferences mPrefs;

但是，为了访问它，你也必须把它初始化为，

mPrefs = getPreferences(MODE_PRIVATE);

您尝试使用前它。

答

，以防万一有人面临着这个问题：

public class listops { 
    Context mcontext; 
    SharedPreferences prefs; 


    public listops(Context context) 
    { 
    mcontext=context; 
    prefs= mcontext.getSharedPreferences("prefs", Context.MODE_PRIVATE); 

    } 
... 
}

这样就解决了问题。

无法访问getPreferences方法

相关推荐