Java 背景任务和Facebook的上下文

我的android应用程序有问题。如果我使用我的“应用程序帐户”访问，就可以了

否则，如果我使用我的Facebook帐户凭据访问，则我的上下文为空

如何解决这个问题

下面是我的代码。先谢谢你

Login.java：

公共类登录扩展了AppCompatActivity{
上下文ctx；
私人登录按钮登录按钮FB；
私有文本视图信息；
私人CallbackManager CallbackManager；
EditText ET_NAME，ET_PASS；
字符串login\u name，login\u pass；
静态最终字符串USERNAME=“USER\u NAME”；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
sdkinInitialize（getApplicationContext（））；
setContentView（R.layout.activity\u登录）；
callbackManager=callbackManager.Factory.create（）；
loginButtonFb=（LoginButton）findViewById（R.id.login\u button\u fb）；
loginButtonFb.setReadPermissions（“用户朋友”）；
ET_NAME=（EditText）findViewById（R.id.user_NAME）；
ET_PASS=（EditText）findViewById（R.id.user_PASS）；
info=（TextView）findViewById（R.id.info）；
registerCallback（callbackManager，newfacebookcallback（））{
@凌驾
成功时公共无效（LoginResult LoginResult）{
新格力探索(
AccessToken.getCurrentAccessToken（），
loginResult.getAccessToken（）.getUserId（），
无效的
HttpMethod.GET，
新建GraphRequest.Callback（）{
未完成公共空白（图形响应）{
试一试{
JSONObject data=response.getJSONObject（）；
字符串idFb=data.getString（“id”）；
字符串名称fb=data.getString（“名称”）；
String method=“loginFb”；
BackgroundTask BackgroundTask=新的BackgroundTask（ctx）；
backgroundTask.execute（方法、名称fb、idFb）；
}捕获（JSONException e）{
e、 printStackTrace（）；
}
}
}
).executeAsync（）；
}
@凌驾
公开作废{
info.setText（“登录尝试已取消”）；
}
@凌驾
公共无效onError（FaceBook例外e）{
info.setText（“登录尝试失败”）；
}
});
}
@凌驾
受保护的void onActivityResult（int请求代码、int结果代码、意图数据）{
callbackManager.onActivityResult（请求代码、结果代码、数据）；
}
公共void userReg（视图）{
意向意向=新意向（此，Registration.class）；
星触觉（意向）；
}
私有类BackgroundTask扩展了AsyncTask{
上下文ctx；
背景任务（上下文ctx）{
this.ctx=ctx；
}
@凌驾
受保护的字符串doInBackground（字符串…参数）{
字符串方法=参数[0]；
if（方法等于（“登录”））{
字符串登录\u url=”http://192.168.1.118:80/webappdb/login.php";
字符串login_name=params[1]；
字符串login_pass=params[2]；
试一试{
URL=新URL（登录\ URL）；
HttpURLConnection HttpURLConnection=（HttpURLConnection）url.openConnection（）；
httpURLConnection.setRequestMethod（“POST”）；
httpURLConnection.setDoOutput（true）；
httpURLConnection.setDoInput（true）；
OutputStream OutputStream=httpURLConnection.getOutputStream（）；
BufferedWriter BufferedWriter=新的BufferedWriter（新的OutputStreamWriter（outputStream，UTF-8））；
字符串数据=urlcoder.encode（“登录名”，“UTF-8”）+“=”+urlcoder.encode（登录名，“UTF-8”）+“&”+
urlcoder.encode（“登录密码”，“UTF-8”）+“=”+urlcoder.encode（登录密码，“UTF-8”）；
bufferedWriter.write（数据）；
bufferedWriter.flush（）；
bufferedWriter.close（）；
outputStream.close（）；
InputStream InputStream=httpURLConnection.getInputStream（）；
BufferedReader BufferedReader=新的BufferedReader（（新的InputStreamReader（inputStream，“iso-8859-1”））；
字符串响应=”；
字符串行=”；
而（（line=bufferedReader.readLine（））！=null）{
响应+=行；
}
bufferedReader.close（）；
inputStream.close（）；
httpURLConnection.disconnect（）；
返回响应；
}捕获（格式错误）{
e、 printStackTrace（）；
}捕获（IOE异常）{
e、 printStackTrace（）；
}
}
else if（方法等于（“loginFb”））{
字符串login_name=params[1]；
字符串id=参数[2]；
字符串loginFb_url=”http://192.168.1.118:80/webappdb/loginFb.php";
试一试{
URL URL=新URL（登录URL）；
HttpURLConnection HttpURLConnection=（HttpURLConnection）url.openConnection（）；
httpURLConnection.setRequestMethod（“POST”）；
httpURLConnection.setDoOutput（true）；
httpURLConnection.setDoInput（true）；
OutputStream OutputStream=httpURLConnection.getOutputStream（）；
BufferedWriter BufferedWriter=新的BufferedWriter（新的OutputStreamWriter（outputStream，UTF-8））；
字符串数据=urlcoder.encode（“登录名FB”、“UTF-8”）+“=”+urlcoder.encode（登录名“UTF-8”）+“&”+
urlcoder.encode（“id”，“UTF-8”）+“=”+urlcoder.encode（id，“UTF-8”）；
bufferedWriter.write（数据）；
bufferedWriter.flush（）；
缓冲写入
public class Login extends AppCompatActivity {

Context ctx;
private LoginButton loginButtonFb;
private TextView info;
private CallbackManager callbackManager;
EditText ET_NAME, ET_PASS;
String login_name, login_pass;
static final String USERNAME = "USER_NAME";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    FacebookSdk.sdkInitialize(getApplicationContext());
    setContentView(R.layout.activity_login);
    callbackManager = CallbackManager.Factory.create();
    loginButtonFb = (LoginButton)findViewById(R.id.login_button_fb);
    loginButtonFb.setReadPermissions("user_friends");

    ET_NAME = (EditText) findViewById(R.id.user_name);
    ET_PASS = (EditText) findViewById(R.id.user_pass);
    info = (TextView)findViewById(R.id.info);

   loginButtonFb.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
        @Override
        public void onSuccess(LoginResult loginResult) {

            new GraphRequest(
                    AccessToken.getCurrentAccessToken(),
                    loginResult.getAccessToken().getUserId(),
                    null,
                    HttpMethod.GET,
                    new GraphRequest.Callback() {
                        public void onCompleted(GraphResponse response) {
                            try {
                                JSONObject data = response.getJSONObject();
                                String idFb = data.getString("id");
                                String nameFb = data.getString("name");
                                String method = "loginFb";
                                BackgroundTask backgroundTask = new BackgroundTask(ctx);
                                backgroundTask.execute(method, nameFb, idFb);
                            } catch (JSONException e) {
                                e.printStackTrace();
                            }

                        }
                    }
            ).executeAsync();

        }

        @Override
        public void onCancel() {
            info.setText("Login attempt canceled.");
        }

        @Override
        public void onError(FacebookException e) {
            info.setText("Login attempt failed.");
        }
    });

    }



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


public void userReg(View view){

    Intent intent = new Intent(this, Registration.class);
    startActivity(intent);
}



private class BackgroundTask extends AsyncTask<String, Void, String> {

    Context ctx;

    BackgroundTask(Context ctx){
        this.ctx = ctx;
    }

    @Override
    protected String doInBackground(String... params) {
        String method = params[0];
        if (method.equals("login")){
            String login_url = "http://192.168.1.118:80/webappdb/login.php";
            String login_name = params[1];
            String login_pass = params[2];
            try {
                URL url = new URL(login_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);
                httpURLConnection.setDoInput(true);
                OutputStream outputStream = httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));

                String data = URLEncoder.encode("login_name", "UTF-8") + "=" + URLEncoder.encode(login_name, "UTF-8") + "&" +
                        URLEncoder.encode("login_pass", "UTF-8") + "=" + URLEncoder.encode(login_pass, "UTF-8");
                bufferedWriter.write(data);
                bufferedWriter.flush();
                bufferedWriter.close();
                outputStream.close();

                InputStream inputStream = httpURLConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader((new InputStreamReader(inputStream, "iso-8859-1")));
                String response = "";
                String line = "";
                while((line = bufferedReader.readLine()) != null){
                    response += line;
                }
                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();
                return response;

            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }


        }

        else if(method.equals("loginFb")){
            String login_name = params[1];
            String id = params[2];
            String loginFb_url = "http://192.168.1.118:80/webappdb/loginFb.php";
            try {
                URL url = new URL(loginFb_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);
                httpURLConnection.setDoInput(true);
                OutputStream outputStream = httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));

                String data = URLEncoder.encode("login_nameFb", "UTF-8") + "=" + URLEncoder.encode(login_name, "UTF-8") + "&" +
                        URLEncoder.encode("id", "UTF-8") + "=" + URLEncoder.encode(id, "UTF-8");
                bufferedWriter.write(data);
                bufferedWriter.flush();
                bufferedWriter.close();
                outputStream.close();

                InputStream inputStream = httpURLConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader((new InputStreamReader(inputStream, "iso-8859-1")));
                String response = "";
                String line = "";
                while((line = bufferedReader.readLine()) != null){
                    response += line;
                }
                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();
                return response;

            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }


        }
        return null;
    }



    @Override
    protected void onPostExecute(String result) {

        if(result.equals("Login failed, try again.")){

            Toast.makeText(ctx, result, Toast.LENGTH_LONG).show();
        }
        if (result.equals("Login success!")){
            Intent intent = new Intent(ctx,UserProfile.class);
            intent.putExtra(USERNAME, login_name);
            startActivity(intent);

            Toast.makeText(ctx, result, Toast.LENGTH_LONG).show();
        }

    }
}




public void userLogin(View view){

    login_name = ET_NAME.getText().toString();
    login_pass = ET_PASS.getText().toString();
    String method = "login";
    BackgroundTask backgroundTask = new BackgroundTask(this);
    backgroundTask.execute(method, login_name, login_pass);

}





}

gamingproject.sellmybooks E/AndroidRuntime: FATAL EXCEPTION: main
        Process: gamingproject.sellmybooks, PID: 30637
        java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
        at android.content.ComponentName.<init>(ComponentName.java:77)
        at android.content.Intent.<init>(Intent.java:4144)
        at gamingproject.sellmybooks.Login$BackgroundTask.onPostExecute(Login.java:228)
        at gamingproject.sellmybooks.Login$BackgroundTask.onPostExecute(Login.java:123)
        at android.os.AsyncTask.finish(AsyncTask.java:632)
        at android.os.AsyncTask.access$600(AsyncTask.java:177)
        at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5536)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1397)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1192)

 mContext = this; 

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
     mContext = this; 
...
}

public void userLogin(View view){

    login_name = ET_NAME.getText().toString();
    login_pass = ET_PASS.getText().toString();
    String method = "login";
    BackgroundTask backgroundTask = new BackgroundTask(mContext);
    backgroundTask.execute(method, login_name, login_pass);

}