空引用onPostExecute

Question

我想得到你的帮助，我试着宣布 “if（结果！= null＆amp;＆amp; result.contains（”login_ok“））{”，但应用程序回答错误传递，同样插入一个真正的传递。

logcat错误

03-31 09:16:51.509 20585-20585 / estudo.br.loginphpmysql E / AndroidRuntime：FATAL EXCEPTION：main进程：estudo.br.loginphpmysql，PID：20585
                                                                     java.lang.NullPointerException：尝试在estudo.br.loginphpmysql.Login $ Askdata.onPostExecute（Login.java）的空对象引用上调用虚方法'boolean java.lang.String.contains（java.lang.CharSequence）'。 85）在                                                                        estudo.br.loginphpmysql.Login $ Askdata.onPostExecute（Login.java:72）at

                                                                       android.os.AsyncTask.finish（AsyncTask.java:667）at                                                                      在左边的android.os.AsyncTask.-wrap1（AsyncTask.java）                                                                      android.os.AsyncTask $ InternalHandler.handleMessage（AsyncTask.java:684）在

                                                                     android.os.Handler.dispatchMessage（Handler.java:102）at                                                                       在左边的android.os.Looper.loop（Looper.java:154）                                                                     android.app.ActivityThread.main（ActivityThread.java:6119）at                                                                       java中的java.lang.reflect.Method.invoke（Native Method）                                                                    com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:886）在
                                        

的com.android.internal.os.ZygoteInit.main（ZygoteInit.java:776）

和类代码

public class Login extends AppCompatActivity {
        EditText txtEmailL, txtPassL;
        Button btnLogin; 
        String url = "";
        String parameters= "";

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.login_activity);    
            txtEmailL = (EditText) findViewById(R.id.txtEmailL);
            txtPassL = (EditText) findViewById(R.id.txtPassL);    
           btnLogin = (Button) findViewById(R.id.btnLogin);
        }    
        public void txtforgot(View view) {
            Intent intent = new Intent(Login.this, RedefinesPass.class);
            startActivity(intent);
        }

        public void txtregister(View view) {
            Intent intent = new Intent(Login.this, Register.class);
            startActivity(intent);
        }

        public void btnlogin(View view) {
            ConnectivityManager connMgr = (ConnectivityManager)
                    getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();    
            if (networkInfo != null && networkInfo.isConnected()) {
                String email = txtEmailL.getText().toString();
                String pass= txtPassL.getText().toString();

                if (email.isEmpty() || pass.isEmpty()) {
                    Toast.makeText(getApplicationContext(), "fill in fields!", Toast.LENGTH_LONG).show();
                } else {
                    parameters = "email= " + email + "&pass= " + pass
                    url = "http://localhost/logintest";
                    Askdata obj = new Askdata();
                    obj.execute(url);
                }
               } else {
                Toast.makeText(getApplicationContext(), "No internet connection", Toast.LENGTH_LONG).show();
            }     
            }   
    line 72       private class Askdata extends AsyncTask<String, Void, String> {    
            @Override
            protected String doInBackground(String... urls) {    
                return Connection.postDados(urls[0], parameters);
            }  
            @Override
            protected void onPostExecute(String result) {    
    line 85                    if (result.contains("login_ok")) {
                        Intent inicio = new Intent(Login.this, MainScreen.class);
                        startActivity(inicio);    
                    } else {
                        Toast.makeText(getApplicationContext(), "User or pass Wrong!", Toast.LENGTH_LONG).show();
                    }    
                }    
            }   
            @Override
        protected void onPause(){
            super.onPause();
            finish();
        }
    }