java - 我的变量loginSuccessful自动更改

Question

我正在尝试创建登录屏幕并使用 ASyncTask 类。我用它来检查用户名和密码在服务器中是否可用。并且任务返回成功。然后我用它来将变量 loginSuccessfull 的值更改为“true”，并且当我使用 logd 检查它时它会发生变化。但是当我使用它来检查 if 语句时，该值会自动更改为较早的值，这是错误的。这是为什么？

public class LoginScreenActivity extends AppCompatActivity {

    EditText usernameEditText;
    EditText passwordEditText;
    Button loginButton;
    public static final String TAG = "LoginScreenActivity";
    protected boolean loginSuccessful = false;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login_screen);
        usernameEditText = findViewById(R.id.username_edit_text);
        passwordEditText = findViewById(R.id.password_edit_text);
        loginButton = findViewById(R.id.login_button);
        final Toast wrongCredentials = Toast.makeText(this, "Wrong username or password", Toast.LENGTH_SHORT);
        final LoginScreenBackground background = new LoginScreenBackground();


        loginButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                background.execute(usernameEditText.getText().toString(), passwordEditText.getText().toString());
                Log.d(TAG, "onClick: " + loginSuccessful);

                if(loginSuccessful){
                    showDeliveryScreen();
                }
                else{
                   wrongCredentials.show();
                }
            }
        });

    }

    class LoginScreenBackground extends AsyncTask<String, Void, String> {

        String loginURLString = "http://localhost/login.php";
        boolean loginSuccess = false;
        public static final String TAG = "BackgroudActivity";

        @Override
        protected void onPostExecute(String s) {
            Log.d(TAG, "onPostExecute: " + s);
            if(s.equals("success")){
                loginSuccessful = true;
                Log.d(TAG, "onPostExecute: " + loginSuccessful);
            }

            //Log.d(TAG, "onPostExecute: " + this.loginSuccess);

        }

        @Override
        protected String doInBackground(String... strings) {
            String responseFromServer = "";
            String username = strings[0];
            String password = strings[1];

            try{
                //Setting up the http connection
                URL url = new URL(loginURLString);
                HttpURLConnection urlConnection =(HttpURLConnection) url.openConnection();
                urlConnection.setRequestMethod("POST");
                urlConnection.setDoOutput(true);
                urlConnection.setDoInput(true);

                //Setting up the output stream to the php file on the server
                OutputStream outputStream = urlConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream));

                //setting up the data need to be sent to the server
                String data = URLEncoder.encode("user", "UTF-8") + "=" + URLEncoder.encode(username, "UTF-8") + "&&" +
                        URLEncoder.encode("pass", "UTF-8") + "=" + URLEncoder.encode(password, "UTF-8");

                //Send data throught the buffered reader
                bufferedWriter.write(data);

                //close connections
                bufferedWriter.flush();
                bufferedWriter.close();
                outputStream.close();

                //Setting up the input stream from the php file on th server
                InputStream inputStream = urlConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                String line = "";
                while((line = bufferedReader.readLine()) != null){
                    responseFromServer += line;
                }
                Log.d(TAG, "doInBackground: " + responseFromServer);


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



            return responseFromServer;

        }
    }

    public void showDeliveryScreen(){
        Intent intent = new Intent(this, DriverDeliveryActivity.class);
        startActivity(intent);
    }

}

预期为

true，但显示的结果为 false。

Answer 1

实际上并非如此，这对您来说只是一种视觉错觉，在您的 OnPostExecute 中，您没有获得成功响应。 因为您在 OnPostExecute

中有 2 个具有相同键的日志

Log.d(TAG, "onPostExecute: " + s);

还有

Log.d(TAG, "onPostExecute: " + loginSuccessful);

这就是为什么您可能会认为 loginSuccessfull 变量值设置为 true，但实际上并非如此。