Android Studio 无法更新公共变量

Question

I am very new to Java and Android Studio. I am creating a login script, everything works but I need to set a variable to false or true . Java tells me I can't update the variable because I am using a public void . So I am trying to work around that but it's not working at all. This is my code

public String errorNumber = "0";

That variable is being used in the following method

public boolean validate() {

        boolean valid = true;


        String email = _emailText.getText().toString().trim();
        String password = _passwordText.getText().toString().trim();

        final String Password = _passwordText.getText().toString().trim();
        final String Email = _emailText.getText().toString().trim();

        if (email.isEmpty() || !android.util.Patterns.EMAIL_ADDRESS.matcher(email).matches()) {
            _emailText.setError("Vul een geldige email in");
            valid = false;


        } else {
            _emailText.setError(null);
        }

        if (password.isEmpty() || password.length() < 8 || password.length() > 20) {
            _passwordText.setError("Vul een geldig wachtwoord in");
             valid = false;


        } else {


            StringRequest stringRequest = new StringRequest(Request.Method.POST, REGISTER_URL,
                    new Response.Listener<String>() {

                        @Override
                        public void onResponse(String response) {

                            String[] output = response.split(":");
                            String output2 = output[2];
                            String[] setNumber = output[1].split(",");
                            String responseDetails1 = output2.replace("\"", "");
                            String responseDetails = responseDetails1.replace("}", "");
                            String responsNumber = setNumber[0];

                            Log.d("RESPONSE1", response);
                            Log.d("RESPONSE2", setNumber[0]);
                            Log.d("RESPONSE3", responseDetails);

                            if(responsNumber.equals("0")){

                                 errorNumber = "0";

                                //Toast.makeText(login.this, responseDetails, Toast.LENGTH_LONG).show();

                                Log.d("THERE IS AN ERROR", responseDetails);
                            }else{

                                _passwordText.setError(null);

                                 errorNumber = "1";

                                //Toast.makeText(login.this,  responseDetails, Toast.LENGTH_LONG).show();

                                Log.d("LOGIN SUCCESS", responseDetails);

                                //Intent i = new Intent(login.this, login.class);

                               // startActivity(i);
                            }


                        }
                    },
                    new Response.ErrorListener() {
                        @Override
                        public void onErrorResponse(VolleyError error) {
                            Toast.makeText(login.this,error.toString(),Toast.LENGTH_LONG).show();
                        }
                    }){
                @Override
                protected Map<String,String> getParams(){
                    Map<String,String> params = new HashMap<>();
                    params.put(KEY_PASSWORD, Password);
                    params.put(KEY_USEREMAIL, Email);

                    return params;
                }

            };

            RequestQueue requestQueue = Volley.newRequestQueue(this);
            requestQueue.add(stringRequest);

        }
        Log.d("ERRORNUMBER", errorNumber);

        if (errorNumber.equals("0")){
            valid = false;
        }

        Log.v("VALID STATUS", ""+ valid);

        return valid;
    }

Sorry for the long block of code, but it basically updates valid to true or false. Because I can't do this from within my if statements I needed to work around it, so I thought why not setup a variable and later check if that is set to 1 or 0? Then update the valid boolean accordingly.

Nothing I have tried so far works and I am out of solutions. I have searched the web but I can't find anything that explains me why I can't update that update variable so I can use it in my last if statement.

Answer 1

If I'm not mistaken, what you are doing wrong is that you are declaring variables IN the method. This results in them being deleted once you reach the end of the method. There are multiple ways to solve this, I will give you two ways.

1. You should declare 'valid', 'email' and 'password' variables outside of every method, at the beginning of the class. That way, when you invoke the method, whatever you did with variables is saved.

2. You could make the validate() method return a variable. For example, have the method return 'valid' variable and then you will get the value of 'valid' once you exit the method.

EDIT: just thought about 3. way you could do this. You could make a separate class, make an object out of it in your validate() method and return the whole object. That way you can get all 3 variables without declaring them for the whole class.

Public class email () {
    Boolean valid;
    String password;
    String email:
}

If this answer is not understandable, ask for further clarification. I can also post example code if needed.