Проверка правильности нулевого значения Edittext в android

Question

Здравствуйте, я хочу, чтобы проверка прошла на моем экране входа в систему. У меня есть два edittext, когда какой-то один из них, кроме кода, показывает ошибку, например, введите имя пользователя и пароль при нажатии кнопки входа в систему.

это мой первый класс activity_login.java

package com.ad_blinds.ad_bliends.ad_bliends; 

import android.app.ProgressDialog; 
import android.content.Intent; 
import android.content.SharedPreferences; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.support.annotation.Nullable; 
import android.support.v7.app.AppCompatActivity; 
import android.view.View; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.Toast; 

import org.json.JSONException; 
import org.json.JSONObject; 

import java.util.HashMap; 

/** 
* Created by jignesh on 20-07-2016. 
*/ 
public class activity_login extends AppCompatActivity implements View.OnClickListener { 

    public static final String USER_NAME =""; 
    public static final String PASSWORD=""; 
    private static final String LOGIN_URL = "http://www.techonlab.com/AdMobileApp/login.php"; 

    private EditText editTextUserName; 
    private EditText editTextPassword; 

    private Button buttonLogin; 

    @Override 
    protected void onCreate(@Nullable Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.login); 
     editTextUserName = (EditText) findViewById(R.id.Username); 
     editTextPassword = (EditText) findViewById(R.id.Password); 

     buttonLogin = (Button)findViewById(R.id.btnLogin); 
     buttonLogin.setOnClickListener(this); 

    } 


    private void login() { 

     String username = editTextUserName.getText().toString().trim(); 
     String password = editTextPassword.getText().toString().trim(); 
     userLogin(username, password); 

    } 

    private void userLogin(String username, String password) { 
     class UserLoginClass extends AsyncTask<String, Void, String> { 

      ProgressDialog loading; 
      @Override 
      protected void onPreExecute() { 
       super.onPreExecute(); 
        loading = ProgressDialog.show(activity_login.this,"Please Wait",null,true,true); 
      } 

      @Override 
      protected void onPostExecute(String s) { 
       super.onPostExecute(s); 
       loading.dismiss(); 
       String jsonValue=s; 

       try { 
        JSONObject jsonReplay = new JSONObject(jsonValue); 
        JSONObject userDetail = jsonReplay.getJSONObject("user_details"); 

        String USER_ID = userDetail.getString("user_id"); 
        String USER_NAME = userDetail.getString("user_name"); 
        String SUCCESS = userDetail.getString("Success"); 

        if(SUCCESS=="1") 
        { 
         SharedPreferences sp=getSharedPreferences("Login",0); 
         SharedPreferences.Editor Ed=sp.edit(); 
         Ed.putString("USER_ID",USER_ID); 
         Ed.putString("USER_NAME",USER_NAME); 
         Ed.putString("LOGIN",SUCCESS); 
         Ed.commit(); 

         Toast.makeText(activity_login.this, "Wel-come "+USER_NAME, Toast.LENGTH_SHORT).show(); 
         Intent intent = new Intent(activity_login.this,activity_home.class); 
         startActivity(intent); 
        } 

       } catch (JSONException e) { 
        e.printStackTrace(); 
       } 
      } 

      @Override 
      protected String doInBackground(String... params) { 
       HashMap<String, String> data = new HashMap<>(); 
       data.put("username", params[0]); 
       data.put("password", params[1]); 

       RegisterUserClass ruc = new RegisterUserClass(); 
       String result = ruc.sendPostRequest(LOGIN_URL, data); 
       return result; 
      } 

     } 
     UserLoginClass ulc = new UserLoginClass(); 
     ulc.execute(username,password); 
    } 


    @Override 
    public void onClick(View v) { 
     if(v == buttonLogin) { 
      login(); 
     } 
    } 
} 

Это мое второе имя класса regsteruserclass.java

package com.ad_blinds.ad_bliends.ad_bliends; 

import java.io.BufferedReader; 
import java.io.BufferedWriter; 
import java.io.InputStreamReader; 
import java.io.OutputStream; 
import java.io.OutputStreamWriter; 
import java.io.UnsupportedEncodingException; 
import java.net.HttpURLConnection; 
import java.net.URL; 
import java.net.URLEncoder; 
import java.util.HashMap; 
import java.util.Map; 

import javax.net.ssl.HttpsURLConnection; 

/** 
* Created by Belal on 8/6/2015. 
*/ 
public class RegisterUserClass { 

    public String sendPostRequest(String requestURL, 
            HashMap<String, String> postDataParams) { 

     URL url; 
     String response = ""; 
     try { 
      url = new URL(requestURL); 

      HttpURLConnection conn = (HttpURLConnection) url.openConnection(); 
      conn.setReadTimeout(15000); 
      conn.setConnectTimeout(15000); 
      conn.setRequestMethod("POST"); 
      conn.setDoInput(true); 
      conn.setDoOutput(true); 


      OutputStream os = conn.getOutputStream(); 
      BufferedWriter writer = new BufferedWriter(
        new OutputStreamWriter(os, "UTF-8")); 
      writer.write(getPostDataString(postDataParams)); 

      writer.flush(); 
      writer.close(); 
      os.close(); 
      int responseCode=conn.getResponseCode(); 

      if (responseCode == HttpsURLConnection.HTTP_OK) { 
       BufferedReader br=new BufferedReader(new InputStreamReader(conn.getInputStream())); 

       response = br.readLine(); 
      } 
      else { 
       response="Error"; 
      } 
     } catch (Exception e) { 
      e.printStackTrace(); 
     } 

     return response; 
    } 

    private String getPostDataString(HashMap<String, String> params) throws UnsupportedEncodingException { 
     StringBuilder result = new StringBuilder(); 
     boolean first = true; 
     for(Map.Entry<String, String> entry : params.entrySet()){ 
      if (first) 
       first = false; 
      else 
       result.append("&"); 

      result.append(URLEncoder.encode(entry.getKey(), "UTF-8")); 
      result.append("="); 
      result.append(URLEncoder.encode(entry.getValue(), "UTF-8")); 
     } 

     return result.toString(); 
    } 
} 

Answer 1

Изменить код ниже, чтобы показать подтверждение:

private void login() { 

    String username = editTextUserName.getText().toString().trim(); 
    String password = editTextPassword.getText().toString().trim(); 

    if (username.equals("")) { 
     Toast.makeText(this, "Please enter username",    Toast.LENGTH_SHORT).show(); 
    } 
    else if (password.equals("")) { 
     Toast.makeText(this, "Please enter password", Toast.LENGTH_SHORT).show(); 
    } 
    else{ 
    userLogin(username, password); 
} 

}