[FIXED] I get an error like this, and application closes

Issue

I get an error like this. The application closes.

Here is my code:

BackgroundTask Class,

public class BackgroundTask extends AsyncTask<String,Void,String> {
AlertDialog alertDialog;
Context ctx;
BackgroundTask(Context ctx)
{
    this.ctx = ctx;
}
@Override
protected void onPreExecute(){
    alertDialog = new AlertDialog.Builder(ctx).create();
    alertDialog.setTitle("Login Information....");
}
@Override
protected String doInBackground(String... params) {
    String reg_url = "http://127.0.0.1/Register.php";
    String login_url = "http://127.0.0.1/Login.php";
    String method = params[0];
    if (method.equals("register"))
    {
        String isim = params [1];
        String soyisim = params[2];
        String plaka = params[3];
        String saseno = params[4];
        String email = params[5];
        String sifre = params[6];
        try {
            URL url = new URL(reg_url);
            HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.setDoOutput(true);
            //httpURLConnection.setDoInput(true);
            OutputStream OS = httpURLConnection.getOutputStream();
            BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(OS,"UTF-8"));
            String data = URLEncoder.encode("isim","UTF-8") +"="+URLEncoder.encode(isim,"UTF-8")+"&"+
            URLEncoder.encode("soyisim","UTF-8") +"="+URLEncoder.encode(soyisim,"UTF-8")+"&"+
            URLEncoder.encode("plaka","UTF-8") +"="+URLEncoder.encode(plaka,"UTF-8")+"&"+
            URLEncoder.encode("saseno","UTF-8") +"="+URLEncoder.encode(saseno,"UTF-8")+"&"+
            URLEncoder.encode("email","UTF-8") +"="+URLEncoder.encode(email,"UTF-8")+"&"+
            URLEncoder.encode("sifre","UTF-8") +"="+URLEncoder.encode(sifre,"UTF-8");
            bufferedWriter.write(data);
            bufferedWriter.flush();
            bufferedWriter.close();
            OS.close();
            InputStream IS = httpURLConnection.getInputStream();
            IS.close();
            //httpURLConnection.connect();
            httpURLConnection.disconnect();
            return  "Registration Success...";
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    else if (method.equals("login"))
    {
        String loginmail = params[1];
        String loginsifre = 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("loginmail","UTF-8")+"="+URLEncoder.encode(loginmail,"UTF-8")+"&"+
                URLEncoder.encode("loginsifre","UTF-8")+"="+URLEncoder.encode(loginsifre,"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 onProgressUpdate(Void... values) {
    super.onProgressUpdate(values);
}
@Override
protected void onPostExecute(String result) {
    if (result.equals("Registration Success..."))
    {
        Toast.makeText(ctx,result,Toast.LENGTH_LONG).show();
    }
    else
    {
        alertDialog.setMessage(result);
        alertDialog.show();
    }
}
}


Login Javaclass,

package com.example.serdar.tipoff;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.widget.EditText;

public class Login extends Activity {
EditText ET_EMAİL_LOGİN,ET_SİFRE_LOGİN;
String loginmail,loginsifre;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    setContentView(R.layout.activity_login);

    ET_EMAİL_LOGİN = (EditText)findViewById(R.id.etmaillogin);
    ET_SİFRE_LOGİN = (EditText)findViewById(R.id.etsifrelogin);
}
public void Regkayit (View view)
{
    startActivity(new Intent(this, Register.class));
}
public void LogGiris ( View view)
{
    loginmail = ET_EMAİL_LOGİN.getText().toString();
    loginsifre = ET_SİFRE_LOGİN.getText().toString();
    String method = "login";
    BackgroundTask backgroundTask = new BackgroundTask(this);
    backgroundTask.execute(method,loginmail,loginsifre);
}
}


Register Javaclass,

package com.example.serdar.tipoff;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.widget.EditText;

public class Register extends Activity {
EditText    ET_İSİM_REG,ET_SOYİSİM_REG,ET_PLAKA_REG,ET_SASENOREG,ET_EMAİL_REG,ET_SİFRE_REG;
String isim,soyisim,plaka,saseno,email,sifre;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    setContentView(R.layout.activity_register);

    ET_İSİM_REG = (EditText)findViewById(R.id.etisimreg);
    ET_SOYİSİM_REG = (EditText)findViewById(R.id.etsoyisimreg);
    ET_PLAKA_REG = (EditText)findViewById(R.id.etplakareg);
    ET_SASENOREG = (EditText)findViewById(R.id.etsasenoreg);
    ET_EMAİL_REG = (EditText)findViewById(R.id.etmailreg);
    ET_SİFRE_REG = (EditText)findViewById(R.id.etsifrereg);
}
public void Regkaydet (View view)
{
    isim = ET_İSİM_REG.getText().toString();
    soyisim = ET_SOYİSİM_REG.getText().toString();
    plaka = ET_PLAKA_REG.getText().toString();
    saseno = ET_SASENOREG.getText().toString();
    email = ET_EMAİL_REG.getText().toString();
    sifre = ET_SİFRE_REG.getText().toString();
    String method = "register";
    BackgroundTask backgroundTask = new BackgroundTask(this);
    backgroundTask.execute(method,isim,soyisim,plaka,saseno,email,sifre);
    finish();
}
}

Solution

I think in your code you are comparing two strings using equals function like String1.equals(String2) in your case String1 is null (not initialized), and it is the root cause of this exception.

For example:

String string1 = getInputText();
boolean status = false;
if(string1 != null) {
    status = string1.equals(string2);
}

So please check and ensure String1 is not null before calling String1.equals(String2).

Answered By - Ranjith KP
Answer Checked By - Gilberto Lyons (JavaFixing Admin)