I get an error like this, and application closes

Question

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();
}
}

Possible duplicate of [What is a NullPointerException, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Phantômaxx, Jan 02 '17 at 10:08
go through http://stackoverflow.com/help/how-to-ask and http://stackoverflow.com/help/mcve — Suraj Rao, Jan 02 '17 at 10:11
Possible duplicate of [Nullpointer exception](http://stackoverflow.com/questions/1277684/nullpointer-exception) — Patel Pinkal, Jan 02 '17 at 10:12

score 0 · Accepted Answer · edited Jan 02 '17 at 11:48

0

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).

edited Jan 02 '17 at 11:48

halfer

19,824
17
99
186

answered Jan 02 '17 at 10:41

Ranjith KP

858
6
18

String string1 = getInputText(); boolean status = false; if(string1 != null) { status = string1.equals(string2) } – Ranjith KP Jan 02 '17 at 11:08
Pro-tip: when adding inline code samples, use backticks rather than bold. See my edits. – halfer Jan 02 '17 at 11:49
ok.thank you..I still have not solved my problem. Please correct this error in My codes – Serdar Recepoğlu Jan 02 '17 at 13:39
`protected void onPostExecute(String result) { if (result.equals("Registration Success..."))` issue is in this code block the string result is null. Please check. – Ranjith KP Jan 03 '17 at 12:37
Thank You,Ranjith KP.. protected void onPostExecute(String result) { if (result.equals("Registration Success...")) I check, but I can not find the fault..I did not do what everybody said..I do not know what to do.. – Serdar Recepoğlu Jan 04 '17 at 09:00
Please print the value in string "result" and check. Are you already tried this ? – Ranjith KP Jan 04 '17 at 10:51
Please share the exception details(exception log). – Ranjith KP Jan 04 '17 at 11:23

score 0 · Answer 2 · answered Jan 02 '17 at 11:52

0

As pointed out earlier you are comparing two strings with Equal Method. e.g string1.equals(string2)

But in your case string1 is null. See the below example to understand it properly.

What should be done

String string1 = "hello";
String string2 = "hello";
string1.equals(string2) will return true

What you are doing

 String string1;
 String string2 = "hello";

string1.equals(string2) will crash the application as string1 is null. Equals Method is not applicable on null because NUll can't be compared with other.

answered Jan 02 '17 at 11:52

Tulsi

719
7
15

Minor detail: it is quite possible to compare a null with a string. The reason `string1.equals()` cannot be invoked is that a null variable cannot point to a viable instance or method, and so the run time environment does not know how to handle that. – halfer Jan 02 '17 at 11:54
I could not understand the answers Send my codes..pleasee – Serdar Recepoğlu Jan 02 '17 at 12:21

I get an error like this, and application closes

2 Answers2