Null pointer exception

Question

I want to build an app that takes input from EditText in a ListView. Basically, I have three columns and in each column I have ediText.Now when I try to get the input from the user and store it in a variable of type String and when I run this is the app, It crashes as it gets NullPointerException.

This is my MainActivity.java

package com.example.manuj.autocalc;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    EditText editTotal;
    EditText editItem;
    EditText editAmt;
    String item;
    String amt;
    String total;
    ListView listView;
    CustomAdapter customAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editItem=findViewById(R.id.itemEdit);
        editTotal=findViewById(R.id.editTotal);
        editAmt=findViewById(R.id.amtEdit);

        item=editItem.getText().toString();
        total=editTotal.getText().toString();
        amt=editAmt.getText().toString();

        final ArrayList<Calc> calcs=new ArrayList<>();
        calcs.add(new Calc("    -","    -","     -"));
        calcs.add(new Calc("    -","    -","     -"));
        calcs.add(new Calc("    -","    -","     -"));
        calcs.add(new Calc("    -","    -","     -"));
        calcs.add(new Calc("    -","    -","     -"));

        listView=findViewById(R.id.listView);
        customAdapter=new CustomAdapter(this,-1,calcs);
        listView.setAdapter(customAdapter);
//        Calc calc=new Calc(item,amt,total);
//        calcs.add(calc);
        customAdapter.notifyDataSetChanged();







    }
}

This is my CustomAdapter class

package com.example.manuj.autocalc;

import android.content.Context;
import android.support.annotation.NonNull;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.EditText;

import java.util.ArrayList;


public class CustomAdapter extends ArrayAdapter<Calc> {
    public CustomAdapter(Context context, int resource, ArrayList<Calc> calcs) {
        super(context, resource, calcs);
    }
    @Override
    public View getView(int position, View view, ViewGroup parent) {

        Calc calc = getItem(position);

        if (view == null){
            view = LayoutInflater.from(getContext()).inflate(
                    R.layout.list_item, parent, false);
        }

        //get and set the items
        EditText item=(EditText)view.findViewById(R.id.itemEdit);
        item.setText(calc.getmItemEdit());

        //get and set the amt
        EditText amt=view.findViewById(R.id.amtEdit);
        amt.setText(calc.getmAmtEdit());

        //get and set the totalAmt
        EditText total=view.findViewById(R.id.editTotal);
        total.setText(calc.getmTotalEdt());

        return view;
    }
}

This is my model class

package com.example.manuj.autocalc;

import android.text.Editable;
import android.widget.EditText;

public class Calc {
    private String mItemEdit;
    private String mTotalEdt;
    private String mAmtEdit;

    Calc(String itemEdit,String totalEdit,String amtEdit){
        this.mItemEdit=itemEdit;
        this.mTotalEdt=totalEdit;
        this.mAmtEdit=amtEdit;
    }

    public String getmItemEdit(){return mItemEdit; }

    public void setmItemEdit(String mItemEdit){
        this.mItemEdit=mItemEdit;
    }

    public String getmTotalEdt(){return mTotalEdt; }

    public void setmTotalEdt(String mTotalEdt){
        this.mTotalEdt=mTotalEdt;
    }

    public String getmAmtEdit(){return mAmtEdit;}

    public void setmAmtEdit(String mAmtEdit){
        this.mAmtEdit=mAmtEdit;
    }

}

This is my Error

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.example.manuj.autocalc, PID: 6618
              java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.manuj.autocalc/com.example.manuj.autocalc.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2984)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3045)
                  at android.app.ActivityThread.-wrap14(ActivityThread.java)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1642)
                  at android.os.Handler.dispatchMessage(Handler.java:102)
                  at android.os.Looper.loop(Looper.java:154)
                  at android.app.ActivityThread.main(ActivityThread.java:6776)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1518)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1408)
               Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
                  at com.example.manuj.autocalc.MainActivity.onCreate(MainActivity.java:36)
                  at android.app.Activity.performCreate(Activity.java:6956)
                  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1126)
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2927)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3045) 
                  at android.app.ActivityThread.-wrap14(ActivityThread.java) 
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1642) 
                  at android.os.Handler.dispatchMessage(Handler.java:102) 
                  at android.os.Looper.loop(Looper.java:154) 
                  at android.app.ActivityThread.main(ActivityThread.java:6776) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1518) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1408)

Application terminated.

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference at com.example.manuj.autocalc.MainActivity.onCreate(MainActivity.java:36) — Manuj Sharma, Sep 08 '18 at 16:18
Looks like `R.id.itemEdit` is not part of layout `R.layout.activity_main` — ADM, Sep 08 '18 at 16:22
Yes in activity_main.xml i ihave only ListView and in list_items.xml i have the id which u mentiond. — Manuj Sharma, Sep 08 '18 at 16:26
You can't do that. You need to handle the writing of the list items in the adapter — kingston, Sep 08 '18 at 16:33
In some ways you are already doing it but then you want to access the item directly in the activity and that does not make sense. — kingston, Sep 08 '18 at 16:37
Ohh okay i understood,But it would be great if u could guide me how to get the input.Please help me. — Manuj Sharma, Sep 08 '18 at 16:43

score 1 · Answer 1 · answered Sep 08 '18 at 16:25

1

On load of Activity, you are reading the text from EditText and then you have added .toString(). First .getText() returns Null and then you are converting Null to String. Hence crash.

To Avoid this crash

just put a null check

if(your_edit_text.getText() != null)
 {
   //Then do your operation
 }

answered Sep 08 '18 at 16:25

Tejas

433
1
4
17

Then what else could i do .Pleasse help im beginner. – Manuj Sharma Sep 08 '18 at 16:27
The stack trace states that it'e the getText that is called on a null object – kingston Sep 08 '18 at 16:30
Please put your xml. – Tejas Sep 08 '18 at 16:30
see this link if it helps: https://stackoverflow.com/questions/7025829/get-value-from-edittext-placed-in-list-view-in-android – Tejas Sep 08 '18 at 16:33
I have added the xml files.Please check it. – Manuj Sharma Sep 08 '18 at 17:12

score 0 · Answer 2 · answered Sep 08 '18 at 16:42

0

Looks like itemEdit, editTotal, amtEdit belongs to your list_item.xml layout not activity_main.xml. You have initialized these three EditTexts inside your MainActivity class, maybe the reason why it is throwing error. But anyways, please provide your xml layouts.

answered Sep 08 '18 at 16:42

Sambit Mallick

155
4
14

Yes you are right.But i am able to display the list items. – Manuj Sharma Sep 08 '18 at 16:48
But i want it to display in MainActivity and hence when i get the input ,it crashes and when i just want o display the list items without the code of getting input then it displays. – Manuj Sharma Sep 08 '18 at 16:50
What is your main objective? Like why are you using ListView? – Sambit Mallick Sep 08 '18 at 16:52
Because i want to build a list notes app .So i thought it would need a listView as the user will add list itmes. – Manuj Sharma Sep 08 '18 at 17:08
Create another editbox in activity_main.xml. Get the inputs from there. – Sambit Mallick Sep 08 '18 at 17:18
I thought of that,but i would like to get the input from listView only. – Manuj Sharma Sep 08 '18 at 17:24
You'll get the list view once you've made an arraylist of string, set it up to the adapter or notify the change as you add the inputs. – Sambit Mallick Sep 08 '18 at 17:28
Yea i did that only previously but not String.I used calc inside the generic.See my code.Please help – Manuj Sharma Sep 08 '18 at 17:42
If u say using ArrayList of String,then should i delete my model class Calc.And if not please providde a sample code of what you suggested – Manuj Sharma Sep 08 '18 at 17:43
What is the point of those three editviews? I believe you have to make a list of your inputs. If that is the objective then arraylist of string would be enough. – Sambit Mallick Sep 08 '18 at 17:51
Those three EditViews are filled bu user as it is a type of calculator,user will enter the item name ,amt and total.So I'm taking the inputs from user.I'm not making my own inputs. – Manuj Sharma Sep 09 '18 at 02:04

Null pointer exception

2 Answers2