Get EditText value on button click and do math with that value?

Question

I am creating a program that is supposed to
1. Get the value of a spinner, either "Fahrenheit to Celsius" or "Celsius to Fahrenheit"
2. Get the value of EditText and convert it into an integer
3. Multiply that integer by 100
4. Set TextView text as that integer.
The problem is that I'm getting java.lang.NumberFormatException.
Here is my code:

 package org.infinitech.degreescalculator.app;
    import android.app.Activity;
    import android.os.Bundle;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.Spinner;
    import android.widget.TextView;
    public class MainActivity extends Activity{
        public Spinner spinner;
        public String selectedItem;
        public EditText input;
        public Button button;
        public String inputValue=findViewById(R.id.input).toString();
        public Integer num=Integer.parseInt(inputValue);
        public String num2;
        public TextView answer;
        @Override
        protected void onCreate(Bundle savedInstanceState){
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            spinner=(Spinner)findViewById(R.id.options);
            selectedItem=(String)spinner.getSelectedItem();
            input=(EditText)findViewById(R.id.input);
            button=(Button)findViewById(R.id.button);
            answer=(TextView)findViewById(R.id.answer);
            button.setOnClickListener(new View.OnClickListener(){
                public void onClick(View v){
                    if(selectedItem.equals("Fahrenheit to Celsius")){
                        num=num*100;
                        num2=num.toString();
                        answer.setText(num2);
                    }
                }
            });
        }
        @Override
        public boolean onCreateOptionsMenu(Menu menu){
            getMenuInflater().inflate(R.menu.main,menu);
            return true;
        }
        @Override
        public boolean onOptionsItemSelected(MenuItem item){
            return super.onOptionsItemSelected(item);
        }
    }

Here is my logcat:
Caused by: java.lang.NumberFormatException: Invalid int: ""

I fixed it! Here is my new modified code:

 package org.infinitech.degreescalculator.app;
 import android.app.Activity;
 import android.os.Bundle;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
 import android.widget.Button;
 import android.widget.EditText;
 import android.widget.Spinner;
 import android.widget.TextView;
 public class MainActivity extends Activity{
     public Spinner spinner;
     public String selectedItem;
     public EditText input;
     public Integer num;
     public Button button;
     public TextView answer;
     @Override
     protected void onCreate(Bundle savedInstanceState){
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         spinner=(Spinner)findViewById(R.id.options);
         selectedItem=(String)spinner.getSelectedItem();
         input=(EditText)findViewById(R.id.input);
         button=(Button)findViewById(R.id.button);
         answer=(TextView)findViewById(R.id.answer);
         button.setOnClickListener(new View.OnClickListener(){
             public void onClick(View v){
                 if(selectedItem.equals("Fahrenheit to Celsius")){
                     num=Integer.parseInt(input.getText().toString())*100;
                     answer.setText(num.toString());
                 }
             }
         });
     }
     @Override
     public boolean onCreateOptionsMenu(Menu menu){
         getMenuInflater().inflate(R.menu.main,menu);
         return true;
     }
     @Override
     public boolean onOptionsItemSelected(MenuItem item){
         return super.onOptionsItemSelected(item);
     }
 }

@yate It was `java.lang.NumberFormatException` I put NullPointerException instead. Fixed. — Kyle Horkley, Jun 23 '14 at 17:40
[See this post](http://stackoverflow.com/questions/18880962/i-would-like-to-set-my-variables-at-the-top-of-my-class-instead-of-in-the-method/18881067#18881067) and [this post](http://stackoverflow.com/questions/19988434/android-check-if-string-contains-characters-other-than-0-9/19988499#19988499) — codeMagic, Jun 23 '14 at 17:44

Giru Bhai · Answer 1 · 2014-06-23T17:59:55.173

1

Remove below lines from your Activity

   public String inputValue=findViewById(R.id.input).toString();
   public Integer num=Integer.parseInt(inputValue);

and Add in OnCreate Method as

 String inputValue= input.getText().toString();
 Integer num=Integer.parseInt(inputValue);

Because input EditText already defined.

And to convert num to String use String.valueOf instead of .toString().So change button Onclick function as

 button.setOnClickListener(new View.OnClickListener(){
                public void onClick(View v){
                    if(selectedItem.equals("Fahrenheit to Celsius")){
                        num=num*100;
                        answer.setText(String.valueOf(num));
                    }
                }
            });

edited Jun 23 '14 at 17:59

answered Jun 23 '14 at 17:36

Giru Bhai

14,370
5
46
74

Is it working for you? And also Check links that @codeMagic suggested. – Giru Bhai Jun 23 '14 at 17:45
I'm afraid it's still not working. I am getting `java.lang.NumberFormatException` – Kyle Horkley Jun 23 '14 at 17:47
@InfiniTech did you change your code,please post logcat exception also. – Giru Bhai Jun 23 '14 at 17:48
@InfiniTech What is input value,i.e. edittext value. try to chnage your code as I suggested. – Giru Bhai Jun 23 '14 at 17:54
Now it is java.lang.NullPointerException – Kyle Horkley Jun 23 '14 at 17:56
@InfiniTech post logcat exception – Giru Bhai Jun 23 '14 at 17:57
Caused by: java.lang.NullPointerException – Kyle Horkley Jun 23 '14 at 17:59
@InfiniTech see my edited answer ,i.e. rewrite onclick function as in my answer. – Giru Bhai Jun 23 '14 at 18:00
@InfiniTech ohh yourself great – Giru Bhai Jun 23 '14 at 18:04

ISURU · Answer 2 · 2014-06-23T18:17:59.843

1

change this

        public String inputValue=findViewById(R.id.input).toString();

as

        public String inputValue=(EditText)findViewById(R.id.input).getText().toString();

edited Jun 23 '14 at 18:17

answered Jun 23 '14 at 17:42

ISURU

923
13
24

score 0 · Answer 3 · answered Jun 23 '14 at 17:42

0

use getText() like so

EditText inputView = (EditText) findViewById(R.id.input);
String inputValue = inputView.getText().toString();

you should do all of this in the onCreate() method

answered Jun 23 '14 at 17:42

bhowden

669
7
15

Get EditText value on button click and do math with that value?

3 Answers3