Question

I need help understanding how to accomplish math between different EditText views. I am not asking someone to write me the code but maybe explain what is involved to get this done.

I wanted to post a picture of this but as a new user I can not. Basicly I have a EditText for the following: Width, Length, Eave Height, Pitch.

I have ID’s for all the TextViews I just dont know how to program the behind the scenes math involved to make them work. I do have the equations needed to perform the math just not sure where and how to put them in java.

Basicly I need the user to enter a number in each of the top 4 boxes. I need to use an equation to generate the answer that will be displayed in the “SQFT” box. The user will also input a number in a cost box which will generat a “Total” that needs to be displayed in a separate TextView.

Any help would be appreciated, even if it is to point me in a direction of a tutorial to get me started. Thanks for your help.

Just to show what type of math I need to use, below is the equation I use for excel to calulate.

(length+width)*(Eave+1)*2 + (((width/2)/12*Pitch)*(width/2)*2)

Answer 1

I’m not sure if you don’t know how to extract the numbers entered in the EditTexts, how to actually do the math calculation, how to let the user initiate the calculate or how to present it.

I created a small demo that has 2 EditTexts, and a TextView that displays the sum of the numbers entered. The user does not need to press any buttons to perform the calculation, it is performed automatically every time the user updates the text (I assumed this is what you wanted).

Please note this code is not good code, it uses lots of internal anonymous classes etc but it supposed to demonstrate the mechanics of how to do this.

This is the main.xml layout file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="horizontal" >

    <EditText
        android:id="@+id/a"
        android:hint="input a"
        android:inputType="number"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:minWidth="60dp"/>
    <EditText 
        android:id="@+id/b"
        android:hint="input b"
        android:inputType="number"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:minWidth="60dp"/>
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:text="a+b = " />
    <TextView
        android:id="@+id/total"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp" />

</LinearLayout>

And this is the sample Activity:

package com.example;

import android.app.Activity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.util.Log;
import android.widget.EditText;
import android.widget.TextView;

public class SumActivity extends Activity
{
    private int a;
    private int b;
    private TextView totalOutput;

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        EditText inputA = (EditText) findViewById(R.id.a);
        EditText inputB = (EditText) findViewById(R.id.b);
        totalOutput = (TextView) findViewById(R.id.total);
        inputA.addTextChangedListener(new TextChangedListener()
        {

            @Override
            public void numberEntered(int number)
            {
                a = number;
                updateTotal();
            }
        });
        inputB.addTextChangedListener(new TextChangedListener()
        {

            @Override
            public void numberEntered(int number)
            {
                b = number;
                updateTotal();
            }
        });
    }

    private void updateTotal()
    {
        int total = a + b; // This is where you apply your function
        totalOutput.setText("" + total); // need to do that otherwise int will
                                            // be treated as res id.
    }

    private abstract class TextChangedListener implements TextWatcher
    {

        public abstract void numberEntered(int number);

        @Override
        public void afterTextChanged(Editable s)
        {
            String text = s.toString();
            try
            {
                int parsedInt = Integer.parseInt(text);
                numberEntered(parsedInt);
            } catch (NumberFormatException e)
            {
                Log.w(getPackageName(), "Could not parse '" + text + "' as a number", e);
            }
        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after)
        {
        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count)
        {
        }
    }

}