Doing Calculations with an EditText

Question 1

Like you have initialised your TextView resultOut you should also initialise your EditTexts which you are using to get the inputs from the user like readingIn = (EditText) findViewById(R.id.your_edit_text).Also when you are assigning the values the readingIn value is null. You can assign all the values in a method and can invoke the method at the time of calculation .

package com.example.tillcounter;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

 public class TillCounter extends Activity implements OnClickListener{

 Button calcButton;
 EditText readingIn, floatIn, noteIn, fiftiesIn, twentiesIn, tensIn, fivesIn, twosIn,....;       
 TextView resultOut;
 double reading, tillFloat, largeNotes, fifties ,…..;

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

resultOut = (TextView) findViewById(R.id.textView1);
readingIn = (TextView) findViewById(R.id. readingIn);
floatIn = (TextView) findViewById(R.id. floatIn);
noteIn = (TextView) findViewById(R.id. noteIn);
twentiesIn = (TextView) findViewById(R.id. twentiesIn);
///So on


Button calcButton = (Button) findViewById(R.id.calcButton);
calcButton.setOnClickListener(this);

}

 @Override
 public void onClick(View v) {
     Log.i("clicks","You Clicked calculate");
     calculate();
     result = (reading - tillFloat - largeNotes - fifties - twenties - tens -            
         fives - twos      - ones - fiftyC - twentyC - tenC);
     if(result > 0){
     resultOut.setText("The till is up by: " + result);
       }else if(result < 0){
     resultOut.setText("The till is down by: " + result);
     }else{
      resultOut.setText("The till is even at: " + reading);
 }

     Intent i=new Intent(TillCounter.this, ResultActivity.class);
     startActivity(i);
   }
    public void calculate(){
      reading = Double.parseDouble(readingIn.getText().toString());
     tillFloat = Double.parseDouble(floatIn.getText().toString());
      largeNotes = Double.parseDouble(noteIn.getText().toString());
      fifties = Double.parseDouble(fiftiesIn.getText().toString());
      twenties = Double.parseDouble(twentiesIn.getText().toString());
     ////so on
 }

}

Question 2

You should reference all the EditText first after setting your Layout i.e setContentView. And write all the code after that.

Code should like

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

    readingIn = (EditText) findViewById(R.id.readingIn);
    //and so on for floatIn, noteIn, fiftiesIn etc..

    //int reading = new Integer(readingIn.intValue());
    reading = Double.parseDouble(readingIn.getText().toString());
    tillFloat = Double.parseDouble(floatIn.getText().toString());
    largeNotes = Double.parseDouble(noteIn.getText().toString());
    fifties = Double.parseDouble(fiftiesIn.getText().toString());
    twenties = Double.parseDouble(twentiesIn.getText().toString());
    tens = Double.parseDouble(tensIn.getText().toString());
    fives = Double.parseDouble(fivesIn.getText().toString());
    twos = Double.parseDouble(twosIn.getText().toString());
    ones = Double.parseDouble(onesIn.getText().toString());
    fiftyC = Double.parseDouble(fiftyCentsIn.getText().toString());
    twentyC = Double.parseDouble(twentyCentsIn.getText().toString());
    tenC = Double.parseDouble(tenCentsIn.getText().toString());

    //other code
}

Question 3

It's Simple. You try to get values before Activity displays on the screen.

Put this lines

double reading = Double.parseDouble(readingIn.getText().toString());
double tillFloat = Double.parseDouble(floatIn.getText().toString());
double largeNotes = Double.parseDouble(noteIn.getText().toString());
double fifties = Double.parseDouble(fiftiesIn.getText().toString());
double twenties = Double.parseDouble(twentiesIn.getText().toString());
double tens = Double.parseDouble(tensIn.getText().toString());
double fives = Double.parseDouble(fivesIn.getText().toString());
double twos = Double.parseDouble(twosIn.getText().toString());
double ones = Double.parseDouble(onesIn.getText().toString());
double fiftyC = Double.parseDouble(fiftyCentsIn.getText().toString());
double twentyC = Double.parseDouble(twentyCentsIn.getText().toString());
double tenC = Double.parseDouble(tenCentsIn.getText().toString());

double result = 0;

in onCreate method,not before.

Question 4

You did't initialized as

readingIn = (EditText) findViewById(R.id.name_edittext);

then you need to write inside OnCreate Activity

double reading = Double.parseDouble(readingIn.getText().toString());