For William Smith

MainActivity.java

import android.content.Context;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    int fuel = 3400;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        EditText fuelLoadField = (EditText) findViewById(R.id.Fuel_load_field);
        fuelLoadField.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {


            }

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

                EditText fuelEditText = (EditText) findViewById(R.id.Fuel_load_field);
                String fuelString = fuelEditText.getText().toString();

                // Error check to avoid a null error
                if ("".equals(fuelString)){
                    fuel = 0;
                    fuelEditText.setText(String.valueOf(fuel));
                    fuelEditText.setSelection(0); //Trying to figure out the best place for cursor

                    // need to add calc here
                    return;
                }

                // Set the fuel value and then perform the W&B Calc.
                fuel = Integer.parseInt(fuelString.toString());

                // Error check to avoid over fuel
                if (fuel > 14518) {
                    fuel = 14518;
                    fuelEditText.setText(String.valueOf(fuel));
                    fuelEditText.setSelection(5);
                }
                
                // need to add calc here

            }

            @Override
            public void afterTextChanged(Editable s) {

            }
        });


    }