Question

On Android Studio, create a 4 function calculator. The only buttons you need are 0-9, *, /, +, -, a clear, and enter button. Use StringTokenizer or String.split for the calculator code.

Answer 1

package com.example.10012698.calculatorproject;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.StringTokenizer;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {

Button button0, button1, button2, button3, button4, button5, button6,
button7, button8, button9, buttonadd, buttonsubtract, buttonmultiply,
buttondivide, buttonequals, buttonclear;
TextView display;
String displaytext="";
double result;
double x, y;
ArrayList<String> list;

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

button0 = (Button) findViewById(R.id.button0);
button1 = (Button) findViewById(R.id.button1);
button2 = (Button) findViewById(R.id.button2);
button3 = (Button) findViewById(R.id.button3);
button4 = (Button) findViewById(R.id.button4);
button5 = (Button) findViewById(R.id.button5);
button6 = (Button) findViewById(R.id.button6);
button7 = (Button) findViewById(R.id.button7);
button8 = (Button) findViewById(R.id.button8);
button9 = (Button) findViewById(R.id.button9);
buttonadd = (Button) findViewById(R.id.buttonadd);
buttonsubtract = (Button) findViewById(R.id.buttonsubtract);
buttonmultiply = (Button) findViewById(R.id.buttonmultiply);
buttondivide = (Button) findViewById(R.id.buttondivide);
buttonclear = (Button) findViewById(R.id.buttonclear);
buttonequals = (Button) findViewById(R.id.buttonequals);
display = (TextView) findViewById(R.id.display);
display.setOnClickListener(this);
list = new ArrayList<>();
}

public void onClick(View view)
{
if(!(view.equals(buttonclear)&&!(view.equals(buttonequals))))
{
display.setText(display.getText()+""+((Button)view).getText());

if(displaytext.equals("0"))
{
display.setText(" ");
}

if(view.equals(buttonclear))
{
display.setText(" ");
}

if(view.equals(buttonequals))
{
displaytext= displaytext.substring(0,displaytext.length()-1);
StringTokenizer operators= new StringTokenizer(displaytext, "+-*/",true);

while(operators.hasMoreTokens())
{
list.add(operators.nextToken());
}

for(int j=0; j<list.size()-1; j++)
{
if (list.get(j).equals("*") || list.get(j).equals("/"))
{
x = Double.parseDouble(list.get(j - 1));
y = Double.parseDouble(list.get(j + 1));

if (list.get(j).equals("*"))
{
result+=(x*y);
}

if (list.get(j).equals("/"))
{
result+=(x/y);
}
}
}
for(int k=0;k<list.size()-1;k++)
{
if (list.get(k).equals("+") || list.get(k).equals("-"))
{
x = Double.parseDouble(list.get(k - 1));
y = Double.parseDouble(list.get(k + 1));

if (list.get(k).equals("+"))
{
result+=(x+y);
}

if (list.get(k).equals("-"))
{
result+=(x-y);
}
}
}
}
display.setText(""+result);

}
}