Drops of Java: Calculator App in Android

CALCULATOR APP

/********************* CalcActivity.java *********************/

package com.android.calc;

import android.app.Activity;

import android.content.SharedPreferences;

import android.content.SharedPreferences.Editor;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.EditText;

public class CalcActivity extends Activity implements OnClickListener{

public static final String PREFS_NAME = "MyPrefsFile";

EditText etNumber;

String numberString;

String lastOperator;

int value2;

String opr;

int lastNum;

SharedPreferences settings;

SharedPreferences.Editor editor;

boolean isAnswerIN = false;

@Override

protected void onCreate(Bundle state) {

super.onCreate(state);

setContentView(R.layout.main);

settings = getSharedPreferences(PREFS_NAME, 0);

editor = settings.edit();

getViews();

numberString = etNumber.getText().toString();

}

private void getViews() {

etNumber = (EditText) findViewById(R.id.number);

((Button)findViewById(R.id.btn_zero)).setOnClickListener(this);

((Button)findViewById(R.id.btn_one)).setOnClickListener(this);

((Button)findViewById(R.id.btn_two)).setOnClickListener(this);

((Button)findViewById(R.id.btn_three)).setOnClickListener(this);

((Button)findViewById(R.id.btn_four)).setOnClickListener(this);

((Button)findViewById(R.id.btn_five)).setOnClickListener(this);

((Button)findViewById(R.id.btn_six)).setOnClickListener(this);

((Button)findViewById(R.id.btn_seven)).setOnClickListener(this);

((Button)findViewById(R.id.btn_eight)).setOnClickListener(this);

((Button)findViewById(R.id.btn_nine)).setOnClickListener(this);

((Button)findViewById(R.id.btn_add)).setOnClickListener(this);

((Button)findViewById(R.id.btn_sub)).setOnClickListener(this);

((Button)findViewById(R.id.btn_mul)).setOnClickListener(this);

((Button)findViewById(R.id.btn_slash)).setOnClickListener(this);

((Button)findViewById(R.id.btn_sqrt)).setOnClickListener(this);

((Button)findViewById(R.id.btn_answer)).setOnClickListener(this);

((Button)findViewById(R.id.btn_ac)).setOnClickListener(this);

((Button)findViewById(R.id.backSpace)).setOnClickListener(this);

}

@Override

public void onClick(View v) {

switch (v.getId()) {

case R.id.btn_zero:

getDisplay(0); break;

case R.id.btn_one:

getDisplay(1); break;

case R.id.btn_two:

getDisplay(2); break;

case R.id.btn_three:

getDisplay(3); break;

case R.id.btn_four:

getDisplay(4); break;

case R.id.btn_five:

getDisplay(5); break;

case R.id.btn_six:

getDisplay(6); break;

case R.id.btn_seven:

getDisplay(7); break;

case R.id.btn_eight:

getDisplay(8); break;

case R.id.btn_nine:

getDisplay(9); break;

case R.id.btn_add:

lastOperator = "+";

save();

break;

case R.id.btn_sub:

lastOperator = "-";

save();

break;

case R.id.btn_mul:

lastOperator = "*";

save();

break;

case R.id.btn_slash:

lastOperator = "/";

save();

break;

case R.id.btn_answer:

compute();

break;

case R.id.btn_ac:

start();

break;

default:

break;

}

public void getDisplay(int id) {

numberString = etNumber.getText().toString();

if(numberString.trim().equals("0") && isAnswerIN == true){

numberString = ""+id ;

}else{

numberString = numberString + id ;

}

etNumber.setText(numberString);

Log.d("\n ********** numberString = "+ numberString, "");

}

private void save() {

isAnswerIN = false;

numberString = etNumber.getText().toString();

lastNum = Integer.parseInt(numberString);

editor.putInt("lastnumber", lastNum);

editor.putString("lastOpr", lastOperator);

etNumber.setText(String.valueOf(""));

Log.d("\n IN SAVE ********* LASTNUM = "+ lastNum, "LASTOPR = " + lastOperator);

}

private void start() {

lastNum = 0;

lastOperator = "";

editor.putInt("lastnumber", lastNum);

editor.putString("lastOpr", lastOperator);

etNumber.setText(String.valueOf(0));

Log.d("\n IN START ********* " , "LASTNUM = " + lastNum);

}

private void compute() {

int answer;

if(isAnswerIN == false){

numberString = etNumber.getText().toString();

if(!numberString.trim().equals(""))

value2 = Integer.parseInt(numberString);

else

value2 = 0;

}

lastNum = settings.getInt("lastnumber", lastNum);

opr = settings.getString("lastOpr", lastOperator);

if (opr == "+") {

answer = lastNum + value2;

}else if(opr == "-"){

answer = lastNum - value2;

}else if(opr == "*"){

answer = lastNum * value2;

}else if(opr == "/"){

answer = lastNum /value2;

}else{

answer = value2;

}

etNumber.setText(String.valueOf(answer));

editor.putInt("value2", value2);

lastNum = answer;

editor.putInt("lastnumber", lastNum);

isAnswerIN = true;

Log.d("\n IN COMPUTE ******** result = "+ value2 ,"lastnum = "+ lastNum+ "answer = " +answer);

}

/********************* main.xml *********************/

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

<EditText

android:id="@+id/number"

android:layout_width="fill_parent" android:layout_height="wrap_content"

android:layout_marginTop="10dp"/>

<Button

android:id="@+id/backSpace" android:text="Backspace"

android:layout_width="180dp" android:layout_height="60dp"

android:layout_below="@+id/number" android:layout_marginTop="20dp"/>

<Button

android:id="@+id/btn_ac" android:text="AC"

android:layout_width="140dp" android:layout_height="60dp"

android:layout_below="@+id/number" android:layout_toRightOf="@+id/backSpace"

android:layout_marginTop="20dp"/>

<Button

android:id="@+id/btn_seven" android:text="7"