STEP 1: Click on Project-->Android Project in the ECLIPSE.
STEP 2:Name the project to be calculator and package as com.calculator(YOU CAN HAVE DESIRE NAME)
STEP 3: On the left pane of the main window,choose layout folder under res folder.
Change the layout folder as follows.
Here we use Relative Layout along with Table Layout to display the numbers in calculator.
Text View is used to make type the numbers on the screen with help of Buttons.
ACTIVITY_MAIN.XML:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TextView
android:id="@+id/txtResultId"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_margin="@dimen/padding_small"
android:background="#cccccc"
android:gravity="right"
android:padding="@dimen/padding_medium" />
<TableLayout
android:id="@+id/tableId"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/txtResultId"
android:layout_margin="@dimen/padding_small" >
<TableRow>
<Button
android:id="@+id/btnNum7Id"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_seven" />
<Button
android:id="@+id/btnNum8Id"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_eight" />
<Button
android:id="@+id/btnNum9Id"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_nine" />
<Button
android:id="@+id/btnDivId"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_div" />
</TableRow>
<TableRow>
<Button
android:id="@+id/btnNum4Id"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_four" />
<Button
android:id="@+id/btnNum5Id"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_five" />
<Button
android:id="@+id/btnNum6Id"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_six" />
<Button
android:id="@+id/btnMulId"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_mul" />
</TableRow>
<TableRow>
<Button
android:id="@+id/btnNum1Id"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_one" />
<Button
android:id="@+id/btnNum2Id"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_two" />
<Button
android:id="@+id/btnNum3Id"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_three" />
<Button
android:id="@+id/btnSubId"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_sub" />
</TableRow>
<TableRow>
<Button
android:id="@+id/btnNum0Id"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_zero" />
<Button
android:id="@+id/btnClearId"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_clear" />
<Button
android:id="@+id/btnEqualId"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_equal" />
<Button
android:id="@+id/btnAddId"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/text_add" />
</TableRow>
</TableLayout>
</RelativeLayout>
Graphical Layout of our Application.
Next to add texts to these buttons we use strings.xml under values folder.
DIMENS.XML:
resources>
<!-- Default screen margins, per the Android Design guidelines. -->
<dimen name="padding_small">16dp</dimen>
<dimen name="padding_medium">16dp</dimen>
STRINGS.XML:
</resources>
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">Calc</string>
<string name="action_settings">Settings</string>
<string name="hello_world">Hello world!</string>
<string name="text_seven">7</string>
<string name="text_eight">8</string>
<string name="text_nine">9</string>
<string name="text_div">/</string>
<string name="text_four">4</string>
<string name="text_five">5</string>
<string name="text_six">6</string>
<string name="text_mul">*</string>
<string name="text_one">1</string>
<string name="text_two">2</string>
<string name="text_three">3</string>
<string name="text_zero">0</string>
<string name="text_clear">C</string>
<string name="text_equal">=</string>
<string name="text_add">+</string>
<string name="text_sub">-</string>
</resources>
Now coming on to main activity that is class file of the application where the main activity takes place for the application to process and compute.
MainActivity.java:
package com.calc;---------->PACKAGE NAME
import android.os.Bundle;
import android.app.Activity;
import android.view.View;
import android.view.View.OnClickListener; --------->IMPORT CLASS
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends Activity {
private TextView txtResult;
private int result =0; --------->LOCAL VARIABLES
private String inStr="0";
//Previous operator:'+','-','*','/','=' or ' '
private char lastOperator =' ';
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// CALLING THE USED VIEWS AND BUTTONS WITH REFERENCE ID(R.ID.......)
txtResult =(TextView)findViewById(R.id.txtResultId);
txtResult.setText("0");
BtnListener listener = new BtnListener();
((Button)findViewById(R.id.btnNum0Id)).setOnClickListener(listener);
((Button)findViewById(R.id.btnNum1Id)).setOnClickListener(listener);
((Button)findViewById(R.id.btnNum2Id)).setOnClickListener(listener);
((Button)findViewById(R.id.btnNum3Id)).setOnClickListener(listener);
((Button)findViewById(R.id.btnNum4Id)).setOnClickListener(listener);
((Button)findViewById(R.id.btnNum5Id)).setOnClickListener(listener);
((Button)findViewById(R.id.btnNum6Id)).setOnClickListener(listener);
((Button)findViewById(R.id.btnNum7Id)).setOnClickListener(listener);
((Button)findViewById(R.id.btnNum8Id)).setOnClickListener(listener);
((Button)findViewById(R.id.btnNum9Id)).setOnClickListener(listener);
((Button)findViewById(R.id.btnAddId)).setOnClickListener(listener);
((Button)findViewById(R.id.btnSubId)).setOnClickListener(listener);
((Button)findViewById(R.id.btnMulId)).setOnClickListener(listener);
((Button)findViewById(R.id.btnDivId)).setOnClickListener(listener);
((Button)findViewById(R.id.btnClearId)).setOnClickListener(listener);
((Button)findViewById(R.id.btnEqualId)).setOnClickListener(listener);
}
//CREATING BUTTONCLICKLISTENER METHOD
private class BtnListener implements OnClickListener{
@Override
public void onClick(View view) {
// TODO Auto-generated method stub
switch(view.getId()){
case R.id.btnNum0Id:
case R.id.btnNum1Id:
case R.id.btnNum2Id:
case R.id.btnNum3Id:
case R.id.btnNum4Id:
case R.id.btnNum5Id:
case R.id.btnNum6Id:
case R.id.btnNum7Id:
case R.id.btnNum8Id:
case R.id.btnNum9Id:
String inDigit =((Button)view).getText().toString();
if(inStr.equals("0")){
inStr=inDigit;
}else{
inStr +=inDigit;
}
txtResult.setText(inStr);
if(lastOperator== '='){
result= 0;
lastOperator = ' ';
}
break;
case R.id.btnAddId:
compute();
lastOperator= '+';
break;
case R.id.btnSubId:
compute();
lastOperator='-';
break;
case R.id.btnMulId:
compute();
lastOperator='*';
break;
case R.id.btnDivId:
compute();
lastOperator= '/';
case R.id.btnEqualId:
compute();
lastOperator='=';
break;
case R.id.btnClearId:
result=0;
inStr="0";
lastOperator=' ';
txtResult.setText("0");
break;
}
}
//COMPUTATION
private void compute() {
// TODO Auto-generated method stub
int inNum = Integer.parseInt(inStr);
inStr="0";
if(lastOperator==' '){
result= inNum;
}else if(lastOperator== '+'){
result +=inNum;
}else if(lastOperator== '-'){
result -=inNum;
}else if(lastOperator== '*'){
--->ALL COMPUTATION RESULTS PROCESS'
result *=inNum;
}else if(lastOperator== '/'){
result /=inNum;
}else if(lastOperator== '='){
// result for next operation
}
txtResult.setText(String.valueOf(result)); ----->SHOWS THE RESULT
}
}
}
OUTPUT: IN LANDSCAPE MODE
Thus,SIMPLE CALCULATOR is made.
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