Android - How To Implement Real Time Calculator

This post is an tutorial for android development

Today we will learn how to implement "Real Time Calculator" In Android.

Sample Screen Shot -

Here is sample code -

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center_horizontal"
    android:orientation="vertical" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Enter Width" />

    <EditText
        android:id="@+id/edit_width"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/actionbar_search"
        android:paddingLeft="10dip"
        android:paddingRight="10dip"
        android:singleLine="true"
        android:text="0" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Enter Height" />

    <EditText
        android:id="@+id/edit_height"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/actionbar_search"
        android:paddingLeft="10dip"
        android:paddingRight="10dip"
        android:singleLine="true"
        android:text="0" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Calculated Area" />

    <EditText
        android:id="@+id/edit_area"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/actionbar_search"
        android:editable="false"
        android:paddingLeft="10dip"
        android:paddingRight="10dip"
        android:text="0" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Calculated Perimeter" />

    <EditText
        android:id="@+id/edit_perimeter"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/actionbar_search"
        android:editable="false"
        android:paddingLeft="10dip"
        android:paddingRight="10dip"
        android:text="0" />

</LinearLayout>

MainActivity.java

package com.example.edittextchange;

import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.text.Editable;
import android.text.TextWatcher;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.os.Build;

public class MainActivity extends ActionBarActivity {

 EditText edit_width, edit_height, edit_area, edit_perimeter;

 double width;
 double height;
 double area;
 double perimeter;

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

  edit_area = (EditText) findViewById(R.id.edit_area);
  edit_height = (EditText) findViewById(R.id.edit_height);
  edit_width = (EditText) findViewById(R.id.edit_width);
  edit_perimeter = (EditText) findViewById(R.id.edit_perimeter);

  edit_width.addTextChangedListener(new TextWatcher() {

   @Override
   public void onTextChanged(CharSequence s, int start, int before,
     int count) {
    // TODO Auto-generated method stub

   }

   @Override
   public void beforeTextChanged(CharSequence s, int start, int count,
     int after) {
    // TODO Auto-generated method stub

   }

   @Override
   public void afterTextChanged(Editable s) {
    // TODO Auto-generated method stub

    String widthString = edit_width.getText().toString();

    // convert the String into a double
    if (widthString.length() > 0) {
     width = Double.parseDouble(widthString);
    }

    // read the height out of heightEdit
    String heightString = edit_height.getText().toString();

    if (heightString.length() > 0) {
     height = Double.parseDouble(heightString);
    }

    // calculate area
    double area = calcArea();

    // calculate perimeter
    double perim = calcPerim();

    // set the label for areaText
    edit_area.setText(Double.toString(area));

    // set the label for perimText
    edit_perimeter.setText(Double.toString(perim));

   }
  });

  edit_height.addTextChangedListener(new TextWatcher() {

   @Override
   public void onTextChanged(CharSequence s, int start, int before,
     int count) {
    // TODO Auto-generated method stub

   }

   @Override
   public void beforeTextChanged(CharSequence s, int start, int count,
     int after) {
    // TODO Auto-generated method stub

   }

   @Override
   public void afterTextChanged(Editable s) {
    // TODO Auto-generated method stub

    String widthString = edit_width.getText().toString();

    // convert the String into a double
    if (widthString.length() > 0) {
     width = Double.parseDouble(widthString);
    }

    // read the height out of heightEdit
    String heightString = edit_height.getText().toString();

    if (heightString.length() > 0) {
     height = Double.parseDouble(heightString);
    }

    // calculate area
    double area = calcArea();

    // calculate perimeter
    double perim = calcPerim();

    // set the label for areaText
    edit_area.setText(Double.toString(area));

    // set the label for perimText
    edit_perimeter.setText(Double.toString(perim));

   }
  });

 }

 double calcArea() {
  return width * height;
 }

 double calcPerim() {
  return 2 * width * height;
 }

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {

  // Inflate the menu; this adds items to the action bar if it is present.
  getMenuInflater().inflate(R.menu.main, menu);
  return true;
 }

 @Override
 public boolean onOptionsItemSelected(MenuItem item) {
  // Handle action bar item clicks here. The action bar will
  // automatically handle clicks on the Home/Up button, so long
  // as you specify a parent activity in AndroidManifest.xml.
  int id = item.getItemId();
  if (id == R.id.action_settings) {
   return true;
  }
  return super.onOptionsItemSelected(item);
 }

 /**
  * A placeholder fragment containing a simple view.
  */
 public static class PlaceholderFragment extends Fragment {

  public PlaceholderFragment() {
  }

  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container,
    Bundle savedInstanceState) {
   View rootView = inflater.inflate(R.layout.fragment_main, container,
     false);
   return rootView;
  }
 }

}

Hope This code helps!!!!!!
Happy Coding!!!!!!!:)