Simple Calculator :
To make a simple calculator first make a basic app(
Don't know? Follow this).
Android consists of Xml(for layout) and Java(for code) files. We need to set up both as per our application requirements.
We will use
OnClickListener to get button clicks and perform tasks. We need to
implement the class
View.OnClickListener within our
MainActivity class, then import
unimplemented methods.
**We implement this class as to avoid setting up individual
OnClickListener for each button we use.
Now the
onClick() method is used to get button view which can be used to get button id that we will declare in layout(xml) file.
Follow these steps to set up files :
1) We need to first create a layout of the calculator.
Paste this code into you
activity_main.xml :
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| <LinearLayout 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"
android:layout_margin="16dp"
android:orientation="vertical"
tools:context=".MainActivity">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:text="Basic Calculator"
android:textSize="30dp" />
<EditText
android:id="@+id/edittext"
android:layout_width="wrap_content"
android:ems="10"
android:inputType="numberDecimal"
android:layout_margin="10dp"
android:layout_gravity="center_horizontal"
android:layout_height="wrap_content" />
<EditText
android:id="@+id/edittext2"
android:layout_width="wrap_content"
android:ems="10"
android:layout_margin="10dp"
android:inputType="numberDecimal"
android:layout_gravity="center_horizontal"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/textview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:text="Result"
android:layout_margin="10dp"
android:textSize="30dp" />
<Button
android:id="@+id/butadd"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Add"
android:ems="9"
android:layout_gravity="center_horizontal"
/>
<Button
android:id="@+id/butsub"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Subtract"
android:ems="9"
android:layout_gravity="center_horizontal"
/>
<Button
android:id="@+id/butmul"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Multiply"
android:ems="9"
android:layout_gravity="center_horizontal"
/>
<Button
android:id="@+id/butdiv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Divide"
android:ems="9"
android:layout_gravity="center_horizontal"
/>
</LinearLayout>
|
Paste this code into you
MainActivity.java :
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| package com.appyware.myfirstapp;
import android.app.Activity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
//implement View.OnClickListener for button clicks
public class MainActivity extends Activity implements View.OnClickListener {
Button butadd, butsub, butmul, butdiv;
EditText editText, editText2;
TextView textView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//definition
butadd = (Button) findViewById(R.id.butadd);
butsub = (Button) findViewById(R.id.butsub);
butmul = (Button) findViewById(R.id.butmul);
butdiv = (Button) findViewById(R.id.butdiv);
editText = (EditText) findViewById(R.id.edittext);
editText2 = (EditText) findViewById(R.id.edittext2);
textView = (TextView)findViewById(R.id.textview);
//setting onClickListener for buttons
butadd.setOnClickListener((View.OnClickListener) this);
butsub.setOnClickListener(this);
butmul.setOnClickListener(this);
butdiv.setOnClickListener(this);
}
@Override
public void onClick(View v) {
//declare variables
float num1 = 0;
float num2 = 0;
float result = 0;
//checking if the input is empty
if (TextUtils.isEmpty(editText.getText().toString())
|| TextUtils.isEmpty(editText2.getText().toString())) {
return;
}
// reading EditText and storing the value into variables
num1 = Float.parseFloat(editText.getText().toString());
num2 = Float.parseFloat(editText2.getText().toString());
// task to perform by buttons when clicked
switch (v.getId()) {
case R.id.butadd:
result = num1 + num2;
break;
case R.id.butsub:
result = num1 - num2;
break;
case R.id.butmul:
result = num1 * num2;
break;
case R.id.butdiv:
if(num2 != 0)
result = num1 / num2;
break;
default:
break;
}
// to display the result
textView.setText("Result = " + result);
}
}
|
2) Save and Run the application.
Complete Source Code :
Simple Calculator
For any doubts you can comment below, i'll respond ASAP.
