Slip 5 - D) Create an Android Application to find the factorial of a number and Display the Result on Alert Box.

Solution:

Main.xml

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

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

    xmlns:app="http://schemas.android.com/apk/res-auto"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity"

    android:orientation="vertical">

    <EditText

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:id="@+id/et_no"

        android:layout_gravity="center"

        android:hint="enter the number">

    </EditText>

    <TextView

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:id="@+id/et_ans"

        android:layout_gravity="center"

        android:hint="answer">

    </TextView>

    <Button

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:id="@+id/bt_cal"

        android:text="calculate factorial">

    </Button>

</LinearLayout>

.java file:

package com.example.demofactorial;

import androidx.appcompat.app.ActionBar;

import androidx.appcompat.app.AppCompatActivity;

import android.app.AlertDialog;

import android.content.DialogInterface;

import android.content.Intent;

import android.os.Bundle;

import android.view.Display;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.TextView;

import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    EditText number;

    TextView answer;

    Button calculate;

    AlertDialog.Builder builder;

    int factorial= 1;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        initialize();

        calcFactorial();

        builder = new AlertDialog.Builder(this);

    }

    public void initialize() {

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

        answer = (TextView) findViewById(R.id.et_ans);

        calculate = (Button) findViewById(R.id.bt_cal);

        calculate.setOnClickListener(this);

    }

    public void calcFactorial() {

        if (number.getText().toString().equals("")) number.setText("0");

        int num = Integer.parseInt(number.getText().toString());

        for (int i = 1; i <= num; i++) {

            factorial = i * factorial;

        }

    }

    @Override

    public void onClick(View v){

        calcFactorial();

            //Setting message manually and performing action on button click

            builder.setMessage("Factorial of " + number.getText().toString() + " is : " + factorial)

                    .setCancelable(false)

                    .setPositiveButton("ok", new DialogInterface.OnClickListener() {

                        public void onClick(DialogInterface dialog, int id) {

                            finish();

                        }

                    })

                    .setNegativeButton("cancel", new DialogInterface.OnClickListener() {

                        public void onClick(DialogInterface dialog, int id) {

                        }

                   });

        //Creating dialog box

        AlertDialog alert = builder.create();

        //Setting the title manually

        alert.setTitle("FactorialAlertDialogExample");

        alert.show();

        answer.setText("Factorial of " + number.getText().toString() + " is : " +     factorial);

    }

}