Android Program : Create an Android Application to find the factorial of a number and Display the Result on Alert Box.

 Android Program : Create an Android Application to find the factorial of a number and Display the Result on Alert Box.

Soln :

activity_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"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:gravity="center">

        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/et_apti_number"
            android:textStyle="bold"
            android:textSize="18sp"
        android:layout_margin="20dp"
        android:padding="10dp"
            />

        <Button
            android:id="@+id/b_apti_calc"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Calculate"
            android:textColor="#ffffff"
            android:textStyle="bold"
            android:textSize="18sp"
            android:layout_margin="20dp"
            android:padding="10dp"/>


        <TextView
            android:id="@+id/tv_apti_answer"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Answer"
            android:textColor="#000000"
            android:textStyle="bold"
            android:textSize="18sp"
            android:layout_margin="20dp"
            android:padding="10dp"/>

    </LinearLayout>

</LinearLayout>

MainActivity.java

package com.example.slipap3a;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;

import android.content.DialogInterface;
import android.os.Bundle;
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;

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

    private void initialize() {
        number = (EditText) findViewById(R.id.et_apti_number);
        number.setHint("Enter number to be factorialized :P");
        answer = (TextView) findViewById(R.id.tv_apti_answer);
        calculate = (Button) findViewById(R.id.b_apti_calc);
        calculate.setOnClickListener(this);
    }

    private long calcFactorial() {

        long factorial = 1;
        try {
            factorial = Long.parseLong(number.getText().toString());
            for (int i = (int) (factorial - 1); i > 0; i--) {
                factorial = i * factorial;
                Toast.makeText(this, "correct", Toast.LENGTH_LONG).show();
            }
        } catch (NumberFormatException e) {
            Toast.makeText(this, "Incorrect Input", Toast.LENGTH_LONG).show();
        } finally {
        }

        return factorial;
    }

    @Override
    public void onClick(View v) {
        answer.setText("Factorial of " + number.getText().toString() + " is : " + calcFactorial());

        // Create the object of
        // AlertDialog Builder class
        AlertDialog.Builder builder
                = new AlertDialog
                .Builder(MainActivity.this);

        // Set the message show for the Alert time
        builder.setMessage("Do you want to exit ?Factorial of " + number.getText().toString() + " is : " + calcFactorial());

        // Set Alert Title
        builder.setTitle("Alert !");

        // Set Cancelable false
        // for when the user clicks on the outside
        // the Dialog Box then it will remain show
        builder.setCancelable(false);

        // Set the positive button with yes name
        // OnClickListener method is use of
        // DialogInterface interface.

        builder
                .setPositiveButton(
                        "Yes",
                        new DialogInterface
                                .OnClickListener() {

                            @Override
                            public void onClick(DialogInterface dialog,
                                                int which)
                            {

                                // When the user click yes button
                                // then app will close
                                finish();
                            }
                        });

        // Set the Negative button with No name
        // OnClickListener method is use
        // of DialogInterface interface.
        builder
                .setNegativeButton(
                        "No",
                        new DialogInterface
                                .OnClickListener() {

                            @Override
                            public void onClick(DialogInterface dialog,
                                                int which)
                            {

                                // If user click no
                                // then dialog box is canceled.
                                dialog.cancel();
                            }
                        });

        // Create the Alert dialog
        AlertDialog alertDialog = builder.create();

        // Show the Alert Dialog box
        alertDialog.show();
    }

}

ScreenShot