part 6 - Understanding Edit Text and return method

 Java Part : 

package first.learn.edittextproject;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import org.w3c.dom.Text;

public class MainActivity extends AppCompatActivity {

    EditText etTwo,
            etOne;

    TextView tvResult;
    Button btnPlus;

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

        etTwo = (EditText) findViewById(R.id.etTwo);
        etOne = (EditText) findViewById(R.id.etOne);

        tvResult = (TextView) findViewById(R.id.tvResult);
        btnPlus = (Button) findViewById(R.id.btnPlus);


        btnPlus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String a = getTextFromEditText(etOne);

                if (a == null) {

                    return;
                }

                if (!isIntegerCharacter(a)) {
                    Toast.makeText(MainActivity.this, "Please Write Valid Number", Toast.LENGTH_SHORT).show();
                    return;
                }

                String b = getTextFromEditText(etTwo);

                if (b == null) {
                    return;
                }


                if (!isIntegerCharacter(b)) {
                    Toast.makeText(MainActivity.this, "Please Write Valid Number", Toast.LENGTH_SHORT).show();
                    return;
                }

                int c = stringToIntger(a);
                int d = stringToIntger(b);

                int e = resultInteger(c, d);

                tvResult.setText("" + e);


            }
        });


    }

    boolean isIntegerCharacter(String s) {

        int c = -1;

        try {
            c = Integer.parseInt(s);
            return true;
        } catch (NumberFormatException e) {
            return false;
        }
    }

    int stringToIntger(String s) {
        return Integer.parseInt(s);
    }


    int resultInteger(int a, int b) {
        return a + b;
    }


    String getTextFromEditText(EditText editText) {
        String s = editText.getText().toString();

        if (TextUtils.isEmpty(s)) {
            editText.setError("Empty");
            return null;
        } else {
            editText.setError(null);
            return s;
        }

    }


}

xml part : 

<?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"
    android:layout_margin="16dp">



    <EditText
        android:hint="number One...."
        android:layout_marginTop="25dp"
        android:id="@+id/etOne"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <EditText
        android:hint="number two..."
        android:layout_marginTop="25dp"
        android:id="@+id/etTwo"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>


    <TextView
        android:textSize="25dp"
        android:textColor="@color/purple_700"
        android:layout_marginTop="20dp"
        android:id="@+id/tvResult"
        android:gravity="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Result..."
        />


    <Button
        android:layout_marginTop="25dp"
        android:id="@+id/btnPlus"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="+"/>

</LinearLayout>