Android Form Validation

activity_submit_frorm.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <EditText
        android:id="@+id/edt_name"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:backgroundTint="@color/colorPrimaryDark"
        android:hint="@string/enter_your_name"
        android:inputType="textPersonName" />

    <EditText
        android:id="@+id/edt_email"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="10dp"
        android:layout_marginTop="10dp"
        android:backgroundTint="@color/colorPrimaryDark"
        android:hint="@string/enter_your_email"
        android:inputType="textEmailAddress" />

    <EditText
        android:id="@+id/edt_message"
        android:layout_width="fill_parent"
        android:layout_height="150dp"
        android:layout_marginBottom="10dp"
        android:layout_marginTop="10dp"
        android:backgroundTint="@color/colorPrimaryDark"
        android:gravity="top"
        android:hint="@string/enter_your_message"
        android:fitsSystemWindows="true"
        android:breakStrategy="balanced"
        android:inputType="textMultiLine"
        android:singleLine="false"
        android:padding="5dp" />

    <Button
        android:id="@+id/btn_send_form"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:background="@color/colorPrimaryDark"
        android:elevation="4dp"
        android:paddingLeft="70dp"
        android:paddingRight="70dp"
        android:text="@string/send"
        android:textColor="#fff" />

</LinearLayout>

FormValidation.java

package com.umandajayobandara.app.util;

import android.widget.EditText;

import java.util.regex.Pattern;


public class FormValidation {

    // Regular Expression
    // you can change the expression based on your need
    private static final String EMAIL_REGEX = "^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";


    // Error Messages
    private static final String REQUIRED_MSG = "required";
    private static final String EMAIL_MSG = "invalid email";


    // call this method when you need to check email validation
    public static boolean isEmailAddress(EditText editText, boolean required) {
        return isValid(editText, EMAIL_REGEX, EMAIL_MSG, required);
    }

    // call this method when you need to check phone number validation
    public static boolean isMessage(EditText editText) {
        return hasText(editText);
    }

    // return true if the input field is valid, based on the parameter passed
    public static boolean isValid(EditText editText, String regex, String errMsg, boolean required) {

        String text = editText.getText().toString().trim();
        // clearing the error, if it was previously set by some other values
        editText.setError(null);

        // text required and editText is blank, so return false
        if ( required && !hasText(editText) ) return false;

        // pattern doesn't match so returning false
        if (required && !Pattern.matches(regex, text)) {
            editText.setError(errMsg);
            return false;
        };

        return true;
    }

    // check the input field has any text or not
    // return true if it contains text otherwise false
    public static boolean hasText(EditText editText) {

        String text = editText.getText().toString().trim();
        editText.setError(null);

        // length 0 means there is no text
        if (text.length() == 0) {
            editText.setError(REQUIRED_MSG);
            return false;
        }

        return true;
    }
}

SubmitForm.java

package com.umandajayobandara.app.activity;


import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.umandajayobandara.app.R;
import com.umandajayobandara.app.util.FormValidation;

public class SubmitForm extends AppCompatActivity {



    private EditText editTextName;
    private EditText editTextEmail;
    private EditText editTextMessage;
    private Button btnSubmit;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_submit_frorm);

        submitContactUsForm();
    }

    private void submitContactUsForm() {
        editTextName = (EditText) findViewById(R.id.edt_name);
        // TextWatcher would let us check validation error on the fly
        editTextName.addTextChangedListener(new TextWatcher() {
            public void afterTextChanged(Editable s) {
                FormValidation.hasText(editTextName);
            }
            public void beforeTextChanged(CharSequence s, int start, int count, int after){}
            public void onTextChanged(CharSequence s, int start, int before, int count){}
        });

        editTextEmail = (EditText) findViewById(R.id.edt_email);
        editTextEmail.addTextChangedListener(new TextWatcher() {
            // after every change has been made to this editText, we would like to check validity
            public void afterTextChanged(Editable s) {
                FormValidation.isEmailAddress(editTextEmail, true);
            }
            public void beforeTextChanged(CharSequence s, int start, int count, int after){}
            public void onTextChanged(CharSequence s, int start, int before, int count){}
        });

        editTextMessage = (EditText) findViewById(R.id.edt_message);
        editTextMessage.addTextChangedListener(new TextWatcher() {
            public void afterTextChanged(Editable s) {
                FormValidation.isMessage(editTextMessage);
            }
            public void beforeTextChanged(CharSequence s, int start, int count, int after){}
            public void onTextChanged(CharSequence s, int start, int before, int count){}
        });

        btnSubmit = (Button) findViewById(R.id.btn_send_form);
        btnSubmit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                /*
                Validation class will check the error and display the error on respective fields
                but it won't resist the form submission, so we need to check again before submit
                 */
                if ( checkValidation () )
                    submitForm();
                else
                    Toast.makeText(getApplicationContext(), "Form contains error", Toast.LENGTH_LONG).show();
            }
        });
    }

    private void submitForm() {
        // Submit your form here. your form is valid
        Toast.makeText(this, "Submitting form...", Toast.LENGTH_LONG).show();
    }

    private boolean checkValidation() {
        boolean ret = true;

        if (!FormValidation.hasText(editTextName)) ret = false;
        if (!FormValidation.isEmailAddress(editTextEmail, true)) ret = false;
        if (!FormValidation.isMessage(editTextMessage)) ret = false;

        return ret;
    }
}