Validations in Android

Validating EditText input in Android is a common task to ensure that the user enters the correct type of data. This can include checking for empty fields, validating email addresses, enforcing a certain length, or ensuring numeric input. Here’s a basic guide on how to perform EditText validations in Android:

1. Empty Field Validation:

• Check if the EditText is empty when the user submits the form.

EditText editText = findViewById(R.id.editText);
String input = editText.getText().toString().trim();

if (input.isEmpty()) {
    // Show an error message, the field is empty
    editText.setError("Field cannot be empty");
} else {
    // Continue processing the input
}

Email Validation:

• Use a regular expression to validate the email format.

String emailPattern = "[a-zA-Z0-9._-]+@[a-z]+\\.+[a-z]+";

if (!input.matches(emailPattern)) {
    // Show an error message, invalid email format
    editText.setError("Invalid email address");
} else {
    // Continue processing the input
}

Numeric Validation:

• Ensure that the input is a valid numeric value.

if (!TextUtils.isDigitsOnly(input)) {
    // Show an error message, non-numeric input
    editText.setError("Please enter a numeric value");
} else {
    // Continue processing the input
}

Password Validation:

• Implement password validation, such as checking for a minimum length

int minLength = 6;

if (input.length() < minLength) {
    // Show an error message, password too short
    editText.setError("Password must be at least " + minLength + " characters");
} else {
    // Continue processing the input
}

Custom Validation:

• Implement custom validation based on your specific requirements.

// Example: Check if the input contains a specific substring
String requiredSubstring = "android";

if (!input.contains(requiredSubstring)) {
    // Show an error message, required substring not found
    editText.setError("Input must contain '" + requiredSubstring + "'");
} else {
    // Continue processing the input
}

Clearing Error:

• Clear the error when the user corrects the input.

MainActivity.Java

editText.setError(null);

package com.androindian.validations;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {
    Button bCancel, bProceed;

    // four text fields
    EditText etFirstName, etLastName, etEmail, etPassword;

    // one boolean variable to check whether all the text fields
    // are filled by the user, properly or not.
    boolean isAllFieldsChecked = false;

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

        // register buttons with their proper IDs.
        bProceed = findViewById(R.id.proceedButton);
        bCancel = findViewById(R.id.cancelButton);

        // register all the EditText fields with their IDs.
        etFirstName = findViewById(R.id.firstName);
        etLastName = findViewById(R.id.lastName);
        etEmail = findViewById(R.id.email);
        etPassword = findViewById(R.id.password);

        // handle the PROCEED button
        bProceed.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                // store the returned value of the dedicated function which checks
                // whether the entered data is valid or if any fields are left blank.
                isAllFieldsChecked = CheckAllFields();

                // the boolean variable turns to be true then
                // only the user must be proceed to the activity2
                if (isAllFieldsChecked) {
                    Toast.makeText(MainActivity.this,"Valid",Toast.LENGTH_LONG).show();
                }
            }
        });

        // if user presses the cancel button then close the
        // application or the particular activity.
        bCancel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                MainActivity.this.finish();
                System.exit(0);
            }
        });
    }

    // function which checks all the text fields
    // are filled or not by the user.
    // when user clicks on the PROCEED button
    // this function is triggered.
    private boolean CheckAllFields() {
        if (etFirstName.length() == 0) {
            etFirstName.setError("This field is required");
            return false;
        }

        if (etLastName.length() == 0) {
            etLastName.setError("This field is required");
            return false;
        }

        if (etEmail.length() == 0) {
            etEmail.setError("Email is required");
            return false;
        }

        if (etPassword.length() == 0) {
            etPassword.setError("Password is required");
            return false;
        } else if (etPassword.length() < 8) {
            etPassword.setError("Password must be minimum 8 characters");
            return false;
        }

        // after all validation return true.
        return true;
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<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:orientation="vertical"
    tools:context=".MainActivity"
    tools:ignore="HardcodedText">

    <EditText
        android:id="@+id/firstName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:hint="First Name"
        android:inputType="text" />

    <EditText
        android:id="@+id/lastName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:hint="Last Name"
        android:inputType="text" />

    <EditText
        android:id="@+id/email"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:hint="Email"
        android:inputType="textEmailAddress" />

    <EditText
        android:id="@+id/password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:hint="Password"
        android:inputType="textPassword" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:gravity="end"
        android:orientation="horizontal">

        <Button
            android:id="@+id/cancelButton"
            style="@style/Widget.AppCompat.Button.Borderless"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginEnd="4dp"
            android:text="CANCEL"
             />

        <Button
            android:id="@+id/proceedButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginEnd="16dp"

            android:text="PROCEED"
            android:textColor="@android:color/white"
            tools:ignore="ButtonStyle" />

    </LinearLayout>
</LinearLayout>