How to Validate Password from Text Input in Android?

Whenever we type the password in most social sites or any web and android application, We get an alert to add a minimum of one lowercase alphabet, minimum one uppercase alphabet, minimum one numerical digit and length of password must be greater than or equal to 8. So In this article, we are going to implement the same.

Step by Step Implementation

Step 1: Create a New Project

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Java as the programming language.

Step 2: Working with the activity_main.xml file

Navigate to the app > res > layout > activity_main.xml and add the below code to that file. Below is the code for the activity_main.xml file. 

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">

    <EditText
        android:id="@+id/addpasss"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="300dp"
        android:hint="Write Password" />

    <TextView
        android:id="@+id/atoz"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="a-z"
        android:textColor="#000"
        android:textSize="20dp" />

    <TextView
        android:id="@+id/AtoZ"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="A-z"
        android:textColor="#000"
        android:textSize="20dp" />

    <TextView
        android:id="@+id/num"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="0-9"
        android:textColor="#000"
        android:textSize="20dp" />

    <TextView
        android:id="@+id/charcount"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="8 characters"
        android:textColor="#000"
        android:textSize="20dp" />

</LinearLayout>

Step 3: Working with the MainActivity.java file

Go to the MainActivity.java file and refer to the following code. Below is the code for the MainActivity.java file. Comments are added inside the code to understand the code in more detail.

Java

import android.graphics.Color;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.widget.EditText;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

import java.util.regex.Pattern;

public class MainActivity extends AppCompatActivity {

    EditText editText;
    TextView atoz, AtoZ, num, charcount;

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

        // initialise layout
        editText = findViewById(R.id.addpasss);
        atoz = findViewById(R.id.atoz);
        AtoZ = findViewById(R.id.AtoZ);
        num = findViewById(R.id.num);
        charcount = findViewById(R.id.charcount);

        // when we start typing
        editText.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {

            }

            @Override
            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
                // get the password when we start typing
                String password = editText.getText().toString();
                validatepass(password);
            }

            @Override
            public void afterTextChanged(Editable editable) {

            }
        });
    }

    public void validatepass(String password) {

        // check for pattern
        Pattern uppercase = Pattern.compile("[A-Z]");
        Pattern lowercase = Pattern.compile("[a-z]");
        Pattern digit = Pattern.compile("[0-9]");

        // if lowercase character is not present
        if (!lowercase.matcher(password).find()) {
            atoz.setTextColor(Color.RED);
        } else {
            // if lowercase character is  present
            atoz.setTextColor(Color.GREEN);
        }

        // if uppercase character is not present
        if (!uppercase.matcher(password).find()) {
            AtoZ.setTextColor(Color.RED);
        } else {
            // if uppercase character is  present
            AtoZ.setTextColor(Color.GREEN);
        }
        // if digit is not present
        if (!digit.matcher(password).find()) {
            num.setTextColor(Color.RED);
        } else {
            // if digit is present
            num.setTextColor(Color.GREEN);
        }
        // if password length is less than 8
        if (password.length() < 8) {
            charcount.setTextColor(Color.RED);
        } else {
            charcount.setTextColor(Color.GREEN);
        }
    }
}

Output: