How to Validate Password from Text Input in Android? - GeeksforGeeks

11 Jun, 2021
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 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:
Android
Java
Java
Android
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