Hello! In this tutorial, we will introduce how to develop Android apps using Java. Specifically, through a project that creates a password confirmation screen similar to KakaoTalk, you will learn various concepts of Android development. This project includes everything from basic UI composition to data validation and event handling, providing you with a near-real experience.
Project Overview
The password confirmation screen requires users to input a password and provides a feature to verify it. This is an essential function in many applications, playing an important role in user authentication and information protection. Through this project, you will learn the following skills:
- Creating a new project in Android Studio
- UI design through XML layout files
- Connecting UI and logic using Java
- Password validation and user feedback handling
1. Setting Up the Development Environment
The first thing you need to do for Android app development is to set up the development environment. Download and install Android Studio to establish a basic development environment. After installation, create a new project. Name the project ‘PasswordCheckApp’ and select the ‘Empty Activity’ template.
2. Configuring the XML Layout
After creating the project, modify the ‘activity_main.xml’ file located in the ‘res/layout’ folder to design the user interface (UI).
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="16dp">
<TextView
android:id="@+id/textViewTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Password Confirmation"
android:textSize="24sp"
android:layout_centerHorizontal="true"
android:layout_marginBottom="24dp"/>
<EditText
android:id="@+id/editTextPassword"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Enter your password"
android:inputType="textPassword"/>
<Button
android:id="@+id/buttonConfirm"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Confirm"
android:layout_below="@id/editTextPassword"
android:layout_centerHorizontal="true"
android:layout_marginTop="16dp"/>
<TextView
android:id="@+id/textViewResult"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/buttonConfirm"
android:layout_centerHorizontal="true"
android:layout_marginTop="16dp"
android:textSize="16sp"/>
</RelativeLayout>
The above XML code creates a title, a password input field, a confirm button, and a TextView to display the result on the screen. Users can enter their passwords and check the results using this layout.
3. Implementing the Main Activity
After configuring the XML layout, let’s connect the UI and logic in the Java file. Open the ‘MainActivity.java’ file and write the following code:
package com.example.passwordcheckapp;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private EditText editTextPassword;
private Button buttonConfirm;
private TextView textViewResult;
private static final String CORRECT_PASSWORD = "mypassword"; // Correct password
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editTextPassword = findViewById(R.id.editTextPassword);
buttonConfirm = findViewById(R.id.buttonConfirm);
textViewResult = findViewById(R.id.textViewResult);
buttonConfirm.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
checkPassword();
}
});
}
private void checkPassword() {
String inputPassword = editTextPassword.getText().toString();
if (inputPassword.isEmpty()) {
Toast.makeText(this, "Please enter your password.", Toast.LENGTH_SHORT).show();
return;
}
if (inputPassword.equals(CORRECT_PASSWORD)) {
textViewResult.setText("The password matches.");
} else {
textViewResult.setText("The password is incorrect.");
}
}
}
The above Java code implements a basic password verification logic. It compares the password entered by the user with the correct password and displays the result in the TextView. If the password is incorrect, the user is notified with a Toast message.
4. Running and Testing the Project
Once you have written the code, you can run the app on the Android Studio emulator or a real device. When the user enters the password and clicks the ‘Confirm’ button, it checks whether the password matches and displays the result on the screen.
5. Implementing Additional Features
The password confirmation screen provides basic functionality, but you can implement additional features to enhance the user experience. For example, you can add a feature to show or hide the password entered in the input field or implement a pattern lock method for password input.
Adding a Show/Hide Password Feature
Let’s add a feature that allows users to hide the password they entered. To do this, first, add an icon corresponding to the ‘EditText’, and implement a click event to show or hide the password.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="16dp">
<TextView
android:id="@+id/textViewTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Password Confirmation"
android:textSize="24sp"
android:layout_centerHorizontal="true"
android:layout_marginBottom="24dp"/>
<EditText
android:id="@+id/editTextPassword"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Enter your password"
android:inputType="textPassword"/>
<ImageView
android:id="@+id/imageViewTogglePassword"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/editTextPassword"
android:layout_marginStart="8dp"
android:src="@drawable/ic_visibility_off"/>
<Button
android:id="@+id/buttonConfirm"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Confirm"
android:layout_below="@id/editTextPassword"
android:layout_centerHorizontal="true"
android:layout_marginTop="16dp"/>
<TextView
android:id="@+id/textViewResult"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/buttonConfirm"
android:layout_centerHorizontal="true"
android:layout_marginTop="16dp"
android:textSize="16sp"/>
</RelativeLayout>
You also need to modify the Java code to add the password visualization toggle function. Add the following code in ‘MainActivity.java’:
imageViewTogglePassword = findViewById(R.id.imageViewTogglePassword);
imageViewTogglePassword.setOnClickListener(new View.OnClickListener() {
boolean isPasswordVisible = false;
@Override
public void onClick(View v) {
if (isPasswordVisible) {
editTextPassword.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_VARIATION_PASSWORD);
imageViewTogglePassword.setImageResource(R.drawable.ic_visibility_off);
} else {
editTextPassword.setInputType(InputType.TYPE_TEXT_VARIATION_VISIBLE_PASSWORD);
imageViewTogglePassword.setImageResource(R.drawable.ic_visibility);
}
isPasswordVisible = !isPasswordVisible;
editTextPassword.setSelection(editTextPassword.length());
}
});With the above code, we have set it up so that users can more conveniently enter their passwords. Now, clicking the icon will allow them to either show or hide the password.
Conclusion
Through this tutorial, you learned how to create a simple password confirmation screen using Java and Android. Since you learned about basic UI composition and handling user interactions, this will provide a good opportunity to expand the app by adding more complex features in the future. After practice, think about additional features and improvements, and trying them out is also a good way to learn.
Additionally, check out more resources and communities related to Android development, and challenge yourself with various projects. I hope this will help you in your Android development journey!