Category: Kotlin Android app development

In Android app development, tasks related to image processing occur very frequently. Various functionalities such as image loading, caching, transformation, and display are required, and there are libraries that help facilitate these tasks. Among them, the library Glide is widely used due to its lightweight nature and efficiency. In this tutorial, we will learn in detail how to efficiently handle images in Android applications using the Glide library.

1. What is the Glide Library?

Glide is an image loading and caching library developed by BumpTech. Glide provides optimized images for various screen resolutions and sizes on Android, enhancing performance and user experience. Its main features include:

• Image Loading: Supports loading images via HTTPS and HTTP.
• Caching: Improves loading speed through memory and disk caching.
• Transformation: Provides various transformation functions to manipulate images into desired shapes.
• Animation: Can add animation effects during image transitions.

2. How to Install Glide

To add the Glide library to your project, you first need to add the following dependencies to the build.gradle (app) file:

dependencies {
    implementation 'com.github.bumptech.glide:glide:4.14.2'
    annotationProcessor 'com.github.bumptech.glide:compiler:4.14.2'
}

After adding the dependencies, sync Gradle to apply the changes. Next, you need to add internet permissions to your manifest file:

<uses-permission android:name="android.permission.INTERNET"/>

3. How to Use Glide

3.1. Loading Images

The basic way to load images using Glide is as follows:

Glide.with(context)
    .load("https://example.com/image.jpg")
    .into(imageView);

The above code loads an image through its URL and displays it in a ImageView.

3.2. Loading Images from Resources

It is also possible to load images from the app’s resources folder. Below is an example of loading an image from drawable resources:

Glide.with(context)
    .load(R.drawable.sample_image)
    .into(imageView);

3.3. Bitmap Conversion

If you need to convert an image into bitmap form, Glide provides a method to easily retrieve the converted image:

Glide.with(context)
    .asBitmap()
    .load("https://example.com/image.jpg")
    .into(new SimpleTarget() {
        @Override
        public void onResourceReady(@NonNull Bitmap resource, @Nullable Transition transition) {
            // Get bitmap here
        }
    });

3.4. Resizing

When loading images with Glide, you can resize the images using the override() method:

Glide.with(context)
    .load("https://example.com/image.jpg")
    .override(600, 400) // width 600px, height 400px
    .into(imageView);

4. Image Transformation and Filtering

Glide provides the ability to apply various transformation filters to images. For example, you can use the CircleCrop transformer to convert an image into a circular shape:

Glide.with(context)
    .load("https://example.com/image.jpg")
    .apply(RequestOptions.circleCropTransform())
    .into(imageView);

5. Caching Strategies

By default, Glide automatically handles memory and disk caching when loading images, but you can set caching strategies as needed. For example, you can change the cache strategy using the diskCacheStrategy method:

Glide.with(context)
    .load("https://example.com/image.jpg")
    .diskCacheStrategy(DiskCacheStrategy.ALL) // use all cache strategies
    .into(imageView);

6. Additional Features of Glide

Glide offers various additional features beyond image loading, and here are a few:

6.1. Animation

You can add animation effects when loading images via Glide:

Glide.with(context)
    .load("https://example.com/image.jpg")
    .transition(DrawableTransitionOptions.withCrossFade()) // fade-in animation
    .into(imageView);

6.2. Placeholder and Error Images

You can set placeholder images to show while loading images and error images to show if loading fails:

Glide.with(context)
    .load("https://example.com/image.jpg")
    .placeholder(R.drawable.loading)  // image to display while loading
    .error(R.drawable.error)           // image to display on load failure
    .into(imageView);

6.3. Loading GIF Images

Glide also supports loading GIF images, allowing for efficient handling of dynamic images:

Glide.with(context)
    .asGif()
    .load("https://example.com/animation.gif")
    .into(imageView);

7. Pros and Cons of Glide

Glide offers powerful features and performance, but it comes with its own advantages and disadvantages.

7.1. Advantages

• Easy to use: You can easily load and process images with just a few lines of code.
• Efficient caching: The loading speed of images is fast due to memory and disk caching.
• Various transformation functions: You can easily change the size and shape of images.

7.2. Disadvantages

• Performance issues: When processing a large number of images, appropriate settings are needed.
• Memory management: Loading too many images at once can cause OOM (Out of Memory) errors.

8. Conclusion

Glide is a very useful library for simplifying and efficiently performing image processing tasks in Android apps. This allows developers easily to implement various functionalities related to image loading, caching, transformation, and display. In today’s tutorial, we learned about the basic usage of Glide and some of its useful features. I hope you utilize Glide in your future projects to build efficient and appealing UIs!

9. References

• Glide GitHub Repository
• Glide Documentation

Android app development is currently one of the preferred fields among many developers. In this article, we will detail how to create a simple image-sharing app using Kotlin. Through this process, you will learn how to handle user authentication, upload and display images, and utilize cloud services like Firebase.

1. Preparing the Project

After installing Android Studio, create a new project. Choose the following settings:

• Project Name: ImageShareApp
• Package Name: com.example.imageshareapp
• Language: Kotlin
• Minimum API Level: API 21 (Lollipop)

2. Firebase Setup

This app stores and manages image data through Firebase. You need to set up Firebase’s Realtime Database and Storage.

1. Log in to the Firebase console.
2. Create a new project.
3. Add an Android app in the project settings and enter the package name.
4. Download the google-services.json file and add it to the app directory of the project.

Now, activate Firebase Realtime Database and Firebase Storage.

Firebase Gradle Setup

Add Firebase dependencies to your project’s build.gradle file:

dependencies {
    implementation platform("com.google.firebase:firebase-bom:30.0.0")
    implementation "com.google.firebase:firebase-storage"
    implementation "com.google.firebase:firebase-database"
}

3. UI Design

Here’s how to design the basic layout of the app. Open the activity_main.xml file and add the following code to create the 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">

    <Button
        android:id="@+id/button_upload"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Upload Image"/>

    <ListView
        android:id="@+id/list_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/button_upload">
    </ListView>

</RelativeLayout>

4. Select and Upload Image

This is the necessary code to select an image and upload it to Firebase Storage. Add the following code in MainActivity.kt:

import android.content.Intent
import android.net.Uri
import android.os.Bundle
import android.view.View
import android.widget.Button
import android.widget.ListView
import androidx.appcompat.app.AppCompatActivity
import androidx.core.app.ActivityCompat
import com.google.firebase.storage.FirebaseStorage
import com.google.firebase.database.FirebaseDatabase

class MainActivity : AppCompatActivity() {

    private lateinit var storage: FirebaseStorage
    private lateinit var database: FirebaseDatabase
    private val IMAGE_PICK_CODE = 1000
    private var imageUri: Uri? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        storage = FirebaseStorage.getInstance()
        database = FirebaseDatabase.getInstance()

        findViewById(R.id.button_upload).setOnClickListener {
            pickImage()
        }
    }

    private fun pickImage() {
        val intent = Intent(Intent.ACTION_PICK)
        intent.type = "image/*"
        startActivityForResult(intent, IMAGE_PICK_CODE)
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if (requestCode == IMAGE_PICK_CODE && resultCode == RESULT_OK && data != null) {
            imageUri = data.data
            uploadImage()
        }
    }

    private fun uploadImage() {
        val fileRef = storage.reference.child("images/${System.currentTimeMillis()}.jpg")
        imageUri?.let { uri ->
            fileRef.putFile(uri).addOnSuccessListener { taskSnapshot ->
                // Get the URL after successfully uploading.
                fileRef.downloadUrl.addOnSuccessListener { uri ->
                    saveImageUrlToDatabase(uri.toString())
                }
            }.addOnFailureListener { e ->
                // Handle errors
            }
        }
    }

    private fun saveImageUrlToDatabase(imageUrl: String) {
        val imageRef = database.reference.child("images").push()
        imageRef.setValue(imageUrl)
    }
}

5. Displaying the Image List

To display the uploaded images in the ListView, add the following code.

import android.widget.AdapterView
import android.widget.ArrayAdapter
import com.google.firebase.database.DataSnapshot
import com.google.firebase.database.DatabaseError
import com.google.firebase.database.ValueEventListener
import com.google.firebase.database.ktx.database
import com.google.firebase.ktx.Firebase

class MainActivity : AppCompatActivity() {
    // omitted...

    override fun onCreate(savedInstanceState: Bundle?) {
        // omitted...

        loadImageUrls()
    }

    private fun loadImageUrls() {
        database.reference.child("images").addValueEventListener(object : ValueEventListener {
            override fun onDataChange(snapshot: DataSnapshot) {
                val imageUrls = mutableListOf()
                for (imageSnapshot in snapshot.children) {
                    val imageUrl = imageSnapshot.getValue(String::class.java)
                    imageUrls.add(imageUrl ?: "")
                }
                displayImages(imageUrls)
            }

            override fun onCancelled(error: DatabaseError) {
                // Handle errors
            }
        })
    }

    private fun displayImages(imageUrls: List) {
        val adapter = ArrayAdapter(this, android.R.layout.simple_list_item_1, imageUrls)
        findViewById(R.id.list_view).adapter = adapter
    }
}

6. Running the App

Once all the code is prepared, run the app. Check if the image upload and list display functions are working well. If issues arise, check the errors via Logcat.

7. Improving the App

After creating the basic image-sharing app, you can improve the app by adding features such as:

• Displaying the image list in thumbnail format
• Adding a preview feature when selecting an image
• Implementing user authentication for personalized image sharing
• Improving the app’s UI/UX

Conclusion

In this lecture, we explored the process of creating a simple image-sharing app using Kotlin. By utilizing Firebase, you can easily store and manage data without setting up a server. Furthermore, you can continuously improve it by adding various features. I hope this lecture helps you in your Android app development journey.

In Android application development, the user interface (UI) is a crucial element that significantly affects user experience. Among these, the App Bar serves as the main navigation and access point of the application, intuitively providing users with important functionalities. In this post, we will delve into the concept of the App Bar, how to use it, and provide an implementation example using Kotlin.

What is an App Bar?

The App Bar is an element primarily used for user interaction within the application, displaying the title and actions. Typically, an App Bar consists of the following components:

• Title: Displays the title of the current screen.
• Navigation Icon: Displays icons for navigation, such as returning to the previous screen.
• Action Icons: Displays icons for actions that the user can perform (e.g., search, add, delete, etc.).

Advantages of an App Bar

• Clear Navigation: Helps users understand their current location and navigate easily.
• Consistent Design: Maintains the same style throughout the application.
• Easy Access to Tasks: Allows frequent functionalities to be quickly accessible.

Implementing an App Bar

In this section, we will look at how to implement an App Bar using Kotlin in Android Studio.

1. Create a Project

Run Android Studio and create a new app project. Select the Empty Activity template to set up the basic structure.

2. Configure Gradle

Check if the following library is included in your project’s build.gradle file:

implementation 'androidx.appcompat:appcompat:1.5.0'

3. Create a Layout File

Edit the activity_main.xml file that composes the application’s UI to add the App Bar. Try using the following code:

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <com.google.android.material.appbar.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
            app:titleTextColor="@android:color/white"
            android:background="@color/purple_500"/>

    </com.google.android.material.appbar.AppBarLayout>

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <!-- Add other UI elements here -->
    </FrameLayout>

</androidx.coordinatorlayout.widget.CoordinatorLayout>

4. Set Up MainActivity

Now, open the MainActivity.kt file and set up the App Bar as follows:

package com.example.myapplication

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.appcompat.widget.Toolbar

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val toolbar: Toolbar = findViewById(R.id.toolbar)
        setSupportActionBar(toolbar)
        supportActionBar?.title = "My App Title"
    }
}

5. Adding Menu Items

To add menu items to the App Bar, create a res/menu directory and add a new XML file (menu_main.xml). Define the menu items as follows:

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/action_settings"
        android:title="Settings"
        android:orderInCategory="100"
        android:showAsAction="never" />
</menu>

6. Connecting the Menu to Activity

Now, connect the menu items in the MainActivity.kt file:

override fun onCreateOptionsMenu(menu: Menu?): Boolean {
    menuInflater.inflate(R.menu.menu_main, menu)
    return true
}

override fun onOptionsItemSelected(item: MenuItem): Boolean {
    return when (item.itemId) {
        R.id.action_settings -> {
            // Action upon clicking the settings menu
            true
        }
        else -> super.onOptionsItemSelected(item)
    }
}

Conclusion

In this post, we examined the concept of the App Bar and how to implement it in Android applications. The App Bar is an essential element for providing a better user experience as users interact with the application. By following the steps outlined above, you can easily add an App Bar to your application.

We will continue to provide in-depth content through various Android app development courses. Thank you!

Android is one of the most widely used mobile operating systems in the world. In the process of developing apps on this Android platform, Kotlin has established itself as one of the most popular languages due to its exceptional expressiveness and conciseness. This tutorial will provide in-depth explanations and practical example codes on how to run Android apps using Kotlin.

1. Setting Up the Android Development Environment

To develop Android apps, you first need to set up your development environment. It is essential to install Android Studio and configure the necessary SDKs and tools.

1. Download and Install Android Studio
   – Download Android Studio from the official website.
   – Run the installer to install the latest version.
2. Install SDK and Tools
   – When you first run Android Studio, you will be prompted to install the necessary SDKs and tools. You should install all the basics at this step.
3. Set Up AVD (Android Virtual Device)
   – Configure a virtual device through the AVD Manager in Android Studio. Select the required device specifications and create the virtual device.

2. Creating a New Project

The first step to run the app is to create a new Android project. To do this, follow these steps in Android Studio.

1. Run Android Studio and select ‘Start a new Android Studio project’.
2. Select ‘Empty Activity’ to start with minimal settings.
3. Set the project name, package name, and save location, and select Kotlin as the language.
4. Finally, click the ‘Finish’ button to create the project.

3. Basic App Structure

In the newly created project, you can see the basic app structure. The main components are as follows.

• Manifest File: The AndroidManifest.xml file defines the components and permissions of the app.
• Layout File: The activity_main.xml file defines the UI elements.
• Kotlin File: The MainActivity.kt file contains the logic of the app.

3.1. AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myfirstapp">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.MyFirstApp">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
    </application>

    </manifest>

3.2. activity_main.xml

The layout file defines the basic UI elements. We will add a button and a text view here.

<?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">

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Hello, Kotlin!"
            android:textSize="24sp"/>

        <Button
            android:id="@+id/button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Click Me!" />

    </LinearLayout>

3.3. MainActivity.kt

The MainActivity file defines the app’s behavior. We will add functionality to change the text when the button is clicked.

package com.example.myfirstapp

    import android.os.Bundle
    import android.widget.Button
    import android.widget.TextView
    import androidx.appcompat.app.AppCompatActivity

    class MainActivity : AppCompatActivity() {
        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)

            val textView: TextView = findViewById(R.id.textView)
            val button: Button = findViewById(R.id.button)

            button.setOnClickListener {
                textView.text = "Button has been clicked!"
            }
        }
    }

4. Running the App

The process of running the app is divided into two main steps.

1. Prepare a Virtual Device or a Real Device
   Use the virtual device set up through the AVD Manager or connect a real Android device with USB debugging mode enabled.
2. Run the App
   Click the ‘Run’ button in Android Studio to run the app. Once the initial build is complete, the app will start on the virtual or real device.

5. Troubleshooting

There are common issues that may occur while running the app. This section introduces some common problems and their solutions.

• Runtime Errors: If a Gradle sync error occurs, click the ‘Sync Now’ button or select ‘Sync Project with Gradle Files’ from the ‘File’ menu.
• App Crashes: Open Logcat to analyze the error logs. Find and fix the issue in the code.
• UI Issues: Double-check the XML layout file to ensure that all views are properly set up.

6. Conclusion

In this tutorial, we learned the basic methods of running Android apps using Kotlin. We covered the overall process from creating a new project, setting up the UI, to running a functioning app. I hope you continue your Android app development journey with the simplicity and powerful features of Kotlin.

7. Additional Resources

For deeper learning about Android app development, please refer to the following resources.

• Official Android Documentation
• Official Kotlin Documentation
• Udacity Android App Development Course