kotlin android app development course, app configuration file analysis

Introduction

To develop an Android app, it is essential to understand and utilize various configuration files. In this tutorial, we will analyze the roles and contents of several important configuration files for Android app development.
Kotlin is a highly effective language for managing these files while providing both productivity and stability.
This article aims to clarify the basic structure of an Android app and explore the features and content of each configuration file in-depth.

1. Basic Components of an Android App

Android apps are composed of several components, each serving a specific function. The commonly used configuration files primarily include the following:

• AndroidManifest.xml
• build.gradle
• res folder (Resource files)
• src folder (Code files)

These files provide the essential information required for the Android app to run, and we will examine the structure and roles of each file one by one.

2. AndroidManifest.xml

AndroidManifest.xml file is the core configuration file for all Android apps.
This file includes various information such as app components, permissions, and API level, enabling the Android system to execute the app correctly.

2.1. Key Attributes

– package: Defines the package name of the app, typically following the reverse order of the domain.
– permissions: Specifies the permissions that the app will require. For example, to access the internet, one must add <uses-permission android:name="android.permission.INTERNET"/>.
– activity: Defines the activities of the app and describes how each activity will operate.

Example Code

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

    <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/AppTheme">

        <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. build.gradle

Android projects utilize Gradle to manage the build process.
The build.gradle file is a critical file that handles project dependencies, SDK version settings, plugins, and more.

3.1. Key Sections

– android: Defines the basic properties of the app, such as the target SDK version and minimum SDK version.
– dependencies: Manages the libraries and modules that the app depends on.
For instance, to use Kotlin coroutines, one must add implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.9".

Example Code

apply plugin: 'com.android.application'

android {
    compileSdkVersion 30
    defaultConfig {
        applicationId "com.example.myapp"
        minSdkVersion 21
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation "androidx.appcompat:appcompat:1.2.0"
    implementation "com.google.android.material:material:1.2.1"
}
            

4. Resource Folder (res)

The res folder is a directory that manages various resources such as images, layouts, and strings.
This folder organizes resources in a structured manner for easy access.

4.1. Key Folders

• drawable: Stores image files.
• layout: Contains UI layout files.
• values: Stores various values like strings, colors, styles, etc.

Example Code

Layout file example (activity_main.xml):

<?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:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/welcome_message" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_text" />

</LinearLayout>
            

5. Code Folder (src)

The src folder is where the Kotlin code that implements the app’s business logic is stored.
It includes each activity, fragment, and other classes, making it crucial to understand the package structure.

5.1. Basic Structure

– Each activity must inherit from the Activity class and is typically controlled by screen units.
– Fragments can be combined with related UI components to construct more efficient screens.

Example Code

Main activity example (MainActivity.kt):

package com.example.myapp

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

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

6. The Importance of Analyzing Configuration Files

Analyzing and understanding configuration files is fundamental to Android app development.
Each file directly impacts the app’s policies and behaviors, user interfaces, and functions.
Therefore, it is essential to thoroughly analyze and comprehend these files before developing the app.