Hunga1ok's blog

Android logging with Timber

2023-09-24T00:00:00+02:00

Android logging with Timber

Triển khai Timber

Logging là một vấn đề không còn xa lạ với các lập trình viên. Hôm nay mình cũng sẽ trình bày về cách implement logging sử dụng thư viện Timber.

Đầu tiên thì Timber là một API cho class Log của Android. Nó bổ trợ và nâng cấp cho chức năng log của Android. Ta làm việc đó bằng cách trồng (plant) một đối tượng Tree. Để sử dụng Timber, ta khai báo việc implement timber vào build.gradle

repositories {
  mavenCentral()
}

implementation 'com.jakewharton.timber:timber:5.0.1'

Việc cài đặt timber rất dễ dàng chúng ta chỉ cần tạo một Timber Tree. Tree ở đây là một dạng cây hỗ trợ việc triển khai cách ghi log vào hệ thống mà ta có thể tự tuỳ chỉnh hoặc dùng tree default là DebugTree. Ví dụ:

class MyApplication: Application() {
    override fun onCreate() {
        super.onCreate()
        Timber.plant(Timber.DebugTree())
    }

    override fun onTerminate() {
        super.onTerminate()
        Timber.uprootAll()
    }
}

Trên đây là một cách cài đặt đợt giản, chúng ta nên cài đặt Timber sớm nhất có thể. Khi dùng chúng ta có thể dùng như log bình thường:

Timber.v("content to log")
Timber.i("content to log")
Timber.d("content to log")

Tạo một cây tuỳ chỉnh với Timber

Sau đây mình cùng tiến hành tạo một Timber Tree cho mình, ta cần override lại function log :

class LoggingCustom : Timber.Tree() {
    override fun log(priority: Int, tag: String?, message: String, t: Throwable?) {
        TODO("Not yet implemented")
    }
}

Dưới đây mình có một ví dụ về lưu custom Tree dùng với logger để lưu log vào file:

tạo 1 file FileLoggingCustom.kt

class FileLoggingCustom private constructor(
    context: Context,
    fileDir: String,
    fileName: String,
    sizeLimit: Int,
    fileLimitCount: Int,
    isAppendable: Boolean,
    tag: String,
    levelLog: Level
): Timber.Tree() {

    private var myLogger: Logger
    init {
        val path: String = File(context.getExternalFilesDir(fileDir), fileName).absolutePath
        val fileHandler: FileHandler
        val logger: Logger = MyLogger(tag)
        logger.level = levelLog
        if (logger.handlers.isEmpty()) {
            fileHandler = FileHandler(path, sizeLimit, fileLimitCount, isAppendable)
            fileHandler.formatter = SimpleFormatter()
            logger.addHandler(fileHandler)
        } else {
            fileHandler = logger.handlers[0] as FileHandler
            logger.addHandler(fileHandler)
        }

        myLogger = logger
    }

    override fun log(priority: Int, tag: String?, message: String, t: Throwable?) {
        myLogger.log(fromPriorityToLevel(priority), message)
    }

    private fun fromPriorityToLevel(priority: Int): Level {
        return when (priority) {
            Log.VERBOSE -> Level.FINER
            Log.DEBUG -> Level.FINE
            Log.INFO -> Level.INFO
            Log.WARN -> Level.WARNING
            Log.ERROR -> Level.SEVERE
            Log.ASSERT -> Level.SEVERE
            else -> Level.FINEST
        }
    }
    data class Builder(
        val context: Context,
        private var fileDir: String = "LogDir",
        private var fileName: String = "File%g.log",
        private var sizeLimit: Int = 1000_000,
        private var fileLimitCount: Int = 3,
        private var isAppendable: Boolean = true,
        private var tag: String = "FileLoggerTree",
        private var levelLog: Level = Level.ALL
    ) {
        fun fileDir(dir: String) = apply { this.fileDir = dir }
        fun fileName(name: String) = apply { this.fileName = name }
        fun sizeLimit(limit: Int) = apply { this.sizeLimit = limit }
        fun fileLimit(limit: Int) = apply { this.fileLimitCount = limit }
        fun isAppendable(append: Boolean) = apply { this.isAppendable = append }
        fun tag(tag: String) = apply { this.tag = tag }
        fun levelLog(level: Level) = apply { this.levelLog = level }
        fun build() = FileLoggingCustom(context, fileDir, fileName, sizeLimit, fileLimitCount, isAppendable, tag, levelLog)
    }
}

Khi khởi tạo Tree:

val t: Tree = FileLoggingCustom.Builder(this).build()
Timber.plant(t)

ta có thể custom lại các thông số của Logging:

val t: Tree = FileLoggingCustom.Builder(this)
                    .fileDir("DirFile")
                    .fileName("file%g.log")
                    .tag("CustomTag")
                    .sizeLimit(1000_000_000) // ~1MB
                    .fileLimit(3) // create limit 3 file
                    .levelLog(Level.ALL) // receive all log
                    .isAppendable(true) // true: append log to file, false: create new file
                    .build()
                Timber.plant(t)

File log sẽ được lưu vào path

sdcard/Android/data/your package name/DirFile/filei.log

Trên đây là một cách triển khai Timber và timber log to file.

Dưới đây là source code: Source Code

Architecture Learning Journey

2023-06-26T00:00:00+02:00

Architecture Learning Journey

In this learning journey you will learn about the Now in Android app architecture: its layers, key classes and the interactions between them.

Goals and requirements

The goals for the app architecture are:

Follow the official architecture guidance as closely as possible.
Easy for developers to understand, nothing too experimental.
Support multiple developers working on the same codebase.
Facilitate local and instrumented tests, both on the developer’s machine and using Continuous Integration (CI).
Minimize build times.

Architecture overview

The app architecture has three layers: a data layer, a domain layer and a UI layer.

The architecture follows a reactive programming model with unidirectional data flow. With the data layer at the bottom, the key concepts are:

Higher layers react to changes in lower layers.
Events flow down.
Data flows up.

The data flow is achieved using streams, implemented using Kotlin Flows.

Example: Displaying news on the For You screen

When the app is first run it will attempt to load a list of news resources from a remote server (when the prod build flavor is selected, demo builds will use local data). Once loaded, these are shown to the user based on the interests they choose.

The following diagram shows the events which occur and how data flows from the relevant objects to achieve this.

Here’s what’s happening in each step. The easiest way to find the associated code is to load the project into Android Studio and search for the text in the Code column (handy shortcut: tap ⇧ SHIFT twice).

Step	Description	Code
1	On app startup, a WorkManager job to sync all repositories is enqueued.	`Sync.initialize`
2	The `ForYouViewModel` calls `GetUserNewsResourcesUseCase` to obtain a stream of news resources with their bookmarked/saved state. No items will be emitted into this stream until both the user and news repositories emit an item. While waiting, the feed state is set to `Loading`.	Search for usages of `NewsFeedUiState.Loading`
3	The user data repository obtains a stream of `UserData` objects from a local data source backed by Proto DataStore.	`NiaPreferencesDataSource.userData`
4	WorkManager executes the sync job which calls `OfflineFirstNewsRepository` to start synchronizing data with the remote data source.	`SyncWorker.doWork`
5	`OfflineFirstNewsRepository` calls `RetrofitNiaNetwork` to execute the actual API request using Retrofit.	`OfflineFirstNewsRepository.syncWith`
6	`RetrofitNiaNetwork` calls the REST API on the remote server.	`RetrofitNiaNetwork.getNewsResources`
7	`RetrofitNiaNetwork` receives the network response from the remote server.	`RetrofitNiaNetwork.getNewsResources`
8	`OfflineFirstNewsRepository` syncs the remote data with `NewsResourceDao` by inserting, updating or deleting data in a local Room database.	`OfflineFirstNewsRepository.syncWith`
9	When data changes in `NewsResourceDao` it is emitted into the news resources data stream (which is a Flow).	`NewsResourceDao.getNewsResources`
10	`OfflineFirstNewsRepository` acts as an intermediate operator on this stream, transforming the incoming `PopulatedNewsResource` (a database model, internal to the data layer) to the public `NewsResource` model which is consumed by other layers.	`OfflineFirstNewsRepository.getNewsResources`
11	`GetUserNewsResourcesUseCase` combines the list of news resources with the user data to emit a list of `UserNewsResource`s.	`GetUserNewsResourcesUseCase.invoke`
12	When `ForYouViewModel` receives the saveable news resources it updates the feed state to `Success`. `ForYouScreen` then uses the saveable news resources in the state to render the screen.	Search for instances of `NewsFeedUiState.Success`

Data layer

The data layer is implemented as an offline-first source of app data and business logic. It is the source of truth for all data in the app.

Each repository has its own models. For example, the TopicsRepository has a Topic model and the NewsRepository has a NewsResource model.

Repositories are the public API for other layers, they provide the only way to access the app data. The repositories typically offer one or more methods for reading and writing data.

Reading data

Data is exposed as data streams. This means each client of the repository must be prepared to react to data changes. Data is not exposed as a snapshot (e.g. getModel) because there’s no guarantee that it will still be valid by the time it is used.

Reads are performed from local storage as the source of truth, therefore errors are not expected when reading from Repository instances. However, errors may occur when trying to reconcile data in local storage with remote sources. For more on error reconciliation, check the data synchronization section below.

Example: Read a list of topics

A list of Topics can be obtained by subscribing to TopicsRepository::getTopics flow which emits List<Topic>.

Whenever the list of topics changes (for example, when a new topic is added), the updated List<Topic> is emitted into the stream.

Writing data

To write data, the repository provides suspend functions. It is up to the caller to ensure that their execution is suitably scoped.

Example: Follow a topic

Simply call UserDataRepository.toggleFollowedTopicId with the ID of the topic the user wishes to follow and followed=true to indicate that the topic should be followed (use false to unfollow a topic).

Data sources

A repository may depend on one or more data sources. For example, the OfflineFirstTopicsRepository depends on the following data sources:

Name	Backed by	Purpose
TopicsDao	Room/SQLite	Persistent relational data associated with Topics
NiaPreferencesDataSource	Proto DataStore	Persistent unstructured data associated with user preferences, specifically which Topics the user is interested in. This is defined and modeled in a .proto file, using the protobuf syntax.
NiaNetworkDataSource	Remote API accessed using Retrofit	Data for topics, provided through REST API endpoints as JSON.

Data synchronization

Repositories are responsible for reconciling data in local storage with remote sources. Once data is obtained from a remote data source it is immediately written to local storage. The updated data is emitted from local storage (Room) into the relevant data stream and received by any listening clients.

This approach ensures that the read and write concerns of the app are separate and do not interfere with each other.

In the case of errors during data synchronization, an exponential backoff strategy is employed. This is delegated to WorkManager via the SyncWorker, an implementation of the Synchronizer interface.

See the OfflineFirstNewsRepository.syncWith for an example of data synchronization.

Domain layer

The domain layer contains use cases. These are classes which have a single invocable method (operator fun invoke) containing business logic.

These use cases are used to simplify and remove duplicate logic from ViewModels. They typically combine and transform data from repositories.

For example, GetUserNewsResourcesUseCase combines a stream (implemented using Flow) of NewsResources from a NewsRepository with a stream of UserData objects from a UserDataRepository to create a stream of UserNewsResources. This stream is used by various ViewModels to display news resources on screen with their bookmarked state.

Notably, the domain layer in Now in Android does not (for now) contain any use cases for event handling. Events are handled by the UI layer calling methods on repositories directly.

UI Layer

The UI layer comprises:

UI elements built using Jetpack Compose
Android ViewModels

The ViewModels receive streams of data from use cases and repositories, and transforms them into UI state. The UI elements reflect this state, and provide ways for the user to interact with the app. These interactions are passed as events to the ViewModel where they are processed.

Modeling UI state

UI state is modeled as a sealed hierarchy using interfaces and immutable data classes. State objects are only ever emitted through the transform of data streams. This approach ensures that:

the UI state always represents the underlying app data - the app data is the source-of-truth.
the UI elements handle all possible states.

Example: News feed on For You screen

The feed (a list) of news resources on the For You screen is modeled using NewsFeedUiState. This is a sealed interface which creates a hierarchy of two possible states:

Loading indicates that the data is loading
Success indicates that the data was loaded successfully. The Success state contains the list of news resources.

The feedState is passed to the ForYouScreen composable, which handles both of these states.

Transforming streams into UI state

ViewModels receive streams of data as cold flows from one or more use cases or repositories. These are combined together, or simply mapped, to produce a single flow of UI state. This single flow is then converted to a hot flow using stateIn. The conversion to a state flow enables UI elements to read the last known state from the flow.

Example: Displaying followed topics

The InterestsViewModel exposes uiState as a StateFlow<InterestsUiState>. This hot flow is created by obtaining the cold flow of List<FollowableTopic> provided by GetFollowableTopicsUseCase. Each time a new list is emitted, it is converted into an InterestsUiState.Interests state which is exposed to the UI.

Processing user interactions

User actions are communicated from UI elements to ViewModels using regular method invocations. These methods are passed to the UI elements as lambda expressions.

Example: Following a topic

The InterestsScreen takes a lambda expression named followTopic which is supplied from InterestsViewModel.followTopic. Each time the user taps on a topic to follow this method is called. The ViewModel then processes this action by informing the user data repository.

How to create a SimpleDateFormat

2022-05-12T00:00:00+02:00

SimpleDateFormat

Table content for reference:

Letter	Date or Time Component	Presentation	Examples
G	Era designator	Text	AD
y	Year	Year	1996; 96
Y	Week year	Year	2009; 09
M	Month in year	Month	July; Jul; 07
w	Week in year	Number	27
W	Week in month	Number	2
D	Day in year	Number	189
d	Day in month	Number	10
F	Day of week in month	Number	2
E	Day name in week	Text	Tuesday; Tue
u	Day number of week (1 = Monday, …, 7 = Sunday)	Number	1
a	Am/pm marker	Text	PM
H	Hour in day (0-23)	Number	0
k	Hour in day (1-24)	Number	24
K	Hour in am/pm (0-11)	Number	0
h	Hour in am/pm (1-12)	Number	12
m	Minute in hour	Number	30
s	Second in minute	Number	55
S	Millisecond	Number	978
z	Time zone	General time zone	Pacific Standard Time; PST; GMT-08:00
Z	Time zone	RFC 822 time zone	-0800
X	Time zone	ISO 8601 time zone	-08; -0800; -08:00

##Some code extensions kotlin:

I use JodaTime library for support handle features

fun String?.formatHour(toPattern: String) = formatHour("HH:mm:ss", toPattern)

fun String?.formatHour(fromPattern: String, toPattern: String): String {
    if (this == null) return ""
    return try {
        DateTime.parse(this, DateTimeFormat.forPattern(fromPattern)).toString(toPattern)
    } catch (e: Exception) {
        "Invalid Date"
    }
}

fun String?.formatDate(toPattern: String): String {
    if (this == null) return ""
    return try {
        DateTime(this).toString(toPattern)
    } catch (e: Exception) {
        "Invalid Date"
    }
}

fun String?.formatDate(fromPattern: String, toPattern: String): String {
    if (this == null) return ""
    return try {
        DateTime.parse(this, DateTimeFormat.forPattern(fromPattern)).toString(toPattern)
    } catch (e: Exception) {
        "Invalid Date"
    }
}

fun String?.parseDate(pattern: String? = null): DateTime? {
    if (this == null) return null
    return try {
        pattern?.let { DateTime.parse(this, DateTimeFormat.forPattern(pattern)) } ?: DateTime(this)
    } catch (e: Exception) {
        null
    }
}

Android Developer Roadmap

2022-05-05T00:00:00+02:00

A complete roadmap to learn Android App Development. This roadmap will help you in becoming a complete Android Developer.

Roadmap to learn Android App Development

Programming
- Java
- Kotlin
Android Studio
- Android Studio IDE Overview
- Project Structure * Java/Kotlin * XML * .gradle files
Android Component
- Activity
  - Activity Lifecycle
  - Tasks & Back Stack
- Service
- Broadcast Receiver
- Content Provider
Intents
- Types of Intent
  - Implicit
  - Explicit
- Intent Filter
Static User Interface
- View
  - Button, ImageView, TextView, EditText etc
- ViewGroup * LinearLayout, RelativeLayout, FrameLayout, ConstraintLayout
Dynamic User Interface
- RecyclerView
- ViewPager
- Spinner
CustomView
- Canvas
- Bitmap
- Paint
UI Resources
- Drawables
- String
- Styles
Fragments
- Fragment Lifecycle
- Fragment Manager
Support User Interface
- ProgressBar
- Dialogs
- Toast & Snackbar
Storage
- Shared Preferences
- File Systems
- Database
  - RoomDB
Build
- Gradle
- Debug / Release Configuration
Threading
- Threads
- Handler / Looper
Debugging
- Memory profiling
- Logging
- Systrace
- Exceptions
- Error Handling
Memory Leak
- Detecting and Fixing Memory Leaks
- Context
3rd Party Library
- Image Loading
  - Glide
  - Picasso
- Dependency Injection
  - Dagger
- Networking
  - Fast Android Networking Library
  - Retrofit
- MultiThreading
  - RxJava
  - Coroutines
Data Format
- JSON
  - GSON
- Flat Buffer
- Protocol Buffer
Android Jetpack
- Foundation Components
  - AppCompat
  - Android KTX
  - Multidex
- Architecture Components
  - LiveData
  - ViewModel
  - DataBinding
  - Paging
  - Work Manager
  - Navigation
- Behaviour Components
  - Download Manager
  - Media Playback
  - Notification
  - Permissions
  - Preference
  - Sharing
  - Slice
- UI Component
  - Animation & Transition
  - Android Auto
  - Emoji
  - Palette
  - Android TV
  - Android Wear
Architecture
- MVVM
- MVI
- MVP
Unit Testing * Local Unit Testing * Instrumentation Testing
Firebase
- FCM
- Crashlytics
- Analytics
- Remote Config
- App Indexing
- Dynamic Link
Security
- Encrypt / Decrypt
- Proguard
- R8
App Release
- .keystore file
- App Bundle
- Playstore
Keep Learning and Improving

Hunga1ok's blog

Android logging with Timber

Android logging with Timber

Triển khai Timber

Tạo một cây tuỳ chỉnh với Timber

Architecture Learning Journey

Architecture Learning Journey

Goals and requirements

Architecture overview

Example: Displaying news on the For You screen

Data layer

Reading data

Writing data

Data sources

Data synchronization

Domain layer

UI Layer

Modeling UI state

Transforming streams into UI state

Processing user interactions

Further reading

How to create a SimpleDateFormat

SimpleDateFormat

Android Developer Roadmap

Roadmap to learn Android App Development