当前位置：网站首页>Android kotlin learning

Android kotlin learning

2022-06-27 18:23:00 【Manon Park】

This is a course that you can learn Kotlin Basic knowledge courses .Android Applications can also use Java Development , but Google in Android Announcement in development Kotlin First And from Kotlin Created an easy to use Android API, So if you want to learn from now on Android, As to the Kotlin Study . Better go to .

Understand in Kotlin Created in Android Application basics .

Introduction to the contents of each course

Because the content is written in English , It may be difficult to get started .
I can explain the content of each course in Japanese , So it may be easier to see the content .

Kotlin Training camp courses

I will explain Kotlin Bootcamp Each project of the course .
https://codelabs.developers.google.com/kotlin-bootcamp/

Welcome to the course

https://codelabs.developers.google.com/codelabs/kotlin-bootcamp-welcome/#0
You need programming experience in object-oriented languages or IDE Development experience to participate in the course . Course content is written .

Start （3 A mission ） 9%

The contents are as follows , You can get to know Kotlin.

  • Kotlin be relative to Java The advantages of
    • robust （ For example, mechanisms that are unlikely to cause null exceptions ）
    • Complete and readable code （Java One line of code can write 20 Row or so ）
    • And Java compatible （ have access to Java library , Can be Kotlin Put it in Java In the project ）
  • How to install JDK（ function Kotlin Program needs to be installed Java）
  • IntelliJ IDEA Installation （Kotlin Easy to write IDE install ）
  • Try to use “Kotlin REPL” Show Hello World
    • Use REPL = Read-Eval-Print Loop, It reads with Kotlin Code written , Execute it and output the results . It's like a shell .
  • Kotlin Basic syntax

Kotlin Of Hello World

fun printHello() {
            println ("Hello World") } printHello()

Kotlin Basic knowledge of （4 A mission ）21%

  • Study Koltin Basic syntax . Let's try to write a program , At the same time Kotlin REPL * Actually enter it in .
    • val, var: Variable declarations , Can be reassigned
    • Int、Double And its transformation
    • Strings and string templates
    • If something else
    • Time ： About Kotlin Version of switch
    • Nullability and how to deal with it
      • Kotlin It is divided into Nullable The type and NunNull type , So if you do it in a programming language that is not yet separate , You should do this .
    • list , Array
    • for loop

* REPL = Read-Eval-Print Loop, Read Kotlin Written code , perform , Output results . It's like a shell .

function （6 A mission ） 40%

  • Create a Kotlin File, Definition main function , Output Hello World.
  • How to pass parameters in the main function
  • stay Kotlin in ,if Statements, etc. have values , So it can be written like this 
val isHot = if (temperature > 50) true else false
  • How to make a function
  • Code examples using functions
  • Default parameters
  • Single expression functions 
fun isTooHot(temperature: Int) {
            return temperature > 30 } fun isTooHot(temperature: Int) = temperature > 30
  • use filter() Filter the contents of the list
  • Sequence And a normal list .（ I think it's a little difficult here , But even if you don't understand , natural Android Development is no problem （ The computational complexity is so high that asSequence Things are difficult to deal with ）, So I think I can skip .)
  • Ramda

object-oriented programming （7 A mission ） 62%

  • Creating Aquarium Class , We will touch Kotlin Class .
  • Data class ： Classes with useful properties
  • Use keywords singleton: object You can easily create a singleton （ There is a story about interface delegation （ class A：B by C）, But this function is very convenient , But it's not a messy function , So even if you continue not to understand . Let's go ）
  • Enumeration class
  • Sealing class ： image enum You can also enumerate , Classes that can be instantiated , It can be used in error handling and other situations , It seems better to have a look .

Expand （4 A mission ） 75%

  • There's a way , Return to one Pair
    , It was written at the beginning , But at first sight it is hard to understand , So let me explain .

It's a story , You can use the following List The return name of the method is Pair Instance of class for ,partition() So that we can put List Divided into two groups. .

>>> data class Fish(val name : String) >>> val fishList = listOf(Fish("medaka"), Fish("koi"), Fish("maguro")) >>> fun isFreshWater(fish: Fish) = listOf("medaka", "koi").contains(fish.name) >>> val twoLists = fishList.partition {
            isFreshWater(it) } //  >>> println(twoLists) ([Fish(name=medaka), Fish(name=koi)], [Fish(name=maguro)]) >>> println("freshwater: ${twoLists.first}") freshwater: [Fish(name=medaka), Fish(name=koi)] >>> println("saltwater: ${twoLists.second}") saltwater: [Fish(name=maguro)]
  • How to make Pair：“A” To “B” You can create “A” and “B” Of Pair Class
  • One can be disassembled Pair The story of . Yes, it can be decomposed into val (a, b) = pair.
  • How to make and use lists .
  • const vs val The story of ：const Is determined at compile time . In this way
  • How to write extension functions 、 attribute

Generic （3 A mission ）84%

It is used for list types , for example List.

  • How to use basic generics
  • How to declare Nullable、NonNull The generic type
  • Generic input and output
  • The story of adding generics to functions
  • Use specific types of stories .（ This will resolve the generic type at compile time , So you can access the class name 、 Cast and determine ）

Function operation （5 A mission ） 100%

About Kotlin There has been a deeper story .

  • How to make and use annotations
  • Break by tag （ Avoid double circulation, etc ）
  • Easy to use ramda
  • Try making it yourself with () and that with ()
  • Operation yield, etc
  • Talk about using inline functions to reduce memory and CPU expenses
  • SAM transformation A story , You can write a method that has only one abstract method as lambda Class implementation of .

Android Kotlin basic course

I will explain Android Kotlin Fundamentals Course Every project of .
https://codelabs.developers.google.com/android-kotlin-fundamentals/

Android Kotlin Basic knowledge of ： Welcome to the course

https://codelabs.developers.google.com/codelabs/kotlin-android-training-welcome/index.html?index=..%2F..android-kotlin-fundamentals
There are explanations for each course .

The first 1.0-1.4 course “ Build your first app ”

  • Explain how to make Android Studio And Kotlin Use a combination of . from “Hello World” Start , Use the image file to view it , And add a click handler .
  • Explain your Android How the project is organized , How to be in Kotlin Of Android Using and modifying views in applications , And how to maintain backward compatibility . You will also learn about Android API Level and Android Jetpack library .

01.0： install Android Studio

01.1： Start

01.2： Basic application analysis

01.3： Picture resources and compatibility

01.4： Learn to help yourself

The first 2.1-2.4 course “ Layout ”

  • How to use Android Studio Layout editor and how to use LinearLayout * 1 and ConstraintLayout * 2.
  • Create an application that receives user input and displays it .findViewById() In this lesson , You will also learn how to use data binding to eliminate inefficiencies .

* 1 LinearLayout： Simple arrangement Views
Layout * 2 ConstraintLayout： Describe the layout with constraints in the current most commonly used layout .

02.1： Use the layout editor for linear layout

02.2： Add user interaction

02.3： Use the layout editor to constrain the layout

02.4: Data binding Basics

The first 3.1-3.3 course “ Navigation ”

  • Explain how to navigate through an application .
  • First , establish Fragment * 1 And add it to the application . And then use Android Studio Navigation map add navigation to your app . Create a navigation drawer * 2 And add an option menu to the application . then , The navigation drawer can be connected with back stack * 3 Used together . Learn how to launch another... From an application Activity * 4.

* 1 fragment ： A component in the user interface .Normal Enter Activity
* 2 Navigation Drawer： Sliding out from the side Menu
* 3 Back stack： A mechanism that can be returned through a return button, etc
* 4 Activity： Components that provide screens , It includes Fragment .

03.1： Create clips

03.2： Define the navigation path

03.3： Start an external activity

The first 4.1-4.2 course “ Activity and fragment lifecycles ”

  • Explained Activity and Fragment And how to deal with it in complex situations .
  • Start developing with applications that contain lifecycle errors , Add logging , Better understand lifecycle Events , Fix bugs and add value to your application . Then understand Android Jetpack Lifecycle Library , It can easily manage lifecycle Events .

04.1： Lifecycle and logging

04.2： Complex life cycle situations

The first 5.1-5.4 course “ Architecture components ”

  • Explain how to use ViewModel and LiveData *.
  • Learn how to use the... That still exists after the screen is rotated ViewModel.
  • take UI Data is packaged in LiveData in , And add a Observer To understand LiveData When the value changes .
  • Use LiveData and ViewModel And DataBinding Direct communication layout and ViewModel And there's no need to be Fragment Middle pass . This technique can reduce code and simplify it .

* ViewModel and LiveData Is a component that moves in consideration of its life cycle . You can learn how it works .

05.1: ViewModel and ViewModelFactory

It seems easier to start after reading this explanation .
https://developer.android.com/topic/libraries/architecture/viewmodel?hl=ja

Overview overview

  • stay Android On , Every time a conflicting change occurs, it is recreated Activity and Fragment Example （ Occurs when the screen rotates, etc ）.
  • As the instance is recreated , The data stored there will be lost .
  • You can to SavedInstanceState Do the same thing , But if you have a lot of data , For example, list data , It's not suitable for .
  • stay Activity or Fragment Direct asynchronous call in API when , It needs to be cleaned at the time of destruction , To avoid memory leaks . Besides , Resources are also wasted , For example, call again .

  • stay Activity or Fragment Write data communication in 、 visit DB etc. , Cause bloated and unpredictable .

  • ViewModel Designed to be more than Fragment、Activity Etc. have a longer survival time .

  • You can also easily provide ViewModel Create the test , Because you are ViewModel There is no view or lifecycle in .

05.2: LiveData and LiveData The observer

It seems easier to start after reading this explanation .
https://developer.android.com/topic/libraries/architecture/livedata?hl=ja

05.3： And ViewModel and LiveData Data binding

05.4: LiveData transformation

Overview overview

  • LiveData Is a class , It holds data that can be observed according to the life cycle .
  • image liveData.observe(activity, {data-> ...}) Same pass Activity And observe .
  • Only when the Activity You will not be notified until the lifecycle is active .
  • When Activity When the lifecycle is deleted , namely onDestory When called , The observer is removed .

Why use LiveData？
Official short

The first 6.1-6.3 course “ Room database and coordination process ”

  • Room * 1 Explain how to use the library .
  • Learn how to use Kotlin The coroutine handles the database instead of the main thread . You can also learn about ViewModel and LiveData.

* 1 One makes SQLite Easy to handle Libraries

06.1： Create a room database

06.2： Assistance and room

06.3： Use LiveData Control button status

The first 7.1-7.5 course “ Recycle bin view ”

  • Explain how to use RecyclerView Effectively display items in lists and gravel .
  • Explain how to use RecyclerView Create lists that are easy to maintain and expand .
  • Allows you to click RecyclerView Projects in China .
  • Explains how to add one or more layouts , For example, when you want to add a header .

07.1：RecyclerView Basics

07.2：DiffUtil and RecyclerView Data binding of

07.3: with RecyclerView Of GridLayout

07.4： And RecyclerView Project interaction

07.5: RecyclerView The title in

The first 8.1-8.3 course “ Connect to the Internet ”

  • I explained how to use a named Retrofit To get and display data .
  • You will learn how to handle errors , How to use the name Glide The library of displays from Internet Image , And how to RecyclerView Display the acquired image in .

08.1： Get data from the Internet

08.2： Load and display images from the Internet

08.3 Use Internet data filtering and detailed view

The first 9.1-9.2 course “ The repository ”

  • Description is used to abstract the data layer and provide clean API Technology .
  • You can also learn how to use WorkManager Perform optimized background tasks .

09.1： The repository

09.2： Work manager

The first 10.1 ~ 10.3 course “ Designed for everyone ”

  • Explain the basics of application design .
  • I'm making an application to find Google Developer Group (GDG) Explain at the party .

10.1： Style and theme

10.2： Material design 、 Size and color

10.3： Designed for everyone

原网站

版权声明
本文为[Manon Park]所创，转载请带上原文链接，感谢
https://yzsam.com/2022/02/202202161458410578.html

边栏推荐

猜你喜欢

随机推荐