Kotlin - coroutine

Concept

• coroutines ： The essence is the thread framework . A set of based on Thread( Threads ) Packaged Tools API（ It's like Java Of Executor 、Android Of AsyncTask Handler as well as RxJava）.
• Suspend function ：
  • The nature of suspension ： After the thread is executed, it will automatically cut back to continue .
  • The suspended function suspends the currently executing coroutine , Then execute your own coordination process . At this point, the suspended coroutine and the thread executing it will be separated , The thread continues to perform other tasks or has nothing to do （ It's the way it was , Recycle or reuse ）, When the suspended function finishes executing, it will cut back to continue executing the suspended coroutine . These coroutines are executed in their respective designated threads （ Created by Dispatchers Schedule instead of Thread, Because it will cut back rather than simply specify the thread ）, They are written in the same code block with intuitive logical order .
  • Due to the elimination of callback nesting, you can customize the hang function ：
    • When to define ： When time-consuming operations are needed （I/O、 Calculation 、 wait for ） Will suspend the current collaboration .
    • suspend keyword ： It is used to restrict the function to be called only in the coroutine or in other suspended functions , because “ Hang up -> After execution -> Cut back ” It can only be achieved by using it in the collaboration process . The real hang operation depends on the hang function of the coroutine finally called . There are also reminders “ It's a time-consuming operation , Is the hang function to be used in the coroutine ” It means .
• Non-blocking type ： The essence is not to jam threads . Compare with others based on Java Multithreading solutions for , The advantage of synergetic process is to rely on Kotlin The advantages of language , Let's make it convenient to use the same code block （ Scope ） Thread switching in （ It seems that asynchronous code is written synchronously ）, That is, the code originally written in serial is now written in parallel （ The code in the same code block is executed in the same thread （ A single thread is a blocking operation, and it will jam the thread if it does time-consuming operations , Cutting threads will not block the threads before ）,Java Thread cutting will cause complex callback relationships to be nested in callbacks , The coroutine switches the thread by suspending the function, and will return after execution to continue , Write up and down in the same code block , Logical intuition and elimination of template code ）, Eliminate the operation difficulty of multi-threaded asynchronous collaborative tasks .

Process scope CoroutineScope

Collaboration context CoroutineContext

The process creates CoroutineBuilder

Suspend function Suspend Function

ViewModelKTX

LifeCycleKTX