Kotlin coroutine suspend function suspend keyword

suspend The pending process

What is the schedule

Namely launch{

}

or

async{

}

Things in the code block

Used suspend after A coroutine will be switched out to perform the operation . Not in the current thread

suspend It's a temporary cut . Cut back after the execution .

launch(Dispatchers.Main) {
                // Switch to the sub thread for operation 
                val repoResponse: Response<FeedBackLists>
                withContext(Dispatchers.IO) {
                    repoResponse = RetrofitClient
                        .instance
                        .getApi()
                        //suspend  The suspended method must be called in Ctrip 
                        .getFeedBack(1, 1)
                }
                // Or in the main thread 
                binding.tvText.text = "repoResponse :${repoResponse.data!!.data[0].content}"
            }

Hanging can be understood as opening a thread . Or cut a thread , It's just that after the function is suspended , The coroutine will automatically switch back to the original thread .

So the so-called hang . Thread switching . This cut back operation

It is called in the thread resume

however suspend No thread switching .

First, customize a suspend function

Then the main thread calls

 

  You will find that it is still running on the main thread .

 withContext You can switch to a child thread

So suspend Switching threads does not happen when the external pending function is called . It is withContext When called

withContext There is no direct thread switching . Still in there

In grammar suspend What's the use of keywords ？

remind , The creator of the function =》 User's reminder

Remind that this is a time-consuming function that is automatically placed in the background .

This reminder can make the main thread not stuck

When to use suspend keyword

Time consuming operations such as io、 File read and write , Network interaction , Blur or beautify the picture .

Waiting situation Such as deley（10000） The long-running