咖啡偶-IT日常

import kotlinx.coroutines.*
fun main() {
   repeat(3) {
        GlobalScope.launch {
            println("Hi from ${Thread.currentThread()}")
        }
    }
}

• 非同步

import kotlinx.coroutines.*
import java.time.LocalDateTime
import java.time.format.DateTimeFormatter

val formatter = DateTimeFormatter.ISO_LOCAL_TIME
val time = { formatter.format(LocalDateTime.now()) }

suspend fun getValue(): Double {
    println("entering getValue() at ${time()}")
    delay(3000)
    println("leaving getValue() at ${time()}")
    return Math.random()
}

fun main() {
    runBlocking {
        val num1 = getValue()
        val num2 = getValue()
        println("result of num1 + num2 is ${num1 + num2}")
    }
}

同步

import kotlinx.coroutines.*
import java.time.LocalDateTime
import java.time.format.DateTimeFormatter

val formatter = DateTimeFormatter.ISO_LOCAL_TIME
val time = { formatter.format(LocalDateTime.now()) }

suspend fun getValue(): Double {
    println("entering getValue() at ${time()}")
    delay(3000)
    println("leaving getValue() at ${time()}")
    return Math.random()
}

fun main() {
    runBlocking {
        val num1 = async { getValue() }
        val num2 = async { getValue() }
        println("result of num1 + num2 is ${num1.await() + num2.await()}")
    }
}

job

val job: Job = GlobalScope.launch(Dispatchers.Main) {
    // launch coroutine in the main thread
    for (i in 10 downTo 1) { // countdown from 10 to 1
        textView.text = "count down $i ..." // update text
        delay(1000) // wait half a second
    }
    textView.text = "Done!"
}
job.cancel()

寫android總是寫不好, 之前取得view要使用findViewByI的方式, 過了一段時間回頭看, 現在又改了改成使用viewBinding 說是比較快…

• gradle(module)

buildFeatures {
    viewBinding = true
}

• main activity

class MainActivity : AppCompatActivity() {

    lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)
    }
}

• 使用方式變簡單了

// 舊版
val myButton: Button = findViewById(R.id.my_button)
myButton.text = "A button"

// 新版
val myButton: Button = binding.myButton
myButton.text = "A button"

// Best way with view binding and no extra variable
binding.myButton.text = "A button"

反正kotlin我很弱啦, 簡單的說

class 外面定義變數就可以當作靜態變數屎用了

var iCounter = 0
class MainActivity : AppCompatActivity(), View.OnClickListener {
  iCounter++
}