1. 数组简单排序 (降序排列)

private val test= arrayListOf(1,5,2).sortedDescending()

2. kotlin 简单协程demo运行死后报错:

Caused by: java.lang.ClassNotFoundException: Didn't find class "android.view.View$OnUnhandledKeyEventListener"

参考解决方案:
https://stackoverflow.com/questions/51782548/androidxappcompat-iart-error-android-view-viewonunhandledkeyeventlistener/52954286#52954286
及
https://blog.csdn.net/weixin_37651459/article/details/80956366
一直提示是targetVersion与 机器的version版本不一致.各种改也没起作用
最后发现:少了个依赖库 加入依赖库就完美解决了.

简单demo 代码如下:

class MainActivity : AppCompatActivity(), CoroutineScope by MainScope() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
//        Toast.makeText(this, "你好", Toast.LENGTH_SHORT
        //加载并显示数据
        loadDataAndShow()
    }

    private fun loadDataAndShow() {
        GlobalScope.launch(Dispatchers.IO) {
            //IO 线程里拉取数据
            Log.d("WUFS", "before")
            var result = fetchData()
            Log.d("WUFS", result)
            withContext(Dispatchers.Main) {
                //主线程里更新 UI
                text.text = result
            }
        }
    }

    suspend fun fetchData(): String {
        delay(2000)
        return "conetent"
    }

    override fun onDestroy() {
        super.onDestroy()
        //取消掉所有协程内容
        cancel()
    }

}