为什么fragment中的lifecycleScope.launch会阻塞UI线程？

Question

这会阻塞 UI 线程，但如果我使用 GlobalScope，则 UI 不会被阻塞。

lifecycleScope.launch {

            activity?.runOnUiThread {
                Toast.makeText(activity, getString(R.string.txt_savinginprogress), Toast.LENGTH_SHORT).show()
            }

            val fileName = "Picture" + System.currentTimeMillis().toString()
            val folderName = "BucketList"

            val bitmap: Bitmap? = photoURI?.let { it1 -> getBitmapFromUri(it1) }

            activity?.let {
                bitmap?.let { it1 ->
                    PhotoSaveHelper(it).savePhoto(fileName, folderName, it1)
                }
            }

            activity?.runOnUiThread {
                Toast.makeText(activity, getString(R.string.txt_saved), Toast.LENGTH_SHORT).show()
            }
        }
    }

Answer 1

lifecycleScope.launch{}main默认在线程上执行里面的代码。尝试使用以下代码在 IO 调度程序中启动协程（适用于长时间运行和密集型任务）。

lifecycleScope.launch(Dispatchers.IO) {
       withContext(Dispatchers.Main) {
            Toast.makeText(activity, getString(R.string.txt_savinginprogress), Toast.LENGTH_SHORT).show()
       }
}