simple code

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val registerLauncher =
            registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { ActivityResult ->
                if (ActivityResult.resultCode == Activity.RESULT_OK) {
                    //當launcher 成功你所要執行的動作
                    getIntentData(ActivityResult.data)
                }
            }

        //點選Image View顯示file picker，選取讀片
        findViewById<ImageView>(R.id.img).setOnClickListener {
            Intent(Intent.ACTION_GET_CONTENT).also {
                it.type = "image/*"
                //底下是實際觸發launch
                registerLauncher.launch(it)
            }
        }
     }


    private fun getIntentData(data: Intent?) {
        data?.data?.let {
            curFile = it
            findViewById<ImageView>(R.id.img).setImageURI(it)
        }
    }
}