将 URL 添加到 MainActivity.kt 时应用程序崩溃

Question

我使用 kotlin，我想在检查 url 响应后显示警报 我在 MainActivity.kt 中的代码：

package com.example.test1

import android.app.AlertDialog
import android.content.DialogInterface
import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import java.net.URL


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

        val username = findViewById<EditText>(R.id.etUserName);
        val password = findViewById<EditText>(R.id.etPassword);
        val btn = findViewById<Button>(R.id.button);


        var url = URL("https://www.sepehrfarm.ir/app/read.php?username=host&password=1111").readText();
            if(url == "okay"){
                        btn.setOnClickListener {
                            val mAlertDialog = AlertDialog.Builder(this@MainActivity)
                            mAlertDialog.setTitle("Show Dialog");
                            mAlertDialog.setMessage("Login successful");
                            mAlertDialog.setIcon(R.mipmap.ic_launcher)
                            mAlertDialog.setPositiveButton("OK") { dialog: DialogInterface, id: Int ->
                                Toast.makeText(
                                    this@MainActivity,
                                    "OK",
                                    Toast.LENGTH_SHORT
                                ).show()
                            }
                            mAlertDialog.show()
                        }
            }
            else{
                btn.setOnClickListener {
                    val mAlertDialog = AlertDialog.Builder(this@MainActivity)
                    mAlertDialog.setTitle("Show Dialog");
                    mAlertDialog.setMessage("Login failed");
                    mAlertDialog.setIcon(R.mipmap.ic_launcher)
               

     mAlertDialog.setPositiveButton("OK") { dialog: DialogInterface, id:Int ->
                            Toast.makeText(
                                this@MainActivity,
                            "OK",
                            Toast.LENGTH_SHORT
                        ).show()
                    }
                    mAlertDialog.show()
                }
            }

    }
    }

在程序中 var url = URL("https://www.sepehrfarm.ir/app/read.php?username=host&password=1111").readText() 期间，应用程序无法工作，当我评论此内容时使应用程序正常运行 为什么？