kotlin을 사용하여 개발 된 Android 애플리케이션의 레이아웃 문제 및 버그

어제 kotlin에 들어가서 Android 스튜디오 3.0 Canary 2, JRE 1.8.0을 사용하여 기본 계산기를 만들려고했습니다. 안타깝게도 애플리케이션을 휴대폰에 설치하면 아래 이미지와 다르게 나타납니다.

내 안드로이드 스튜디오에서 디자인은 이렇게

다음은 내 XML입니다.

 <?xml version="1.0" encoding="utf-8"?>
    <android.support.constraint.ConstraintLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.jeffrey.kotlincalculator.MainActivity">

    <EditText
        android:id="@+id/editText_num1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="number"
        android:hint="Input Number 1"
        tools:layout_editor_absoluteX="40dp"
        tools:layout_editor_absoluteY="27dp" />

    <EditText
        android:id="@+id/editText_num2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="number"
        android:hint="Input Number 2"
        tools:layout_editor_absoluteX="40dp"
        tools:layout_editor_absoluteY="92dp" />

    <TextView
        android:id="@+id/textview_result"
        android:layout_width="345dp"
        android:layout_height="39dp"
        android:text="Result"
        android:textAppearance="@android:style/TextAppearance"
        android:textAlignment="center"
        tools:ignore="MissingConstraints"
        tools:layout_editor_absoluteY="159dp"
        tools:layout_editor_absoluteX="20dp" />

    <Button
        android:id="@+id/button_add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="48dp"
        android:text="+"
        app:layout_constraintLeft_toLeftOf="parent"
        tools:layout_editor_absoluteY="219dp" />

    <Button
        android:id="@+id/button_minus"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="-"
        tools:layout_editor_absoluteY="291dp"
        tools:layout_editor_absoluteX="48dp" />

    <Button
        android:id="@+id/button_multiple"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="*"
        tools:layout_editor_absoluteX="266dp"
        tools:layout_editor_absoluteY="219dp" />

    <Button
        android:id="@+id/button_divide"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="/"
        tools:layout_editor_absoluteX="266dp"
        tools:layout_editor_absoluteY="291dp" />
</android.support.constraint.ConstraintLayout>

두 번째 문제가 있지만

숫자 필드에 숫자를 입력하려고했는데 + (추가) 버튼을 클릭하면 즉시 충돌이 발생합니다.

오류는 다음과 같습니다.

FATAL EXCEPTION: main
  Process: com.example.jeffrey.kotlincalculator, PID: 20432
  java.lang.NumberFormatException: Invalid int: ""
      at java.lang.Integer.invalidInt(Integer.java:138)
      at java.lang.Integer.parseInt(Integer.java:358)
      at java.lang.Integer.parseInt(Integer.java:334)
      at com.example.jeffrey.kotlincalculator.MainActivity.getNum1(MainActivity.kt:42)
      at com.example.jeffrey.kotlincalculator.MainActivity$onCreate$1.onClick(MainActivity.kt:24)
      at android.view.View.performClick(View.java:5207)
      at android.view.View$PerformClick.run(View.java:21177)
      at android.os.Handler.handleCallback(Handler.java:739)
      at android.os.Handler.dispatchMessage(Handler.java:95)
      at android.os.Looper.loop(Looper.java:148)
      at android.app.ActivityThread.main(ActivityThread.java:5438)
      at java.lang.reflect.Method.invoke(Native Method)
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:739)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:629)

INT가 오류임을 분명히 보여줍니다.

다음은 내 MainActivity 코드입니다.

package com.example.jeffrey.kotlincalculator

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.Button
import android.widget.EditText
import android.widget.TextView
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

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

        val result = findViewById(R.id.textview_result) as TextView
        val button_add = findViewById(R.id.button_add) as Button
        val button_minus = findViewById(R.id.button_minus) as Button
        val button_multiple = findViewById(R.id.button_multiple) as Button
        val button_divide = findViewById(R.id.button_divide) as Button

        button_add.setOnClickListener(View.OnClickListener{
            view -> result.text = (getNum1() + getNum2()).toString()
        })

        button_minus.setOnClickListener(View.OnClickListener{
            view -> result.text = (getNum1() - getNum2()).toString()
        })

        button_multiple.setOnClickListener(View.OnClickListener{
            view -> result.text = (getNum1() * getNum2()).toString()
        })

        button_divide.setOnClickListener(View.OnClickListener{
            view -> result.text = (getNum1() / getNum2()).toString()
        })
    }

    fun getNum1(): Int{
        val input_num1 = findViewById(R.id.editText_num1) as EditText;
        return Integer.parseInt(input_num1.text.toString());
    }

    fun getNum2(): Int{
        val input_num2 = findViewById(R.id.editText_num2) as EditText;
        return Integer.parseInt(input_num2.text.toString());
    }
}

전화에서 검색 한 String의 parseInt가 오류 인 것으로 밝혀졌습니다. 도와주세요:)