android studio / kotlin 기본. 버튼 클릭시 숫자 1증가하는 앱

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버튼 클릭시 숫자 1씩 증가하는 기본적인 앱 만들기

 

package com.example.livedata

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.TextView
import com.example.livedata.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {

    var count = 0;
    private lateinit var binding : ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        //setContentView(R.layout.activity_main)

//        val txtView = findViewById<TextView>(R.id.txtView)
//        var btnGo = findViewById<Button>(R.id.button)
//        btnGo.setOnClickListener {
//            count ++;
//            txtView.text = count.toString()
//        }

        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        binding.button.setOnClickListener{
            count++;
            binding.txtView.text = count.toString();
        }


    }

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".MainActivity">

    <TextView
        android:id="@+id/txtView"
        android:layout_width="191dp"
        android:layout_height="120dp"
        android:text="Hello World!"
        android:textSize="34sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.453" />

    <Button
        android:id="@+id/button"
        android:layout_width="127dp"
        android:layout_height="58dp"
        android:layout_marginTop="72dp"
        android:text="Button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.531"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/txtView" />

</androidx.constraintlayout.widget.ConstraintLayout>

 

build.grade(:app)에 추가

buildFeatures {
    viewBinding = true
}