[안드로이드, Kotlin] 계산기 앱 만들기 - 개인 프로젝트 3

개요

• 계산기능 구현

 

 

뷰바인딩

 

 

 

 

 

 

activity_main.xml

<pre id="code_1637046272621" class="xml" data-ke-laguage="xml"><code>

<?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/equationTextView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:gravity="end"
        android:text="equation"
        android:textSize="30sp"
        app:layout_constraintBottom_toTopOf="@+id/resultTextView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />


    <TextView
        android:id="@+id/resultTextView"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:gravity="end"
        android:padding="16dp"
        android:text="result"
        android:textSize="36sp"
        app:layout_constraintBottom_toTopOf="@id/KeyPad"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />


    <androidx.constraintlayout.helper.widget.Flow
        android:id="@+id/KeyPad"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:padding="8dp"
        app:constraint_referenced_ids="Button1, Button2, Button3, ButtonClear, Button4, Button5, Button6, ButtonPlus, Button7, Button8, Button9, ButtonMinus, Button0, ButtonEqul"
        app:flow_horizontalGap="8dp"
        app:flow_maxElementsWrap="4"
        app:flow_verticalBias="1"
        app:flow_wrapMode="chain"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHeight_percent="0.7"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="1.0" />

    <Button
        android:id="@+id/Button1"
        style="@style/numberKeyPad"
        android:text="1"
        android:onClick="numberClicked"
        tools:layout_editor_absoluteX="287dp" />


    <Button
        android:id="@+id/Button2"
        style="@style/numberKeyPad"
        android:text="2"
        android:onClick="numberClicked"
        tools:layout_editor_absoluteX="162dp"
        tools:ignore="MissingConstraints" />


    <Button
        android:id="@+id/Button3"
        style="@style/numberKeyPad"
        android:text="3"
        android:onClick="numberClicked"
        tools:layout_editor_absoluteX="37dp"
        tools:ignore="MissingConstraints"/>


    <Button
        android:id="@+id/Button4"
        style="@style/numberKeyPad"
        android:text="4"
        android:onClick="numberClicked"
        tools:layout_editor_absoluteX="287dp"
        tools:ignore="MissingConstraints"/>


    <Button
        android:id="@+id/Button5"
        style="@style/numberKeyPad"
        android:text="5"
        android:onClick="numberClicked"
        tools:layout_editor_absoluteX="162dp"
        tools:ignore="MissingConstraints"/>


    <Button
        android:id="@+id/Button6"
        style="@style/numberKeyPad"
        android:text="6"
        android:onClick="numberClicked"
        tools:layout_editor_absoluteX="37dp"
        tools:ignore="MissingConstraints"/>



    <Button
        android:id="@+id/Button7"
        style="@style/numberKeyPad"
        android:text="7"
        android:onClick="numberClicked"
        tools:layout_editor_absoluteX="287dp"
        tools:ignore="MissingConstraints"/>


    <Button
        android:id="@+id/Button8"
        style="@style/numberKeyPad"
        android:text="8"
        android:onClick="numberClicked"
        tools:layout_editor_absoluteX="162dp"
        tools:ignore="MissingConstraints"/>


    <Button
        android:id="@+id/Button9"
        style="@style/numberKeyPad"
        android:text="9"
        android:onClick="numberClicked"
        tools:layout_editor_absoluteX="37dp"
        tools:ignore="MissingConstraints"/>

    <Button
        android:id="@+id/Button0"
        style="@style/numberKeyPad"
        android:text="0"
        android:onClick="numberClicked"
        app:layout_constraintHorizontal_weight="1"
        tools:layout_editor_absoluteX="37dp"
        tools:ignore="MissingConstraints"/>

    <Button
        android:id="@+id/ButtonEqul"
        style="@style/numberKeyPad"
        android:text="="
        android:onClick="equalClicked"
        app:layout_constraintHorizontal_weight="2"
        tools:layout_editor_absoluteX="37dp"
        tools:ignore="MissingConstraints"/>

    <Button
        android:id="@+id/ButtonPlus"
        style="@style/numberKeyPad"
        android:text="+"
        android:onClick="operatorClicked"
        app:layout_constraintHorizontal_weight="2"
        tools:layout_editor_absoluteX="37dp"
        tools:ignore="MissingConstraints"/>

    <Button
        android:id="@+id/ButtonMinus"
        style="@style/numberKeyPad"
        android:text="-"
        android:onClick="operatorClicked"
        app:layout_constraintHorizontal_weight="2"
        tools:layout_editor_absoluteX="37dp"
        tools:ignore="MissingConstraints"/>

    <Button
        android:id="@+id/ButtonClear"
        style="@style/numberKeyPad"
        android:text="C"
        android:onClick="clearClicked"
        app:layout_constraintHorizontal_weight="2"
        tools:layout_editor_absoluteX="37dp"
        tools:ignore="MissingConstraints"/>


</androidx.constraintlayout.widget.ConstraintLayout>

맨 윗줄은 티스토리가 xml을 지원하지 않아서 넣어준 코드니 빼주세요

 

 

values에 style.xml을 만들어 주세요

 

style.xml

<pre id="code_1637046272621" class="xml" data-ke-laguage="xml"><code>

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <style name="numberKeyPad">
        <item name="android:textSize">40sp</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:layout_width">wrap_content</item>
        <item name="android:backgroundTint">@color/teal_200</item>
    </style>


    <color name="teal_200">#00BCD4</color>
</resources>

 

 

MainActivity

package com.example.calculator

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.Button
import android.widget.Toast
import com.example.calculator.databinding.ActivityMainBinding
import java.text.DecimalFormat

class MainActivity : AppCompatActivity() {
    private lateinit var binding: ActivityMainBinding
    private val firstNumberText = StringBuilder("")
    private val secondNumberText = StringBuilder("")
    private val operatorText = StringBuilder("")
    private val decimalFormat = DecimalFormat("#, ###")


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding= ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)
    }

    fun numberClicked(view: View) {
        val numberString = (view as? Button)?.toString() ?: ""
        val numberText = if(operatorText.isEmpty()) firstNumberText else secondNumberText


        numberText.append(numberString)
        updateEquationTextView()
    }

    fun clearClicked(view : View) {
        firstNumberText.clear()
        secondNumberText.clear()
        operatorText.clear()
        updateEquationTextView()
        binding.resultTextView.text = ""
    }

    fun equalClicked(view : View) {
        if (firstNumberText.isEmpty() || secondNumberText.isEmpty() || operatorText.isEmpty()) {
            Toast.makeText(this, "올바르지 않은 수식입니다.", Toast.LENGTH_SHORT).show()
            return
        }

        val firstNumber = firstNumberText.toString().toBigDecimal()
        val secondNumber = secondNumberText.toString().toBigDecimal()


        val result = when(operatorText.toString()) {
            "+" -> decimalFormat.format(firstNumber + secondNumber)
            "-" -> decimalFormat.format(firstNumber - secondNumber)
            else ->
                "잘못된 수식 입니다."
        }.toString()
        binding.resultTextView.text = result

    }

    fun operatorClicked(view : View) {
        val operatorString = (view as? Button)?.toString() ?: ""
        if (firstNumberText.isEmpty()) {
            Toast.makeText(this, "먼저 숫자를 입력해주세요.", Toast.LENGTH_SHORT).show()
            return
        }

        if (secondNumberText.isNotEmpty()) {
            Toast.makeText(this, "1개의 연산자에 대해서만 연산이 가능합니다.", Toast.LENGTH_SHORT).show()
            return
        }

        operatorText.append(operatorString)
        updateEquationTextView()

    }

    private fun updateEquationTextView() {
        val firstFormattedNumber = if(firstNumberText.isEmpty()) decimalFormat.format(firstNumberText.toString().toBigDecimal()) else ""
        val secondFormattedNumber = if(secondNumberText.isEmpty()) decimalFormat.format(secondNumberText.toString().toBigDecimal()) else ""
        binding.equationTextView.text = "$firstNumberText $operatorText $secondNumberText"
    }
}