MainActivity.kt

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import android.content.Intent
import android.graphics.PorterDuff
import android.os.Bundle
import android.text.Editable
import android.text.Spannable
import android.text.SpannableString
import android.text.TextWatcher
import android.text.style.ForegroundColorSpan
import android.text.style.RelativeSizeSpan
import android.util.Log
import android.view.View
import android.widget.Button
import android.widget.EditText
import android.widget.ImageButton
import androidx.appcompat.app.AppCompatActivity
import androidx.core.content.ContextCompat
import com.google.android.gms.ads.AdListener
import com.google.android.gms.ads.AdRequest
import com.google.android.gms.ads.AdView
import com.google.android.gms.ads.FullScreenContentCallback
import com.google.android.gms.ads.LoadAdError
import com.google.android.gms.ads.MobileAds
import com.google.android.gms.ads.interstitial.InterstitialAd
import com.google.android.gms.ads.interstitial.InterstitialAdLoadCallback
import net.objecthunter.exp4j.ExpressionBuilder

class MainActivity : AppCompatActivity() {

    private lateinit var editText: EditText
    private var interstitialAd: InterstitialAd? = null
    private lateinit var imageButton: ImageButton
    private var bannerAd: AdView? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        loadInterstitialAd()
        editText = findViewById(R.id.editText)

        setupInputChangeListener()
        bannerAd = findViewById(R.id.adView)

        MobileAds.initialize(this) {}

        loadBannerAd()

        val buttonIds = arrayOf(
            R.id.button0, R.id.button1, R.id.button2, R.id.button3, R.id.button4,
            R.id.button5, R.id.button6, R.id.button7, R.id.button8, R.id.button9,
            R.id.buttonDot, R.id.buttonAdd, R.id.buttonSubtract, R.id.buttonMultiply,
            R.id.buttonDivide, R.id.buttonBr1, R.id.buttonBr2, R.id.backspace,
            R.id.AC, R.id.buttonEquals
        )

        for (buttonId in buttonIds) {
            val button = findViewById<Button>(buttonId)
            styleButton(button, buttonId)
            button.setOnClickListener { onButtonClick(it) }
        }

        findViewById<Button>(R.id.buttonEquals).setOnClickListener { onEqualsButtonClick() }

        findViewById<ImageButton>(R.id.historyButton).setOnClickListener {
            if (interstitialAd != null) {
                interstitialAd?.show(this)
            } else {
                navigateToHistory()
            }
        }
    }

    private fun loadInterstitialAd() {
        val adRequest = AdRequest.Builder().build()
        InterstitialAd.load(
            this,
            "ca-app-pub-3940256099942544/1033173712",
            adRequest,
            object : InterstitialAdLoadCallback() {
                override fun onAdLoaded(ad: InterstitialAd) {
                    interstitialAd = ad
                    interstitialAd?.fullScreenContentCallback =
                        object : FullScreenContentCallback() {
                            override fun onAdDismissedFullScreenContent() {
                                interstitialAd = null
                                navigateToHistory()
                            }

                            override fun onAdFailedToShowFullScreenContent(adError: com.google.android.gms.ads.AdError) {
                                navigateToHistory()
                            }
                        }
                }

                override fun onAdFailedToLoad(adError: LoadAdError) {
                    interstitialAd = null
                }
            }
        )
    }

    private fun navigateToHistory() {
        val intent = Intent(this, HistoryActivity::class.java)
        startActivity(intent)
    }

    private fun styleButton(button: Button, buttonId: Int) {
        val color = when (buttonId) {
            in arrayOf(
                R.id.buttonDot,
                R.id.button0, R.id.button1, R.id.button2,
                R.id.button3, R.id.button4, R.id.button5,
                R.id.button6, R.id.button7, R.id.button8, R.id.button9
            ) -> R.color.navi

            in arrayOf(
                R.id.buttonEquals, R.id.buttonAdd,
                R.id.buttonSubtract, R.id.buttonMultiply,
                R.id.buttonDivide
            ) -> R.color.yellow

            in arrayOf(R.id.backspace, R.id.AC) -> R.color.yellow
            else -> R.color.yellow
        }

        val drawable = ContextCompat.getDrawable(this, R.drawable.numberbkg)
        drawable?.setColorFilter(ContextCompat.getColor(this, color), PorterDuff.Mode.SRC)
        button.background = drawable
    }

    private fun saveCalculation(expression: String, result: String) {
        val operators = setOf("+", "-", "×", "÷")
        if (expression.any { it.toString() in operators }) {
            val sharedPreferences = getSharedPreferences("CalculatorHistory", MODE_PRIVATE)
            val editor = sharedPreferences.edit()
            val historySet =
                sharedPreferences.getStringSet("history", mutableSetOf()) ?: mutableSetOf()
            historySet.add("$expression = $result")
            editor.putStringSet("history", historySet)
            editor.apply()
        }
    }

    private fun setupInputChangeListener() {
        editText.addTextChangedListener(object : TextWatcher {
            override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
                val expression = s.toString()
                try {
                    val result = evaluateExpression(expression).toString()
                    saveCalculation(expression, result)
                } catch (_: Exception) {
                }
            }

            override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {}
            override fun afterTextChanged(s: Editable?) {}
        })
    }

    private fun updateExpressionWithResult(expression: String) {
        try {
            val result = evaluateExpression(expression).toString()
            val fullText = "$expression\n= $result"

            val spannable = SpannableString(fullText)
            val start = expression.length + 1

            spannable.setSpan(
                RelativeSizeSpan(0.8f),
                start,
                fullText.length,
                Spannable.SPAN_EXCLUSIVE_EXCLUSIVE
            )
            spannable.setSpan(
                ForegroundColorSpan(ContextCompat.getColor(this, R.color.white)),
                start, fullText.length,
                Spannable.SPAN_EXCLUSIVE_EXCLUSIVE
            )

            editText.setText(spannable)
            editText.setSelection(expression.length)
        } catch (e: Exception) {
        }
    }

    private fun onButtonClick(view: View) {
        val button = view as Button
        val buttonText = button.text.toString()
        var currentText = editText.text.toString().substringBefore("\n")

        val operators = setOf("+", "-", "×", "÷")

        when (buttonText) {
            "AC" -> editText.setText("")
            "C" -> if (currentText.isNotEmpty()) editText.setText(currentText.dropLast(1))
            "=" -> onEqualsButtonClick()
            else -> {
                if (currentText == "0") {
                    editText.setText(buttonText)
                } else {
                    if (buttonText in operators) {
                        if (currentText.isNotEmpty() && operators.contains(currentText.last().toString())) {
                            editText.setText(currentText.dropLast(1) + buttonText)
                        } else {
                            editText.setText(currentText + buttonText)
                        }
                    } else {
                        editText.setText(currentText + buttonText)
                    }
                }
            }
        }
    }

    private fun onEqualsButtonClick() {
        val expression = editText.text.toString().substringBefore("\n")
        try {
            val result = evaluateExpression(expression).toString()
            editText.setText("$expression\n= $result")
            saveCalculation(expression, result)
            editText.setSelection(editText.text.length)
        } catch (e: Exception) {
            editText.setText("Error")
        }
    }

    private fun evaluateExpression(expression: String): String {
        val result = ExpressionBuilder(expression).build().evaluate()
        return if (result % 1 == 0.0) {
            result.toInt().toString()
        } else {
            result.toString()
        }
    }

    private fun loadBannerAd() {
        val adRequest = AdRequest.Builder().build()
        bannerAd?.loadAd(adRequest)
        bannerAd?.adListener = object : AdListener() {
            override fun onAdLoaded() {
                Log.d("BannerAd", "Ad loaded successfully.")
            }

            override fun onAdFailedToLoad(adError: LoadAdError) {
                Log.e("BannerAd", "Failed to load ad: ${adError.message}")
            }
        }
    }
}
</code></pre>