【Kotlinプログラム入門】。今回はAndroidアプリケーションでQRコードの読み取りに挑戦します！

plugins {
    id 'com.android.application'
    id 'org.jetbrains.kotlin.android'
}

android {
    namespace 'com.sample.qrreader'
    compileSdk 34

    defaultConfig {
        applicationId "com.sample.qrreader"
        minSdk 29
        targetSdk 34
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        vectorDrawables {
            useSupportLibrary true
        }
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }
    buildFeatures {
        compose true
    }
    composeOptions {
        kotlinCompilerExtensionVersion '1.3.2'
    }
    packagingOptions {
        resources {
            excludes += '/META-INF/{AL2.0,LGPL2.1}'
        }
    }
}

dependencies {

    implementation 'androidx.core:core-ktx:1.8.0'
    implementation platform('org.jetbrains.kotlin:kotlin-bom:1.8.0')
    implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.3.1'
    implementation 'androidx.activity:activity-compose:1.5.1'
    implementation platform('androidx.compose:compose-bom:2022.10.00')
    implementation 'androidx.compose.ui:ui'
    implementation 'androidx.compose.ui:ui-graphics'
    implementation 'androidx.compose.ui:ui-tooling-preview'
    implementation 'androidx.compose.material3:material3'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.5'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
    androidTestImplementation platform('androidx.compose:compose-bom:2022.10.00')
    androidTestImplementation 'androidx.compose.ui:ui-test-junit4'
    debugImplementation 'androidx.compose.ui:ui-tooling'
    debugImplementation 'androidx.compose.ui:ui-test-manifest'
    implementation 'com.journeyapps:zxing-android-embedded:4.1.0'
    implementation 'androidx.appcompat:appcompat:1.0.2'
}

package com.sample.qrreader

import android.Manifest
import android.content.Intent
import android.net.Uri
import android.os.Bundle
import android.webkit.URLUtil
import androidx.activity.ComponentActivity
import androidx.activity.compose.rememberLauncherForActivityResult
import androidx.activity.compose.setContent
import androidx.activity.result.contract.ActivityResultContracts
import androidx.appcompat.app.AppCompatActivity
import androidx.compose.foundation.layout.*
import androidx.compose.foundation.text.ClickableText
import androidx.compose.material3.*
import androidx.compose.runtime.*
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.text.AnnotatedString
import com.google.zxing.integration.android.IntentIntegrator

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            QRCodeReaderScreen()
        }
    }
}

@Composable
fun QRCodeReaderScreen() {
    var qrCodeContent by remember { mutableStateOf(null) }
    val context = LocalContext.current

    val qrCodeResultLauncher = rememberLauncherForActivityResult(ActivityResultContracts.StartActivityForResult()) { result ->
        if (result.resultCode == AppCompatActivity.RESULT_OK) {
            val intentResult = IntentIntegrator.parseActivityResult(result.resultCode, result.data)
            intentResult?.contents?.let {
                qrCodeContent = it
            }
        }
    }

    val launcher = rememberLauncherForActivityResult(ActivityResultContracts.RequestPermission()) { isGranted ->
        if (isGranted) {
            val integrator = IntentIntegrator(context as ComponentActivity)
            integrator.setOrientationLocked(false)
            qrCodeResultLauncher.launch(integrator.createScanIntent())
        } else {
            // アクセス許可が拒否されたケースを処理する
        }
    }

    Column(
        modifier = Modifier.fillMaxSize(),
        verticalArrangement = Arrangement.Center,
        horizontalAlignment = Alignment.CenterHorizontally
    ) {
        Button(onClick = { launcher.launch(Manifest.permission.CAMERA) }) {
            Text("Open Camera")
        }
        if (qrCodeContent != null) {
            Text("QR Code Content:")
            ClickableText(
                text = AnnotatedString(qrCodeContent!!),
                onClick = { offset ->
                    // URLをタップした際にはブラウザで開く
                    qrCodeContent?.let { url ->
                        if (URLUtil.isValidUrl(url)) {
                            val intent = Intent(Intent.ACTION_VIEW, Uri.parse(url))
                            context.startActivity(intent)
                        }
                    }
                },
            )
        }
    }
}