Kotlin 扫描二维码

您可以使用 ZXing 库来实现 Kotlin 中的二维码扫描。以下是一个简单的示例代码：

1. 添加依赖

在您的项目的 build.gradle 文件中添加以下依赖：

dependencies {
    implementation 'com.google.zxing:core:3.4.0'
    implementation 'com.journeyapps:zxing-android-embedded:3.4.0'
}

2. 在布局文件中添加 SurfaceView

在您的布局文件中添加一个 SurfaceView 元素，用于显示相机预览：

<SurfaceView
    android:id="@+id/surface_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

3. 在 Kotlin 代码中实现扫描逻辑

在您的 Kotlin 代码中，使用 ZXing 库来实现扫描逻辑。以下是一个简单的示例代码：

import android.Manifest
import android.content.pm.PackageManager
import android.os.Bundle
import android.util.Log
import android.view.SurfaceHolder
import android.view.SurfaceView
import androidx.appcompat.app.AppCompatActivity
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
import com.google.zxing.BarcodeFormat
import com.google.zxing.Result
import com.google.zxing.client.android.BeepManager
import com.google.zxing.client.android.camera.CameraManager
import com.journeyapps.barcodescanner.BarcodeCallback
import com.journeyapps.barcodescanner.BarcodeResult
import com.journeyapps.barcodescanner.DecoratedBarcodeView
import com.journeyapps.barcodescanner.DefaultDecoderFactory

class MainActivity : AppCompatActivity(), SurfaceHolder.Callback {

    private lateinit var cameraManager: CameraManager
    private lateinit var beepManager: BeepManager
    private lateinit var surfaceView: SurfaceView
    private lateinit var barcodeView: DecoratedBarcodeView
    private lateinit var barcodeCallback: BarcodeCallback

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

        surfaceView = findViewById(R.id.surface_view)
        barcodeView = findViewById(R.id.barcode_view)

        // Request camera permission if not granted
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
            != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this,
                arrayOf(Manifest.permission.CAMERA), REQUEST_CAMERA_PERMISSION)
        } else {
            surfaceView.holder.addCallback(this)
        }

        cameraManager = CameraManager(this)
        beepManager = BeepManager(this)

        // Set decoder factory
        val formats = mutableListOf<BarcodeFormat>()
        formats.add(BarcodeFormat.QR_CODE)
        val decoderFactory = DefaultDecoderFactory(formats)

        barcodeView.decoderFactory = decoderFactory
        barcodeView.initializeFromIntent(intent)
        barcodeView.decodeContinuous(barcodeCallback)
    }

    override fun surfaceCreated(holder: SurfaceHolder) {
        try {
            cameraManager.openDriver(holder)
        } catch (e: Exception) {
            Log.e(TAG, "Failed to open camera", e)
        }
    }

    override fun surfaceChanged(holder: SurfaceHolder, format: Int, width: Int, height: Int) {}

    override fun surfaceDestroyed(holder: SurfaceHolder) {
        cameraManager.closeDriver()
    }

    override fun onResume() {
        super.onResume()
        barcodeView.resume()
    }

    override fun onPause() {
        super.onPause()
        barcodeView.pause()
    }

    override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>,
                                            grantResults: IntArray) {
        if (requestCode == REQUEST_CAMERA_PERMISSION) {
            if (grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                surfaceView.holder.addCallback(this)
            }
        }
    }

    companion object {
        private const val TAG = "MainActivity"
        private const val REQUEST_CAMERA_PERMISSION = 1
    }
}

在上面的代码中，我们创建了一个 `BarcodeCallback` 对象，用于处理扫描结果。在 `onCreate` 方法中，我们设置了解码器工厂，并将 `BarcodeCallback` 对象传递给 `barcodeView.decodeContinuous` 方法，以启动连续扫描模式。

注意：这个示例代码仅供参考，具体的实现可能因应用需求而异。