在Android中，PreviewView 是一個用于預覽相機捕獲的圖像和視頻的視圖。要在應用中使用 PreviewView，你需要遵循以下步驟：

1. 添加依賴項

在你的項目的 build.gradle 文件中，添加以下依賴項：

dependencies {
    implementation 'androidx.camera:camera-core:1.0.0'
    implementation 'androidx.camera:camera-預覽:1.0.0'
    implementation 'androidx.camera:camera-view:1.0.0'
}

2. 在布局文件中添加 PreviewView

在你的應用的布局文件（例如 activity_main.xml）中，添加一個 PreviewView 控件：

<androidx.camera.core.PreviewView
    android:id="@+id/previewView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

3. 配置相機源和預覽

在你的 Activity 或 Fragment 中，配置相機源和預覽。首先，獲取 PreviewView 的引用，然后創建一個 CameraProvider 實例。接下來，為 PreviewView 設置一個預覽回調，以便在捕獲圖像時顯示預覽。

import android.Manifest
import android.content.Context
import android.content.pm.PackageManager
import androidx.camera.core.*
import androidx.camera.core.ImageAnalysis
import androidx.camera.core.ImageProxy
import androidx.camera.lifecycle.ProcessCameraProvider
import androidx.camera.view.PreviewView
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
import java.util.concurrent.ExecutorService
import java.util.concurrent.Executors

class MainActivity : AppCompatActivity() {

    private lateinit var previewView: PreviewView
    private lateinit var cameraProviderFuture: ProcessCameraProvider
    private lateinit var cameraProvider: ProcessCameraProvider
    private lateinit var imageAnalyzer: ImageAnalyzer

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

        previewView = findViewById(R.id.previewView)

        // 檢查相機權限
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, arrayOf(Manifest.permission.CAMERA), REQUEST_CAMERA_PERMISSION)
            return
        }

        // 創建一個單線程的 ExecutorService 用于運行相機操作
        val cameraExecutor = Executors.newSingleThreadExecutor()

        // 獲取 CameraProvider
        cameraProviderFuture = ProcessCameraProvider.getInstance(this, cameraExecutor)

        // 創建一個 ImageAnalyzer
        imageAnalyzer = ImageAnalyzer()

        // 設置預覽回調
        previewView.setSurfaceProvider(previewView.surfaceProvider)
        cameraProviderFuture.addListener({
            cameraProvider = cameraProviderFuture.get()
            bindPreviewView()
        }, ContextCompat.getMainExecutor(this))
    }

    private fun bindPreviewView() {
        cameraProvider.unbindAll()
        val preview = Preview.Builder().build().also {
            it.setSurfaceProvider(previewView.surfaceProvider)
        }

        val cameraSelector = CameraSelector.Builder().requireLensFacing(CameraSelector.LENS_FACING_BACK).build()

        try {
            cameraProvider.bindToLifecycle(this, cameraSelector, preview, imageAnalyzer)
        } catch (exc: Exception) {
            // 處理異常
        }
    }

    override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        if (requestCode == REQUEST_CAMERA_PERMISSION && grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            // 相機權限被授予，重新嘗試綁定預覽視圖
            bindPreviewView()
        }
    }

    companion object {
        private const val REQUEST_CAMERA_PERMISSION = 1
    }
}

4. 創建 ImageAnalyzer

創建一個繼承自 ImageAnalysis 的類，用于分析捕獲的圖像。在這個類中，你可以使用 ImageProxy 對象來處理圖像數據。

import android.renderscript.Allocation
import android.renderscript.Element
import android.renderscript.RenderScript
import androidx.camera.core.ImageProxy
import java.nio.ByteBuffer

class ImageAnalyzer : ImageAnalysis {

    private lateinit var rs: RenderScript
    private lateinit var inAllocation: Allocation
    private lateinit var outAllocation: Allocation

    override fun createImageAnalyzer(context: Context): ImageAnalyzer {
        rs = RenderScript.create(context)
        inAllocation = Allocation.createFromBitmap(rs, BitmapFactory.decodeResource(context.resources, R.drawable.ic_launcher_background))
        outAllocation = Allocation.createTyped(rs, Element.U8_4(rs))
        return this
    }

    override fun analyze(imageProxy: ImageProxy) {
        val buffer = imageProxy.image?.planes?.firstOrNull()?.buffer
        val byteArray = ByteArray(buffer?.capacity() ?: 0)
        buffer?.get(byteArray)

        // 處理圖像數據，例如識別物體、人臉等

        imageProxy.close()
    }

    override fun close() {
        inAllocation.destroy()
        outAllocation.destroy()
        rs.destroy()
    }
}

現在，當你運行應用時，你應該能夠看到一個預覽窗口，實時顯示相機捕獲的圖像和視頻。你可以根據需要對 ImageAnalyzer 類進行擴展，以實現更高級的圖像處理功能。