Flutter集成CameraX遇问题：权限未弹窗+预览无法全屏

一、相机权限未自动弹窗问题处理 #

要实现权限自动申请，需在Flutter端触发权限请求，配合原生端完成权限检查与回调：

1. 配置AndroidManifest权限
   确保AndroidManifest.xml中添加相机相关权限：

<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" android:required="true" />
<uses-feature android:name="android.hardware.camera.autofocus" />

2. Flutter端触发权限请求
   通过MethodChannel调用原生方法发起权限申请：

final MethodChannel _cameraChannel = MethodChannel('com.example/camerax');

Future<void> checkAndRequestCameraPermission() async {
  try {
    final bool isGranted = await _cameraChannel.invokeMethod('requestCameraPermission');
    if (isGranted) {
      // 权限通过，初始化CameraX预览
      _initializeCameraPreview();
    } else {
      // 提示用户前往设置开启权限
      // 可使用Flutter的AlertDialog实现
    }
  } on PlatformException catch (e) {
    print('权限请求异常: ${e.message}');
  }
}

3. 原生端处理权限逻辑
   在MethodChannel实现类中完成权限检查、请求及回调：

class CameraXPlatformView(private val activity: Activity) : MethodCallHandler {
    private val CAMERA_PERMISSION_CODE = 1001
    private var permissionResult: MethodChannel.Result? = null

    override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
        when (call.method) {
            "requestCameraPermission" -> {
                permissionResult = result
                if (ContextCompat.checkSelfPermission(activity, Manifest.permission.CAMERA)
                    != PackageManager.PERMISSION_GRANTED
                ) {
                    ActivityCompat.requestPermissions(
                        activity,
                        arrayOf(Manifest.permission.CAMERA),
                        CAMERA_PERMISSION_CODE
                    )
                } else {
                    result.success(true)
                }
            }
        }
    }

    // 处理权限回调
    fun onPermissionsResult(requestCode: Int, grantResults: IntArray) {
        if (requestCode == CAMERA_PERMISSION_CODE) {
            permissionResult?.success(grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED)
        }
    }
}

同时在Activity的onRequestPermissionsResult方法中传递回调：

override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults)
    cameraXPlatformView?.onPermissionsResult(requestCode, grantResults)
}

二、Camera预览高度异常问题处理 #

需确保PreviewView布局参数正确，同时配置CameraX的缩放模式：

1. 原生端布局设置
   使用占满父容器的布局包裹PreviewView：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.camera.view.PreviewView
        android:id="@+id/camera_preview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</FrameLayout>

2. 配置CameraX预览缩放模式
   初始化Preview用例时，设置PreviewView的缩放模式为铺满屏幕类型：

val previewView = layoutInflater.inflate(R.layout.camera_preview_layout, null) as PreviewView
// 设置缩放模式，确保预览铺满屏幕
previewView.scaleType = PreviewView.ScaleType.FILL_CENTER

// 初始化Preview用例
val preview = Preview.Builder()
    .build()
    .also { it.setSurfaceProvider(previewView.surfaceProvider) }

// 绑定相机生命周期
val cameraProviderFuture = ProcessCameraProvider.getInstance(context)
cameraProviderFuture.addListener({
    val cameraProvider = cameraProviderFuture.get()
    val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA

    try {
        cameraProvider.unbindAll()
        cameraProvider.bindToLifecycle(
            this, cameraSelector, preview
        )
    } catch (e: Exception) {
        print("相机绑定失败: ${e.message}")
    }
}, ContextCompat.getMainExecutor(context))

3. Flutter端PlatformView布局设置
   确保Flutter侧的PlatformView容器占满屏幕：

Container(
  width: MediaQuery.of(context).size.width,
  height: MediaQuery.of(context).size.height,
  child: AndroidView(
    viewType: 'com.example/camerax_preview',
    creationParams: const {},
    creationParamsCodec: const StandardMessageCodec(),
  ),
)

内容的提问来源于stack exchange，提问作者BraveEvidence