Flutter OS 外接纹理适配简介
Flutter 在 OHOS 平台使用外接纹理，视频播放和相机预览使用方法是一致的，在注册纹理时，flutter engine 返回 surfaceId。图片场景，则是以 PixelMap 的形式注册到 flutter engine。
注：1. 一般而言，为了方便复用，会将 ohos 对接 flutter 外接纹理的功能代码作为一个 module 模块组件单独写一个插件注册到 Flutter engine
外接纹理背景色为白色，暂不支持修改
相机预览
实现说明
1． 实现插件，在 onAttachedToEngine 中，从入参 FlutterPluginBinding 中获取 TextureRegistry
const TAG = "CameraPlugin";export class CameraPlugin implements FlutterPlugin, MethodCallHandler { private binding: FlutterPluginBinding | null = null; private mMethodChannel: MethodChannel | null = null; private textureRegistry: TextureRegistry | null = null; private textureId: number = -1; private surfaceId: number = -1;
getUniqueClassName(): string {return TAG; }
onAttachedToEngine(binding: FlutterPluginBinding): void {Log.e(TAG, "CameraPlugin onAttachedToEngine");this.binding = binding;this.mMethodChannel = new MethodChannel(binding.getBinaryMessenger(), "CameraControlChannel");this.mMethodChannel.setMethodCallHandler(this);this.textureRegistry = binding.getTextureRegistry();
}
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2． 在 onMethodCall 中实现注册纹理的响应方法
onMethodCall(call: MethodCall, result: MethodResult): void {let method: string = call.method;Log.e(TAG, "Received '" + method + "' message.");switch (method) { case "registerTexture":this.registerCameraTexture();result.success(this.textureId);break; case "startCamera":this.startCamera();result.success(null);break; case "unregisterTexture":this.unregisterTexture(call.argument("textureId"));result.success(null);break;} }
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registerCameraTexture 中实现注册纹理，先获取 textureId，再使用该 textureId 去注册纹理到 flutter engine，返回 surfaceId。
registerCameraTexture(): void {Log.i(TAG, "start register Camera texture in flutter engine");this.textureId = this.textureRegistry!.getTextureId();this.surfaceId = this.textureRegistry!.registerTexture(this.textureId)!.getSurfaceId(); }
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3． 在启动相机预览中，使用前面获取到的 surfaceId。
startSession() {console.log(`[camera test] 已经授权，相机开始拍摄`);let cameraManager = getCameraManager(getContext(this) as common.BaseContext);let cameraDevices = getCameraDevices(cameraManager);let cameraInput = getCameraInput(cameraDevices[0], cameraManager);if (cameraInput != null) { getSupportedOutputCapability(cameraDevices[0], cameraManager, cameraInput).then((supportedOutputCapability) => { if (supportedOutputCapability != undefined) {let previewOutput = getPreviewOutput(cameraManager, supportedOutputCapability, this.surfaceId.toString());let captureSession = getCaptureSession(cameraManager);if (captureSession != undefined && previewOutput != undefined && cameraInput != null) { beginConfig(captureSession); setSessionCameraInput(captureSession, cameraInput); setSessionPreviewOutput(captureSession, previewOutput); startSession(captureSession);} }});} }
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4 . dart 侧通过 MethodChannel 触发，触发纹理注册和启动相机预览。
class _CameraPageState extends State<CameraPage> { final MethodChannel _channel = MethodChannel('CameraControlChannel');
int textureId = -1;
@override void initState() {super.initState();
newTexture();startCamera(); }
@override void dispose() {super.dispose();if (textureId >= 0) { _channel.invokeMethod('unregisterTexture', {'textureId': textureId});} }
void startCamera() async {await _channel.invokeMethod('startCamera'); }
void newTexture() async {int id = await _channel.invokeMethod('registerTexture');setState(() { this.textureId = id;}); }
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预览画面使用获取到的 textureId 构造一个 texture widget。
Widget getTextureBody(BuildContext context) {return Container( width: 500, height: 500, child: Texture(textureId: textureId, ),); }
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