第38篇｜双拍完成闭环：合成、保存、失败重试和相册落点

第38篇双拍完成闭环合成、保存、失败重试和相册落点第 38 篇把双拍主链路收束起来。并发双摄触发后后摄和前摄会分别产生 JPEG 回调只有两路都交付项目才尝试合成双镜作品。合成成功时记录指向 compositePath合成失败时保留原始两张图最终都进入GalleryMoment和相册刷新闭环。本文是 21 天「智能相机开发实战」训练营中的一篇实操记录。所有代码片段都来自当前项目配图围绕运行页面和源码关键路径展开读完以后可以直接回到工程里按函数名定位。本篇目标读懂 triggerDualCapture 如何同时触发两路拍照。理解两路回调到齐后才创建同一条记录。掌握 composeDualCaptureIfPossible 的成功与失败返回。把双拍、合成、入库、相册地图刷新串成完整闭环。代码位置entry/src/main/ets/pages/Index.etsentry/src/main/ets/services/DualPhotoComposerService.etsentry/src/main/ets/services/GalleryRecordService.ets一、双拍闭环的难点是“两路结果一致归档”双拍不是触发两次单拍。它需要保证后摄图、前摄图、地点快照、captureId、合成文件和相册记录属于同一次作品。任意一路晚到、失败或合成异常都要有明确落点。图1 双拍闭环两路 JPEG、合成尝试、GalleryMoment 和相册地图刷新二、triggerDualCapture同时触发前后两路 PhotoOutput双摄路径先确认dualCameraSupported、两路 PhotoOutput、会话状态和两路预览 live。随后它构建地点快照生成后摄和前摄两个目标路径设置水印上下文最后通过Promise.all同时触发两路 capture。图2 triggerDualCapture 同时触发前后摄拍照private async triggerDualCapture(): Promisevoid { if (this.captureBusy) { return; } if (!this.dualCameraSupported) { await this.triggerSequentialCapture(); return; } if (!this.backPhotoOutput || !this.frontPhotoOutput || !this.cameraSessionActive || !this.backPreviewLive || !this.frontPreviewLive) { this.cameraStatusText ; this.lastCaptureSummary this.cameraStatusText; return; } const locationSnapshot await this.buildCaptureLocationSnapshot(); const timestamp ${Date.now()}; this.captureBusy true; this.pendingCaptureMode dual; this.pendingSingleCaptureRole back; this.backCaptureDelivered false; this.frontCaptureDelivered false; this.pendingCaptureId timestamp; this.pendingBackCapturePath this.buildCaptureFilePath(back, timestamp); this.pendingFrontCapturePath this.buildCaptureFilePath(front, timestamp); this.pendingCaptureLatitude locationSnapshot.latitude; this.pendingCaptureLongitude locationSnapshot.longitude; this.pendingCapturePlace locationSnapshot.place; this.pendingCaptureTitle locationSnapshot.memoryTitle; this.armPendingWatermark(parseInt(timestamp, 10), locationSnapshot.place, dual); this.cameraStatusText ; this.lastCaptureSummary this.buildCaptureSummary(locationSnapshot); this.setPhotoOutputReady(dualBack, false); this.setPhotoOutputReady(dualFront, false); const backCaptureSetting: camera.PhotoCaptureSetting { quality: this.captureQualityLevel, rotation: camera.ImageRotation.ROTATION_0, mirror: false }; const frontCaptureSetting: camera.PhotoCaptureSetting { quality: this.captureQualityLevel, rotation: camera.ImageRotation.ROTATION_0, mirror: true }; try { await Promise.all([ this.backPhotoOutput.capture(backCaptureSetting), this.frontPhotoOutput.capture(frontCaptureSetting) ]); } catch (error) { const err error as BusinessError; this.failDualCapture(双镜拍照触发失败 ${err.code}); } }这里的路径是成对生成的地点快照也是同一个。这样两张照片虽然来自不同摄像头但仍属于同一条记忆。三、composeDualCaptureIfPossible合成失败也要返回可用结果两张图都写入后上层调用composeDualCaptureIfPossible。如果输入路径缺失或相同它直接返回如果合成成功则删除原始临时图并返回 compositePath如果合成失败则记录日志并返回原始路径。这样一次图像处理失败不会毁掉拍摄结果。图3 composeDualCaptureIfPossible 合成失败时保留原始路径private async composeDualCaptureIfPossible( captureId: string, backPath: string, frontPath: string ): PromiseCaptureOutputPaths { if (backPath.length 0 || frontPath.length 0) { return { backPath: backPath, frontPath: frontPath, composited: false }; } if (backPath frontPath) { return { backPath: backPath, frontPath: frontPath, composited: true }; } const compositePath this.buildCompositeCaptureFilePath(captureId); try { this.logCaptureTrace(compose-dual-capture-start, output${compositePath}); await DualPhotoComposerService.composeDualPhoto(backPath, frontPath, compositePath); this.unlinkLocalFileQuietly(backPath); this.unlinkLocalFileQuietly(frontPath); this.logCaptureTrace(compose-dual-capture-finished, output${compositePath}); return { backPath: compositePath, frontPath: compositePath, composited: true }; } catch (error) { const message error instanceof Error ? error.message : JSON.stringify(error); console.error(Failed to compose dual capture: ${message}); this.logCaptureTrace(compose-dual-capture-failed, message); return { backPath: backPath, frontPath: frontPath, composited: false }; } }这个函数体现了作品优先级能合成最好不能合成也要保留照片让用户有结果可看。四、两路交付后创建同一条 GalleryMomentmarkCaptureDelivered会分别标记后摄和前摄是否交付。只有backCaptureDelivered和frontCaptureDelivered都为 true才会合成、加水印、创建记录、复位 pending 状态并调用appendGalleryRecord。图4 两路照片都交付后生成同一条 GalleryMomentif (role back) { this.backCaptureDelivered true; } else { this.frontCaptureDelivered true; } if (this.backCaptureDelivered this.frontCaptureDelivered) { const selectedMemory this.getSelectedMapMemory(); const captureId this.pendingCaptureId.length 0 ? this.pendingCaptureId : ${Date.now()}; const createdAt parseInt(captureId, 10); const capturePlace this.pendingCapturePlace.length 0 ? this.pendingCapturePlace : selectedMemory.place; const captureTitle this.pendingCaptureTitle.length 0 ? this.pendingCaptureTitle : selectedMemory.title; const capturePaths await this.composeDualCaptureIfPossible( captureId, this.pendingBackCapturePath, this.pendingFrontCapturePath ); await this.applyPendingWatermarkToCapturePaths(capturePaths); const nextPairCount this.capturePairCount 1; const galleryRecord GalleryRecordService.createRecord({ id: captureId, createdAt: createdAt, pairIndex: nextPairCount, place: capturePlace, memoryTitle: captureTitle, latitude: this.pendingCaptureLatitude, longitude: this.pendingCaptureLongitude, backPath: capturePaths.backPath, frontPath: capturePaths.frontPath, watermarkStyle: this.pendingWatermarkStyle, watermarkText: this.pendingWatermarkText }); this.captureBusy false; this.sequentialCaptureQueued false; this.capturePairCount nextPairCount; this.backCaptureDelivered false; this.frontCaptureDelivered false; this.pendingCaptureMode dual; this.pendingSingleCaptureRole back; this.pendingCaptureId ; this.pendingBackCapturePath ; this.pendingFrontCapturePath ; this.pendingCaptureLatitude 0; this.pendingCaptureLongitude 0; this.pendingCapturePlace ; this.pendingCaptureTitle ; this.clearPendingWatermark(); this.cameraStatusText capturePaths.composited ? : 双摄合成失败已保留原片; this.lastCaptureSummary this.cameraStatusText; void this.appendGalleryRecord(galleryRecord);这也是双拍和两次单拍的区别最终用户得到的是一个作品记录而不是两个互不相关的文件。工程检查清单双摄拍照前确认两路预览都 live避免半路触发。后摄和前摄路径要在同一 captureId 下生成。两路回调都完成后再创建记录不能先到先入库。合成失败要保留原片路径并给用户可理解提示。入库后复用第 33 篇的相册、地图和持久化刷新闭环。今日练习真机触发一次双拍按日志顺序记录 back/front 两路回调是否都到达。人为让合成失败一次确认相册是否仍能看到原片记录。把第 34-38 篇的函数画成一条完整时序线。下一篇会继续沿着同一条工程链路往下拆先看用户能看到的效果再回到源码确认状态、文件和服务边界是否闭合。