### 代码 ``` private fun setModeIntoDownload(camera: Camera, media: MediaFile) { if (camera.isFlatCameraModeSupported) { // like Mavic Air 2 camera.enterPlayback { enterError -> if (enterError != null) { // post enter error return@enterPlayback } fetchDJIPreview(media) } } else { // like p4p, mavic 2 camera.setMode(SettingsDefinitions.CameraMode.MEDIA_DOWNLOAD) { setModeDjiError -> if (setModeDjiError != null) { // post set mode error return@setMode } fetchDJIPreview(media) } } } private fun fetchDJIPreview(media: MediaFile) { media.fetchPreview { fetchError -> if (fetchError != null) { // post fetch error return@fetchPreview } val previewBitmap = media.preview // not null // post preview } } ``` ### 流程 1. 异步将无人机进入下载模式 2. 异步从无人机上下载图片的Preview到SDK 3. 同步获取Preview 4. 切换到UI线程展示图片