flutter

2023-05-12 17:42| 来源: 网络整理| 查看: 265

flutter_downloader 我们用来下载照片,需求是下载后要保存到相册在下载进度回调中需要获取相关的任务拿到下载图片的路径,即可保存资源到相册问题代码:

initDownLoad() async { if (!FlutterDownloader.initialized) { await FlutterDownloader.initialize( debug: BaseConfig.isDebug, ignoreSsl: true); } if (!_isInitialized) { await FlutterDownloader.registerCallback(downloadCallback); } _isInitialized = true; } @pragma('vm:entry-point') static void downloadCallback( String id, DownloadTaskStatus status, int progress) async { if (status.value == DownloadTaskStatus.complete.value && progress == 100) { final list = await FlutterDownloader.loadTasksWithRawQuery( query: 'SELECT * FROM task WHERE task_id = \"$id\"'); if (list != null && list.isNotEmpty) { return list.first.savedDir + '/' + (list.first.filename ?? ''); } } }

下载完成后使用FlutterDownloader.loadTasksWithRawQuery获取相应的下载任务,来获取下载资源路径,但是明明已经初始化了下载器,但是调用该方法会触发assert(_initialized, 'plugin flutter_downloader is not initialized'); 在该回调方法外部调用FlutterDownloader.loadTasksWithRawQuery就么有该问题,没找到具体的原因

解决: 看插件介绍是在回调方法中使用IsolateNameServer,同步下载进度,进行更改,代码为

@pragma('vm:entry-point') static void downloadCallback( String id, DownloadTaskStatus status, int progress) async { final SendPort? send = IsolateNameServer.lookupPortByName('downloader_send_port'); send?.send([id, status.value, progress]); } initDownLoad() async { if (!FlutterDownloader.initialized) { await FlutterDownloader.initialize( debug: BaseConfig.isDebug, ignoreSsl: true); } if (!_isInitialized) { IsolateNameServer.registerPortWithName( _port.sendPort, 'downloader_send_port'); _port.listen((dynamic data) async { String id = data[0]; DownloadTaskStatus status = DownloadTaskStatus(data[1]); int progress = data[2]; sysDownloadProgress(id, progress, status.value); if (status.value == DownloadTaskStatus.complete.value && progress == 100) { print('=========status: ${status.value}'); String path = await AlbumDownloadManager().handleOriginPath(id); if (path.length > 0) { studySaveImage(bytesList: File(path).readAsBytesSync()); } } }); await FlutterDownloader.registerCallback(downloadCallback); } _isInitialized = true; }

更改后竟可以获取路径了,网上相关的资料比较少,在这里记录一下,有遇到相关问题的,同时找到原因的,希望不吝赐教

补充:

原因其实在callback方法的说明中已经给出 Your UI is rendered on the main isolate, while download events come from a background isolate (in other words, code in [callback] is run in the background isolate), so you have to handle the communication between two isolates. 意思是下载进度和UI刷新分属于两个不同的isolates,两个isolates的内存是不共享的,所以出现了开始的在下载回调中获取任务提示下载器没有初始化,我们需要处理两个isolates的通信,所以修改后问题解决,具体的可参考这两篇文章 isolates FlutterEngine 欢迎评论 + 私信

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