初始化

m3u8_downloader-master/lib/callback_dispatcher.dart

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+import 'dart:io';
+import 'dart:ui';
+
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+
+// 必须标注：原生启动后台 isolate 时要从 native 闭包化这个入口函数，
+// 新版 Flutter/Dart 不加 @pragma('vm:entry-point') 会报 "To closurize ... it must be annotated"，
+// 后台 isolate 起不来 → 下载进度/成功回调永远到不了 Dart，进度条不刷新。
+@pragma('vm:entry-point')
+void callbackDispatcher() {
+
+  // Initialize state necessary for MethodChannels.
+  WidgetsFlutterBinding.ensureInitialized();
+  const MethodChannel backgroundChannel = MethodChannel('vincent/m3u8_downloader_background', JSONMethodCodec());
+
+  backgroundChannel.setMethodCallHandler((MethodCall call) async {
+    final dynamic args = call.arguments;
+    final CallbackHandle handle = CallbackHandle.fromRawHandle(args[0]);
+
+    final Function? closure = PluginUtilities.getCallbackFromHandle(handle);
+
+    if (closure == null) {
+      print('Fatal: could not find callback');
+      exit(-1);
+    }
+
+    closure(args[1]);
+  });
+
+  backgroundChannel.invokeMethod('didInitializeDispatcher');
+}