feat(player): 增加进度条拖动画面预览

ios/Runner/AppDelegate.swift

@@ -1,5 +1,24 @@
 import Flutter
 import UIKit
+import AVFoundation
+
+private final class ThumbnailResponseGate {
+  private let lock = NSLock()
+  private var completed = false
+
+  func send(_ result: @escaping FlutterResult, data: Data?) {
+    lock.lock()
+    if completed {
+      lock.unlock()
+      return
+    }
+    completed = true
+    lock.unlock()
+    DispatchQueue.main.async {
+      result(data)
+    }
+  }
+}
 
 /// Keeps the system LaunchScreen as the only splash. Flutter would otherwise
 /// instantiate that storyboard again and the icon appears a second time.
@@ -16,6 +35,11 @@ final class RunnerFlutterViewController: FlutterViewController {
 
 @main
 @objc class AppDelegate: FlutterAppDelegate, FlutterImplicitEngineDelegate {
+  private let thumbnailQueue = DispatchQueue(
+    label: "com.stormg.lumadrama.thumbnail",
+    qos: .userInitiated
+  )
+
   override func application(
     _ application: UIApplication,
     didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
@@ -44,5 +68,66 @@ final class RunnerFlutterViewController: FlutterViewController {
       activity.completionWithItemsHandler = { _, _, _, _ in result(nil) }
       controller.present(activity, animated: true)
     }
+
+    let thumbnailChannel = FlutterMethodChannel(
+      name: "com.stormg.lumadrama/thumbnail",
+      binaryMessenger: engineBridge.applicationRegistrar.messenger()
+    )
+    thumbnailChannel.setMethodCallHandler { [weak self] call, result in
+      guard call.method == "frame" else {
+        result(FlutterMethodNotImplemented)
+        return
+      }
+      guard let self,
+            let arguments = call.arguments as? [String: Any],
+            let timeNumber = arguments["timeMs"] as? NSNumber else {
+        result(nil)
+        return
+      }
+      let localPath = arguments["localPath"] as? String ?? ""
+      let remoteUrl = arguments["url"] as? String ?? ""
+      let headers = arguments["headers"] as? [String: String] ?? [:]
+      let assetUrl: URL?
+      if !localPath.isEmpty {
+        assetUrl = localPath.hasPrefix("file:")
+          ? URL(string: localPath)
+          : URL(fileURLWithPath: localPath)
+      } else if !remoteUrl.isEmpty {
+        assetUrl = URL(string: remoteUrl)
+      } else {
+        assetUrl = nil
+      }
+      guard let assetUrl else {
+        result(nil)
+        return
+      }
+
+      let options: [String: Any]? = headers.isEmpty
+        ? nil
+        : [AVURLAssetHTTPHeaderFieldsKey: headers]
+      let asset = AVURLAsset(url: assetUrl, options: options)
+      let generator = AVAssetImageGenerator(asset: asset)
+      generator.appliesPreferredTrackTransform = true
+      generator.maximumSize = CGSize(width: 240, height: 426)
+      generator.requestedTimeToleranceBefore = CMTime(seconds: 0.5, preferredTimescale: 600)
+      generator.requestedTimeToleranceAfter = CMTime(seconds: 0.5, preferredTimescale: 600)
+      let time = CMTime(value: timeNumber.int64Value, timescale: 1000)
+      let gate = ThumbnailResponseGate()
+
+      self.thumbnailQueue.async {
+        do {
+          let image = try generator.copyCGImage(at: time, actualTime: nil)
+          let data = UIImage(cgImage: image).jpegData(compressionQuality: 0.7)
+          gate.send(result, data: data)
+        } catch {
+          gate.send(result, data: nil)
+        }
+      }
+      DispatchQueue.global(qos: .userInitiated).asyncAfter(
+        deadline: .now() + 1.5
+      ) {
+        gate.send(result, data: nil)
+      }
+    }
   }
 }