添加删除机制

lib/app_upgrade_plugin_method_channel.dart

@@ -284,6 +284,9 @@ class MethodChannelAppUpgradePlugin extends AppUpgradePluginPlatform {
       }
       debugPrint('下载路径: $savePath');
 
+      // 下载前清理历史APK文件
+      await _clearHistoryApkFiles(savePath);
+
       // 创建文件名
       final fileName = 'app_${DateTime.now().millisecondsSinceEpoch}.apk';
       final filePath = '$savePath/$fileName';
@@ -349,6 +352,38 @@ class MethodChannelAppUpgradePlugin extends AppUpgradePluginPlatform {
     }
   }
 
+  /// 清理下载目录中的历史APK文件
+  /// [downloadPath] 下载目录路径
+  Future<void> _clearHistoryApkFiles(String downloadPath) async {
+    try {
+      final dir = Directory(downloadPath);
+      if (!await dir.exists()) {
+        debugPrint('下载目录不存在，跳过清理: $downloadPath');
+        return;
+      }
+
+      final files = await dir.list().toList();
+      int deletedCount = 0;
+      for (final file in files) {
+        if (file is File && file.path.endsWith('.apk')) {
+          try {
+            await file.delete();
+            deletedCount++;
+            debugPrint('已删除历史APK文件: ${file.path}');
+          } catch (e) {
+            debugPrint('删除历史APK文件失败: ${file.path}, 错误: $e');
+          }
+        }
+      }
+      if (deletedCount > 0) {
+        debugPrint('清理完成，共删除 $deletedCount 个历史APK文件');
+      }
+    } catch (e) {
+      debugPrint('清理历史APK文件失败: $e');
+      // 清理失败不影响下载流程，继续执行
+    }
+  }
+
   @override
   Future<bool> installApk(String filePath) async {
     if (!Platform.isAndroid) {