Flutter版本升级后iOS应用构建失败求助

我是Flutter iOS开发新手，升级Flutter版本后应用无法构建iOS包，此前运行正常。以下是报错信息：

Xcode构建完成，耗时10.7s
构建iOS应用失败
Xcode构建错误输出：
↳ ** BUILD FAILED **
Xcode输出：
↳ === 构建Pods项目的map_view目标（Debug配置）===
/Users/harshavardhan/Workspace/fleetconnect_flutter/ios/Pods/FMDB/src/fmdb/FMDatabase.m:1486:15: 警告：'sqlite3_wal_checkpoint_v2'仅在iOS 5.0或更高版本可用 [-Wunguarded-availability]
int err = sqlite3_wal_checkpoint_v2(_db, dbName, checkpointMode, logFrameCount, checkpointCount);
^~~~~~~~~~~~~~~~~~~~~~~~~
在从/Users/harshavardhan/Workspace/fleetconnect_flutter/ios/Pods/FMDB/src/fmdb/FMDatabase.m:8导入的'SQLite3'模块中：
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator12.1.sdk/usr/include/sqlite3.h:8244:16: 注释：'sqlite3_wal_checkpoint_v2'已被明确标记为部分可用
SQLITE_API int sqlite3_wal_checkpoint_v2(
^
/Users/harshavardhan/Workspace/fleetconnect_flutter/ios/Pods/FMDB/src/fmdb/FMDatabase.m:1486:15: 注释：将'sqlite3_wal_checkpoint_v2'包裹在@available检查中以消除警告
int err = sqlite3_wal_checkpoint_v2(_db, dbName, checkpointMode, logFrameCount, checkpointCount);
^~~~~~~~~~~~~~~~~~~~~~~~~
生成1条警告。
=== 构建Pods项目的map_view目标（Debug配置）===
/Users/harshavardhan/Workspace/fleetconnect_flutter/ios/Pods/FMDB/src/fmdb/FMDatabaseQueue.m:101:9: 警告：'dispatch_queue_set_specific'仅在iOS 5.0或更高版本可用 [-Wunguarded-availability]
dispatch_queue_set_specific(_queue, kDispatchQueueSpecificKey, (__bridge void *)self, NULL);
^~~~~~~~~~~~~~~~~~~~~~~~~~~
在从/Users/harshavardhan/Workspace/fleetconnect_flutter/ios/Pods/FMDB/src/fmdb/FMDatabaseQueue.h:9导入的'Foundation'模块中：
在从/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator12.1.sdk/System/Library/Frameworks/Foundation.framework/Headers/Foundation.h:6导入的'CoreFoundation'模块中：
在从/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator12.1.sdk/System/Library/Frameworks/CoreFoundation.framework/Headers/CFStream.h:20导入的'Dispatch'模块中：
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator12.1.sdk/usr/include/dispatch/queue.h:1352:1: 注释：'dispatch_queue_set_specific'已被明确标记为部分可用
dispatch_queue_set_specific(dispatch_queue_t queue, const void *key, 
^
/Users/harshavardhan/Workspace/fleetconnect_flutter/ios/Pods/FMDB/src/fmdb/FMDatabaseQueue.m:101:9: 注释：将'dispatch_queue_set_specific'包裹在@available检查中以消除警告
dispatch_queue_set_specific(_queue, kDispatchQueueSpecificKey, (__bridge void *)self, NULL);
^~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/harshavardhan/Workspace/fleetconnect_flutter/ios/Pods/FMDB/src/fmdb/FMDatabaseQueue.m:184:54: 警告：'dispatch_get_specific'仅在iOS 5.0或更高版本可用 [-Wunguarded-availability]
FMDatabaseQueue *currentSyncQueue = (__bridge id)dispatch_get_specific(kDispatchQueueSpecificKey);
^~~~~~~~~~~~~~~~~~~~~
在从/Users/harshavardhan/Workspace/fleetconnect_flutter/ios/Pods/FMDB/src/fmdb/FMDatabaseQueue.h:9导入的'Foundation'模块中：
在从/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator12.1.sdk/System/Library/Frameworks/Foundation.framework/Headers/Foundation.h:6导入的'CoreFoundation'模块中：
在从/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator12.1.sdk/System/Library/Frameworks/CoreFoundation.framework/Headers/CFStream.h:20导入的'Dispatch'模块中：
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator12.1.sdk/usr/include/dispatch/queue.h:1408:1: 注释：'dispatch_get_specific'已被明确标记为部分可用
dispatch_get_specific(const void *key);
^
/Users/harshavardhan/Workspace/fleetconnect_flutter/ios/Pods/FMDB/src/fmdb/FMDatabaseQueue.m:184:54: 注释：将'dispatch_get_specific'包裹在@available检查中以消除警告
FMDatabaseQueue *currentSyncQueue = (__bridge id)dispatch_get_specific(kDispatchQueueSpecificKey);
^~~~~~~~~~~~~~~~~~~~~
生成2条警告。
/Users/harshavardhan/development/flutter/.pub-cache/hosted/pub.dartlang.org/fluttertoast-2.2.11/ios/Classes/FluttertoastPlugin.m:19:23: 警告：未使用变量'viewController' [-Wunused-variable]
UIViewController *viewController = 
^
/Users/harshavardhan/development/flutter/.pub-cache/hosted/pub.dartlang.org/fluttertoast-2.2.11/ios/Classes/FluttertoastPlugin.m:48:19: 警告：未使用变量'size' [-Wunused-variable]
NSNumber *size = call.arguments[@"size"];
^
生成2条警告。
=== 构建Runner项目的Runner目标（Debug配置）===
ld: 未找到Flutter框架
clang: error: 链接命令失败，退出代码1（使用-v查看调用详情）
无法为模拟器构建应用。
在iPhone XR上启动应用失败。
已退出（sigterm）

先别急着重装Flutter！从报错里能看出来，前面一堆警告都是第三方库（FMDB、fluttertoast）的版本兼容提示，这些警告不会导致构建失败，真正的核心问题是ld: 未找到Flutter框架，咱们先针对这个问题来解决：

• 第一步先试试清理iOS依赖缓存，重新安装：

  1. 打开终端，进入项目的ios目录：cd ios
  2. 删除Podfile.lock文件：rm Podfile.lock
  3. 删除整个Pods文件夹：rm -rf Pods
  4. 重新安装pod依赖：pod install
  5. 回到项目根目录，清理Flutter缓存：flutter clean，之后再尝试构建：flutter run

• 如果上面的步骤没用，检查Xcode里的框架引用路径：
  打开Xcode，选中Runner项目，进入Build Settings，搜索Framework Search Paths，确保里面包含$(inherited)和$(FLUTTER_FRAMEWORK_DIR)这两个路径，如果没有就手动添加进去。

• 要是还是不行，试试强制同步Flutter版本：
  在终端执行flutter upgrade --force，完成后再重复一遍flutter clean和pod install的步骤。

• 最后说下那些警告，虽然不影响构建，但看着闹心的话可以处理下：

  • 升级依赖包：在项目的pubspec.yaml里把fluttertoast升级到最新版本；FMDB是map_view依赖的，也可以尝试升级map_view的版本；
  • 或者在Xcode里针对这些警告设置忽略，但更推荐升级依赖来彻底解决。

内容的提问来源于stack exchange，提问作者Harsha Vardhan