Flutter iOS端Firebase Messaging推送图片不显示问题求助

一、Swift版Notification Service Extension配置步骤 #

• 1. 添加Extension目标：打开Xcode主项目，点击顶部菜单栏File > Target > Notification Service Extension，命名（如NotificationService），语言选择Swift，完成创建。
• 2. 配置Pod依赖：在项目根目录的Podfile中新增Extension的Target块，添加Firebase Messaging依赖：

target 'NotificationService' do
  use_frameworks!
  pod 'Firebase/Messaging'
end

执行终端命令pod install，确保依赖安装完成。

• 3. 替换Extension核心代码：打开NotificationService.swift，替换默认代码为以下内容，实现图片下载与附件添加逻辑：

import UserNotifications
import FirebaseMessaging

class NotificationService: UNNotificationServiceExtension {

    var contentHandler: ((UNNotificationContent) -> Void)?
    var bestAttemptContent: UNMutableNotificationContent?

    override func didReceive(_ request: UNNotificationRequest, withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void) {
        self.contentHandler = contentHandler
        bestAttemptContent = (request.content.mutableCopy() as? UNMutableNotificationContent)
        
        guard let bestAttemptContent = bestAttemptContent else {
            contentHandler(request.content)
            return
        }
        
        // 从推送payload中获取图片URL（key可根据实际自定义）
        guard let imageURLString = bestAttemptContent.userInfo["image"] as? String,
              let imageURL = URL(string: imageURLString) else {
            contentHandler(bestAttemptContent)
            return
        }
        
        // 下载图片并添加为通知附件
        downloadAttachment(from: imageURL) { attachment in
            if let attachment = attachment {
                bestAttemptContent.attachments = [attachment]
            }
            contentHandler(bestAttemptContent)
        }
    }
    
    override func serviceExtensionTimeWillExpire() {
        // 超时场景下返回原始通知内容
        if let contentHandler = contentHandler, let bestAttemptContent = bestAttemptContent {
            contentHandler(bestAttemptContent)
        }
    }
    
    private func downloadAttachment(from url: URL, completion: @escaping (UNNotificationAttachment?) -> Void) {
        let task = URLSession.shared.downloadTask(with: url) { tempURL, _, error in
            guard let tempURL = tempURL, error == nil else {
                completion(nil)
                return
            }
            
            let fileManager = FileManager.default
            let tempDir = NSTemporaryDirectory()
            let fileName = url.lastPathComponent
            let destinationURL = URL(fileURLWithPath: tempDir).appendingPathComponent(fileName)
            
            do {
                // 清理已存在的旧文件
                if fileManager.fileExists(atPath: destinationURL.path) {
                    try fileManager.removeItem(at: destinationURL)
                }
                try fileManager.copyItem(at: tempURL, to: destinationURL)
                
                // 创建通知附件
                let attachment = try UNNotificationAttachment(identifier: "", url: destinationURL, options: nil)
                completion(attachment)
            } catch {
                completion(nil)
            }
        }
        task.resume()
    }
}

• 4. 配置Extension的Info.plist：确保NSExtension节点下的NSExtensionAttributes包含以下配置（用于通知展开显示）：
  • 添加键UNNotificationExtensionInitialContentSizeRatio，值设为0.5（可根据需求调整）
  • 可选：添加键UNNotificationExtensionCategory，值与推送payload中的category字段对应
• 5. 推送Payload格式要求：必须包含mutable-content: 1（开启通知可修改权限），并携带图片URL字段，示例：

{
  "aps": {
    "alert": {
      "title": "测试图片推送",
      "body": "这是一条带图片的通知"
    },
    "mutable-content": 1
  },
  "image": "https://example.com/your-image.jpg"
}

二、Objective-C版报错修复方案 #

若选择Objective-C语言创建Extension后出现编译/链接报错，按以下步骤修复：

• 1. 配置Pod依赖：同样在Podfile中为Extension Target添加Firebase依赖：

target 'NotificationService' do
  use_frameworks!
  pod 'Firebase/Messaging'
end

执行pod install后，重新打开项目。

• 2. 替换Extension核心代码：打开NotificationService.m，替换为以下代码：

#import "NotificationService.h"
#import <FirebaseMessaging/FirebaseMessaging.h>
#import <UserNotifications/UserNotifications.h>

@interface NotificationService ()

@property (nonatomic, strong) void (^contentHandler)(UNNotificationContent *contentToDeliver);
@property (nonatomic, strong) UNMutableNotificationContent *bestAttemptContent;

@end

@implementation NotificationService

- (void)didReceiveNotificationRequest:(UNNotificationRequest *)request withContentHandler:(void (^)(UNNotificationContent * _Nonnull))contentHandler {
    self.contentHandler = contentHandler;
    self.bestAttemptContent = [request.content mutableCopy];
    
    // 解析推送中的图片URL
    NSString *imageURLString = self.bestAttemptContent.userInfo[@"image"];
    if (imageURLString && imageURLString.length > 0) {
        NSURL *imageURL = [NSURL URLWithString:imageURLString];
        [self downloadAttachmentFromURL:imageURL completion:^(UNNotificationAttachment *attachment) {
            if (attachment) {
                self.bestAttemptContent.attachments = @[attachment];
            }
            self.contentHandler(self.bestAttemptContent);
        }];
    } else {
        self.contentHandler(self.bestAttemptContent);
    }
}

- (void)serviceExtensionTimeWillExpire {
    self.contentHandler(self.bestAttemptContent);
}

- (void)downloadAttachmentFromURL:(NSURL *)url completion:(void (^)(UNNotificationAttachment *))completion {
    NSURLSessionDownloadTask *task = [[NSURLSession sharedSession] downloadTaskWithURL:url completionHandler:^(NSURL *tempFileURL, NSURLResponse *response, NSError *error) {
        if (error || !tempFileURL) {
            completion(nil);
            return;
        }
        
        NSFileManager *fileManager = [NSFileManager defaultManager];
        NSString *tempDir = NSTemporaryDirectory();
        NSString *fileName = url.lastPathComponent;
        NSURL *destinationURL = [NSURL fileURLWithPath:[tempDir stringByAppendingPathComponent:fileName]];
        
        NSError *fileError;
        if ([fileManager fileExistsAtPath:destinationURL.path]) {
            [fileManager removeItemAtURL:destinationURL error:&fileError];
        }
        [fileManager copyItemAtURL:tempFileURL toURL:destinationURL error:&fileError];
        
        if (fileError) {
            completion(nil);
            return;
        }
        
        NSError *attachmentError;
        UNNotificationAttachment *attachment = [UNNotificationAttachment attachmentWithIdentifier:@"" URL:destinationURL options:nil error:&attachmentError];
        completion(attachment);
    }];
    [task resume];
}

@end

• 3. 排查编译错误：若出现头文件找不到，检查Extension Target的Build Settings > Framework Search Paths是否包含Pods/Headers/Public路径；若出现链接错误，添加Other Linker Flags为-ObjC。
• 4. 推送Payload要求与Swift版一致，必须包含mutable-content:1和图片URL字段。

内容的提问来源于stack exchange，提问作者Sulaymon Ne'matov