将 Cloud Functions for Firebase 提供的 Remote Config 后台函数触发功能与 FCM 结合使用，您可以实时传播 Remote Config 更新动态。在此情形下，您需要创建一个函数，使其在您通过信息中心或 API 发布或回滚远程配置模板时触发。模板更新会触发此函数发送 FCM 消息，告知客户端它们当前的配置已过时，下次应从服务器提取配置：
本文档的其余部分将逐步介绍实时传播远程配置更新动态的操作。
为客户端应用实例订阅 FCM 主题
要向大量客户端应用实例（例如整个用户群）发送 FCM 消息，主题消息传递是最有效的机制。
需要接收实时 Remote Config 更新动态的每个应用实例都必须订阅一个主题名称，例如 PUSH_RC：
Swift
extension AppDelegate : MessagingDelegate {
func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String) {
messaging.subscribe(toTopic: "PUSH_RC") { error in
print("Subscribed to PUSH_RC topic")
}
}
}
Objective-C
- (void)messaging:(FIRMessaging *)messaging didReceiveRegistrationToken:(NSString *)fcmToken {
[[FIRMessaging messaging] subscribeToTopic:@"PUSH_RC" completion:^(NSError * _Nullable error) {
NSLog(@"Subscribed to PUSH_RC topic");
}];
}
Android
@Override
public void onNewToken(String s) {
FirebaseMessaging.getInstance().subscribeToTopic("PUSH_RC");
}
创建一个函数以在模板更新时发送 FCM ping
您可以触发一个函数来响应远程配置事件（包括发布新的配置版本或回滚到旧版本）。 要实时传播模板更新动态，请创建一个函数来侦听模板发布事件，然后在函数中使用 FCM Admin SDK 向客户端应用实例发送静默 ping：
exports.pushConfig = functions.remoteConfig.onUpdate(versionMetadata => {
// Create FCM payload to send data message to PUSH_RC topic.
const payload = {
topic: "PUSH_RC",
data: {
"CONFIG_STATE": "STALE"
}
};
// Use the Admin SDK to send the ping via FCM.
return admin.messaging().send(payload).then(resp => {
console.log(resp);
return null;
});
});
此函数会设置 CONFIG_STATE 参数，然后将其作为 FCM 消息的数据载荷发送给所有订阅了 PUSH_RC 主题的客户端。
在客户端上设置远程配置状态
在应用的共享偏好设置中，上一步中所示的数据载荷始终会将 CONFIG_STATE 设置为 STALE。它表示由于创建了更新后的新模板（该模板的发布触发了相应函数），之前存储在应用上的远程配置模板已经过时。请更新您的通知处理程序并针对这种状况进行测试：
Swift
func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable: Any],
fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
if (userInfo.index(forKey: "CONFIG_STATE") != nil) {
print("Config set to stale")
UserDefaults.standard.set(true, forKey:"CONFIG_STALE")
}
completionHandler(UIBackgroundFetchResult.newData)
}
Objective-C
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {
if (userInfo[@"CONFIG_STATE"]) {
NSLog(@"Config set to stale");
[[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"CONFIG_STALE"];
}
completionHandler(UIBackgroundFetchResultNewData);
}
Android
@Override
public void onMessageReceived(RemoteMessage remoteMessage) {
if (remoteMessage.getData().containsKey("CONFIG_STATE")) {
SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
sharedPreferences.edit().putBoolean("CONFIG_STALE", true).apply();
}
}
在应用启动时提取远程配置更新
Swift
func fetchConfig() {
welcomeLabel.text = remoteConfig[loadingPhraseConfigKey].stringValue
var expirationDuration = 3600
// If your app is using developer mode, expirationDuration is set to 0, so each fetch will
// retrieve values from the service.
if remoteConfig.configSettings.isDeveloperModeEnabled || UserDefaults.standard.bool(forKey: "CONFIG_STALE") {
expirationDuration = 0
}
remoteConfig.fetch(withExpirationDuration: TimeInterval(expirationDuration)) { (status, error) -> Void in
if status == .success {
print("Config fetched!")
self.remoteConfig.activateFetched()
} else {
print("Config not fetched")
print("Error: \(error?.localizedDescription ?? "No error available.")")
}
self.displayWelcome()
}
}
Objective-C
- (void)fetchConfig {
self.welcomeLabel.text = self.remoteConfig[kLoadingPhraseConfigKey].stringValue;
long expirationDuration = 3600;
// If your app is using developer mode, expirationDuration is set to 0, so each fetch will
// retrieve values from the Remote Config service.
if (self.remoteConfig.configSettings.isDeveloperModeEnabled || [[NSUserDefaults standardUserDefaults] boolForKey:@"CONFIG_STALE"]) {
expirationDuration = 0;
}
[self.remoteConfig fetchWithExpirationDuration:expirationDuration completionHandler:^(FIRRemoteConfigFetchStatus status, NSError *error) {
if (status == FIRRemoteConfigFetchStatusSuccess) {
NSLog(@"Config fetched!");
[self.remoteConfig activateFetched];
[[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"CONFIG_STALE"];
} else {
NSLog(@"Config not fetched");
NSLog(@"Error %@", error.localizedDescription);
}
[self displayWelcome];
}];
}
Android
private void fetchWelcomeMessage() {
mWelcomeTextView.setText(mFirebaseRemoteConfig.getString("loading_phrase"));
long cacheExpiration = 43200; // 12 hours in seconds.
// If your app is using developer mode or cache is stale, cacheExpiration is set to 0,
// so each fetch will retrieve values from the service.
if (mFirebaseRemoteConfig.getInfo().getConfigSettings().isDeveloperModeEnabled() ||
mSharedPreferences.getBoolean("CONFIG_STALE", false)) {
cacheExpiration = 0;
}
mFirebaseRemoteConfig.fetch(cacheExpiration)
.addOnCompleteListener(this, new OnCompleteListener<Void>() {
@Override
public void onComplete(@NonNull Task<Void> task) {
if (task.isSuccessful()) {
Toast.makeText(MainActivity.this, "Fetch Succeeded",
Toast.LENGTH_SHORT).show();
// After config data is successfully fetched, it must be activated before newly fetched
// values are returned.
mFirebaseRemoteConfig.activateFetched();
} else {
Toast.makeText(MainActivity.this, "Fetch Failed",
Toast.LENGTH_SHORT).show();
}
mWelcomeTextView.setText(mFirebaseRemoteConfig.getString("welcome_message"));
}
});
}
最后，在您的应用中添加逻辑以在 CONFIG_STATE 为 STALE 时强制从网络中提取 Remote Config（忽略本地存储空间）。如果您的应用过于频繁地从网络中进行提取，则可能会受到 Firebase 的限制。请参阅限制。