App退出与启动功能异常咨询：三Activity应用故障排查

Answer #

Great to hear your Google Sign-In flow is working smoothly! Let's tackle that scenario where your Rating Activity can't find today's rating in SharedPreferences. Here are a few robust approaches you can implement:

Option 1: Fetch the latest rating from your Node.js API

If the user might have submitted a rating on another device or local data was cleared, you can make a GET request to your backend to check for an existing today's rating. Here's a quick example using Retrofit (you could also use OkHttp):

// Retrofit service interface
interface RatingApi {
    @GET("/ratings/today")
    suspend fun getTodayRating(@Header("Authorization") authToken: String): RatingResponse
}

// In your ViewModel/repository
suspend fun fetchAndSaveTodayRating(): Rating? {
    return try {
        val response = ratingApi.getTodayRating(currentUserToken)
        if (response.isSuccessful) {
            response.body()?.let { rating ->
                // Save back to SharedPreferences for future quick access
                val prefsEditor = sharedPreferences.edit()
                prefsEditor.putString("rating_${LocalDate.now()}", Gson().toJson(rating))
                prefsEditor.apply()
                rating
            }
        } else null
    } catch (e: IOException) {
        // Handle network errors (e.g., no internet connection)
        null
    }
}

Option 2: Prompt the user to submit a new rating

If both local SharedPreferences and the API return no today's rating, the logical next step is to present the rating UI to the user. For better UX:

• Clear any stale rating data from SharedPreferences if needed
• Pre-fill a neutral default rating (like 3/5 stars) to reduce friction
• After submission, save the rating to SharedPreferences and send it to your Node.js API immediately

Option 3: Handle offline scenarios gracefully

If the user is offline and no local record exists:

• Show a snackbar explaining we can't verify existing ratings right now
• Let the user submit a rating locally first, then queue it to sync with the API once internet is restored (use WorkManager for reliable background sync)

Bonus: Optimize SharedPreferences key structure

Avoid missing records by using date-specific keys, like rating_2024-05-20 (ISO format). This makes retrieval straightforward and lets you clean up old ratings over time:

val todayKey = "rating_${LocalDate.now()}"
val todayRating = sharedPreferences.getString(todayKey, null)

内容的提问来源于stack exchange，提问作者Navaneeth