如何将异常消息传播到活动？

Question

I am using several layers of classes to fetch data from internet and display in Android app.

Activity - ViewModel - Repository - NetworkDataSource ----// Internet

I handle HTTP error messages in NetworkDataSource, where I have try/catch block. However, I would like to propagate this error message to Activity, where I would display a Toast.

How to fire an event in the Activity from NetworkDataSource class?

static String getResponseFromHttpUrl(URL url) throws IOException {
    HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
    String response = "";
    try {
        urlConnection.setConnectTimeout(5000);
        int responseCode = urlConnection.getResponseCode();

        switch (responseCode) {
            case HttpURLConnection.HTTP_OK:
                response = getPayload(urlConnection);
                break;
            case HttpURLConnection.HTTP_UNAVAILABLE:
                throw new IOException("HTTP_UNAVAILABLE");
            case HttpURLConnection.HTTP_NOT_FOUND:
                throw new IOException("HTTP_NOT_FOUND");
            case HttpURLConnection.HTTP_GATEWAY_TIMEOUT:
                throw new IOException("HTTP_GATEWAY_TIMEOUT");
        }

    } catch (IOException e) {
        Log.v(TAG, e.getMessage());
        throw new IOException(e.getMessage());
    } finally {
        urlConnection.disconnect();
    }
    return response;
}

Answer 1

You can use the eventbus. BY eventbus you can send event and can receive ay anyplace you want in the app on whichever thread you want.

https://github.com/greenrobot/EventBus

Answer 2

正如Kirtan指出的那样，除了EventBus外，还可以使用接口回调/ RxJava。