Android的改造-如何进行顺序网络调用

Question

in my android app i have 3 network calls and they are dependent on the call before it. So 1 must finish, then 2 can go and finally 3 gets run with the data from the previous ones. So i need the network calls to run sequentially is the goal. after one call is finished it will have data passed to the next call, etc. I dont want to use rxJava. Is there a way with retrofit to make this happen ? My project is already using retrofit thus i want to continue using it ? I've tried playing around with asynchTask but its not clean and since im using retrofit i thought i would ask.

Answer 1

If you're using Retrofit with the asynchronous Callback s then for the first network call you can pass in the generated interface which represents the web service that you're interacting with. In the success method you can then use the instance of the generated interface to make a second network call, using the data which came back in success under the parametrised type T , and so on for the third call inside a second callback. For example:

class FirstCallback implements Callback<First> {

  private Api api;

  public FirstCallback(Api api) {
    this.api = api;
  }

  void success(First data, Response response) {
    api.secondCall(data, new SecondCallback(api))
  }
}

// somewhere else in your code
api.firstCall(new FirstCallback(api));

This is a quick solution using chaining with the asynchronous calls. This would most likely look more sequential and easier to read inside of an AsyncTask using the synchronous calls, which would return the type T directly. For example:

class MyTask extends AsyncTask<Void, Void, Void> {

  protected Void doInBackground(Void... params) {
    First first = api.firstCall();
    Second second = api.secondCall(first);
    // ...and so on until you return the final result
  }
}