如何从改装API返回对象获取呼叫

Question

我正在尝试通过Retrofit获得API调用的对象列表，但我只是找不到这样做的方法:(这是我构建的功能：

 private List<Business> businesses getBusinesses()
{
    List<Business> businessesList = new ArrayList<>();
    Call<List<Business>> call = jsonPlaceHolderApi.getBusinesses();
    call.enqueue(new Callback<List<Business>>() {
        @Override
        public void onResponse(Call<List<Business>> call, Response<List<Business>> response) {
            if(!response.isSuccessful())
            {
                textViewResult.setText("Code: " + response.code());
                return;
            }
            List<Business> businesses = response.body();
            for(Business business : businesses)
            {
                String content = "";
                content += "ID: " + business.getId() + "n";
                content += "Name: " + business.getName() + "n";
                content += "On promotion: " + business.isOnPromotion() + "nn";
                textViewResult.append(content);
            }
            businessesList = businesses;
        }
        @Override
        public void onFailure(Call<List<Business>> call, Throwable t) {
            call.cancel();
            textViewResult.setText(t.getMessage());
        }
    });
}

我正在尝试获得企业的响应并将其返回。谁能帮我？感到沮丧：（

Answer 1

使用 call.enqueue执行改造调用的方式是异步的。这种方法没有错。实际上，这也许是最好的选择，因为网络呼叫可能需要一段时间，而您不想不必要地阻止。

不幸的是，这意味着您无法从功能中返回结果。在大多数情况下，如果您这样做了，返回后可能会完成电话，从而使您的返回无用。

有几种处理方法，最简单的方法是使用回调。例如：

interface OnBusinessListReceivedCallback {
     void onBusinessListReceived(List<Business> list);
}
private void businesses getBusinesses(OnBusinessListReceivedCallback callback){
  Call<List<Business>> call = jsonPlaceHolderApi.getBusinesses();
  call.enqueue(new Callback<List<Business>>() {
    @Override
    public void onResponse(Call<List<Business>> call, Response<List<Business>> response) {
        if(!response.isSuccessful()){
            textViewResult.setText("Code: " + response.code());
            return;
        }
        callback.onBusinessListReceived(response.body());
    }
    @Override
    public void onFailure(Call<List<Business>> call, Throwable t) {
        call.cancel();
        textViewResult.setText(t.getMessage());
    }
  });
}

您可以这样称呼：

getBusinesses(new OnBusinessListReceivedCallback() {
     public void onBusinessListReceived(List<Business> list){
        // list holds your data
     }
});