Java Android AsyncHttpClient 将 byte[]responseBody 转换为 InputStream

Question

我想创建一个返回 InputStream 的方法，我这样做了:

 public static InputStream sendGetDataRequest(Context context,
                                                 String version, String power, String lon, String lat, String radius)  throws MalformedURLException, ConnectTimeoutException, IOException

    {
        AsyncHttpClient client = new AsyncHttpClient();
        String url = Util.getServerUrl(context) + "/GetData";
//        ContentValues values=new ContentValues();
        RequestParams values = new RequestParams();

        values.put("token", String.valueOf(E_Gps.TOKEN));
        values.put("xml", login_xml);
        StringEntity entity = null;
        try {
            entity = new StringEntity(values.toString());
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        entity.setContentType(new BasicHeader("Content-Type","application/xml"));
        final InputStream[] is = new InputStream[1];
        final InputStream inputStream;
        client.post(context,url,values , new AsyncHttpResponseHandler(Looper.getMainLooper()) {

            @Override
            public void onSuccess(int statusCode, Header[] headers, byte[] responseBody) {
                Log.e("success_noti", new String(responseBody) + "");
                is[0] = new ByteArrayInputStream(responseBody);
                Log.e("Status " , statusCode + " ");
                Log.e("is" , convertStreamToString(is[0]));
            }

            @Override
            public void onFailure(int statusCode, Header[] headers, byte[] responseBody, Throwable error) {
                Log.e("success_noti", new String(responseBody) + "");
                Log.e("Status " , statusCode + " ");


}
    });
return is[0];
}

当我返回 is[0] is a null 但当我登录 onSuccess 时，我遇到了问题:

Log.e("is" , convertStreamToString(is[0]));

is not null 为什么我有 null 对象 is[0] ？

Answer 1

因为client.post是异步调用，而return is[0]是同步调用。这意味着只要异步调用尚未完成，is[0] 就为 null。解决方法之一是让 sendGetDataRequest 返回 void 并接受回调，例如

public static void sendGetDataRequest(final YourCallback callback, ...)

创建一个名为YourCallback的新接口(interface)

public interface YourCallback{
  void onSuccess(String string);
  void failure();
}

并在异步方法中使用该回调

 client.post(context,url,values , new AsyncHttpResponseHandler(Looper.getMainLooper()) {

            @Override
            public void onSuccess(int statusCode, Header[] headers, byte[] responseBody) {
                callback.onSuccess(convertStreamToString(is[0]));
            }

            @Override
            public void onFailure(int statusCode, Header[] headers, byte[] responseBody, Throwable error) {
              callback.onFailure(); 
            }
}

最后你像这样调用静态方法

sendGetDataRequest(new YourCallback(){/* Override the methods */}, ...);

顺便说一句，您还可以使用 android 包中的 AsyncTask 来完成上述所有操作。这是个人喜好。