java - OnPost执行结果为空

Question

我正在将一些数据从我的应用程序发送到外部服务器。

public class PostKey extends AsyncTask<String, String, String> {
    public AsyncResponse delegate = null;

    @Override
    protected String doInBackground(String... params) {
        postData(params[0]);
        return null;
    }

    @Override
    protected void onPostExecute(String result){
        Log.d(String.valueOf(result), " Result?");
        delegate.processFinish(result); // Returns NullPointerException
    }

    public void postData(String valueIWantToSend) {
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost     = new HttpPost("http://domain.com/post.php");

        try {
            List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
            nameValuePairs.add(new BasicNameValuePair("hoi", "test"));
            httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

            HttpResponse response = httpclient.execute(httppost);
            String responseStr = EntityUtils.toString(response.getEntity());

            Log.d(responseStr, "");
        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
        } catch (IOException e) {
            // TODO Auto-generated catch block
        }
    }

    public interface AsyncResponse {
        void processFinish(String output);
    }
}

Log.d(responseStr, "");根据发送的数据返回 true 或 false，并记录它。

delegate.processFinish(result);返回 NullPointerException 还提到 public class PostKey extends AsyncTask<String, String, String>即使所有参数都声明为 Strings .

我也尝试过替换 result与 responseStr但这也不起作用。

Answer 1

您的方法调用出现问题delegate.processFinish(result);委托(delegate)未初始化。因此，您正在调用 null 对象上的方法。