当我尝试使用httpclient获取网页时，为什么我的Android应用程序强制关闭？

Question

我正在使用此代码，

class RequestTask extends AsyncTask<String, String, String>{

@Override
// username, password, message, mobile
protected String doInBackground(String... url) {
    // constants
    int timeoutSocket = 5000;
    int timeoutConnection = 5000;

    HttpParams httpParameters = new BasicHttpParams();
    HttpConnectionParams.setConnectionTimeout(httpParameters, timeoutConnection);
    HttpConnectionParams.setSoTimeout(httpParameters, timeoutSocket);
    HttpClient client = new DefaultHttpClient(httpParameters);

    HttpGet httpget = new HttpGet(url[0]);

    try {
        HttpResponse getResponse = client.execute(httpget);
        final int statusCode = getResponse.getStatusLine().getStatusCode();

        if(statusCode != HttpStatus.SC_OK) {
            Log.w("MyApp", "Download Error: " + statusCode + "| for URL: " + url);
            return null;
        }

        String line = "";
        StringBuilder total = new StringBuilder();

        HttpEntity getResponseEntity = getResponse.getEntity();

        BufferedReader reader = new BufferedReader(new InputStreamReader(getResponseEntity.getContent()));  

        while((line = reader.readLine()) != null) {
            total.append(line);
        }

        line = total.toString();
        return line;
    } catch (Exception e) {
        Log.w("MyApp", "Download Exception : " + e.toString());
    }
    return null;
}

@Override
protected void onPostExecute(String result) {
    // do something with result
}
}

我在onCreate方法中调用execute方法。 当我试图启动应用程序时，它始终强制关闭。 我试图缩小错误，我发现了 HttpResponse getResponse = client.execute(httpget); 这导致了错误。我不知道为什么这对我不起作用？有什么帮助吗？