我想将值传递给HTTP POST并获得一些结果，但是我从服务器获取结果时遇到小问题。所有内容都在同一个文件中
我的Asycn任务
private class GetCustomerDataTask extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... urls) {
// params comes from the execute() call: params[0] is the url.
try {
return downloadUrl(urls[0]);
} catch (IOException e) {
return "Unable to retrieve web page. URL may be invalid.";
}
}
// onPostExecute displays the results of the AsyncTask.
@Override
protected void onPostExecute(String result) {
parseData(result);// i am going to call method here
}
}
private String downloadUrl(String myurl) throws IOException {
InputStream is = null;
// Only display the first 500 characters of the retrieved
// web page content.
int len = 500;
List<NameValuePair> params = new ArrayList<>();
params.add(new BasicNameValuePair("cus_name", cus_names));
params.add(new BasicNameValuePair("created_date1", createddate));
params.add(new BasicNameValuePair("created_date2", created_date));
//String urlParameters ="cus_name=" + URLEncoder.encode(cus_names, "UTF-8") + "&created_date1=" + URLEncoder.encode(createddate, "UTF-8") + "&created_date2=" + URLEncoder.encode(created_date, "UTF-8");
String urlParameters = URLEncoder.encode("cus_name", "UTF-8")+ "=" + URLEncoder.encode(cus_names, "UTF-8");
urlParameters += "&" + URLEncoder.encode("created_date1", "UTF-8") + "=" + URLEncoder.encode(createddate, "UTF-8");
urlParameters += "&" + URLEncoder.encode("created_date2", "UTF-8") + "=" + URLEncoder.encode(created_date, "UTF-8");
URL url;
HttpURLConnection connection = null;
try {
//Create connection
url = new URL(myurl);
connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
connection.setRequestProperty("Content-Length", "" + Integer.toString(urlParameters.getBytes().length));
connection.setRequestProperty("Content-Language", "en-US");
connection.setUseCaches(false);
connection.setDoInput(true);
connection.setDoOutput(true);
//Send request
DataOutputStream wr = new DataOutputStream(
connection.getOutputStream());
wr.writeBytes(getQuery(params));
wr.flush();
wr.close();
//Get Response
is = connection.getInputStream();
BufferedReader rd = new BufferedReader(new InputStreamReader(is));
String line;
StringBuffer response = new StringBuffer();
System.out.println(response);
while ((line = rd.readLine()) != null) {
response.append(line);
response.append('\r');
}
rd.close();
return response.toString();
} catch (Exception e) {
e.printStackTrace();
return null;
} finally {
if (connection != null) {
connection.disconnect();
}
}
}
private String getQuery(List<NameValuePair> params) throws UnsupportedEncodingException {
StringBuilder result = new StringBuilder();
boolean first = true;
for (NameValuePair pair : params) {
if (first)
first = false;
else
result.append("&");
result.append(URLEncoder.encode(pair.getName(), "UTF-8").replace("+", "%20"));
result.append("=");
result.append(URLEncoder.encode(pair.getValue(), "UTF-8").replace("+", "%20"));
}
return result.toString();
}
如果是对或错，因为我的应用程序不幸被停止。我认为这是正确的方式（可能是）。
我的ParseData方法
public void parseData(String result) {
try {
JSONObject parentObject = new JSONObject(result);
JSONArray data = parentObject.getJSONArray("sales_customer_repo");
//JSONArray data = new JSONArray(getJSONUrl(url,params));
ArrayList<CustomerData> customerArrayList = new ArrayList<CustomerData>();
for (int i = 0; i < data.length(); i++) {
JSONObject c = data.getJSONObject(i);
String S_No = c.getString("S_No");
String createdDate = c.getString("created_date");
String orderNo = c.getString("order_no");
String goods_name = c.getString("goods_name");
String supply_qty = c.getString("supply_qty");
customerArrayList.add(new CustomerData(S_No, createdDate, orderNo, goods_name, supply_qty));
}
ImageAdapter imageAdapter = new ImageAdapter(this, customerArrayList);
listView1 = (ListView) findViewById(R.id.listview_customername);
listView1.setAdapter(imageAdapter);
imageAdapter.notifyDataSetChanged();
registerForContextMenu(listView1);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
调试我的应用程序此行以达到让我的应用程序崩溃
JSONObject parentObject = new JSONObject（result）; JSONArray data = parentObject.getJSONArray（＆＃34; sales_customer_repo＆＃34;）;
logcat的：
07-04 15:43:59.775 12998-12998/com.example.vari.new_varri E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.vari.new_varri, PID: 12998
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116)
at org.json.JSONTokener.nextValue(JSONTokener.java:94)
at org.json.JSONObject.<init>(JSONObject.java:156)
at org.json.JSONObject.<init>(JSONObject.java:173)
at com.example.vari.new_varri.Sales_Customers_wise.parseData(Sales_Customers_wise.java:311)
at com.example.vari.new_varri.Sales_Customers_wise$GetCustomerDataTask.onPostExecute(Sales_Customers_wise.java:191)
at com.example.vari.new_varri.Sales_Customers_wise$GetCustomerDataTask.onPostExecute(Sales_Customers_wise.java:176)
at android.os.AsyncTask.finish(AsyncTask.java:651)
at android.os.AsyncTask.-wrap1(AsyncTask.java)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:668)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
答案 0 :(得分：0)
这对我有用，请检查您使用带有协议的正确网址（http://www.ursite.com）：
x <- sample(
seq(as.Date('1000/01/01'), as.Date('2000/01/01'), by="day"),
400000, replace = T)
system.time({
y <- substr(x, 1, 4)
m <- substr(x, 6, 7)
d <- substr(x, 9, 10)
})
# user system elapsed
# 3.775 0.004 3.779
system.time({
y <- format(x,"%y")
m <- format(x,"%m")
d <- format(x,"%d")
})
# user system elapsed
# 1.118 0.000 1.118
system.time({
y <- year(x)
m <- month(x)
d <- day(x)
})
# user system elapsed
# 0.951 0.000 0.951
x1 <- as.character(x)
system.time({
y <- substr(x1, 1, 4)
m <- substr(x1, 6, 7)
d <- substr(x1, 9, 10)
})
# user system elapsed
# 0.082 0.000 0.082