问题
I debugged my Program and I noticed that I wasent able to run Networking on the same Thread (I searched for this Error like 2 Days because in the Virtual Device the App worked without Problems -.- ). So now I know how I must fix it but I dont have a clue how I can give some parameteres that are not all String to the doinBackground Method.
My Method requires a url a method these i could access afaik with params[0] and params[1] in the doInBackground method. But whats with the List of NameValuePairs how can I access that in the doInBackground method?
Thank you very much for your help :)
This is my class:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.List;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.params.ClientPNames;
import org.apache.http.client.params.CookiePolicy;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;
import android.os.AsyncTask;
import android.util.Log;
public class JSONParser extends AsyncTask<String, Void, JSONObject>{
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
// Funktion um JSON aus einer URL zu holen
// Es wird ein POST oder ein GET Request gesendet
public JSONObject makeHttpRequest(String url, String method,
List<NameValuePair> params) {
// HTTP Request erstellen
try {
// Überprüfen welche Request Methode benutzt werden soll
if(method == "POST"){
DefaultHttpClient httpClient = new DefaultHttpClient();
httpClient.getParams().setParameter(ClientPNames.COOKIE_POLICY,
CookiePolicy.BROWSER_COMPATIBILITY);
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}else if(method == "GET"){
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
//Stream in ein String umwandeln
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Fehler!", "Fehler mein umwandeln von Stream in String: " + e.toString());
}
// JSON Object parsen
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// Das JSONObject zurückgeben
return jObj;
}
@Override
protected JSONObject doInBackground(String... params) {
// TODO Auto-generated method stub
return null;
}
}
回答1:
I don't think you fully understand the full concept of AsyncTasks. You use these when you want to run an operation in a background thread and this is a very nice/flexible way of accomplishing this task. What is really nice to me is onPostExecute() executes on the main thread, so it can really do some powerful things once your work is completed in doInBackground(). You should keep in mind though that because onPostExecute() does execute on the main thread, you do not want to perform any networking operations here.
Here is a simple example of an AsyncTask:
private class myAsyncTask extends AsyncTask<String, Void, Boolean> {
@Override
protected void onPreExecute() {
// before we start working
}
@Override
protected Boolean doInBackground(String... args) {
//do work in the background
return true;
}
@Override
protected void onPostExecute(Boolean success) {
// the work is done.. now what?
}
}
doInBackground() is where you are going to be doing the bulk of your work, so I will try to help you out with the basic structure you want. I just copied and pasted your code where I thought it should go so this is not 100% gauranteed, but hopefully it will help kick off what you want to do:
private class JSONParser extends AsyncTask<String, Void, JSONObject> {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// variables passed in:
String url;
String method;
List<NameValuePair> params;
// constructor
public JSONParser(String url, String method,
List<NameValuePair> params) {
this.url = url;
this.method = method;
this.params = params;
}
@Override
protected JSONObject doInBackground(String... args) {
try {
if(method == "POST"){
DefaultHttpClient httpClient = new DefaultHttpClient();
httpClient.getParams().setParameter(ClientPNames.COOKIE_POLICY,
CookiePolicy.BROWSER_COMPATIBILITY);
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} else if(method == "GET"){
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Fehler!", "Fehler mein umwandeln von Stream in String: " + e.toString());
}
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
return jObj;
}
@Override
protected void onPostExecute(JSONObject obj) {
// Now we have your JSONObject, play around with it.
}
}
Edit:
I forgot to mention that you can also pass in args which is a string array. You can just create args and pass it in when you call your AsyncTask:
new JSONParser(url, method, params).execute(args);
and you can access args in doInBackground()
Here is some more information on AyncTask: http://developer.android.com/reference/android/os/AsyncTask.html
来源：https://stackoverflow.com/questions/13092956/android-asynctask-method-that-i-dont-know-how-to-solve