从AsyncTask的返回JSON数组 [英] Return JSON Array from AsyncTask
问题描述
我有得到JSON数组的AsyncTask。我怎么会返回JSON数组是这样的：
JSONArray渠道=新的JSON（）执行（富，吧）;包com.example.tvrplayer;
ECLIPS告诉我，我不能做到这一点，它应该是：
的AsyncTask＆LT;对象，整型，JSONArray＆GT;渠道=新的JSON（）执行（http://192.168.2.136:8080/rest/channel/+的linkID +/+用户名，GET）。
JSON的异步类：
公共类的Json扩展的AsyncTask＆LT;对象，整型，JSONArray＆GT; { JSON（）{
超（）;
} @覆盖
保护JSONArray doInBackground（对象... PARAMS）{
// Log.i（JSON，URL）;
字符串URL =（字符串）PARAMS [0];
字符串的方法=（字符串）PARAMS [1];
InputStream为= NULL;
字符串结果=;
JSONArray JSONObject的= NULL; // HTTP
尝试{
HttpClient的HttpClient的=新DefaultHttpClient（）; //为80端口的请求！
如果（方法==GET）{
HTTPGET HTTPGET =新HTTPGET（URL）;
HTT presponse响应= httpclient.execute（HTTPGET）;
HttpEntity实体= response.getEntity（）;
是= entity.getContent（）;
}否则如果（方法==POST）{
HttpPost httppost =新HttpPost（URL）;
HTT presponse响应= httpclient.execute（httppost）;
HttpEntity实体= response.getEntity（）;
是= entity.getContent（）;
}
}赶上（例外五）{
Log.e（JSON - 1 - ，e.toString（））;
返回null;
} //读取响应字符串
尝试{
读者的BufferedReader =新的BufferedReader（新的InputStreamReader（是，UTF-8），8）;
StringBuilder的SB =新的StringBuilder（）;
串线= NULL;
而（（行= reader.readLine（））！= NULL）{
sb.append（行+\\ n）;
}
is.close（）;
结果= sb.toString（）;
//结果= result.substring（1，result.length（） - 1）;
// Log.d（JSON结果，结果）;
}赶上（例外五）{
Log.e（JSON - 2 - ，e.toString（））;
返回null;
} //字符串转换为对象
尝试{
的JSONObject =新JSONArray（结果）;
}赶上（JSONException E）{
Log.e（JSON - 3 - ，e.toString（））;
返回null;
}
返回的JSONObject;
}
@覆盖
保护无效onPostExecute（JSONArray结果）
{
super.onPostExecute（结果）;
最后的消息味精=新的Message（）;
msg.obj =结果;
}
}
这就是我试着做到：
JSONArray渠道=新的JSON（）执行（http://192.168.2.136:8080/rest/channel/+的linkID +/+用户名，GET ）;
尝试{
的for（int i = 0; I＆LT; channels.length（）;我++）{
JSONObject的channel_data = channels.getJSONObject（I）
。字符串的channelID = channel_data.getString（渠道ID）与toLowerCase（）;
JSONArray JSON =新的JSON（）执行（http://192.168.2.136:8080/rest/program/+的linkID +/+用户名+/+的channelID，GET）。
您不要收益从的AsyncTask 。您指示的AsyncTask 称它是前一天做的东西，但不会收益来你任何东西。这就是为什么它被称为异步：你不等待它，它不会等你。
例如，借此code以 SyncTask ：
结果= SyncTask（）;
label.setText（结果）;
这意味着的setText（）行将不会被执行到 SyncTask（）完成，并产生一个结果。这是同步的。相反，随着异步，你做的：
新的AsyncTask（）{
@覆盖
无效onPostExecute（结果）{
label.setText（结果）
}
}。开始（）
这带来了一个全新的世界麻烦。我建议你先看看装载机，这同样的工作，但提供更强的抽象。
另外，我要告诉你的事实，这意味着有很多事情，你不明白。您可能希望谷歌了相关文件，教程和文章。
I have an AsyncTask that gets a JSON Array. How would I return the JSON array like this:
JSONArray channels = new Json().execute(foo, bar);package com.example.tvrplayer;
Eclips tells me I cant do that, it should be:
AsyncTask<Object, Integer, JSONArray> channels = new Json().execute("http://192.168.2.136:8080/rest/channel/"+ linkid +"/"+ username, "GET");
The Json Async Class:
public class Json extends AsyncTask<Object, Integer, JSONArray> {
Json(){
super();
}
@Override
protected JSONArray doInBackground(Object... params) {
// Log.i("JSON",url);
String url = (String) params[0];
String method = (String) params[1];
InputStream is = null;
String result = "";
JSONArray jsonObject = null;
// HTTP
try {
HttpClient httpclient = new DefaultHttpClient(); // for port 80 requests!
if ( method == "GET") {
HttpGet httpget = new HttpGet(url);
HttpResponse response = httpclient.execute(httpget);
HttpEntity entity = response.getEntity();
is = entity.getContent();
} else if (method == "POST") {
HttpPost httppost = new HttpPost(url);
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
}
} catch(Exception e) {
Log.e("JSON - 1 -", e.toString());
return null;
}
// Read response to string
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"utf-8"),8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
// result = result.substring(1,result.length()-1);
// Log.d("JSON result",result);
} catch(Exception e) {
Log.e("JSON - 2 -", e.toString());
return null;
}
// Convert string to object
try {
jsonObject = new JSONArray(result);
} catch(JSONException e) {
Log.e("JSON - 3 -", e.toString());
return null;
}
return jsonObject;
}
@Override
protected void onPostExecute(JSONArray result)
{
super.onPostExecute(result);
final Message msg = new Message();
msg.obj = result;
}
}
this is what Im trying to accomplish:
JSONArray channels = new Json().execute("http://192.168.2.136:8080/rest/channel/"+ linkid +"/"+ username, "GET");
try {
for (int i=0; i < channels.length(); i++) {
JSONObject channel_data = channels.getJSONObject(i);
String channelID = channel_data.getString("ChannelID").toLowerCase();
JSONArray json = new Json().execute("http://192.168.2.136:8080/rest/program/"+ linkid +"/"+ username +"/" + channelID, "GET");
You don't return from AsyncTask. You instruct the AsyncTask to do stuff before calling it a day, but it won't return to you with anything. This is why it's called "asynchronous": you don't wait for it, it doesn't wait for you.
For example, take this code with a SyncTask:
result = SyncTask();
label.setText(result);
That implies that the setText() line won't be executed until SyncTask() is done and yields a result. It's synchronous. Instead, with async, you do:
new AsyncTask() {
@Override
void onPostExecute(result) {
label.setText(result)
}
}.start()
This brings in a whole new world of trouble. I recommend you take a look at Loaders, which work similarly but provide a stronger abstraction.
Also, the fact that I'm telling you this means that there's a lot going on that you don't understand. You may want to google up relevant documentation, tutorials or articles.
这篇关于从AsyncTask的返回JSON数组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
