我想创建一个类来从URL检索JsonArray。 此类扩展的AsyncTask,以避免在接口上创建多个AsyncTasks。
I'm trying to create a class to retrieve a JsonArray from a url. This class extends AsyncTask to avoid creating multiple AsyncTasks on interfaces.
类正常工作的调试器,但我不知道该怎么做才能得到返回的对象。谁能帮我?
The class works fine on debugger, but I do not know what to do to get the return object. Can anyone help me?
下面是我的类:
public class QueryJsonArray extends AsyncTask<String, Void, Void>{
JSONArray jsonRetorno = null;
@Override
protected Void doInBackground(String... params) {
InputStream is = null;
String result = "";
try {
Log.i(getClass().getName(), params[0]);
HttpClient httpclient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet( params[0]);
HttpResponse response = httpclient.execute(httpGet);
if(response.getStatusLine().getStatusCode()==200){
HttpEntity entity = response.getEntity();
is = entity.getContent();
}else{
is = null;
}
} catch(Exception e) {
e.printStackTrace();
}
if(is!=null){
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();
} catch(Exception e) {
e.printStackTrace();
}
try {
jsonRetorno = new JSONArray(result);
} catch(JSONException e) {
e.printStackTrace();
}
}
return null;
}
}
和我要找回这样的:
QueryJsonArray obj = new QueryJsonArray();
JSONArray jArray = obj.execute(myUrl);
在此先感谢。
Thanks in advance.
您需要使用的回调的。只需添加以下...
You need to use a callback. Simply add the following…
变量:
private Callback callback;
内部接口:
public interface Callback{
public void call(JSONArray array);
}
构造器:
public QueryJsonArray(Callback callback) {
this.callback = callback;
}
此外,改变你的类声明:
Additionally, change your class declaration to:
public class QueryJsonArray extends AsyncTask<Void, Void, JSONArray>
和修改 doInBackground
的返回类型为 JSONArray
。
在 doInBackground
的末尾添加:
return jsonRetorno;
最后,与内容添加下面的方法:
Finally, add the following method with contents:
public void onPostExecute(JSONArray array) {
callback.call(array);
}
现在,为了执行任务,只是做:
Now, to execute the task, just do:
QueryJsonArray obj = new QueryJsonArray(new Callback() {
public void call(JSONArray array) {
//TODO: here you can handle the array
}
});
JSONArray jArray = obj.execute(myUrl);
作为一个方面说明,可以大大简化这一切使用第三方库,如 droidQuery ,这将凝聚所有上述code到:
As a side note, you could greatly simplify all of this using a third party library, such as droidQuery, which would condense all of the above code to:
$.ajax(new AjaxOptions().url(myUrl).success(new Function() {
public void invoke($ d, Object… args) {
JSONArray array = (JSONArray) args[0];
//TODO handle the json array.
}
});