[英]Fragment implementing AsyncTask and Listview in android
这是我的Java代码
但它不起作用我不会得到我的错误。
package info.androidhive.slidingmenu;
import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Fragment;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
public class CommunityFragment extends Fragment {
public CommunityFragment(){}
// Declare Variables
JSONObject jsonobject;
JSONArray jsonarray;
ListView listview;
ListViewAdapter adapter;
ProgressDialog mProgressDialog;
ArrayList<HashMap<String, String>> arraylist;
static String RANK = "rank";
static String COUNTRY = "country";
static String POPULATION = "population";
static String FLAG = "flag";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_community, container, false);
new DownloadJSON().execute();
return rootView;
}
// DownloadJSON AsyncTask
private class DownloadJSON extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Create a progressdialog
mProgressDialog = new ProgressDialog(CommunityFragment.this);
// Set progressdialog title
mProgressDialog.setTitle("Student Government App");
// Set progressdialog message
mProgressDialog.setMessage("Loading...");
mProgressDialog.setIndeterminate(false);
// Show progressdialog
mProgressDialog.show();
}
@Override
protected Void doInBackground(Void... params) {
// Create an array
arraylist = new ArrayList<HashMap<String, String>>();
// Retrieve JSON Objects from the given URL address
jsonobject = JSONFunctions
.getJSONfromURL("http://app-dlslsg.azurewebsites.net/json/postList.php");
try {
// Locate the array name in JSON
jsonarray = jsonobject.getJSONArray("post");
for (int i = 0; i < jsonarray.length(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
jsonobject = jsonarray.getJSONObject(i);
// Retrive JSON Objects
map.put("rank", jsonobject.getString("id"));
map.put("country", jsonobject.getString("body"));
map.put("population", jsonobject.getString("stamp"));
map.put("flag", jsonobject.getString("image"));
// Set the JSON Objects into the array
arraylist.add(map);
//Log.i("body",COUNTRY);
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void args) {
// Locate the listview in listview_main.xml
listview = (ListView) findViewById(R.id.listview);
// Pass the results into ListViewAdapter.java
adapter = new ListViewAdapter(CommunityFragment.this, arraylist);
// Set the adapter to the ListView
listview.setAdapter(adapter);
// Close the progressdialog
mProgressDialog.dismiss();
}
}
}
我今天尝试在网上搜索,但我没有机会看到任何相关的问题。 有人会帮我解决这个问题吗? 我会尽快回复那些回复, 感谢您的帮助!
片段不是Context。 你必须使用getActivity()
,你正在使用CommunityFragment.this
。
更换
mProgressDialog = new ProgressDialog(CommunityFragment.this);
同
mProgressDialog = new ProgressDialog(getActivity());
和
adapter = new ListViewAdapter(CommunityFragment.this, arraylist);
同
adapter = new ListViewAdapter(getActivity(), arraylist);
哦,所以有多个错误:
Fragment.getActivity()
来获取Fragment.getActivity()
的活动,但前提是它已附加。 Fragment.getActivity()
。 findViewById()
表单。 这是一个仅在Activity内部可用的方法,因此您需要再次获取Activity并通过Activity对象调用该方法。
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