我正在尝试将storelist放入StoreList变量。但它没有用。
doInBackground方法工作正常但onPostexecute无效。
这是我的代码，
public class guest_main extends Fragment implements View.OnClickListener,GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener, com.google.android.gms.location.LocationListener {
Location mCurrentLocation, mDestination;
private GoogleApiClient mGoogleApiClient;
private LocationRequest mLocationRequest;
String currentLon, currentLat;
private ListView mListView = null;
private ListViewAdapter mAdapter = null;
public ArrayList<HashMap<String, String>> StoreList;
class BackgroundWorker3 extends AsyncTask<String, Void,ArrayList<HashMap<String, String>>> {
Context context;
AlertDialog alertDialog;
BackgroundWorker3(Context ctx) {
context = ctx;
}
JSONArray store = null;
ArrayList<HashMap<String, String>> storeList;
protected ArrayList<HashMap<String, String>> doInBackground(String... params) {
String type = params[0];
storeList = new ArrayList<HashMap<String, String>>();
if (type.equals("Select2")) {
try {
String link = "...";
URL url = new URL(link);
URLConnection conn = url.openConnection();
conn.setDoOutput(true);
OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
wr.flush();
BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
StringBuilder sb = new StringBuilder();
String json;
while ((json = reader.readLine()) != null) {
sb.append(json);
}
String s = sb.toString().trim();
JSONObject jsonObject = new JSONObject(s);
store = jsonObject.getJSONArray("result");
for (int i = 0; i < store.length(); i++) {
JSONObject c = store.getJSONObject(i);
String name = c.getString("name");
String tel = c.getString("tel");
String latitude = c.getString("latitude");
String longitude = c.getString("longitude");
HashMap<String, String> stores = new HashMap<String, String>();
stores.put("name", name);
stores.put("tel", tel);
stores.put("latitude", latitude);
stores.put("longitude", longitude);
storeList.add(stores);
}
return storeList;
} catch (Exception e) {
return null;
}
}
return storeList;
}
@Override
protected void onPreExecute() {
alertDialog = new AlertDialog.Builder(context).create();
alertDialog.setTitle("Login Status");
}
@Override
protected void onPostExecute(ArrayList<HashMap<String, String>> arrayList) {
StoreList = arrayList;
}
}
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.guest_main, container, false);
StoreList = new ArrayList<HashMap<String, String>>();
getData();
buildGoogleApiClient();
mListView = (ListView)v.findViewById(R.id.mList);
mAdapter = new ListViewAdapter(getActivity());
for(int i=0; i<StoreList.size(); i++){
HashMap<String, String> each = StoreList.get(i);
String name = each.get("name");
String tel = each.get("tel");
String lat = each.get("latitude");
String lon = each.get("longitude");
mDestination.setLatitude(Double.valueOf(lat).doubleValue());
mDestination.setLongitude(Double.valueOf(lon).doubleValue());
float distance = mCurrentLocation.distanceTo(mDestination);
mAdapter.addItem(getResources().getDrawable(R.drawable.sin), name, tel,Float.toString(distance));
}
mListView.setAdapter(mAdapter);
Button btn = (Button) v.findViewById(R.id.button1);
btn.setOnClickListener(this);
return v;
}
public void getData(){
BackgroundWorker3 bk2 = new BackgroundWorker3(getActivity());
bk2.execute("Select2");
}
@Override
public void onClick(View view) {
switch (view.getId()){
case R.id.button1:
Intent intent = new Intent(getActivity().getApplicationContext(), gmenu_list.class);
startActivity(intent);
}
}
private class ViewHolder {
public ImageView mIcon;
public TextView mText;
public TextView mDate;
public TextView mDistance;
}
private class ListViewAdapter extends BaseAdapter {
private Context mContext = null;
private ArrayList<g_ListData> mListData = new ArrayList<g_ListData>();
public ListViewAdapter(Context mContext) {
super();
this.mContext = mContext;
}
@Override
public int getCount() {
return mListData.size();
}
@Override
public Object getItem(int position) {
return mListData.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
public void addItem(Drawable icon, String mTitle, String mDate, String mDistance){
g_ListData addInfo = null;
addInfo = new g_ListData();
addInfo.mIcon = icon;
addInfo.mTitle = mTitle;
addInfo.mDate = mDate;
addInfo.mDistance = mDistance;
mListData.add(addInfo);
}
public void remove(int position){
mListData.remove(position);
dataChange();
}
public void sort(){
Collections.sort(mListData, g_ListData.ALPHA_COMPARATOR);
dataChange();
}
public void dataChange(){
mAdapter.notifyDataSetChanged();
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
holder = new ViewHolder();
LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.gmenu_list_item, null);
holder.mIcon = (ImageView) convertView.findViewById(R.id.mImage);
holder.mText = (TextView) convertView.findViewById(R.id.mText);
holder.mDate = (TextView) convertView.findViewById(R.id.mDate);
holder.mDistance = (TextView)convertView.findViewById(R.id.mDistance);
convertView.setTag(holder);
}else{
holder = (ViewHolder) convertView.getTag();
}
g_ListData mData = mListData.get(position);
if (mData.mIcon != null) {
holder.mIcon.setVisibility(View.VISIBLE);
holder.mIcon.setImageDrawable(mData.mIcon);
}else{
holder.mIcon.setVisibility(View.GONE);
}
holder.mText.setText(mData.mTitle);
holder.mDate.setText(mData.mDate);
holder.mDate.setText(mData.mDistance);
return convertView;
}
}
@Override
public void onConnected(Bundle bundle) {
mLocationRequest = LocationRequest.create();
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
mLocationRequest.setInterval(100000); // Update location every second
try{
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
mCurrentLocation = LocationServices.FusedLocationApi.getLastLocation(
mGoogleApiClient);}catch (SecurityException e){
}
if (mCurrentLocation != null) {
currentLat = String.valueOf(mCurrentLocation.getLatitude());
currentLon = String.valueOf(mCurrentLocation.getLongitude());
}
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onLocationChanged(Location location) {
currentLat = String.valueOf(location.getLatitude());
currentLon = String.valueOf(location.getLongitude());
}
@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
}
synchronized void buildGoogleApiClient(){
mGoogleApiClient = new GoogleApiClient.Builder(getActivity())
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build();
}
@Override
public void onStart() {
super.onStart();
mGoogleApiClient.connect();
}
@Override
public void onDestroy() {
super.onDestroy();
mGoogleApiClient.disconnect();
}
}
答案 0 :(得分：-1)
好的..问题出在你的情况下，Async任务在UI线程的单独线程上运行所以当你在getData方法中调用BackgroundWorker3时，UI线程不等待异步任务响应（separte线程）和StoreList有null值。所以你看到StoreList没有任何值，在listView中什么都不会显示。
将此代码写入onPostExecute方法而不是onCreate ..
@Override
protected void onPostExecute(ArrayList<HashMap<String, String>> arrayList) {
StoreList = arrayList;
mListView = (ListView)v.findViewById(R.id.mList);
mAdapter = new ListViewAdapter(getActivity());
for(int i=0; i<StoreList.size(); i++){
HashMap<String, String> each = StoreList.get(i);
String name = each.get("name");
String tel = each.get("tel");
String lat = each.get("latitude");
String lon = each.get("longitude");
mDestination.setLatitude(Double.valueOf(lat).doubleValue());
mDestination.setLongitude(Double.valueOf(lon).doubleValue());
float distance = mCurrentLocation.distanceTo(mDestination);
mAdapter.addItem(getResources().getDrawable(R.drawable.sin), name, tel,Float.toString(distance));
}
mListView.setAdapter(mAdapter);
}
希望这会对你有所帮助。