我想将 ListView 设置为从 Web 服务获取的数据。我在 AsyncTask 实例中获取数据，但是当我尝试设置一些 ListView 属性时，它崩溃了（在线“lv.setVisibility(View.VISIBLE);”）。有人可以帮忙吗？
谢谢
public class Atable extends Activity {
private EditText mSearch;
private static final int ACTIVITY_EDIT=0;
private Button mSearchButton;
private TextView mNoresults;
private ListView lv;
private CheckBox checkBox;
private LocationManager locationManager;
private RestaurantList restaurantList;
private Criteria criteria;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
lv= (ListView)findViewById(R.id.listview);
mNoresults = (TextView) findViewById(R.id.noresults);
mNoresults.setVisibility(View.GONE);
mSearchButton = (Button)this.findViewById(R.id.button);
checkBox = (CheckBox) findViewById(R.id.local_check);
locationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_FINE);
mSearchButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
mNoresults.setVisibility(View.GONE);
mSearch = (EditText) findViewById(R.id.search);
String tmp_str = mSearch.getText().toString().replace(" ","+");
String url = "http://www.atable.org/getRestaurantByQuery/?query=" + tmp_str;
if (checkBox.isChecked()) {
//get location
String provider = locationManager.getBestProvider(criteria, true);
Location location = locationManager.getLastKnownLocation(provider);
if (location!=null) {
String lat = String.valueOf(location.getLatitude());
String lng = String.valueOf(location.getLongitude());
url += "&lat="+lat+"&lng="+lng;
}
}
new GetRestaurantData().execute(url);
}
});
};
private class GetRestaurantData extends AsyncTask<String, Boolean, RestaurantList> {
private HttpClient httpclient = new DefaultHttpClient();
@Override
protected RestaurantList doInBackground(String... url) {
publishProgress(true);
HttpGet httpget = new HttpGet(url[0]);
// Execute the request
HttpResponse response;
try {
response = httpclient.execute(httpget);
HttpEntity entity = response.getEntity();
if (entity != null) {
InputStream instream = entity.getContent();
Reader r = new InputStreamReader(instream);
Gson gson = new Gson();
restaurantList = gson.fromJson(r, RestaurantList.class);
int nResults = restaurantList.getSize();
if (nResults>0) {
lv.setVisibility(View.VISIBLE); //app crashes here
lv.setAdapter( new ArrayAdapter<String>(Atable.this ,android.R.layout.simple_list_item_1,restaurantList.getRestaurantNames()));
lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(Atable.this, RestaurantDescription.class);
Restaurant tmp_resto = restaurantList.getRestaurant((int)id);
String tmp_categories = tmp_resto.getCategories().get(0);
for (int i=1; i<tmp_resto.getCategories().size(); i++) {
tmp_categories+=", "+tmp_resto.getCategories().get(i);
}
String address = tmp_resto.getStreet()+", "+tmp_resto.getStreetNumber()+"\n"+tmp_resto.getCity()+
" "+tmp_resto.getPostalCode()+"\n"+tmp_resto.getCountry();
intent.putExtra("name", tmp_resto.getName());
intent.putExtra("address", address);
intent.putExtra("rating", tmp_resto.getRating());
intent.putExtra("price_range", tmp_resto.getPriceRange());
intent.putExtra("categories", tmp_categories);
intent.putExtra("latitude", tmp_resto.getLatitude());
intent.putExtra("longitude", tmp_resto.getLongitude());
startActivityForResult(intent, ACTIVITY_EDIT);
}
});
}
else {
lv.setVisibility(View.GONE);
mNoresults.setVisibility(View.VISIBLE);
}
//Closing the input stream will trigger connection release
instream.close();
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return restaurantList;
}
@Override
protected void onProgressUpdate(Boolean... progress) {
// line below coupled with
// getWindow().requestFeature(Window.FEATURE_INDETERMINATE_PROGRESS)
// before setContentView
// will show the wait animation on the top-right corner
Atable.this.setProgressBarIndeterminateVisibility(progress[0]);
}
@Override
protected void onPostExecute(RestaurantList result) {
publishProgress(false);
// Do something with result in your activity
}
}