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獲取JSON數據到mapview中，我仍然獲取地圖，但沒有在JSON文件中給出的Map Locations，並且每當我運行我的應用程序時，不幸的是應用程序已經停止，logcat的說： -引起java.lang.NullPointerException，不幸的是應用程序已停止
10-27 13:02:18.573: E/AndroidRuntime(719): Caused by: java.lang.NullPointerException
10-27 13:02:18.573: E/AndroidRuntime(719): at com.erachnida.restaurant.versionoct.MapView.onCreate(MapView.java:52)
請參閱下面的代碼： -
public class MapView extends MapActivity {
public GeoPoint point;
TapControlledMapView mapView; // use the custom TapControlledMapView
List<Overlay> mapOverlays;
Drawable drawable;
SimpleItemizedOverlay itemizedOverlay;
JSONObject json = null;
@Override
protected void onCreate(final Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
mapOverlays = mapView.getOverlays();
drawable = getResources().getDrawable(R.drawable.ic_launcher);
itemizedOverlay = new SimpleItemizedOverlay(drawable, mapView);
itemizedOverlay.setShowClose(false);
itemizedOverlay.setShowDisclosure(true);
itemizedOverlay.setSnapToCenter(false);
new AsyncTask<Void, Void, Void>() {
@Override
protected Void doInBackground(Void... params) {
// TODO Auto-generated method stub
HttpClient client = new DefaultHttpClient();
// Perform a GET request for a JSON list
HttpUriRequest request = new HttpGet(
"https://dl.***.com/maps.json");
// Get the response that sends back
HttpResponse response = null;
try {
response = client.execute(request);
} catch (ClientProtocolException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
// Convert this response into a readable string
String jsonString = null;
try {
jsonString = StreamUtils.convertToString(response
.getEntity().getContent());
} catch (IllegalStateException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
// Create a JSON object that we can use from the String
JSONObject json = null;
try {
json = new JSONObject(jsonString);
} catch (JSONException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
try {
JSONArray jsonArray = json.getJSONArray("maps");
Log.e("log_tag", "Opening JSON Array ");
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
String latitude = jsonObject.getString("latitude");
String longitude = jsonObject.getString("longitude");
String title = jsonObject.getString("title");
String country = jsonObject.getString("country");
double lat = Double.parseDouble(latitude);
double lng = Double.parseDouble(longitude);
Log.e("log_tag", "ADDING GEOPOINT" + title);
point = new GeoPoint((int) (lat * 1E6),
(int) (lng * 1E6));
OverlayItem overlayItem = new OverlayItem(point, title,
country);
itemizedOverlay.addOverlay(overlayItem);
}
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
itemizedOverlay.populateNow();
mapOverlays.add(itemizedOverlay);
if (savedInstanceState == null) {
MapController controller = mapView.getController();
controller.setCenter(point);
controller.setZoom(7);
} else {
// example restoring focused state of overlays
int focused;
focused = savedInstanceState.getInt("focused_1", -1);
if (focused >= 0) {
itemizedOverlay.setFocus(itemizedOverlay
.getItem(focused));
}
}
}
}.execute();
}
hardik謝謝哥們，請你把我的代碼放在我身上，這樣對我來說會更容易理解 – Stanley
你首先參考http://www.androidhive.info/2012/01/android-json-parsing -tutorial/this。如果有任何問題，請告訴我。它是你的問題的一個很好的例子。 –
我已經使用相同的代碼來使用json解析器，但我很努力地知道需要在onPostExecute（）方法中移動哪些代碼，以及在哪裏放置onPostExecute（）方法，請告訴我bro – Stanley