我的应用程序中有一个 MapsActivity，它通过单击 MainActivity 中的按钮启动，当活动开始时，我将通过 JSON 获取标记坐标并在 MapsActivity 中显示它们，但这只会在第一次发生，一旦我按下返回并转到MainActivity 并再次按下按钮 MapsActivity 启动，但标记不会显示在其中。我试图结束或破坏活动，但这没有帮助。 任何帮助将不胜感激
这是我的 MapsActivity 代码：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps);
check_activity = 1;
backgroundTask2 = new BackgroundTask2(textView);
backgroundTask2.execute();
ma_fin = this;
MainActivity.maps_adv = 1;
if (flag == 1) {
map_update();
maps_adv = 0;
}
getWindow().getDecorView().setLayoutDirection(View.LAYOUT_DIRECTION_RTL);
checkLocationPermission();
setUpMapIfNeeded();
map_update();
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build();
// Create the LocationRequest object
mLocationRequest = LocationRequest.create()
.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
.setInterval(10 * 1000) // 10 seconds, in milliseconds
.setFastestInterval(1 * 1000); // 1 second, in milliseconds
}
@Override
protected void onResume() {
super.onResume();
setUpMapIfNeeded();
mGoogleApiClient.connect();
}
@Override
protected void onPause() {
super.onPause();
if (mGoogleApiClient.isConnected()) {
LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient,
this);
mGoogleApiClient.disconnect();
}
}
}
private void setUpMap() {
mMap.addMarker(new MarkerOptions().position(new LatLng(0,
0)).title("Marker"));
}
private void handleNewLocation(Location location) {
Log.d(TAG, location.toString());
double currentLatitude = location.getLatitude();
double currentLongitude = location.getLongitude();
LatLng latLng = new LatLng(currentLatitude, currentLongitude);
MarkerOptions options = new MarkerOptions()
.position(latLng)
.title("Your Location");
mMap.addMarker(options);
float zoomLevel = 13.0f; //This goes up to 21
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(latLng, zoomLevel));
}
@Override
public void onConnected(Bundle bundle) {
if (ActivityCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION) !=
PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_COARSE_LOCATION) !=
PackageManager.PERMISSION_GRANTED) {
return;
}
Location location = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
if (location == null) {
LocationServices.FusedLocationApi.requestLocationUpdates(
mGoogleApiClient, mLocationRequest, this);
} else {
handleNewLocation(location);
}
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
/*
* Google Play services can resolve some errors it detects.
* If the error has a resolution, try sending an Intent to
* start a Google Play services activity that can resolve
* error.
*/
if (connectionResult.hasResolution()) {
try {
// Start an Activity that tries to resolve the error
connectionResult.startResolutionForResult(
this, CONNECTION_FAILURE_RESOLUTION_REQUEST);
/*
* Thrown if Google Play services canceled the original
* PendingIntent
*/
} catch (IntentSender.SendIntentException e) {
// Log the error
e.printStackTrace();
}
} else {
/*
* If no resolution is available, display a dialog to the
* user with the error.
*/
Log.i(TAG, "Location services connection failed with code " +
connectionResult.getErrorCode());
}
}
@Override
public void onLocationChanged(Location location) {
handleNewLocation(location);
}
public static final int MY_PERMISSIONS_REQUEST_LOCATION = 1;
public boolean checkLocationPermission() {
if (ContextCompat.checkSelfPermission(this,
android.Manifest.permission.ACCESS_COARSE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
if (ActivityCompat.shouldShowRequestPermissionRationale(this,
android.Manifest.permission.ACCESS_COARSE_LOCATION)) {
requestPermissions(new String[]{
android.Manifest.permission.ACCESS_COARSE_LOCATION
},
MY_PERMISSIONS_REQUEST_LOCATION);
} else {
requestPermissions(new String[]{
android.Manifest.permission.ACCESS_COARSE_LOCATION
},
MY_PERMISSIONS_REQUEST_LOCATION);
}
return false;
} else {
return true;
}
}
@Override
public void onMapReady(GoogleMap googleMap) {
try {
final ArrayList myList;
if (checker==0) {
myList = (ArrayList<Object>) getIntent().getSerializableExtra("maps");
}
else
{
checker = 0;
myList = maps;
}
mMap = googleMap;
mMap.clear();
for (int i = 0; i < myList.size(); i++) {
LatLng sydney = new LatLng(((Double) (((ArrayList) myList.get(i))).get(2)).doubleValue(), ((Double) (((ArrayList) myList.get(i))).get(3)).doubleValue());
mMap.addMarker(new MarkerOptions().position(sydney).title((String) (((ArrayList) myList.get(i))).get(1)).icon(BitmapDescriptorFactory.fromResource(R.drawable.location_icon)));
}
mMap.setOnMarkerClickListener(new GoogleMap.OnMarkerClickListener() {
@Override
public boolean onMarkerClick(Marker marker) {
String position = "0";
String title = marker.getTitle();
for (int i = 0; i < myList.size(); i++) {
if (title.equals(((ArrayList) myList.get(i)).get(1).toString())) {
position = ((ArrayList) myList.get(i)).get(0).toString();
titlename = ((ArrayList) myList.get(i)).get(1).toString();
address = ((ArrayList) myList.get(i)).get(4).toString();
}
}
foo = Integer.valueOf(position);
a = ((ArrayList) myList.get(foo)).get(0).toString();
backgroundTask = new BackgroundTask(textView);
backgroundTask.execute();
map_check = 1;
MainActivity.maps_adv = 0;
return true;
}
});
} catch (RuntimeException e) {
e.printStackTrace();
}
}
private class BackgroundTask extends AsyncTask<Void, Void, String> {
private final WeakReference<TextView> messageViewReference;
private BackgroundTask(TextView textView) {
this.messageViewReference = new WeakReference<>(textView);
}
@Override
protected String doInBackground(Void... voids) {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(MainActivity.url);
try {
jsonobj = new JSONObject();
jsonobj.put("hotel_id_post", foo);
Log.i("EEE", a);
List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("req", jsonobj.toString()));
nameValuePairs.add(new BasicNameValuePair("func", "2"));
nameValuePairs.add(new BasicNameValuePair("adv", MainActivity.features.toString()));
nameValuePairs.add(new BasicNameValuePair("adv_cont", ("" + features_count).toString()));
nameValuePairs.add(new BasicNameValuePair("date", MainActivity.current_date));
nameValuePairs.add(new BasicNameValuePair("during", "1"));
Log.e("mainToPost", "mainToPost" + nameValuePairs.toString());
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
InputStream inputStream = response.getEntity().getContent();
InputStreamToStringExample str = new InputStreamToStringExample();
responseServerhotel = str.getStringFromInputStream(inputStream);
Log.e("responseqqqqqqq", "response -----" + responseServerhotel);
HotelList.jsonroom = new JSONObject(responseServerhotel);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
TextView textView = messageViewReference.get();
if (textView != null) {
textView.setText(s);
}
if (responseServerhotel.equals("{\"types\":null}"))
{
MainActivity.nothing = "no room to show";
Intent intent = new Intent(MapsActivity.this,Nothing.class);
startActivity(intent);
}
else
{
Intent intent = new Intent(MapsActivity.this, RoomList.class);
startActivity(intent);
}
}
}
private class BackgroundTask1 extends AsyncTask<Void, Void, String> {
private final WeakReference<TextView> messageViewReference;
private BackgroundTask1(TextView textView) {
this.messageViewReference = new WeakReference<>(textView);
}
@Override
protected String doInBackground(Void... voids) {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(MainActivity.url);
try {
//mMap.clear();
jsonadv = new JSONObject();
jsonadv_cont = new JSONObject();
jsonobj = new JSONObject();
jsonads = new JSONObject();
MainActivity.features = "";
features_count = 0;
List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("func", "11"));
nameValuePairs.add(new BasicNameValuePair("adv",
MainActivity.features.toString()));
nameValuePairs.add(new BasicNameValuePair("adv_cont", ("" +
features_count).toString()));
nameValuePairs.add(new BasicNameValuePair("date",
MainActivity.current_date));
nameValuePairs.add(new BasicNameValuePair("during", num));
Log.e("mainToPost", "mainToPost" + nameValuePairs.toString());
// Use UrlEncodedFormEntity to send in proper format which we need
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
// Execute HTTP Post Request
HttpResponse response = httpclient.execute(httppost);
InputStream inputStream = response.getEntity().getContent();
InputStreamToStringExample str = new InputStreamToStringExample();
responseServer = str.getStringFromInputStream(inputStream);
Log.e("response", "response -----" + responseServer);
jsonmap = new JSONObject(responseServer);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
TextView textView = messageViewReference.get();
if (textView != null) {
textView.setText(s);
}
backgroundTask2 = new BackgroundTask2(textView);
backgroundTask2.execute();
}
}
@Override
protected void onDestroy() {
super.onDestroy();
if (backgroundTask != null) {
backgroundTask.cancel(true);
}
if (backgroundTask1 != null) {
backgroundTask1.cancel(true);
}
if (backgroundTask2 != null) {
backgroundTask2.cancel(true);
}
finish();
}
private class BackgroundTask2 extends AsyncTask<Void, Void, String> {
private final WeakReference<TextView> messageViewReference;
private BackgroundTask2(TextView textView) {
this.messageViewReference = new WeakReference<>(textView);
}
@Override
protected String doInBackground(Void... voids) {
HttpHandler sh = new HttpHandler();
// Making a request to url and getting response
String jsonStr = sh.makeServiceCall(MainActivity.url);
Log.e(TAG, "Response from url: " + jsonStr);
if (jsonStr != null) {
try {
JSONArray mapsarr = jsonmap.getJSONArray("maps");
for (int i = 0; i < mapsarr.length(); i++) {
ArrayList<Object> mapping = new ArrayList<>();
JSONObject c = mapsarr.getJSONObject(i);
String id = c.getString("hotel_id");
String name = c.getString("hotel_name");
Double x = c.getDouble("hotel_x");
Double y = c.getDouble("hotel_y");
String address = c.getString("hotel_address");
mapping.add(0, id);
mapping.add(1, name);
mapping.add(2, x);
mapping.add(3, y);
mapping.add(4, address);
maps.add(i, mapping);
}
Log.i("MAPTEST", mapsarr.toString());
} catch (final JSONException e) {
Log.e(TAG, "Json parsing error: " + e.getMessage());
runOnUiThread(new Runnable() {
@Override
public void run() {
}
});
}
} else {
Log.e(TAG, "Couldn't get json from server.");
runOnUiThread(new Runnable() {
@Override
public void run() {
}
});
}
return null;
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
final TextView textView = messageViewReference.get();
if (textView != null) {
textView.setText(s);
}
onMapReady(mMap);
checker = 1;
}
}
public static class InputStreamToStringExample {
public static void main(String[] args) throws IOException {
// intilize an InputStream
InputStream is =
new ByteArrayInputStream("file content..blah blah".getBytes());
String result = getStringFromInputStream(is);
System.out.println(result);
System.out.println("Done");
}
// convert InputStream to String
private static String getStringFromInputStream(InputStream is) {
BufferedReader br = null;
StringBuilder sb = new StringBuilder();
String line;
try {
br = new BufferedReader(new InputStreamReader(is));
while ((line = br.readLine()) != null) {
sb.append(line);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (br != null) {
try {
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return sb.toString();
}
}
}
public void map_update() {
maps.clear();
backgroundTask1 = new BackgroundTask1(textView);
backgroundTask1.execute();
}
public static void refresh()
{
flag = 0;
MapsActivity ma = new MapsActivity();
ma.map_update();
}
我面临同样的问题（我退出应用程序并重新打开标记仍然不会显示），你是如何解决的？