I'm developing an Android application containing a Webview. The HTML corresponding to the webview contains mainly JavaScript code ; it retrieves a map of a building from a Geoserver. I use Leaflet to display the different layers. Each base layer is a floor.
I'm adding 2 overlays to the base layers from Android ; one is a heatmap, the other is a set of markers representing the locations of some sensors. Thanks to a JavaScript interface in Android, the JavaScript code can get datasets created from Android.
It works when I display only ONE of the overlays. As soon as I want to display both overlays, or after I displayed an overlay, hid it, and display the other, the application crashes. I have different errors according to the overlay added first.
Something really strange : it only happens with my tablet (which is very cheap), not with the AVD.
Here is my JavaScript code :
<script type="text/javascript" charset="utf-8">
var map, baseLayers, heatmapLayer, sensorsLayer;
var ground_floor = new L.tileLayer.wms('http://192.168.1.16/geoserver/wms',
{
layers: 'ground_floor',
format: 'image/png'
});
var first_floor = new L.tileLayer.wms('http://192.168.1.16/geoserver/wms',
{
layers: 'first_floor',
format: 'image/png'
});
var second_floor = new L.tileLayer.wms('http://192.168.1.16/geoserver/wms',
{
layers: 'second_floor',
format: 'image/png'
});
var current_floor = ground_floor;
baseLayers = {
"Ground floor": ground_floor,
"First floor": first_floor,
"Second floor": second_floor
};
map = new L.Map('map', {
center: new L.LatLng(-45, 170),
zoom: 30,
layers: [ground_floor],
crs: L.CRS.EPSG900913
}).setView([-45.8668664, 170.5185323], 31);
var control = L.control.layers(baseLayers).addTo(map);
map.on('baselayerchange', onBaseLayerChanged);
// Called when the base layer (meaning the floor) is changed
function onBaseLayerChanged(event) {
// Update the current floor
if (event.layer == ground_floor)
current_floor = ground_floor;
else if (event.layer == first_floor)
current_floor = first_floor;
else if (event.layer == second_floor)
current_floor = second_floor;
else
Android.debug("Wrong base layer");
Android.debug("yo1");
// Update the heatmap and sensors' location
// if they are displayed
if (map.hasLayer(heatmapLayer)) {
removeHeatmap();
addHeatmap();
}
Android.debug("yo2");
if (map.hasLayer(sensorsLayer)) {
Android.debug("yo3");
removeSensors();
addSensors();
Android.debug("yo4");
}
}
function addHeatmap() {
heatmapLayer = L.TileLayer.heatMap({
// radius could be absolute or relative
// absolute: radius in meters, relative: radius in pixels
radius: { value: 5, absolute: true },
opacity: 0.8,
gradient: {
0.45: "rgb(0,0,255)",
0.55: "rgb(0,255,255)",
0.65: "rgb(0,255,0)",
0.95: "yellow",
1.0: "rgb(255,0,0)"
}
});
var dataSet;
if (current_floor == ground_floor)
dataSet = JSON.parse(Android.getDataSetGroundFloor());
else if (current_floor == first_floor)
dataSet = JSON.parse(Android.getDataSetFirstFloor());
else if (current_floor == second_floor)
dataSet = JSON.parse(Android.getDataSetSecondFloor());
else
Android.debug("Error getDataSet : wrong floor");
heatmapLayer.setData(dataSet.data);
control.addOverlay(heatmapLayer, "Heatmap");
heatmapLayer.addTo(map);
}
function removeHeatmap() {
control.removeLayer(heatmapLayer);
map.removeLayer(heatmapLayer);
}
function addSensors() {
var sLat, sLon;
var markers = new Array();
if (current_floor == ground_floor) {
sLat = JSON.parse(Android.getLatitudesGroundFloor());
sLon = JSON.parse(Android.getLongitudesGroundFloor());
}
else if (current_floor == first_floor) {
sLat = JSON.parse(Android.getLatitudesFirstFloor());
sLon = JSON.parse(Android.getLongitudesFirstFloor());
}
else if (current_floor == second_floor) {
sLat = JSON.parse(Android.getLatitudesSecondFloor());
sLon = JSON.parse(Android.getLongitudesSecondFloor());
}
else
Android.debug("Error getCoordinates : wrong floor");
for (i=0; i<sLat.length && i<sLon.length; i++) {
var marker = L.marker([sLat[i],sLon[i]]);
markers.push(marker);
}
sensorsLayer = L.layerGroup(markers);
control.addOverlay(sensorsLayer, "Sensors");
sensorsLayer.addTo(map);
}
function removeSensors() {
control.removeLayer(sensorsLayer);
map.removeLayer(sensorsLayer);
}
</script>
If I add the heatmap first, and then the sensors I have a NullPointerException on "sensorsLatFloor" of the following code :
public JSONArray getLatitudesGroundFloor() {
if (!isSensorsQueryDone())
new SelectSensorsLocationATask(SensorsFragment.this).execute();
// Wait for the end of the query
while (!querySuccessful) {}
JSONArray latJSON = null;
latJSON = new JSONArray(sensorsLatGroundFloor);
return latJSON;
}
This is for the ground floor but it does the same for every floor. "sensorsLatGroundFloor" is an ArrayList filled by the AsyncTask SelectSensorsLocationATask after a query in the local database. The code works, since it works when I only want to display sensors.
When I display the sensors first, and then the heatmap, the app crashes and I have the following error in the LogCat :
JNI ERROR (app bug): accessed staled weak global reference 0xffffffff (index 65535 in a table of size 8)
VM aborting
Fatal signal 11 (SIGSEV) at 0xdeadd00d
This is very odd, because I don't manipulate JNI code at all...
Besides, I have another error, which must be very stupid but I don't figure out why it doesn't work. Have a look at this part of my JavaScript code :
// Called when the base layer (meaning the floor) is changed
function onBaseLayerChanged(event) {
// Update the current floor
if (event.layer == ground_floor)
current_floor = ground_floor;
else if (event.layer == first_floor)
current_floor = first_floor;
else if (event.layer == second_floor)
current_floor = second_floor;
else
Android.debug("Wrong base layer");
Android.debug("yo1");
// Update the heatmap and sensors' location
// if they are displayed
if (map.hasLayer(heatmapLayer)) {
removeHeatmap();
addHeatmap();
}
Android.debug("yo2");
if (map.hasLayer(sensorsLayer)) {
Android.debug("yo3");
removeSensors();
addSensors();
Android.debug("yo4");
}
}
This function is supposed to update the overlay(s) displayed when I switch the base layer (meaning the floor). It works with the heatmap, but not with the sensors... If the heatmap is not on the map, the function is finished, it doesn't even look at my second if. You can see my "Android.debug", it displays in the LogCat the message I put as parameter. Here, the LogCat only displays "yo1".
EDIT : I figured something out about this last error. The problem seems to be the Leaflet function "hasLayer". If the map has the layer indicated, it returns true. So in my mind, if it doesn't, it's supposed to return false... It makes sense. But instead of it, it makes the code bug, so the code after the function is ignored. Either I'm making a mistake that I don't see when I call it, or Leaflet made a useless function... So I must have done a silly mistake but I don't find it !
I hope I've been clear enough to let you understand my problems... Let me know if you need more Android code, although I don't think it would be helpful.
Thanking you in advance.
* PROBLEM FIXED *
The errors were caused by a problem of task synchronisation in the Android code. You can see that I wait for the end of the query with the variable "querySuccessful". Actually I was manipulating this variable from the AsyncTask only : I set it to false at the beginning and true at the end. Now I set it to true before I start the AsyncTask, and the application works, I have no more errors.
I still have some problems with the Leaflet function hasLayer ; it works when I switch the base layer once, sometimes twice, but then it stops working. But apparently it might be an error from Leaflet, which will be fixed in the next release.
