Create a polygon using FeaturesCollection

MIT App Inventor Help
1

Hello friends.

I´m trying to create a polygon from geojson but not working. What am I doing wrong?

{
  "type": "Feature",
  "properties": {
    "Description": "Polígono Irregular en Camagüey",
    "Draggable": false,
    "EnableInfobox": true,
    "FillColor": "#4488004e",
    "FillOpacity": 0.3,
    "ImageAsset": "",
    "StrokeColor": "#000000",
    "StrokeOpacity": 1.0,
    "StrokeWidth": 2,
    "Title": "Camagüey",
    "Visible": true
  },
  "geometry": {
    "type": "Polygon",
    "coordinates": [
      [
        [-77.90744304656984, 21.393422951386587],
        [-77.90880560874939, 21.395840413279284],
        [-77.91027545928956, 21.398257835208145],
        [-77.91045784950258, 21.401584222359443],
        [-77.90774345397949, 21.4008150644897],
        [-77.90516853332521, 21.400415500362858],
        [-77.90319442749023, 21.400375543890117],
        [-77.90160655975343, 21.40141440863241],
        [-77.89980411529542, 21.40089497718403],
        [-77.89834499359131, 21.39981615212504],
        [-77.89873123168947, 21.397818306921025],
        [-77.90744304656984, 21.393422951386587]
      ]
    ]
  }
}

I tested this using geojson.io and looks fine but not for app inventor.

It works like this:

{
  "type": "Feature",
  "properties": {
    "title": "La Guernica"
  },
  "geometry": {
    "type": "Polygon",
    "coordinates": [
      [
        [-77.90744304656984, 21.393422951386587],
        [-77.90880560874939, 21.395840413279284],
        [-77.91027545928956, 21.398257835208145],
        [-77.91045784950258, 21.401584222359443],
        [-77.90774345397949, 21.4008150644897],
        [-77.90516853332521, 21.400415500362858],
        [-77.90319442749023, 21.400375543890117],
        [-77.90160655975343, 21.40141440863241],
        [-77.89980411529542, 21.40089497718403],
        [-77.89834499359131, 21.39981615212504],
        [-77.89873123168947, 21.397818306921025],
        [-77.90744304656984, 21.393422951386587]
      ]
    ]
  }
}

But when trying to include properties it crash
Showing this:
An internal error has occurred. Report a bug?

2

Can you check with these data?

{
  "type": "Feature",
  "geometry": {
    "type": "Polygon",
    "coordinates": [
      [
        [-77.90744304656984, 21.393422951386587],
        [-77.90880560874939, 21.395840413279284],
        [-77.91027545928956, 21.398257835208145],
        [-77.91045784950258, 21.401584222359443],
        [-77.90774345397949, 21.4008150644897],
        [-77.90516853332521, 21.400415500362858],
        [-77.90319442749023, 21.400375543890117],
        [-77.90160655975343, 21.40141440863241],
        [-77.89980411529542, 21.40089497718403],
        [-77.89834499359131, 21.39981615212504],
        [-77.89873123168947, 21.397818306921025],
        [-77.90744304656984, 21.393422951386587]
      ]
    ]
  }
}
4

Can you check with these data?

It works fine in App Inventor, but it creates solid green polygons, and I would like to have polygons with all their properties set.

5 
When Screen1.Initialize
    // Set up your polygon coordinates
    Set coordinates to
        [
          [-77.90744304656984, 21.393422951386587],
          [-77.90880560874939, 21.395840413279284],
          // Add the rest of your coordinates
          [-77.90744304656984, 21.393422951386587] // Closing the polygon
        ]
    
    // Add the polygon to the map
    Call Map1.AddPolygon with coordinates
    
    // Set the visual properties
    Set Map1.Polygon.FillColor to '#4488004e'
    Set Map1.Polygon.FillOpacity to 0.3
    Set Map1.Polygon.StrokeColor to '#000000'
    Set Map1.Polygon.StrokeOpacity to 1.0
    Set Map1.Polygon.StrokeWidthto 2
6

That would be using bloks not using features collection and geoJson.
By the way, I don´t find Call Map1.AddPolygon block.

7

I guess it was in other platform

Ok try this

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {
        "Description": "Polígono Irregular en Camagüey",
        "FillColor": "#4488004e",
        "StrokeColor": "#000000",
        "StrokeWidth": 2
      },
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [-77.90744304656984, 21.393422951386587],
            [-77.90880560874939, 21.395840413279284],
            [-77.91027545928956, 21.398257835208145],
            [-77.91045784950258, 21.401584222359443],
            [-77.90774345397949, 21.4008150644897],
            [-77.90516853332521, 21.400415500362858],
            [-77.90319442749023, 21.400375543890117],
            [-77.90160655975343, 21.40141440863241],
            [-77.89980411529542, 21.40089497718403],
            [-77.89834499359131, 21.39981615212504],
            [-77.89873123168947, 21.397818306921025],
            [-77.90744304656984, 21.393422951386587]
          ]
        ]
      }
    }
  ]
}
8

No way... still the same error: An internal error has occurred. Report a bug?

Only title and coordinates are acceptable for geojson in app inventor. All other properties returns error.

Thanks

9

blocks
blocks984×312 35.3 KB

Mmmmm....
Changing properties after creating polygons...

10

Are you working on Android or iOS ?

For iOS

image
image1101×262 25.3 KB

FeaturesFromGeoJSON are not yet functional

11

I´m using Android.

But not clear yet on how to use it. I can not achieve the results I want, that is to load all polygon´s properties from FeartureCollection.

Could you, please :pray:, provide a functional example of a GeoJson with Title, Coordinates and all possible Properties? I have done many attempts but always failed.

12

I don´t know what happen. I paste this geojson on FeaturesFromGeoJSON
and works once, showing solid green polygons. I deleted the featureCollection and created again. When paste the same geojson, it creates solid red polygons in companion, not functional at all. No posible to change properties.

13

Screenshot_20250416_172018
Screenshot_20250416_1720181080×2340 194 KB

This is the result
Is like a red layer over all polygons.
I dragged a polygon in designer and was shown as it should in companion.
Screenshot_20250416_172608
Screenshot_20250416_1726081080×2340 188 KB

14

Now I loaded a polygons.json file and it´s functional again...
Can someone help me to understand?

15

First problem, this:

"FillColor": "#4488004e"

what is this meant to be?

16

I tryed fillcolor and fill for the inner color of polygon
None of those works
#4488004e was the value of one of many atempts

17

For me, some of the properties just do not seem to be working.

You may have to "translate" (back) some of the properties names, see here:

https://ai2.appinventor.mit.edu/reference/components/maps.html#FeatureCollection

@SteveJG may have a better idea of what is happening.

18

map4
map4720×1600 100 KB

The json posted is for a single polygon. It renders green with no problem. I can change it's color easily. His image with the red polygons contains 32 or more polygons. @Aramis_Garcia did not provide the entire json file so I only have the single json to work with.

I suspect his issue when the entire set of Features is loaded and he may not have a robust internet.

When i worked a project that has 258 polygons, it wouldn't load on the main server but did on the code server and took a long time . There may be a similar issue on Aramis' data. Does he load a large file or a bunch of small files to features one at a time. :frowning_face:

Aramis', you might post all the json.

Steve

19

rGeoJson.json (164.2 KB)
This is my full geojson.
I put it iin app inventor as a file and works fine, and put it in app inventor as plain text in FeaturesFromGeoJSON and got the issue I posted before.
But... BUT... It could be I do not have a robust internet. The first time I loaded data as plain text it was successful, but not the second time I did it. I remember first time it took a long time before companion shows app interface.
By the other hand... why the red layer? When I dragged a polygon out off red layer, polygon came to light and works as it is supposed to be.

20

blocks
blocks1428×182 22.9 KB

Result: The same red solid polygons, not useful.

21

If working with the FeaturesCollection component is just not happening, you could always workaround this by parsing the geojson file and generating runtime polygons, with all your properties, using blocks:

Here is an example - with a couple of random polygons added.
geojson.aia (6.8 KB)

image

(I included a hexToColour procedure which you will need if setting the FIllColor,StrokeColour etc.)

Blocks

blocks (15)
blocks (15)1596×2666 568 KB

1 Like