22 lines
1.1 KiB
Markdown
22 lines
1.1 KiB
Markdown
# Distance Expression
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{{ activity_source_note("DistanceExpressionActivity.kt") }}
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This example shows how you can modify a style to only show certain features within a certain distance to a point. For this the [distance expression](https://maplibre.org/maplibre-style-spec/expressions/#within) is used.
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<figure markdown="span">
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![Screenshot of map where only labels inside some circular area are shown]({{ s3_url("distance_expression_activity.png") }}){ width="400" }
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{{ openmaptiles_caption() }}
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</figure>
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First we add a [fill layer](https://maplibre.org/maplibre-style-spec/layers/#fill) and a GeoJSON source.
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```kotlin
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--8<-- "MapLibreAndroidTestApp/src/main/java/org/maplibre/android/testapp/activity/style/DistanceExpressionActivity.kt:FillLayer"
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```
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Next, we only show features from symbol layers that are less than a certain distance from the point. All symbol layers whose identifier does not start with `poi` are completely hidden.
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```kotlin
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--8<-- "MapLibreAndroidTestApp/src/main/java/org/maplibre/android/testapp/activity/style/DistanceExpressionActivity.kt:distanceExpression"
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``` |