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https://github.com/p-lr/MapCompose

A fast, memory efficient Jetpack Compose library to display tiled maps, with support for markers, paths, and rotation.
https://github.com/p-lr/MapCompose

android android-library compose kotlin-library map mapview tiles tileview tiling zoom

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A fast, memory efficient Jetpack Compose library to display tiled maps, with support for markers, paths, and rotation.

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README 

        
[![Maven Central](https://img.shields.io/maven-central/v/ovh.plrapps/mapcompose)](https://mvnrepository.com/artifact/ovh.plrapps/mapcompose)

[![GitHub License](https://img.shields.io/badge/license-Apache%20License%202.0-blue.svg?style=flat)](http://www.apache.org/licenses/LICENSE-2.0)

[![](https://img.shields.io/badge/ComposeBOM-2024.02.00-brightgreen)](https://developer.android.com/jetpack/compose/bom/bom)



🎉 News:

- New path dash pattern api: ability to define a sequence made of dash, dot, and gap.

- Paths rendering has been improved, and paths are automatically simplified depending on the scale to improve performance

- New gestures added (zoom fling, double tap to zoom, two fingers tap)



# MapCompose



MapCompose is a fast, memory efficient Jetpack compose library to display tiled maps with minimal effort.

It shows the visible part of a tiled map with support of markers and paths, and various gestures

(flinging, dragging, scaling, and rotating).



An example of setting up:



```kotlin

/* Inside your view-model */

val tileStreamProvider = TileStreamProvider { row, col, zoomLvl ->

    FileInputStream(File("path/{$zoomLvl}/{$row}/{$col}.jpg")) // or it can be a remote HTTP fetch

}



val state = MapState(4, 4096, 4096).apply {

    addLayer(tileStreamProvider)

    enableRotation()

}



/* Inside a composable */

@Composable

fun MapContainer(

    modifier: Modifier = Modifier, viewModel: YourViewModel

) {

    MapUI(modifier, state = viewModel.state)

}

```



This project holds the source code of this library, plus a demo app - which is useful to get started.

To test the demo, just clone the repo and launch the demo app from Android Studio.



## Clustering



Marker clustering regroups markers of close proximity into clusters. The video below shows how it works.



https://github.com/p-lr/MapCompose/assets/15638794/de48cb1b-396b-44d3-b47a-e3d719e8f38a



The sample below shows the relevant part of the code. We can still add regular markers (not managed by a clusterer), such as the red marker in the video.

See the [full code](demo/src/main/java/ovh/plrapps/mapcompose/demo/viewmodels/MarkersClusteringVM.kt).



```kotlin

/* Add clusterer */

state.addClusterer("default") { ids ->

   { Cluster(size = ids.size) }

}



/* Add marker managed by the clusterer */

state.addMarker(

    id = "marker",

    x = 0.2,

    y = 0.3,

    renderingStrategy = RenderingStrategy.Clustering("default"),

) {

    Marker()

}

```



There's an example in the demo app.



## Installation



Add this to your module's build.gradle

```groovy

implementation 'ovh.plrapps:mapcompose:2.12.0'

```



Starting with v.2.4.1, the library is using the 

[compose BOM](https://developer.android.com/jetpack/compose/bom/bom). The version of the BOM is

specified in the release notes. The demo app shows an example of how to use it.



## Basics



MapCompose is optimized to display maps that have several levels, like this:










Each next level is twice bigger than the former, and provides more details. Overall, this looks like

 a pyramid. Another common name is "deep-zoom" map.

This library comes with a demo app featuring various use-cases such as using markers, paths,

map rotation, etc. All examples use the same map stored in the assets, which is a great example of

deep-zoom map.



MapCompose can also be used with single level maps.



### Usage



With Jetpack Compose, we have to change the way we think about views. In the previous `View`

system, we had references on views and mutated their state directly. While that could be done right,

the state often ended-up scattered between views own state and application state. Sometimes, it was

difficult to predict how views were rendered because there were so many things to take into account.



Now, the rendering is a function of a state. If that state changes, the "view" updates accordingly.



In a typical application, you create a `MapState` instance inside a `ViewModel` (or whatever

component which survives device rotation). Your `MapState` should then be passed to the `MapUI`

composable. The code sample at the top of this readme shows an example. Then, whenever you need to

update the map (add a marker, a path, change the scale, etc.), you invoke APIs on your `MapState`

instance. As its name suggests, `MapState` also _owns_ the state. Therefore, composables will always

render consistently - even after a device rotation.



All public APIs are located under the [api](mapcompose/src/main/java/ovh/plrapps/mapcompose/api) 

package. The following sections provide details on the `MapState` class, and give examples of how to

add markers, callouts, and paths.



### MapState



The `MapState` class expects three parameters for its construction:

* `levelCount`: The number of levels of the map,

* `fullWidth`: The width of the map at scale 1.0, which is the width of last level,

* `fullHeight`: The height of the map at scale 1.0, which is the height of last level



### Layers



MapCompose supports layers - e.g it's possible to add several tile pyramids. Each level is made of

the superposition of tiles from all pyramids at the given level. For example, at the second level

(starting from the lowest scale), tiles would look like the image below when three layers are added.










Your implementation of the `TileStreamProvider` interface (see below) is what defines a tile

pyramid. It provides `InputStream`s of image files (png, jpg). MapCompose will request tiles using

the convention that the origin is at the top-left corner. For example, the tile requested with

`row` = 0, and `col = 0` will be positioned at the top-left corner.



```kotlin

fun interface TileStreamProvider {

    suspend fun getTileStream(row: Int, col: Int, zoomLvl: Int): InputStream?

}

```



Depending on your configuration, your `TileStreamProvider` implementation might fetch local files,

as well as performing remote HTTP requests - it's up to you. You don't have to worry about threading,

MapCompose takes care of that (the main thread isn't blocked by `getTileStream` calls). However, in

case of HTTP requests, it's advised to create a `MapState` with a higher than default `workerCount`.

That optional parameter defines the size of the dedicated thread pool for fetching tiles, and defaults

to the number of cores minus one. Typically, you would want to set `workerCount` to 16 when performing

HTTP requests. Otherwise, you can safely leave it to its default.



To add a layer, use the `addLayer` on your `MapState` instance. There are others APIs for reordering,

removing, setting alpha - all dynamically.



### Markers



To add a marker, use the [addMarker](https://github.com/p-lr/MapCompose/blob/982caf29ab5e86b58c56812735f60bfe405638ea/mapcompose/src/main/java/ovh/plrapps/mapcompose/api/MarkerApi.kt#L30)

API, like so:



```kotlin

/* Add a marker at the center of the map */

mapState.addMarker("id", x = 0.5, y = 0.5) {

    Icon(

        painter = painterResource(id = R.drawable.map_marker),

        contentDescription = null,

        modifier = Modifier.size(50.dp),

        tint = Color(0xCC2196F3)

    )

}

```










A marker is a composable that you supply (in the example above, it's an `Icon`). It can be

whatever composable you like. A marker does not scale, but it's position updates as the map scales,

so it's always attached to the original position. A marker has an anchor point defined - the point

which is fixed relatively to the map. This anchor point is defined using relative offsets, which are

applied to the width and height of the marker. For example, to have a marker centered horizontally 

and aligned at the bottom edge (like a typical map pin would do), you'd pass -0.5f and -1.0f as

relative offsets (left position is offset by half the width, and top is offset by the full height).

If necessary, an absolute offset expressed in pixels can be applied, in addition to the

relative offset.



Markers can be moved, removed, and be draggable. See the following APIs: [moveMarker](https://github.com/p-lr/MapCompose/blob/2fbf0967290ffe01d63a6c65a3022568ef48b9dd/mapcompose/src/main/java/ovh/plrapps/mapcompose/api/MarkerApi.kt#L72),

[removeMarker](https://github.com/p-lr/MapCompose/blob/2fbf0967290ffe01d63a6c65a3022568ef48b9dd/mapcompose/src/main/java/ovh/plrapps/mapcompose/api/MarkerApi.kt#L61),

[enableMarkerDrag](https://github.com/p-lr/MapCompose/blob/2fbf0967290ffe01d63a6c65a3022568ef48b9dd/mapcompose/src/main/java/ovh/plrapps/mapcompose/api/MarkerApi.kt#L89).



### Callouts



Callouts are typically message popups which are, like markers, attached to a specific position.

However, they automatically dismiss on touch down. This default behavior can be changed. 

To add a callout, use [addCallout](https://github.com/p-lr/MapCompose/blob/2fbf0967290ffe01d63a6c65a3022568ef48b9dd/mapcompose/src/main/java/ovh/plrapps/mapcompose/api/MarkerApi.kt#L220).










Callouts can be programmatically removed (if automatic dismiss was disabled).



### Paths



To add a path, use the `addPath` api:



```kotlin

mapState.addPath("pathId", color = Color(0xFF448AFF)) {

  addPoints(points)

}

```



The demo app shows a complete example.










## Animate state change



It's pretty common to programmatically animate the scroll and/or the scale, or even the rotation of

the map.



*scroll and/or scale animation*



When animating the scale, we generally do so while maintaining the center of the screen at

a specific position. Likewise, when animating the scroll position, we can do so with or without 

animating the scale altogether, using [scrollTo](https://github.com/p-lr/MapCompose/blob/08c0f68f654c1ce27a295f3fb6c25e9cf4274de9/mapcompose/src/main/java/ovh/plrapps/mapcompose/api/LayoutApi.kt#L188)

and [snapScrollTo](https://github.com/p-lr/MapCompose/blob/08c0f68f654c1ce27a295f3fb6c25e9cf4274de9/mapcompose/src/main/java/ovh/plrapps/mapcompose/api/LayoutApi.kt#L161).



*rotation animation*



For animating the rotation while keeping the current scale and scroll, use the

[rotateTo](https://github.com/p-lr/MapCompose/blob/08c0f68f654c1ce27a295f3fb6c25e9cf4274de9/mapcompose/src/main/java/ovh/plrapps/mapcompose/api/LayoutApi.kt#L149) API.



Both `scrollTo` and `rotateTo` are suspending functions. Therefore, you know exactly when

an animation finishes, and you can easily chain animations inside a coroutine.



```kotlin

// Inside a ViewModel

viewModelScope.launch {

    mapState.scrollTo(0.8, 0.8, destScale = 2f)

    mapState.rotateTo(180f, TweenSpec(2000, easing = FastOutSlowInEasing))

}

```



For a detailed example, see the "AnimationDemo".



## Design changes and differences with MapView



* In MapView, you had to define bounds before you could add markers. There's no such concept

in MapCompose anymore. Now, coordinates are normalized. For example, (x=0.5, y=0.5) is a point located at

the center of the map. Normalized coordinates are easier to reason about, and application code can

still translate this coordinate system to a custom one.



* In MapView, you had to build a configuration and use that configuration to create a `MapView`

instance. There's no such thing in MapCompose. Now, you create a `MapState` object with required

parameters.



* A lot of things which couldn't change after MapView configuration can now be changed dynamically

in MapCompose. For example, the `zIndex` of a marker, or the minimum scale mode can be changed at

runtime.



## Difference with `1.x` version



* There's now a way to set initial values for various properties such as scroll, scale, etc using

the `InitialValuesBuilder` in the `MapState` constructor. To produce similar behavior in 1.x, one

had to launch a coroutine right after `MapState` creation - which wasn't perfect since some

undesired tile loading could happen between the initialization and the destination state.



* Having a `TileStreamProvider` at `MapState` construction is no longer mandatory.

`TileStreamProvider`s are now added using the `addLayer` api, which is completely dynamic.



* While 1.x version had a non-suspending `TileStreamProvider`, 2.x greatly benefits from the new

suspend version. If you're using a library like Retrofit to perform remote http fetch (and suspend

calls), tile loading will be optimal since all layers are fetched concurrently. That was already the

case in 1.x, but not thanks to suspending calls.



## Contributors



Marcin (@Nohus) has contributed and fixed some issues. He also thoroughly tested the new layers 

feature – which made `MapCompose` better.