Efficient way to change color of Map Marker

Question

I'm using a GoogleMap with lots of small markers loaded. We are talking perhaps 400-500 markers. Upon user interaction, I want to have a subset of those markers change color, perhaps 100-300 of them. I want to achieve this ideally in 30ms or under, but up to 50-60ms would be acceptable.

Right now I have code something like:

onUserInteraction... {
    changeColors(getTheSubset)
}

changeColors(subset) {
    getMarkersForSubset(subset).removeAllFromMap();
    map.addNewMarkers(subset)
}

So I remove the old markers in some color (say, green), and add new markers for those locations (say, black). When the subset is no longer relevant, I do the opposite process.

On the busiest parts of the map I am seeing this take 500ms or more, and there's noticeable lag with different markers changing colors at different times. So I am curious if there is a better math-based way to draw small circles on a map and change their colors without removing/adding markers and while minimizing alloc/gc.

Answer 1

Have you considered using LevelListDrawable s? Rather than removing and re-adding all of your markers when updating, you could have your various drawables with each color as the levels of a LevelListDrawable . Then you can call setLevel() to set the appropriate drawable with the color you want when you update your set of pins. I'm not 100% sure you can use a LevelListDrawable for the map pin, but it is worth a shot.

API: http://developer.android.com/reference/android/graphics/drawable/LevelListDrawable.html

Example: http://iserveandroid.blogspot.com/2010/10/progress-bar-implementation-using-level.html

Answer 2

So LevelListDrawable s are not an option, due to Gmap's use of BitmapDescriptorFactory .

One solution I found was to draw a Marker on top of the old one with the new color, then delete the old one from underneath.

There were two issues to that.

• One, google-maps-android-v2 doesn't support z-indexing for Marker s.
• Two, if you have a lot of Marker s to change the color of, the performance of it causes artifacts.

Now, recently Google released an update that made Marker s with a common Bitmap a lot faster to draw, but you can always throw more Markers at it and break it.

I also attempted to draw a Marker on top, but with its visibility set to false , and to then set it to true when that location got "selected". This didn't seem too much faster although in fairness I did not benchmark it.

The conclusion: Don't change Bitmap s on Marker s. (For now)