JustWe JustWe - 1 month ago 16
Android Question

Google direction and voice navigation

I have been working on a android project.
Then I came up with 2 question.

Q1. how to implement navigation drive ?
My logic and some work
- I am be able to draw path between 2 address. And my thought is that, use the onLocationChanged(current) method then call https://maps.googleapis.com/maps/api/directions/output?parameters with the current location and destination which through some method to draw the path on the map.
Upon every onLocationChanged() method call, I redraw the path on the map again.
" Is it how we would do it for navigation ? "

Q2. how to implement voice navigation to work with Q1 ?
- Did some research, can't find anything that seems clearly helpful. All I know its that, in the return JSON from the /api/directions, there are direction instruction in it.
" Do I use it for voice from the return JSON ? Or there is a better way ? "

Would be very helpful with some link or example in details.
Thanks in adavnce

Answer

Here is what I know, hope it helps you out.

Regarding the first question:

After retrieving the directions and the necessary data, you have to draw the direction once and only once! yes, you have to use the onLocationChanged() but not to redraw the whole thing again.. if you notice in most of the navigation application they still keep the main route, they don't remove the passed parts... but you have to use onLocationChanged() to check if the user is out of the drawn path (by maybe 100m) so you have to re-calculate and redraw it again... redraw the path every time the user move is a costly operation it is better to be avoided...

For the second question:

As you said, the data retrieved already has the navigation commands.. so what you have to do is create a class to map the command with the voice.. and if you notice within the legs -> steps tags, there is a start and ending coordinates for each sub-path, so you can use these data to calculate the distance between them on each 200m say the command that "how far the user is to turn left" for example.

Hope this gives you a general idea of how it works. Good luck and happy programming.

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