Count number of good locations before showing Start button.

[mizutori]

This is a demo to show how we can count good locations before allowing user to track their locations.
Here is the step

1.

Add a varibale goodGpsCount to count the number of initial good locations.
https://github.com/mizutori/AndroidLocationStarterKit/pull/6/files#diff-93d98e0953cbfe5d527fa9991537cb545dd5dbe6d4b4dfc65992105478fc2077R59

2.

In onLocationUpdate, after filtering the new location, if it passes the filter, count up goodGpsCount.
If goodGpsCount becomes more than or equal to 3, send broadcast to MainActivity.
https://github.com/mizutori/AndroidLocationStarterKit/pull/6/files#diff-93d98e0953cbfe5d527fa9991537cb545dd5dbe6d4b4dfc65992105478fc2077R286

3.

In MainActivity, make the startButton invisible in the beginning.
https://github.com/mizutori/AndroidLocationStarterKit/pull/6/files#diff-40c5403e3f39c3d55b4e8d6447d31e6378231d346d6d955214bcc10bc9c3aa31R198

4.

When receiving the broadcast of goodGpsCount, make startButton visible.
https://github.com/mizutori/AndroidLocationStarterKit/pull/6/files#diff-40c5403e3f39c3d55b4e8d6447d31e6378231d346d6d955214bcc10bc9c3aa31R147

Other Note

• I changed the function filterAndAddLocation to filterLocation to return null (if location doesn't pass the filter) or location (if the location passes the filter). This is because I want to use this function even before the user presses startButton.
• I removed Kalman filter to demonstrate this idea with maximum simplicity.