GridLayout spitting out "inconsistent constraint" debug-level logs
I've been using GridLayout for a few weeks now and I've noticed that when I call
gridLayout.requestLayout()
it spits out the following debug-level message in LogCat:
D/android.widget.GridLayout(14048): horizontal constraints: x5 - x0 > 1115, x5 - x4 < 221, x4 - x3 < 221, x3 - x2 < 221, x2 - x1 < 221, x1 - x0 < 221 are inconsistent; permanently removing: x5 - x4 < 221.
I've looked through the source of GridLayout to try and find out the possible reason as to why the "contraints are inconsistent", but I haven't been able to figure it out.
The fact that these messages are appearing - is this something that I should be concerned about? I don't see any issues with the way things are being laid out. I have a GridLayout in Fragments that are loaded as the pages in a ViewPager so I as the user scrolls between the pages I see the above output in LogCat multiple times.
Answer
From the GridLayout source:
Bellman-Ford variant - modified to reduce typical running time from O(N^2) to O(N)
GridLayout converts its requirements into a system of linear constraints of the form:
x[i] - x[j] < a[k]
Where the x[i] are variables and the a[k] are constants.
For example, if the variables were instead labeled x, y, z we might have:
x - y < 17
y - z < 23
z - x < 42
This is a special case of the Linear Programming problem that is, in turn, equivalent to the single-source shortest paths problem on a digraph, for which the O(n^2) Bellman-Ford algorithm the most commonly used general solution.
It has a solve method that is using linear programming to guarantee the consistency of the constraints it has to satisfy, given its configuration. You can probably improve your layout performance if you figure out which configuration is associated with the constraint x5 - x4 < 221 and remove it. Then the solver won't have to solve that it can't be satisfied and remove it itself.