private GridLayout.LayoutParams createLayoutParams() {
        return new GridLayout.LayoutParams(
                GridLayout.spec(GridLayout.UNDEFINED, 1, GridLayout.FILL), GridLayout.spec(GridLayout.UNDEFINED, 1, GridLayout.FILL));
    }
(re-)initializes the matrix with given data. Matrix data is deleted in the process
main/src/main/java/cgeo/geocaching/ui/CheckboxMatrixView.java