The ornamental design for a basketballtrainingdevice, as shown and described.
FIG. 1 is a perspective view of the basketball training device showing my new design, together with corner pieces in broken lines;
FIG. 2 is a top view thereof, the side and bottom views being the same as the top view shown; and,
FIG. 3 is a perspective view showing the basketball training device fitted on a basketball.
The broken lines showing the corner pieces in FIGS. 1-3 and a basketball in FIG. 3 are for illustrative purposes only; and form no part of the claimed design.