Pistons don't power with a redstone dust line behind them.

On Android ZTE N9132

1. Set up two rows of pistons on top of each-other.
2. Place a row of solid Blocks behind the bottom row with redstone dust along the top.
3. Power with a lever or torch.
4. The bottom row of pistons extends, but top row stays retracted.

You can power every other piston on second row with single dust on block, no line, and repeaters in the backs of the blocks.