我怎么能只掷下一张或上一张牌?

RecyclerView有fling方法,您只需重写它。

float FLING_SPEED = 0.5f;

@Override
public boolean fling(int velocityX, int velocityY)
{
    // FLING_SPEED between (0, 1) => slow down, greater 1 => speed up
    // velocityY for vertical, velocityX for horizontal
    velocityY *= FLING_SPEED; 
    return super.fling(velocityX, velocityY);
}