Computer Programming Concepts and Visual Basic David I. Schneider

304 Computer Programming Concepts and Visual Basic
FIGURE 10-10 A Simple FlexGrid Control
The width, measured in twips (there are about 1440 twips to an inch), of each column
can be specified only at run time with the ColWidth property. A typical statement is
msgFlex.ColWidth(3) = 1200, which sets the width of column 3 to 1200 twips. (The default
column width is 555 twips.) Similarly, the RowHeight property specifies the height of each
row. The width and height of the entire grid can be specified at design time by dragging the
mouse or by setting the Width and Height properties.
The grayed row and column in Figure 10-10 are referred to as fixed. Fixed rows and
columns must be at the top and left sides of the grid. The number of fixed rows and columns
is specified by the FixedRows and FixedCols properties. The grid in Figure 10-10 has the
default settings FixedRows = 1 and FixedCols = 1.
If the width of the grid is too small to show all the columns, a horizontal scroll bar will
automatically appear across the bottom of the grid. Then, during run time, the nonfixed
columns can be scrolled to reveal the hidden columns. Similarly, a vertical scroll bar appears
when the height of the grid is too small to show all the rows. Scroll bars can be suppressed
by setting the ScrollBars property of the grid to 0 – flexScrollBarNone. (The default value
of the ScrollBars property is 3 – flexScrollBarBoth.)
The individual small rectangles are called cells. Each cell is identified by its row and
column numbers. At any time, one cell is singled out as the current cell. Initially, the cell in
row 1, column 1 is the current cell. The pair of statements msgFlex.Row = m, msgFlex.Col
= n set the current cell to the cell in the mth row and nth column. When the user clicks on a
nonfixed cell, it becomes the current cell. The cell’s border becomes dotted, its row number
is assigned to the Row property, and its column number is assigned to the Col property. (In
Figure 10-10 the cell in row 2, column 4 is the current cell.) The horizontal and vertical lines
forming the cells can be turned off by setting the GridLines property to 0 – flexGridNone.
Unfortunately, you can’t just place text into a cell by clicking on the cell and typing, as
you would with a text box. The statement msgFlex.Text = str places the value of str into the
current cell and the statement str = msgFlex.Text reads the contents of the current cell. The
text inside all the nonfixed cells of column n can be displayed left-aligned, right-aligned, or
centered with a statement of the form msgFlex.ColAlignment(n) = r, where r is 1 for leftalignment,
7 for right-alignment, and 4 for centered. The fixed cells of column n can be justified
with a statement of the form msgFlex.FixedAlignment(n) = r.
EXAMPLE 1
The following program uses a grid to display an improved version of the table of student expenses from
Example 5 of Section 2.5. The five expense categories and numeric data for the table are stored in the
sequential file STCOSTS.TXT. Each record of the file consists of a string followed by four numbers.
Object Property Setting
frmCosts Caption Average Expenses of Commuter Students (1995–96)
msgCosts BorderStyle 0 – flexBorderNone
Cols 5
FixedCols 0
FixedRows 0
Font Courier New
GridLines 0 – flexGridNone