Node:radiobutton, Next:, Previous:checkbutton, Up:Widget Creation


Radiobuttons are buttons that are grouped together to select one value among many. Each button has a value, but only one in the button group is active at any one time. In Tcl/Tk this is achieved by creating a series of radiobutton that share an associated variable. Each button has a value. When a radiobutton is clicked on, the variable has that value and all the other buttons in the group are put into the off state. Similarly, setting the value of the variable is reflected in the state of the button group. An example is:

radiobutton .first -value one -text one -variable count
radiobutton .second -value two -text two -variable count
radiobutton .third -value three -text three -variable count

which creates three radiobuttons that are linked through the variable count. If button .second is active, for example, then the other two buttons are in the inactive state and count has the value two. The following code sets the button group to make the button .third active and the rest inactive regardless of the current state:

set count three

If the value of count does not match any of the values of the radiobuttons then they will all be off. For example executing the script

set count four

will turn all the radiobuttons off.