How do you make arrow key event handlers in Ruby/Tk

Question

In Ruby/Tk I'm am currently making a length converter but I want to be able to allow the user to either press the up or down arrow key and it will increase or decrease the number the user inputed into the Entry box.

require "tk"
require "tkextlib/tile"


root = TkRoot.new {title "Length converter"}
content = Tk::Tile::Frame.new(root){padding "50 15 50 15"}.grid


$input_variable = TkVariable.new
$output_variable = TkVariable.new
input_frame = Tk::Tile::Labelframe.new(content) {text 'Input'; borderwidth 5; relief "sunken"; width 300; height 200; padding "5 0 5 5"}
output_frame = Tk::Tile::Labelframe.new(content) {text 'Conversion'; borderwidth 5; relief "sunken"; width 300; height 200; padding "5 0 5 5"}
go_button = Tk::Tile::Button.new(content) {text 'Calculate'command {func1}}
input_box = Tk::Tile::Entry.new(content) {width 10; textvariable $input_variable}
output_text = Tk::Tile::Label.new(content) {textvariable $output_variablefont TkFont.new('sans 12')}
underbutton_text = Tk::Tile::Label.new(content) {text 'is equivalent to'}
unit_label = Tk::Tile::Label.new(content) {textvariable $unitfont TkFont.new('sans 12')}

$input_dom = TkVariable.new
$unit = TkVariable.new
feet = Tk::Tile::RadioButton.new(input_frame){
    text 'Feet' 
    variable $input_dom 
    value 1
    pack('fill'=>'x')

}
meters = Tk::Tile::RadioButton.new(input_frame){
    text 'Meters'
    variable $input_dom
    value 2
    pack('fill'=>'x')
}
inches = Tk::Tile::RadioButton.new(input_frame){
    text 'Inches'
    variable $input_dom
    value 3
    pack('fill'=>'x')
}
centi = Tk::Tile::RadioButton.new(input_frame){
    text 'Centimeters'
    variable $input_dom
    value 4
    pack('fill'=>'x')
}
miles = Tk::Tile::RadioButton.new(input_frame){
    text 'Miles'
    variable $input_dom
    value 5
    pack('fill'=>'x')
}
kilometers = Tk::Tile::RadioButton.new(input_frame){
    text 'Kilometers'
    variable $input_dom
    value 6
    pack('fill'=>'x')
}



$output_dom = TkVariable.new
feet = Tk::Tile::RadioButton.new(output_frame){
    text 'Feet'
    variable $output_dom
    value 1
    pack('fill'=>'x')
}
meters = Tk::Tile::RadioButton.new(output_frame){
    text 'Meters' 
    variable $output_dom 
    value 2
    pack('fill'=>'x')
}
inches = Tk::Tile::RadioButton.new(output_frame){
    text 'Inches'
    variable $output_dom
    value 3
    pack('fill'=>'x')
}
centi = Tk::Tile::RadioButton.new(output_frame){

    text 'Centimeters'
    variable $output_dom
    value 4
    pack('fill'=>'x')
}
miles = Tk::Tile::RadioButton.new(output_frame){
    text 'Miles'
    variable $output_dom
    value 5
    pack('fill'=>'x')
}
kilometers = Tk::Tile::RadioButton.new(output_frame){
    text 'Kilometers'
    variable $output_dom
    value 6
    pack('fill'=>'x')
}



content.grid(:column => 0, :row => 0)
input_frame.grid(:column => 0, :row => 0, :columnspan => 5, :rowspan =>6)
output_frame.grid(:column => 9, :row => 0, :columnspan => 5, :rowspan =>6)
input_box.grid(:column => 0, :row => 7)
go_button.grid( :column => 7, :row => 7)
output_text.grid(:column => 9, :row => 7)
underbutton_text.grid( :column => 7, :row => 9)
unit_label.grid(:column => 10, :row => 7)


def func1
    calculate()
    unit()
end


def calculate
  begin
    if $input_dom == $output_dom
        $output_variable.value = $input_variable

    #Feet to ...
    elsif $input_dom == 1 && $output_dom == 2
        $output_variable.value = (($input_variable/3.2808)*10000000.0).round()/10000000.0
    elsif $input_dom == 1 && $output_dom == 3
        $output_variable.value = (($input_variable*12.000)*10000000.0).round()/10000000.0
    elsif $input_dom == 1 && $output_dom == 4
        $output_variable.value = (($input_variable/0.032808)*10000000.0).round()/10000000.0
    elsif $input_dom == 1 && $output_dom == 5
        $output_variable.value = (($input_variable/0.00018939)*10000000.0).round()/10000000.0
    elsif $input_dom == 1 && $output_dom == 6
        $output_variable.value = (($input_variable/3280.8)*10000000.0).round()/10000000.0

    #Meters to ...
    elsif $input_dom == 2 && $output_dom == 1
        $output_variable.value = (($input_variable*3.2808)*10000000.0).round()/10000000.0
    elsif $input_dom == 2 && $output_dom == 3
        $output_variable.value = (($input_variable*39.370)*10000000.0).round()/10000000.0
    elsif $input_dom == 2 && $output_dom == 4
        $output_variable.value = (($input_variable/0.010000)*10000000.0).round()/10000000.0
    elsif $input_dom == 2 && $output_dom == 5
        $output_variable.value = (($input_variable*0.00062137)*10000000.0).round()/10000000.0
    elsif $input_dom == 2 && $output_dom == 6
        $output_variable.value = (($input_variable/1000.000)*10000000.0).round()/10000000.0

    #Inches to ...
    elsif $input_dom == 3 && $output_dom == 1
        $output_variable.value = (($input_variable*0.083333)*10000000.0).round()/10000000.0
    elsif $input_dom == 3 && $output_dom == 2
        $output_variable.value = (($input_variable/39.370)*10000000.0).round()/10000000.0
    elsif $input_dom == 3 && $output_dom == 4
        $output_variable.value = (($input_variable/0.39370)*10000000.0).round()/10000000.0
    elsif $input_dom == 3 && $output_dom == 5
        $output_variable.value = (($input_variable*0.0000157828281218333)*10000000.0).round()/10000000.0
    elsif $input_dom == 3 && $output_dom == 6
        $output_variable.value = (($input_variable/39370.0)*10000000.0).round()/10000000.0

    #Centimeters to ...
    elsif $input_dom == 4 && $output_dom == 1
        $output_variable.value = (($input_variable*0.032808)*10000000.0).round()/10000000.0
    elsif $input_dom == 4 && $output_dom == 2
        $output_variable.value = (($input_variable/100.000)*10000000.0).round()/10000000.0
    elsif $input_dom == 4 && $output_dom == 3
        $output_variable.value = (($input_variable*0.39370)*10000000.0).round()/10000000.0
    elsif $input_dom == 4 && $output_dom == 5
        $output_variable.value = (($input_variable*0.0000062137119)*10000000.0).round()/10000000.0
    elsif $input_dom == 4 && $output_dom == 6
        $output_variable.value = (($input_variable/100000.000)*10000000.0).round()/10000000.0

    #miles to...
    elsif $input_dom == 5 && $output_dom == 1
        $output_variable.value = (($input_variable*5280.0)*10000000.0).round()/10000000.0
    elsif $input_dom == 5 && $output_dom == 2
        $output_variable.value = (($input_variable/0.00062137)*10000000.0).round()/10000000.0
    elsif $input_dom == 5 && $output_dom == 3
        $output_variable.value = (($input_variable*63360.000)*10000000.0).round()/10000000.0
    elsif $input_dom == 5 && $output_dom == 4
        $output_variable.value = (($input_variable/0.0000062137119)*10000000.0).round()/10000000.0
    elsif $input_dom == 5 && $output_dom == 6
        $output_variable.value = (($input_variable/0.62137)*10000000.0).round()/10000000.0

    #kilometers to...
    elsif $input_dom == 6 && $output_dom == 1
        $output_variable.value = (($input_variable*3280.8)*10000000.0).round()/10000000.0
    elsif $input_dom == 6 && $output_dom == 2
        $output_variable.value = (($input_variable/0.0010000)*10000000.0).round()/10000000.0
    elsif $input_dom == 6 && $output_dom == 3
        $output_variable.value = (($input_variable*39370.000)*10000000.0).round()/10000000.0
    elsif $input_dom == 6 && $output_dom == 4
        $output_variable.value = (($input_variable/0.00001)*10000000.0).round()/10000000.0
    elsif $input_dom == 6 && $output_dom == 5
        $output_variable.value = (($input_variable*0.62137)*10000000.0).round()/10000000.0
    end

  rescue
     $output_variable.value = ''
  end
end

def unit
    begin
        if $output_dom == 1
            $unit.value = 'ft'
        elsif $output_dom == 2
            $unit.value = 'm'
        elsif $output_dom == 3
            $unit.value = 'in'
        elsif $output_dom == 4
            $unit.value = 'cm'
        elsif $output_dom == 5
            $unit.value = 'mi'
        elsif $output_dom == 6
            $unit.value = 'km'
        end
    rescue
     $unit.value = ''
    end
end


Tk.mainloop

MarkDBlackwell · Answer 1 · 2019-04-10T12:47:07.363

Adding this line (after you've defined $input_variable):

$input_variable.value = 0.0

as well as adding the following lines (after you've defined input_box):

input_box.bind 'Down', lambda {$input_variable.value = $input_variable - 1.0}
input_box.bind 'Up',   lambda {$input_variable.value = $input_variable + 1.0}

should get you closer to seeing it work.

See also this question about determining things like Down and Up.

How do you make arrow key event handlers in Ruby/Tk

1 Answers1