Add a new project for hosting and testing the new control. Create the projectįirst, create a blank solution. And I hope you will get enough knowledge to solve the proposed exercises by yourself. In the end, I'll show you an interesting and unexpected way to extend the usage of this control. This way, not only the control would accept decimals, thousands separators, or scientific exponent notation, but will also allow and validate pasted values in the box. In this article, I'm going to present another approach: just let the monkey type whatever and do the validation in the end. Maybe just one dot as the decimal point? What about commas as separators for thousands? Well, maybe accept a minus for the first char. What we need to edit is the first item, as it is the one seen by the user.It seems common sense that when building a Numeric Edit (Text) Box, one should validate each character by the time it is typed and reject whatever is not a digit. the Key character, which absorbs the same as that pressed, but can be edited to contain only numeric entries. Thus, the OnKeyPress of the editbox gives at least two outputs.Ģ. no matter how you code it to chop off non-numeric variables will not matter, for the character added to the textbox is not the value of the key, but the actual character as pressed! but then again Key is not what is entered in the Keypress. we can then add conditions so that Key would become empty if the key pressed is not numeric. It means that upon keypress, the variable Key recieves the same character. however, lazarus treats Key and the character added in the textbox to be somewhat independent. it absorbs the character being pressed by the user. the event contains a variable named Key, which is of character type. actually i've already tried the OnKeyPress event of lazarus before posting the question. i'm a bit uncomfortable with using EditMask though, since using it would require sacrificing of format of the editbox.
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