"0" and space-only strings like " " are true as a boolean.The notable exceptions where people usually make mistakes are: Most of these rules are easy to understand and memorize. An error gives NaN.īoolean Conversion – Occurs in logical operations. The string is read “as is”, whitespaces (includes spaces, tabs \t, newlines \n etc.) from both sides are ignored. Numeric Conversion – Occurs in math operations. The conversion to string is usually obvious for primitive values. String Conversion – Occurs when we output something. The three most widely used type conversions are to string, to number, and to boolean. As you found yourself: if your user input is 9 as a char or String, you have little chance of knowing whether this value was entered using the numeric pad or the alphabet part of the keyboard…įinally, depending on the complexity of your task, the scijava/ui-behaviour project (by and might actually be of use.Alert( Boolean(" ") ) // spaces, also true (any non-empty string is true) Summary So in general, your approach of collecting a user input char and trying to guess a key code from this might not always work. keyboard layout will generate VK_A when using a French keyboard layout. For example, the key that generates VK_Q when using a U.S. Virtual key codes do not identify a physical key: they depend on the platform and keyboard layout. Some more explanation about the “Virtual Keys” defined by the VK_* constants can be found in the KeyEvent class. VK keys don’t care about upper/lowercase, so it gives the code for capital H, which is 72. Yes, this is in line with the comment on this answer on stackoverflow: The returned ASCII code always correspond to the capitalised version of the char It ‘natively’ returns symbols like % and to get numbers you have to use CAPS.Īs far as I am concerned my problem is solved For instance on a french keyboard the top digit row is the opposite of the german. One thing that I dont know is whether this depends on your keyboard mapping. This probably prevent the conflicts mentioned previously. I always got the keycode for the CAPS UNLOCK version. The result is that contrary to the numpad with the numlock, switching between CAPS LOCK and CAPS UNLOCK does not have any effect. On my german keyboard I have to do a ‘CAPS + 5’ or CAPS LOCK then 5. I though that there might be conflicts if a numpad stroke correspond to ‘%’ so I tried typing ‘%’ in the keylistener. I still want to use the numpad so I will just manually write down the keycode returned by the KeyListener for 0 to 9 and have a dictionary for the correspondance.īetween numpad on and off (using the numlock key which usually light up a led on the keyboard) t he resulting keycode is not the same for a given number, but in both case it does not correspond to the ASCII decimal code for this particular number (it will point to the char ‘%’ for instance) However if you use the digit row at the top of the keyboard you will get the proper ASCII decimal code for that digit. The returned value does not correspond to the ASCII table at all. The second difference is for digits typed using the numpad on the right side of a keyboard (which I initially wanted to use for the categories). However with the KeyListener in imageJ, the returned ASCII code always correspond to the capitalised version of the char so if you type ‘a’ you will get 65 and not 97. But playing a bit longer with the KeyListener you posted earlier I found that the keystroke mapping is almost like ASCII except :Īccording to the ASCII table, the decimal code is case sensitive, meaning that ‘A’ and ‘a’ do not have the same decimal ASCII code. Thanks Jan, that works indeed ! Actually the output of getKe圜ode() is the same as ord() which is the ASCII Decimal code associated to the Char. I also tried the getExtendedKe圜odeForChar(MyStringShortCut) method but it returns that the type cant be cast to int… I also though it might be a simple ASCII mapping but apparently not (or at least not with a german keyboard). I have tried the method in this post but the keycode returned is always 0 ! My problem is that the shortcut the user is inputting is a one-character string (or character but in Jython there is no such difference), and I would like to recover the associated Ke圜ode to be able to associate the keyboard event to this string. The idea is then to read the key typed for each image to do the classification. Then I pop up a second window accordingly where the user can give a name and a keyboard shortcut (in the form it is also a string object) to the categories. So I am first requesting the user for the number of categories. (The output would be something like a table with a column for image name and a column for group) I am currently trying to write a Jython macro that use keyboard shortcut to interactively/manually classify images into groups (1 keyboard shortcut/group).
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