If unfortunately the turtle sits on its own trace, x-y is slightly modified). The color of every pixel that currently has the playground color is then changed to the pen color (see here for more information). (The flood-fill algorithm implemented in our library looks for all pixels in a closed region defined by the given x-y position. We must call setDragEnabled(true) to enable them.) When we lift the finger, the playgroundRelease() notification is invoked that fills a closed region with the current pen color. (To avoid system overload, the drag events are disabled by default. While moving the finger, playgroundDrag() notifications are called in frequent repetition. In the following example we draw a line by 'dragging' the turtle (moving the finger while remaining in contact with the screen). (To overcome this difficulty, you could use the annotation.) There is a drawback of this simple design: If you misspell the name of the notification method, the program compiles, but fails to work. By simply overriding one of these methods in your application class (derived from Playground), you get your own notification.
The event notification methods (also called callbacks) are part of the Playground class and declared there with an empty body. With JTurtleLib it is extremely simple to use screen touch events.
#Downlink rubber bands android#
(You need the latest version of JRE.)Ĭreate QR code to download Android app to your smartphone.Īndroid app for installation on a smartphone or emulator. If we watch the value of i in the error console, we easily track the bug.Īs you see there are many interesting system messages, most of them generated by our JTurtleLib library code. In the following example we consciously make the common error, not to increment the variable i in the while-loop. Now you are ready to write your own debugging messages using the L.i() method. If an attached device is found, the LogCat window opens.
(This is a WebStart signed by University of Berne that installs all necessary files in.
#Downlink rubber bands install#
Its like writing your debug messages in a console using ().įirst you install and start the LogCat console using the link here (link also found in the right column). Moreover you can display your own string message very simply by calling the static L.i() method (L stands for the LogCat class and is kept short for convenience).
#Downlink rubber bands Pc#
During the development phase, when the device is connected to the development PC via USB, the system outputs important messages in a console window. Fortunately the Android development guys created a debugging environment called LogCat. To get an insight what is going on in your program, we need a powerful debugging tool that reports run-time errors. divide-by-zero), the application just dies without saying anything about the location in the source code. Debugging is a special challenge for App programmers, because the usual debugging techniques does not work. Therefore debugging methods are essential and should be trained at every level of programming education. The art of programming is not so much to avoid programming bugs, but to track them down rapidly without getting frustrated. Programming errors are not a shame, but common to all programmers, not only beginners.
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