Java Fun – 5 Posts

• 10/16/2024 13:00

  sniperkid 00

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  Hello!
  
  I am currently looking into messing around in java and i was wondering if it was possible (maybe a hint on towards the correct route if not) to draw multiple filled rectangles/circles but to make them interactive - ie, clicking on a rectangle would show properties in a mouseover and/or separate static panel. As well as using the mousewheel for zooming/panning etc.
  During my research i have been able to draw objects but they draw as an image rather than an object (it would be possible on mouse click to get x/y and workout if an object was selected if no other alternative), i have not investigated the mouseovers or adding other panels. Just want to make sure i'm not wasting my precious time .
  
  Any advice/examples is welcomed!
  
  Thanks!
  

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• 10/16/2024 13:00

  quangntenemy 00

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  Maybe there's a third party lib somewhere but I'm too lazy to look for it haha

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• 10/16/2024 13:00

  aceldama 00

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  the answer you're looking for is mathematical. you can see whether a cursor is inside of a circle by using the equation \"r^2=x^2+y^2\". therefore, if you have the radius of the circle you drew, you can derive x=sqrt((r^2)-(y^2))... ...so! if you have your x and y mouse offset, you can calculate whether the cursor is inside a circle like so:
  

  dim cX as integer = 100 'circle X (Center)
  dim cY as integer = 100 'circle Y (Center)
  dim cR as integer = 30  'circle radius
  
  dim mX as integer = 10  'Mouse X
  dim mY as integer = 100 'Mouse Y
  
  dim offsX as integer = Math.Abs(mX - cX) 'calculate the mouse offset
  dim offsY as integer = Math.Abs(mY - cY)
  
  'WARNING: a square root of a negative number will throw an error so make sure the offsets aren't bigger than the radius first!!
  if (offsX <= cR) and (offsY <= cR) then 'Check whether or not it's inside the circle's \"rectangle\"
      dim Range as integer = Math.Round(Math.Sqrt((cR * cR) - (offsY * offsY)))
      if offsX <= Range then
          'you're inside the circle
      else
          'you're not inside the circle
      endif
  endif
  

  
  
  sorry for giving you VB code, and apologies if there are any errors. i did this top-down without testing. converting it should not be a problem. it's fairly basic code after all.

  Edited by aceldama 04/07/2014 18:01 ago

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• 10/16/2024 13:00

  aceldama 00

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  as an afterthought, if you store all these in an array you can have a neat little Z-Order going. so, iterate through the array, breaking once you reach your first range, thus ignoring all other circles below it. further optimisation can be done by pre-calculating one quadrant of the circle (usually the one with all positive x and y-values) and saving them in a separate array. and then just calculating wither the absolute offset is smaller than the range (from 0)

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• 10/16/2024 13:00

  aceldama 00

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  hah! damn you quang! i only just saw that the original was posted almost exactly a year ago

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