tim/prune/data/MidpointData.java

   1 package tim.prune.data;
   2
   3 /**
   4  * Class to hold information about the mid-points between
   5  * adjacent track points.  Used by the MapCanvas for creating
   6  * points by dragging.
   7  */
   8 public class MidpointData
   9 {
  10         // track object
  11         private Track _track = null;
  12         // Scaled x, y values
  13         private double[] _xValues = null;
  14         private double[] _yValues = null;
  15         // Validity flags
  16         private boolean[] _valids = null;
  17         // Flag to set data stale
  18         private boolean _needRefresh = true;
  19
  20
  21         /**
  22          * Flag the data as needing to be updated
  23          * @param inTrack track object from which to get the data
  24          */
  25         public void updateData(Track inTrack)
  26         {
  27                 _track = inTrack;
  28                 _needRefresh = true;
  29         }
  30
  31         /**
  32          * Update the arrays of data from the track
  33          */
  34         private synchronized void updateData()
  35         {
  36                 _needRefresh = false;
  37                 if (_track == null) return;
  38                 // Make arrays the right size
  39                 final int numPoints = _track.getNumPoints();
  40                 if (_xValues == null || _xValues.length != numPoints)
  41                 {
  42                         _xValues = new double[numPoints];
  43                         _yValues = new double[numPoints];
  44                         _valids  = new boolean[numPoints];
  45                 }
  46                 if (numPoints <= 0) return;
  47                 _valids[0] = false;
  48
  49                 // Loop over the points in the track
  50                 for (int i=1; i<numPoints; i++)
  51                 {
  52                         boolean pointValid = false;
  53                         DataPoint point = _track.getPoint(i);
  54                         if (point != null && !point.getSegmentStart() && !point.isWaypoint())
  55                         {
  56                                 _xValues[i] = (_track.getX(i) + _track.getX(i-1)) / 2.0;
  57                                 _yValues[i] = (_track.getY(i) + _track.getY(i-1)) / 2.0;
  58                                 pointValid = true;
  59                         }
  60                         _valids[i] = pointValid;
  61                 }
  62         }
  63
  64         /**
  65          * Find the nearest point to the specified x and y coordinates
  66          * or -1 if no point is within the specified max distance
  67          * @param inX x coordinate
  68          * @param inY y coordinate
  69          * @param inMaxDist maximum distance from selected coordinates
  70          * @return index of nearest point or -1 if not found
  71          */
  72         public int getNearestPointIndex(double inX, double inY, double inMaxDist)
  73         {
  74                 if (_track == null) return -1;
  75                 if (_needRefresh) updateData();
  76                 final int numPoints = _track.getNumPoints();
  77                 int nearestPoint = 0;
  78                 double nearestDist = -1.0;
  79                 double currDist;
  80                 for (int i=1; i < numPoints; i++)
  81                 {
  82                         if (_valids[i])
  83                         {
  84                                 currDist = Math.abs(_xValues[i] - inX) + Math.abs(_yValues[i] - inY);
  85                                 if (currDist < nearestDist || nearestDist < 0.0)
  86                                 {
  87                                         nearestPoint = i;
  88                                         nearestDist = currDist;
  89                                 }
  90                         }
  91                 }
  92                 // Check whether it's within required distance
  93                 if (nearestDist > inMaxDist && inMaxDist > 0.0) {
  94                         return -1;
  95                 }
  96                 return nearestPoint;
  97         }
  98 }