How to draw a filled triangle in android canvas

Question

So I m drawing this triangle in android maps using the code below in my draw method   paint setARGB 255  153  29  29   paint setStyle Paint Style FILL AND STROKE   paint setAntiAlias true    Path path   new Path    path moveTo point1 returned x  point1 returned y   path lineTo point2 returned x  point2 returned y   path moveTo point2 returned x  point2 returned y   path lineTo point3 returned x  point3 returned y   path moveTo point3 returned x  point3 returned y   path lineTo point1 returned x  point1 returned y   path close     canvas drawPath path  paint     The pointX returned are the coordinates which I m getting from the fields  They are basically latitudes and longitudes  The result is a nice triangle but the insider is empty and therefore I can see the map  Is there a way to fill it up somehow

User · Answer

you can also use vertice     private static final int verticesColors           Color LTGRAY  Color LTGRAY  Color LTGRAY  0xFF000000  0xFF000000  0xFF000000    float verts           point1 x  point1 y  point2 x  point2 y  point3 x  point3 y    canvas drawVertices Canvas VertexMode TRIANGLES  verts length  verts  0  null  0  verticesColors    0  null  0  0  new Paint

User · Answer

You probably need to do something like    Paint red   new Paint     red setColor android graphics Color RED   red setStyle Paint Style FILL     And use this color for your path  instead of your ARGB  Make sure the last point of your path ends on the first one  it makes sense also   Tell me if it works please

User · Answer

Don t moveTo   after each lineTo    In other words  remove every moveTo   except the first one   Seriously  if I just copy-paste OP s code and remove the unnecessary moveTo   calls  it works   Nothing else needs to be done     EDIT  I know the OP already posted his  final working solution   but he didn t state why it works  The actual reason was quite surprising to me  so I felt the need to add an answer

User · Answer

this function shows how to create a triangle from bitmap  That is  create triangular shaped cropped image  Try the code below or download demo  example   public static Bitmap getTriangleBitmap Bitmap bitmap  int radius            Bitmap finalBitmap          if  bitmap getWidth      radius    bitmap getHeight      radius              finalBitmap   Bitmap createScaledBitmap bitmap  radius  radius                      false           else             finalBitmap   bitmap          Bitmap output   Bitmap createBitmap finalBitmap getWidth                    finalBitmap getHeight    Bitmap Config ARGB 8888           Canvas canvas   new Canvas output            Paint paint   new Paint            final Rect rect   new Rect 0  0  finalBitmap getWidth                    finalBitmap getHeight              Point point1 draw   new Point 75  0           Point point2 draw   new Point 0  180           Point point3 draw   new Point 180  180            Path path   new Path            path moveTo point1 draw x  point1 draw y           path lineTo point2 draw x  point2 draw y           path lineTo point3 draw x  point3 draw y           path lineTo point1 draw x  point1 draw y           path close            canvas drawARGB 0  0  0  0           paint setColor Color parseColor   BAB399             canvas drawPath path  paint           paint setXfermode new PorterDuffXfermode PorterDuff Mode SRC IN            canvas drawBitmap finalBitmap  rect  rect  paint            return output          The function above returns an triangular image drawn on canvas  Read more

User · Answer

private void drawArrows Point   point  Canvas canvas  Paint paint         float    points    new float 8                    points 0    point 0  x            points 1    point 0  y            points 2    point 1  x            points 3    point 1  y               points 4    point 2  x            points 5    point 2  y                    points 6    point 0  x            points 7    point 0  y       canvas drawVertices VertexMode TRIANGLES  8  points  0  null  0  null  0  null  0  0  paint       Path path   new Path        path moveTo point 0  x   point 0  y       path lineTo point 1  x point 1  y       path lineTo point 2  x point 2  y       canvas drawPath path paint

User · Answer

Using  Pavel s answer as guide  here s a helper method if you don t have the points but have start x y and height and width  Also can draw inverted upside down - which is useful for me as it was used as end of vertical barchart     private void drawTriangle int x  int y  int width  int height  boolean inverted  Paint paint  Canvas canvas            Point p1   new Point x y           int pointX   x   width 2          int pointY   inverted   y   height   y - height           Point p2   new Point pointX pointY           Point p3   new Point x width y             Path path   new Path            path setFillType Path FillType EVEN ODD           path moveTo p1 x p1 y           path lineTo p2 x p2 y           path lineTo p3 x p3 y           path close             canvas drawPath path  paint

User · Answer

Ok I ve done it  I m sharing this code in case someone else will need it   super draw canvas  mapView  true    Paint paint   new Paint Paint ANTI ALIAS FLAG    paint setStrokeWidth 2   paint setColor android graphics Color RED        paint setStyle Paint Style FILL AND STROKE   paint setAntiAlias true    Point point1 draw   new Point            Point point2 draw   new Point        Point point3 draw   new Point     mapView getProjection   toPixels point1  point1 draw   mapView getProjection   toPixels point2  point2 draw   mapView getProjection   toPixels point3  point3 draw    Path path   new Path    path setFillType Path FillType EVEN ODD   path moveTo point1 draw x point1 draw y   path lineTo point2 draw x point2 draw y   path lineTo point3 draw x point3 draw y   path lineTo point1 draw x point1 draw y   path close     canvas drawPath path  paint      canvas drawLine point1 draw x point1 draw y point2 draw x point2 draw y  paint    return true    Thanks for the hint Nicolas

User · Answer

You need remove path moveTo after first initial   Path path   new Path    path moveTo point1 returned x  point1 returned y   path lineTo point2 returned x  point2 returned y   path lineTo point3 returned x  point3 returned y   path lineTo point1 returned x  point1 returned y   path close

[java] How to draw a filled triangle in android canvas?

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