Android uses canvas to draw arrows

It is too troublesome to draw arrows. I began to draw arrows and rotate them at the specified point. However, the effect has been poor. I want to use a mathematical method to draw a picture, but I find that the calculation is very complicated. So Google, found a middleware using Java when AWT implementation of the draw arrow (http://www.bangchui.org/simple? T16755.html), so I borrowed it and changed it. The result is actually usable. The results cannot be exclusive. Here we will share with you:

Public class mycanvas extends view {private canvas mycanvas; private paint mypaint = new paint (); Public mycanvas (context) {super (context ); // todo auto-generated constructor stub} public mycanvas (context, attributeset attrs, int defstyle) {super (context, attrs, defstyle ); // todo auto-generated constructor stub} public mycanvas (context, attributeset attrs) {super (context, attrs ); // todo auto-generated constructor stub} @ overrideprotected void ondraw (canvas) {// todo auto-generated method stubsuper. ondraw (canvas); this. mycanvas = canvas; drawal (0, 0,100,100);}/*** set the paint brush default style */Public void setpaintdefaultstyle () {mypaint. setantialias (true); mypaint. setcolor (color. red); mypaint. setstyle (paint. style. stroke); mypaint. setstrokewidth (3);}/** circle * @ Param x coordinate * @ Param YY coordinate * @ Param radius circle radius */Public void drawcircle (float X, float y, float radius) {mycanvas. drawcircle (X, Y, radius, mypaint); invalidate ();} /*** draw a straight line * @ Param fromx start point X coordinate * @ Param fromy start point y coordinate * @ Param tox end point X coordinate * @ Param toy end point y coordinate */Public void drawline (float fromx, float fromy, float tox, float toy) {path linepath = New Path (); linepath. moveTo (fromx, fromy); linepath. lineto (Tox, toy); linepath. close (); mycanvas. drawpath (linepath, mypaint); invalidate ();} /*** draw an arrow * @ Param SX * @ Param Sy * @ Param ex * @ Param ey */Public void drawal (INT Sx, int Sy, int ex, int ey) {double H = 8; // arrow height double L = 3.5; // half of the bottom edge int X3 = 0; int Y3 = 0; int X4 = 0; int Y4 = 0; double awrad = math. atan (L/h); // arrow angle double arraow_len = math. SQRT (L * L + H * H); // double [] arrxy_1 = rotatevec (ex-Sx, ey-sy, awrad, true, arraow_len ); double [] arrxy_2 = rotatevec (ex-Sx, ey-sy,-awrad, true, arraow_len); double X_3 = ex-arrxy_1 [0]; // (X3, Y3) is the first endpoint of double y_3 = ey-arrxy_1 [1]; double x_4 = ex-arrxy_2 [0]; // (X4, Y4) is the second endpoint double y_4 = ey-arrxy_2 [1]; double X3 = new double (X_3); X3 = x3.intvalue (); double Y3 = new double (y_3 ); y3 = y3.intvalue (); double X4 = new double (x_4); X4 = x4.intvalue (); double Y4 = new double (y_4); Y4 = y4.intvalue (); // draw mycanvas. drawline (sx, Sy, ex, ey, mypaint); Path triangle = New Path (); triangle. moveTo (ex, ey); triangle. lineto (X3, Y3); triangle. lineto (X4, Y4); triangle. close (); mycanvas. drawpath (triangle, mypaint);} // calculate public double [] rotatevec (int px, int py, double Ang, Boolean ischlen, double newlen) {double mathstr [] = new double [2]; // vector rotation function, the parameter meanings are X, Y, rotation angle, whether the length is changed, and the new length is double vx = px * Math. cos (ANG)-py * Math. sin (ANG); double Vy = px * Math. sin (ANG) + py * Math. cos (ANG); If (ischlen) {double D = math. SQRT (VX * VX + Vy * Vy); vx = vx/D * newlen; Vy = Vy/D * newlen; mathstr [0] = VX; mathstr [1] = Vy;} return mathstr ;}}

Shows the display effect:

Hope to help you!