java - Android - getting the current rotation of a matrix

Question

I need to be able to set the rotation of a matrix rather than add to it. I believe the only way to set the rotation is to know the current rotation of the matrix.

Note: matrix.setRotate() will not do, because the matrix needs to retain its information.

Answer 1

float[] v = new float[9];
matrix.getValues(v);
// translation is simple
float tx = v[Matrix.MTRANS_X];
float ty = v[Matrix.MTRANS_Y];

// calculate real scale
float scalex = v[Matrix.MSCALE_X];
float skewy = v[Matrix.MSKEW_Y];
float rScale = (float) Math.sqrt(scalex * scalex + skewy * skewy);

// calculate the degree of rotation
float rAngle = Math.round(Math.atan2(v[Matrix.MSKEW_X], v[Matrix.MSCALE_X]) * (180 / Math.PI));

from here http://judepereira.com/blog/calculate-the-real-scale-factor-and-the-angle-of-rotation-from-an-android-matrix/