How to rotate a canvas at a specific point using android.graphics.Camera.rotateX(angle)

Question

I am trying to use the Camera (android.graphics.Camera not the hardware camera) to rotate a views canvas around a specific point, in this instance the middle of the canvas.

Answer 1

Use this as the transformation in your animation class

protected void applyTransformation(float interpolatedTime, Transformation t) {

    final float fromDegrees = 0;

    float degrees = fromDegrees

    + ((180- fromDegrees) * interpolatedTime);

    final float centerX = mCenterX;

    final float centerY = mCenterY;

    final Camera camera = mCamera;

    final Matrix matrix = t.getMatrix();

    camera.save();

    camera.rotateX(degrees);

    camera.getMatrix(matrix);

    camera.restore();

    matrix.preTranslate(-centerX, -centerY);

    matrix.postTranslate(centerX, centerY);

}