VTK textactor not showing

Question

I'm using VTK to show textactor with info 'ID' added to the actors. When my mouse is over an actor, the MouseEvent will call an 'add_text' function. The function was called and printed the correct 'ID' but there's no textactor adding to the window, is there any problem with my program?

class MouseInteractorHighLightActor(vtk.vtkInteractorStyleTrackballCamera):
    def __init__(self, parent=None):
        self.AddObserver("MouseMoveEvent", self.MouseMove)
        self.LastPickedActor = None
        self.LastPickedProperty = vtk.vtkProperty()
        self.new = vtkTextActor()
        self.old = vtkTextActor()
        self.on_actor = False

    def add_text(self,renderer,ID):
        self.new.SetInput(ID)
        txtprop = self.new.GetTextProperty()
        txtprop.SetFontSize(36)
        self.new.SetDisplayPosition(0,0)
        # renderer.RemoveActor(self.old)
        self.old = self.new

        if self.on_actor:
            renderer.AddActor(self.new)
            print("add_text called , ID : ",ID)
        else:
            pass
            # renderer.RemoveActor(self.old)
            # renderer.RemoveActor(self.new)

    def MouseMove(self,obj,event):
        Mousepos = self.GetInteractor().GetEventPosition()
        picker = vtk.vtkPropPicker()
        picker.Pick(Mousepos[0], Mousepos[1], 0, self.GetDefaultRenderer())
        self.NewPickedActor = picker.GetActor()

        if self.NewPickedActor:
            if not self.on_actor:
                self.on_actor = True
                print("on actor")
                info = self.NewPickedActor.GetProperty().GetInformation()
                info = str(info)
                pattern_1 = re.compile(r"ID.*\d+")
                pattern_2 = re.compile(r"\d+")
                string = pattern_1.findall(info)[0]
                ID = pattern_2.findall(string)[0]
                # print("ID : ",ID)
                self.add_text(self.GetDefaultRenderer() , ID)
                if self.LastPickedActor:
                    self.LastPickedActor.GetProperty().DeepCopy(self.LastPickedProperty)
                self.LastPickedProperty.DeepCopy(self.NewPickedActor.GetProperty())
                self.NewPickedActor.GetProperty().SetDiffuse(1.0)
                self.NewPickedActor.GetProperty().SetSpecular(0.0)
                self.LastPickedActor = self.NewPickedActor
            else:
                pass
        else:
            print("not on actor")
            self.on_actor = False

Update , the problem is solved, source code :

class MouseInteractorHighLightActor(vtk.vtkInteractorStyleTrackballCamera):
    def __init__(self, parent=None):
        self.AddObserver("LeftButtonPressEvent", self.leftButtonPressEvent)
        self.AddObserver("LeftButtonReleaseEvent", self.leftButtonReleaseEvent)
        self.AddObserver("MouseMoveEvent", self.MouseMove)
        self.LastPickedActor = None
        self.LastPickedProperty = vtk.vtkProperty()
        self.new = vtkTextActor()
        self.old = vtkTextActor()
        self.on_actor = False
        self.picker = vtk.vtkPropPicker()


    def add_text(self,renderer,ID):
        self.new.SetInput(ID)
        txtprop = self.new.GetTextProperty()
        txtprop.SetFontSize(72)
        self.new.SetDisplayPosition(0,0)
        self.old = self.new
        if self.on_actor:
            renderer.AddActor(self.new)
            # print("ID : ",ID)

    def MouseMove(self,obj,event):
        Mousepos = self.GetInteractor().GetEventPosition()
        picker = vtk.vtkPropPicker()
        picker.Pick(Mousepos[0], Mousepos[1], 0, self.GetDefaultRenderer())
        self.NewPickedActor = picker.GetActor()
        if self.NewPickedActor:
            self.on_actor = True
            # print("on actor")
            info = self.NewPickedActor.GetProperty().GetInformation()
            info = str(info)
            pattern_1 = re.compile(r"ID.*\d+")
            pattern_2 = re.compile(r"\d+")
            string = pattern_1.findall(info)[0]
            ID = pattern_2.findall(string)[0]
            # print("ID : ",ID)
            self.add_text(self.GetDefaultRenderer() , ID)
            
            if self.LastPickedActor:
                self.LastPickedActor.GetProperty().DeepCopy(self.LastPickedProperty)

            self.LastPickedProperty.DeepCopy(self.NewPickedActor.GetProperty())
            self.NewPickedActor.GetProperty().SetDiffuse(1.0)
            self.NewPickedActor.GetProperty().SetSpecular(0.0)
            self.LastPickedActor = self.NewPickedActor
            self.OnLeftButtonDown()
            self.OnLeftButtonUp()
                    
        else:
            if self.LastPickedActor:
                self.LastPickedActor.GetProperty().DeepCopy(self.LastPickedProperty)
            self.on_actor = False
            self.GetDefaultRenderer().RemoveActor(self.new)
            self.GetDefaultRenderer().RemoveActor(self.old)
            self.OnLeftButtonDown()
            self.OnLeftButtonUp()

    def leftButtonPressEvent(self, obj, event):
        self.RemoveObservers("MouseMoveEvent")
        self.OnLeftButtonDown()

    def leftButtonReleaseEvent(self, obj, event):
        self.AddObserver("MouseMoveEvent",self.MouseMove)
        self.OnLeftButtonUp()