wxPython ImageViewer

I am to create a simple image viewer using wxPython. I am using a panel and a button upon which by clicking a picture would be shown from a directory (Images). Below is the code. I have taken pieces from different websites.

My question is if I maximize the window, the picture viewer as well as the button remain same. I want the picture viewer to increase as well.

Another thing is, after I press the "Load" button, it moves to the left. How do I fix these two problems?

I understand for those 2 above questions, this so big program might be unnecessary. I am a newbie to Python.

Thanks in advance.

import wx, os

class Panel1(wx.Panel):
    def __init__(self, *args, **kwds):
        wx.Panel.__init__(self, *args, **kwds)
        self.jpgs = self.GetJpgList("./Images")
        self.CurrentJpg = 0
        self.MaxImageSize = 200
        self.img = wx.EmptyImage(self.MaxImageSize,self.MaxImageSize)
        self.imageCtrl = wx.StaticBitmap(self, wx.ID_ANY, wx.BitmapFromImage(self.img))
        self.button_1 = wx.Button(self, wx.ID_ANY, "Load")
        self.Bind(wx.EVT_BUTTON, self.OnLoad, self.button_1)
        self.__do_layout()
        self.Layout()

    def GetJpgList(self, dir):
        jpgs = [f for f in os.listdir(dir) if f[-4:] == ".JPG"]
        return [os.path.join(dir, f) for f in jpgs]

    def __do_layout(self):
        sizer_1 = wx.BoxSizer(wx.HORIZONTAL)
        sizer_2 = wx.BoxSizer(wx.VERTICAL)
        sizer_1.Add((1,1),1)
        sizer_1.Add(self.imageCtrl, 0, wx.ALL|wx.EXPAND, 5)
        sizer_1.Add((1,1),1)
        sizer_1.Add(wx.StaticLine(self, wx.ID_ANY), 0, wx.ALL|wx.EXPAND, 5)
        sizer_2.Add(self.button_1, 0, wx.ALL|wx.TOP, 5)
        sizer_1.Add(sizer_2, 0, wx.ALL, 5)
        self.SetSizer(sizer_1)
        sizer_1.Fit(self)

    def OnNext(self, event):
        path = self.jpgs[self.CurrentJpg]
        self.Img = wx.Image(path, wx.BITMAP_TYPE_ANY)
        W = self.Img.GetWidth()
        H = self.Img.GetHeight()
        if W > H:
            NewW = self.MaxImageSize
            NewH = self.MaxImageSize * H / W
        else:
            NewH = self.MaxImageSize
            NewW = self.MaxImageSize * W / H
        self.Img = self.Img.Scale(NewW,NewH)
        self.imageCtrl.SetBitmap(wx.BitmapFromImage(self.Img))
        #self.Fit()
        #self.Layout()
        self.Refresh()

        self.CurrentJpg += 1
        if self.CurrentJpg > len(self.jpgs) -1:
            self.CurrentJpg = 0

# end of class Panel1

class Frame1(wx.Frame):
    def __init__(self, *args, **kwds):
        wx.Frame.__init__(self, *args, **kwds)
        self.__set_properties()
        self.__do_layout()

    def __set_properties(self):
        self.SetTitle("Picture")

    def __do_layout(self):
        panel1 = Panel1(self)
        self.sizer = wx.BoxSizer(wx.VERTICAL)
        self.sizer.Add(panel1, 1, wx.EXPAND)
        self.SetSizer(self.sizer)
        self.sizer.Fit(self)
        self.Layout()
        self.Centre()

# end of class Frame1

class Game1(wx.App):
    def OnInit(self):
        wx.InitAllImageHandlers()
        frame1 = Frame1(None, wx.ID_ANY, "")
        self.SetTopWindow(frame1)
        frame1.Show()
        return 1

# end of class Game1

if __name__ == "__main__":
    game1 = Game1(0)
    game1.MainLoop()