You will have to set the toggle button in onCreate() and onResume() using the toggle button's method as such:
toggleButton.setChecked(wifiManager.isWifiEnabled());
E.g.
@Override
protected void onResume()
{
super.onResume();
WifiManager wifiManager = (WifiManager) this.getSystemService(Context.WIFI_SERVICE);
ToggleButton toggleButton = (ToggleButton) findViewById(R.id.toggleButton1);
toggleButton.setChecked(wifiManager.isWifiEnabled());
}