Custom preview gui with buttons

So Im trying to reproduce this example:

https://de.mathworks.com/help/imaq/previewing-data.html#f11-76072

by using a figure window made with GUIDE.

At the moment, my code looks like this:

function varargout = aufnehmen_speichern(varargin)
% AUFNEHMEN_SPEICHERN MATLAB code for aufnehmen_speichern.fig
%      AUFNEHMEN_SPEICHERN, by itself, creates a new AUFNEHMEN_SPEICHERN or raises the existing
%      singleton*.
%
%      H = AUFNEHMEN_SPEICHERN returns the handle to a new AUFNEHMEN_SPEICHERN or the handle to
%      the existing singleton*.
%
%      AUFNEHMEN_SPEICHERN('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in AUFNEHMEN_SPEICHERN.M with the given input arguments.
%
%      AUFNEHMEN_SPEICHERN('Property','Value',...) creates a new AUFNEHMEN_SPEICHERN or raises the
%      existing singleton*.  Starting from the left, property value pairs are
%      applied to the GUI before aufnehmen_speichern_OpeningFcn gets called.  An
%      unrecognized property name or invalid value makes property application
%      stop.  All inputs are passed to aufnehmen_speichern_OpeningFcn via varargin.
%
%      *See GUI Options on GUIDE's Tools menu.  Choose "GUI allows only one
%      instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES

% Edit the above text to modify the response to help aufnehmen_speichern

% Last Modified by GUIDE v2.5 25-Sep-2017 10:32:37

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @aufnehmen_speichern_OpeningFcn, ...
                   'gui_OutputFcn',  @aufnehmen_speichern_OutputFcn, ...
                   'gui_LayoutFcn',  [] , ...
                   'gui_Callback',   []);
if nargin && ischar(varargin{1})
    gui_State.gui_Callback = str2func(varargin{1});
end

if nargout
    [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
    gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT

% --- Executes just before aufnehmen_speichern is made visible.
function aufnehmen_speichern_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to aufnehmen_speichern (see VARARGIN)

% Choose default command line output for aufnehmen_speichern
handles.output = hObject;

imaqreset;

vid1 = videoinput('gige', 1,'Mono8');
vid2 = videoinput('gige', 2,'Mono8');

vidRes = vid1.VideoResolution;
imWidth = vidRes(1);
imHeight = vidRes(2);
nBands = vid1.NumberOfBands;
hImage1 = image(zeros(imHeight,imWidth,nBands),'Parent',handles.axes1);

src1 = getselectedsource(vid1);
src2 = getselectedsource(vid2);

set(vid1, 'LoggingMode', 'memory');
set(vid2, 'LoggingMode', 'memory');

src1.AcquisitionStartTriggerMode = 'On';
src2.AcquisitionStartTriggerMode = 'On';

triggerconfig(vid1, 'hardware', 'DeviceSpecific', 'DeviceSpecific');
triggerconfig(vid2, 'hardware', 'DeviceSpecific', 'DeviceSpecific');

src1.AcquisitionStartTriggerActivation = 'FallingEdge';
src2.AcquisitionStartTriggerActivation = 'FallingEdge';

src1.AcquisitionStartTriggerSource = 'Line1';
src2.AcquisitionStartTriggerSource = 'Line1';

src1.AcquisitionEndTriggerSource = 'Line1';
src2.AcquisitionEndTriggerSource = 'Line1';

src1.AcquisitionRecordTriggerSource = 'Line1';
src2.AcquisitionRecordTriggerSource = 'Line1';

src1.StreamBytesPerSecond = 60000000;
src2.StreamBytesPerSecond = 60000000;

src1.AcquisitionFrameRateAbs = 30.000300003;
src2.AcquisitionFrameRateAbs = 30.000300003;

src1.PacketSize = 1500;
src2.PacketSize = 1500;

vid1.FramesPerTrigger = Inf;
vid2.FramesPerTrigger = Inf;

start(vid1);
start(vid2);
preview(vid1, hImage1);
preview(vid2);
imaqmem(1000000000000);

%setappdata(hImage1,'UpdatePreviewWindowFcn',@mypreview_fcn);

%setappdata(hImage1,'HandleToTimestampLabel',handles.text1);
%setappdata(hImage1,'HandleToResolution',handles.text2);
%setappdata(hImage1,'HandleToStatus',handles.text3);

% Update handles structure
guidata(hObject, handles);

% UIWAIT makes aufnehmen_speichern wait for user response (see UIRESUME)
% uiwait(handles.figure1);

% --- Outputs from this function are returned to the command line.
function varargout = aufnehmen_speichern_OutputFcn(hObject, eventdata, handles) 
% varargout  cell array for returning output args (see VARARGOUT);
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Get default command line output from handles structure
varargout{1} = handles.output;

% --- Executes on button press in zurueck.
function return_Callback(hObject, eventdata, handles)
% hObject    handle to zurueck (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
close;
main;

% --- Executes on button press in exit.
function exit_Callback(hObject, eventdata, handles)
% hObject    handle to exit (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
close;

% --- Executes on button press in get_data.
function get_data_Callback(hObject, eventdata, handles)
% hObject    handle to get_data (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
imaqmem(1000000000000);

diskLogger1 = VideoWriter('D:\Matlab Sciebo\Hummeln 2017\Kalibrierung\Test\links01.avi', 'Grayscale AVI');
diskLogger2 = VideoWriter('D:\Matlab Sciebo\Hummeln 2017\Kalibrierung\Test\rechts01.avi', 'Grayscale AVI');
diskLogger1.FrameRate = 35;
diskLogger2.FrameRate = 35;
open(diskLogger1);
open(diskLogger2);

data1 = getdata(vid1, vid1.FramesAvailable);
data2 = getdata(vid2, vid2.FramesAvailable);
numFrames1 = size(data1, 4);
numFrames2 = size(data2, 4);

   for ii = 1:numFrames1 

       writeVideo(diskLogger1, data1(:,:,:,ii));
       %Wenn die Aufnahmedauer länger als 10000 Frames geht, kann es zu Problemen kommen. Über die If- break kann die Dauer eingestellt werden.
       %if (vid1==10000) 
       %break;
       %end
   end
    for ii = 1:numFrames2 

       writeVideo(diskLogger2, data2(:,:,:,ii));
       %if (vid2==4000)
       %break;
       %end
    end

   close(diskLogger1);
   close(diskLogger2);

% --- Executes during object creation, after setting all properties.
function mypreview_fcn(hObject, eventdata, handles)
% hObject    handle to text1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called
tstmpstr = eventdata.Timestamp;
ts = getappdata(handles,'HandleToTimestampLabel');
ts.String = tstmpstr;

%rl = getappdata(handles,'HandleToResolution');
%rl.String = eventdata.Resolution;

%st = getappdata(handles,'HandleToStatus');
%st.String = eventdata.Status;

%handles.CData = eventdata.Data;

My problems that I currently have are, that whenever I press the get_data button, the get_data_Callback executes but throws the following error:

Warning: No video frames were written to this file. The filde may be invalid.

> In VideoWriter.VideoWriter>VideoWriter.close at 307

In VideoWriter.VideoWriter>VideoWriter.delete at 256

In gui_mainfcn at 220

In aufnehmen_speichern at 42

The other thing is that I don't understand how the strings on my buttons change from Resolution to 1292x734 for example. Do I have to use handles? But I did try using handles here:

 %setappdata(hImage1,'HandleToTimestampLabel',handles.text1);
 %setappdata(hImage1,'HandleToResolution',handles.text2);
 %setappdata(hImage1,'HandleToStatus',handles.text3);

At least thats what the example on mathworks.com says.

By the way:

 preview(vid1, hImage1);
 preview(vid2);

are present, because my buttons won't work correctly as in the normal preview window of preview(vid2).