How can i repeat my trial?

i'm very new to matlab ( first time project) so naturally i came across some problems. For my experiment i want to show a picture which the participant response yes/no to, using two different keys (f&g) and then the next picture is presented and it repeats so onward.

i so far managed to get 1 picture displayed and the key press works. however the next trial doesn't not open. thus my question what do i need to change or add so that the next picture ( and the next again) will open?

this is my code so far:

    function try1_6()

    cleanupObj= onCleanup(@() myCleanupFxn);

   % PRETEST
   % Initialize screen with black background
   winID = Screen('openWindow',0, [0 0 0]);

%Parameter
backcol=255;
textcol=0;

% Load image file(s)
structimages= [];
TheImagesdir = dir('theImagesdir/*.jpg');
for i=1: length(TheImagesdir);
  TheImages  = imread(['theImagesdir/' TheImagesdir(i).name], 'JPEG');

    % Get width and height
    imageX = size(TheImages,2);
    imageY = size(TheImages,1);

    % Convert to texture
    myTexture = Screen('MakeTexture', winID, TheImages);

    % Set destination rectangle
    destRect = [50  100  50+imageX  100+imageY];

    %save to structure
    structimages(end+1).filename=TheImagesdir(i).name;
    structimages(end).destRect= destRect;
    structimages(end).texture= myTexture;
end

%Make triallist
numberOfItems= [5]; %list of all possible items
Nrepeats=4;
Response=0;
TrialList=HH_mkTrialList({numberOfItems Response},Nrepeats); 

%PRESENTATION

for trialnum=1:size(TrialList,1)
  nitems = TrialList(trialnum,1);

    Screen('FillRect', winID,backcol); % makes the screen blank

    %displays text
    DrawFormattedText(winID,'dkjfghaslkdfglksdjgfh','center','center',textcol);
    Screen('Flip', winID)
    HH_waitForKeyPress({'space'}); % waits for spacebar to be pressed
    Screen('FillRect',winID,backcol);
    Screen('Flip',winID);
    WaitSecs(1);

    %display picture
    whichTheImages= randi(length(TheImagesdir)); % randomly selects image for directory
    Screen('FillRect',winID,backcol);
    Screen('DrawTexture', winID, myTexture, [], destRect);

    Screen('Flip', winID);
    HH_waitForKeyPress({'f','j'},5)

    if resp==-1
       break
    end 

    TrialList(trialnum,4)= response; %records response

end

end

function myCleanupFxn()
  Screen('CloseAll')
end

[per isakson]

http://docs.psychtoolbox.org/Psychtoolbox

[myrte druyvesteyn]

i already look in there before, but its so much info and i have no idea what is applicable to my specific question. which section should i look at in particular?

[per isakson]

Yes, but you cannot assume that many persons here know about the "Psychophysics Toolbox". I don't. You might put the name of the toolbox in the title of your question to catch the eye of someone, who is able (and interested) to answer.

[Stephen23]

@myrte druyvesteyn: Your current question title "How can i repeat my trial?" is so general that it could apply to almost any research that might be analysed using MATLAB. You should edit your question and make the title more attractive to those people who might know about the "Psychophysics Toolbox".