screenNum=0;
[wPtr,rect]=Screen('OpenWindow',screenNum);
black=BlackIndex(wPtr);
white=WhiteIndex(wPtr);
Screen('FillRect',wPtr,black);
%%vbl=Screen(wPtr, 'Flip');
for i=1:10
Screen('FillRect',wPtr,[0 0 255], [100 150 200 250]);
Screen('DrawLine',wPtr,[0 255 255], 500, 200, 700 ,600, 5);
Screen('TextSize', wPtr , 150);
Screen('DrawText', wPtr, 'There is no garden without its weeds. ', 200, 20, [255 50 255]);
vbl=Screen(wPtr, 'Flip', 10000);

Screen('DrawOval',wPtr,[255 0 0], [250 250 300 300])
Screen('FillOval',wPtr,[255 255 0], [ 400 400 900 700]);
vbl=Screen(wPtr, 'Flip', 10000);
end
Screen('CloseAll')

这一段程序运行之后总是闪了一下就退出了，更改了时间之后还是一样问题