Display grid view of videos - objective-c

Question

I'm trying to display a grid view in a portrait and horizontal view of the iPad. Right now im just trying to pull this off on the portrait view, so you will see the according X, Y in the following code where i'm stuck.
- (void)renderPlaylist {
cellsArray = [[NSMutableArray alloc] init];
CGFloat xPos = 0.0f;
CGFloat yPos = 0.0f;
int i = 4;
int y = 1;
int p = 1;
for (BCVideo *video in [[self playlist] videos]) {
if (i > 0) {
ScrollCellViewController *cell = [[ScrollCellViewController alloc] initWithBCVideo:video];
[cell setDelegate:self];
[[cell view] setFrame:CGRectMake(xPos, yPos, 768.0f, 245.0f)];
[scrollView addSubview:[cell view]];
[cellsArray addObject:cell];
yPos = y * 235.0f;
y++;
i--;
}else{
i = 4;
xPos = p * 245.0f;
yPos = 0.0f;
y = 1;
p++;
}
//blabla lazy
CGSize size = CGSizeMake(2000.0f, 2000.0f);
[scrollView setContentSize:size];
}
}
The total of videos is 17. I want to display 4 videos in each row, and then move right, for the next row, the scroll view will be horizontal (like the TED app). It obviously needs to display four rows of 4, and then one row of 1. This currently outputs 3 rows of 4, and then 1 of 2. For a total of 14?
what?
exactly.
If i adjust the code to rows of 5, you get a total of 15 videos. If i just the code to rows of 6, you get a total of 16 videos.
Screenshot http://i53.tinypic.com/15oj687.png

Answer 1

Your code is wrong in several parts.
By following it and calling U the upper part of the "if" and L the lower part of the if, you repeat this pattern:
UUUULUUUULUUUULUU
Now every 4th U you calculate y=4*235=940 as upper-left corner and it is probably out of your view (e.g. if you have a navigation bar your view height will be exactly 940 pixels height!). So the 4th row is not visible because out of screen.
Besides each U cycle draws a view which is 768px wide and 245 high so it is an horizontal stripe. Now the first 3 Us from the first three videos draw the first three lines, the 4th U draws the line out of screen. Then the "L" does nothing, it skips the video (sic!) and set "p" such that the next sequence of 4 stripes will be shifted 245px right, which is probably buggy as the stripes are still 768px wide, so the next cycles these stripes will be partially out of screen (over the right border). Besides when you will start drawing the second sequence of UUUU you will overwrite them over the existing ones but shifted 245px right.
Well, I don't know what you want to do, but it seems quite complex for a grid and it is obviously buggy. You should take care of your "swiping" code before and then you can debug it by printing in the console the position of all your videos and try to debug it. Don't try to fix it by looking for magic numbers in the parameters.

Answer 2

Solution:
- (void)renderPlaylist {
cellsArray = [[NSMutableArray alloc] init];
CGFloat xPos = 0.0f;
CGFloat yPos = 0.0f;
// y => counter for position of vertical videos
int y = -1;
// p => number of rows
int p = 0;
// r => check
int r = 0;
for (BCVideo *video in [[self playlist] videos]) {
r++;
// vertical rows
if (y < 3) {
y++;
yPos = y * 200.0f;
}else{
// move sideways to the right one row, and reset the vertical row
p++;
xPos = p * 255.0f;
yPos = 0.0f;
y = 0;
}
//print video
ScrollCellViewController *cell = [[ScrollCellViewController alloc] initWithBCVideo:video];
[cell setDelegate:self];
[[cell view] setFrame:CGRectMake(xPos, yPos, 255.0f, 210.0f)];
[scrollView addSubview:[cell view]];
[cellsArray addObject:cell];
CGSize size = CGSizeMake(xPos + 250.0f, 1024.0f);
[scrollView setContentSize:size];
}
}