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So well come back again.

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This is actually an exercise on what you're supposed to be doing is you have to make a school of you

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with a page control.

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So essentially you have to find a way to control the page controller's place with the scroll of use

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Koren's place of the scroll as well as the opposite of it controlling the scroll do you.

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When they use the taps on the page control.

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Now I would encourage you to do this on your own and if you felt like you needed some help you can look

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at my solution as well.

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Pushover Let's start in just a few seconds.

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If you're still wondering how that relationship should be between the page controller and a scroll if

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you just look at the main view of your iPhone or your simulator when you scroll one whole page it goes

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for the next one.

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I mean you type on the page controller it just crawls the whole view.

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One more page to this site that you have typed on.

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So this relationship is what you have to be doing in this exercise.

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So I'm going to start in a few seconds if you want to compose the video now and then hopefully we'll

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get there.

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And if you want to look at my solution as well.

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OK.

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Let's get started.

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I'm going to go to school and in yeah I'm going to start a new application called the scroll of view

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page control of and you might ask for a view with page control.

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I'm going ahead to the storyboard and I will have to make a scroll for you as well as a page controller.

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So you are a page control.

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I'm going to place it maybe around here make it much wider.

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I'm going to give it a thank you.

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Color of black.

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So it's quite visible.

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Then I'm going to are this cruel of you.

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I will place it right under the page controller but place it here.

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You can cover the entire screen.

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I'm not doing that just to show you that you don't have to.

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So the page can do it I'm going to have to add some constraints for it.

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It has a constant from the top a leading constraint and a trailing constraint that they have to reset

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it to be zero.

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So it's trailing will be also a constant value of zero.

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So it covers the entire width of the screen.

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And if you can actually add it as well so it has equal weights.

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The view was a super view.

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Now my school view I'm going to make it a background that is a light very great.

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It has a kind of strange to the page control the vertical spacing and that the value is actually going

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to make sure it is zero.

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It is.

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So it has no constant value then it has a leading space a trailing space.

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It has an equal right to the actual view and the one that I have an aspect ratio on it that says As

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find that aspect ratio it says the height of the scroll view.

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So I'm going to have to reverse it.

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The height of a school equals the Vittal feet in a one to one.

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So again you don't have to necessarily follow these instructions.

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These are just the settings I'm using.

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I'm going to have a square shaped scroll view and I want to be right underneath the page control there

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are a lot of thumbs.

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Actually most often the page one too is actually at the bottom of this global view but all of these

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things you can just decide on your own.

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So the next thing is we need to have a view that is a container of view that is the view that we to

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put everything else in sight.

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So let's go ahead and say I have a of view and I went at that view and place it right there.

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On here.

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Exactly.

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And if you recall the last time we had to do a constraint that would automatically set the vet of this

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you to be one fifth of the scroll view or essentially making the scroll of you accommodate for five

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of these.

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This time I'm going to do things a little differently.

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So it's going here and I'm going to say I have a leading space constraint so that's something that they

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have to have.

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I'm going to have a top space constraint.

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That's something that they have to have and when I have them one.

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So that's again something we should have if you read the appels documentation.

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They specifically suggest that for a school of use you add your constraints from left to right and from

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top to bottom.

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So that's what they have done so far.

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I have a top concern I have to buy them first thing.

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I have a leading constraint.

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I'm going to go ahead and say Give me a trailing constraint and the trailing constantly would be just

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like the last time Super of view equals the view trailing the stand the constant of it is zero.

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Just like the last time it was.

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Then the next thing I'm going to do is this I'm going to go ahead and say my view compared to the scroll

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view.

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It always has an equal height to the height.

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Not exactly the same at all times.

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And then I'm going to go ahead and say and this is the part that is different than what you have done

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last time.

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Just to remind you the last time we actually added the constraint that set our view against the school

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view has a constraint that makes it five times larger.

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Now this time I'm going to say my view as a vet can sustain itself.

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So it's a it is always said Art at the moment 375 and you will see why am I doing this because I want

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to use this feet inside my programming interface and change it on the fly.

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It's your hobby can do all of these things.

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I'm going to go to my split screen to my assistant editor and here I'm going to have to add a few outlets

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one outlet which is very simple to understand.

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Is this one the scroll wheel.

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So that's going to be my Sproull view.

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And then I even have my page controller which is again very easy.

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My page controller I will have my content to you which is this guide the view that is embedded inside

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the school view.

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So that's going to be called my content's view and I have one more item that they have to add in here

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and that is this constraint the constraint that they made for the vet of my view this one.

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So this one I'm going to I'm going to call it that constrains.

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So David constraint is essentially going to be blowing me to change the weight of the content based

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on the number of the pages to do a quick recap of what we have done in the past and what we should remember

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is we need to have a certain number of pages on this page control that if it has five the content size

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should be five times the size of the Scroll of view if it is to the content size should be twice as

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wide as the scroll view.

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So because we don't know what that number is.

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And most likely that number will come to us from somebody else such has a network or a backend or so

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on and so forth.

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We should have a programmatic way of changing that number because of that.

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So they have a constraint that they can change it whenever I want to change it.

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For now it is sort of 375.

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If you want you can actually change you to a random number such as a thousand.

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So it becomes a little bit longer than the size of the scroll view and we can test everything now just

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to make sure that everything is actually functioning.

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Yes go ahead and run the application and if it all works we should be able to see some sort of a scrolling

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happening even though there are no content.

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So here are my simulator I can go in here now and say this is scroll and I can see the scroll.

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And I know that the colors are exactly the same simply because the view what they have in here is white

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and the actual view is white as well.

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But then I reached the end you can see the light gray background color of view or at the beginning.

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So before I leave this story about the last thing I want to do in here is I want to go to my school

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of you and say for this school if your paging is a neighborhood because you want to be able to scroll

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one page at a time like that one.

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And now let's go to our programming site in here.

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I'm going to go ahead and say I learned a lot.

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They do need is this I need to decide how many pages I have something to say that number of pages to

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be let's say 7 for not this is the number that you will get it from somewhere else but for our experiment

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I'm just going to make it a static value then I'm going to say once you've laid out depending on the

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type of the device you're using I need to know what's the score of you and I need that David because

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I need to make my content seven times larger so that what I'm going to call it to be a valuable call

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to the vet and that is going to be a CEG float.

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But we don't know what that value is just yet where we can get these two values or primarily the value

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is within the view will appear that is when the view has been laid out and we can know the size of the

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scroll wheel.

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So I'm going to go in here and say you will appear and the superb view will appear through in here.

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I'm going to say it is actually going to be my you dot bounds dot it.

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So we find the of the school view after the view has properly laid out now that they have that value.

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I don't know how much should be the overall weight of my content.

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That's not the way it's going to be constrained.

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I have to get it in your constant and that Konstanz is going to be my favorite multiplied by how many

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pages I have a number of pages.

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So we get it we want like by the number of pages it is giving me a little error saying that you cannot

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multiply something of the type CEG floored by something that is an integer.

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And fixing this is very easy because integers can easily become C.G. flawed so I'm going to say give

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me the CGU float value of the number of pages and then multiply them together and that becomes the value

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of the constant.

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So once that is sent or it's constant it's going to become larger numbers seven times bigger than my

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school view.

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And he's going to push my content views Vitt to become seven times larger.

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Now let's go right up to here to make sure everything is working the way we wanted it.

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Now in my simulator I can see that I have as much as three.

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This is four.

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That's actually true but that's how we count it.

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This is five.

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This is six.

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And this is the seventh page.

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Great.

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Is also working the way we wanted it.

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And I think 17 is actually a lot so maybe this down to say four.

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So it would be a little bit easier to do all the testing and to view things the way I wanted to view

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them.

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And then again I'm going to see that I have that one too.

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And this is tricky.

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Perfect So everything is working the way we want it.

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Now it becomes about connecting the page control that the scroll view.

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So the first thing we could do which is actually very easy I could say in my view it appears going say

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my page control of dot current page set it at 0 and see my page control the number of pages becomes

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my valuable number of pages.

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Maybe I should have a slightly better now naming because the two of them they seem very similar.

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Now with one of them is obviously and actually view of the page one Trauner the other one is my variable

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and if I run the application now we should be able to see a page story that has the same number of pages

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as does the scroll view.

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So now that has four.

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And here there are four pages.

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Now we want to be able to connect these two together.

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And before I do that now some content to my content view.

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So when we're scrolling we can actually see some colors or something of the sort.

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Now that I'm going to have to use a combination of force view of will appear and view that lot.

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So that's sort of I have two views let's call them they're read the view which is a you and I have another

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one which is the green view and the green review is going to become a view again.

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So I'm going to go in here.

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In my view the Lord which I'm going to have to take in my hand and say so as the view that lot I'm going

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to have to initialize both red and green.

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I'm going to say red because I'm going to say initialize it with a frame and that frame is going to

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become cjra like that zero.

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So for now they don't have really a space that they take they're just there.

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And of course I'm going to have to say my content to you dad I saw you read to you and since this is

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called read you maybe we should make the read view that background color become white color got to red.

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So this is one of them.

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Then I'm going to have the next one.

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The next one is the green of you so I will say Green of you again in view adds a frame.

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There is no body for it.

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And then green becomes green and then my content you the your tweets.

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Now the reason I put these two in the view that lot which no actual cjra is simply because they have

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to be initialized in here.

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But their frame can only be said in here in the view of will appear.

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Now you might be wondering so why can't we do all of these things in the view of in appier.

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Well if we do all of these things in the view will appear every time the view is about to appear.

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All of these things will be done again so you will have multiple copies of your red and green view.

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But using a view that this happens only once we get all of these initialized.

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But then based on the time that the view is about to appear we sit there size which is a very common

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practice and a very good practice.

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So in the overlap you may have to set the frame for red if you want to say read you door frame.

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Make it a C direct and seizure ex-nun number actually use a different format which is based on origin

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and the size so the size of it is actually very easy to see just size of weight and height and those

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height are both exactly the same thing.

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They are fit because you want them to be exactly the same size of the scroll wheel.

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So I copied that and save it and it's the origin of it.

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However the C-g point do they have to make out of an x and y values.

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One of them is going to be simple.

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That's why it has to be zero because we want them to stick to the top corner of the scroll or the content

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view which is inside the SQL view.

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However the X effect that is for the viridis view is going to be placed between the content of view

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and a horizontal level.

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I want it to be in the second page so that second page is essentially the index one.

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So I will saved it multiplied by 1 so this would essentially push this view as much as one page to the

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right.

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Let's see that happening before I actually make the green frame as well in the view up here.

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So right now in my simulator we should be able to see light after one whole page.

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The red one has a start and then everything else is still white.

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So let's go ahead and said the same thing for the green one for the green one.

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I want to play it not immediately after the read but rather the last page.

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So if that is what they want to do I'm going to go ahead and say green view that frame every time without

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having to be its size.

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It's always going to still be zero.

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But the origin x value of it is going to be multiplied by three.

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And that's simply because right now at the very beginning of this school view the top left corner is

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zero.

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If I score as much as 1 this is now 1 the whole of it.

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This is not to hold rates have gone to the left side of the screen and this is now true of all of it's

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have gone to left of the screen.

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Let's see if that actually plays the same way I'm expecting in the simulator of so once the simulator

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is up and be a scroll you see the red one and we see the white one and we see the green one.

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Now we have to find a way to connect these two together.

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Let's go ahead in here.

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In my of programming side and I'm going to have to add a new function and that's actually a function

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from that delegation.

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So I have to go up here and say if you can show that it also conforms to you on a scroll you delegate

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and the method that I want to get access to is a scroll if you did the escrowed.

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So every time that the scroll I want to know about the scrolling and I want to know where I am in the

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scroll.

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Now the very you all in the scroll is actually has a certain value for it right now.

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This girl is at the very beginning is zero.

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That is what we call it the content of set.

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Imagine this large view that is under the scroll of view being white red white and green.

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That's a very wide view that is there.

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And if you would imagine it is spilling outside the simulator you could view something like this.

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It would be a view that is like this is much larger but you're seeing only a portion of it.

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Now that view we are currently at a certain offset in a certain place right now the offset is zero.

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Right now the offset is one hole.

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And that's exactly the number that we need someone to go in here and say let's I'm going to call this

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one x origin let's call it my scroll of view or the scroll of view because they are both referring to

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the same value scroll view that the content of set dot X so find the content of set for me then I'm

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going to go ahead and say let.

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Next page.

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Just the page that you want to show on the page control.

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That's going to be the value of dividing this by the value of the V.

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So for instance if the X origin is twice as much as the weight that number becomes two if the value

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of this division is thrice as big that value becomes three.

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So on and so forth.

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Now there is a little problem.

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These two are both C.G. floats and obviously this value is becoming a C.G. float.

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Well I knew that to be an integer and if I tried to force it is going to give me an error saying Well

262
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both of these guys are C.G. frauds.

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So I'm going to say actually give me the integer value of these two.

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Now I want explain something else for you guys which I know is going to come up obviously.

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I've done this before and I know it happening.

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And even if you don't you can just try it once and you will see the problem.

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The problem is this If the division of X or Asian by it is for instance two point eight It still is

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going to become true because an integer value while at 2.8 we are half way past and we would like to

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be able to go to the next page.

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So essentially any number within the decimal values which is above 0.5 should become the next one and

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a number in order pointwise 5 should become the previous one to fix that.

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I'm going to say let's get the round of these numbers.

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So let's round it to be whatever number you find between these two.

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So basically when you're around it anything that is like 2.5 1 it becomes three things.

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But it's like two point four nine it becomes two.

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So this splits point the breaking point becomes at point five which is exactly what we need.

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And finally I'm going to say my page controller that current page becomes the next stage.

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Now before I run the code there is a tiny teeny bit of code that I have totally forgot and I'm hoping

279
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that you guys remember it.

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And that is even though we are using a delegate method we are using a score you delegate.

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I never delegate at my school.

282
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So let's go ahead and do that.

283
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Our That lot so down in here in my view that lot I'm going to go ahead and say my school view that delegate

284
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becomes self you could either do this in the code or do it in the Interface Builder.

285
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Most of them would essentially mean the same thing I would do exactly the same thing.

286
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But I'm glad to hear in the court now once my simulator boots up I should be able to scroll and then

287
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half the zoom up to the left that was a very bad idea.

288
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Halfway through each to the other side.

289
00:21:14,150 --> 00:21:15,120
Exactly.

290
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Let's go ahead and show it again.

291
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Purrfect that next one and then next one.

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Right at the half a breaking point it decides which way it has to go to.

293
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Now that's all good and well and working the way we want it to work.

294
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But there's still one piece missing and that is what if I type on the page controller shouldn't we go

295
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and I made this scroll of you what will happen.

296
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So to do that we need to have a function connected to our page controllers.

297
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We can't do that either by code or using the storyboard.

298
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I usually do it in the story but I actually want to do it in the coding interface because I want to

299
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see that happening in here as well.

300
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So I want to go ahead and say my page controller in the view that lot is going to have a target and

301
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that target is within your self and the action for it is at select all.

302
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And we have to find an action for it and the control event for it is value changed.

303
00:22:16,280 --> 00:22:22,730
So we have to get that then I'm going to add a new function then your function is called the function

304
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page function.

305
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And there's an argument for it that I'm going to call it send there.

306
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And that said there is a page control and I don't have any return for it is void.

307
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So we're going to call paged and since for using this page as a selector.

308
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I have to export it as an objective c so objective c page.

309
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And then this selector is going to be calling that.

310
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And then the body of the function.

311
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Here's what they want to do.

312
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I want to know which page we are on the controller here or view at zero like one break right now two

313
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or three.

314
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And then depending on that I want to scroll the school view to slumber.

315
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So for that I'm going to go ahead and say let's let's call it index.

316
00:23:09,300 --> 00:23:16,290
It's going to become center there which is the page where they're sending us that Clarence Page.

317
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So we know which page we are out on let's call it next page.

318
00:23:20,490 --> 00:23:22,260
Actually a better name for it.

319
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So next page is send that current page.

320
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Then we have to produce a new frame where we want a score of you to go to.

321
00:23:31,050 --> 00:23:38,610
So I'm going to go ahead and say let me frame the new frame I'm going to be it's called a CGI record

322
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on my CGI recked is made just like the last time.

323
00:23:41,940 --> 00:23:46,500
But the point on a size the size of it is that easier once I'm going to write it first.

324
00:23:46,500 --> 00:23:49,120
The size is going to be the same size.

325
00:23:49,140 --> 00:23:55,380
It has been for a while and that is the way to unhide both of them are equivalent to our vet because

326
00:23:55,380 --> 00:23:58,860
we are not changing the size of the frame of our skull.

327
00:23:59,130 --> 00:24:05,840
What we are changing is where does it points to a single point and the point is going to become the

328
00:24:06,690 --> 00:24:09,080
x and y values of it are important.

329
00:24:09,080 --> 00:24:15,370
The wife is obviously 0 the X of it becomes which page you are trying to show.

330
00:24:15,900 --> 00:24:19,660
And we have to multiply that by that.

331
00:24:19,950 --> 00:24:20,860
Let me explain this.

332
00:24:20,880 --> 00:24:21,750
There's going to be an error.

333
00:24:21,750 --> 00:24:22,600
Don't worry about that.

334
00:24:22,620 --> 00:24:25,070
Will fix that in a second but let me explain this.

335
00:24:25,260 --> 00:24:32,840
So what's happening is I'm saying if the next page that you have to show is 0 0 multiplied by whatever

336
00:24:32,860 --> 00:24:40,350
fish going be sure the very top left corner of the scroll or if the next page is 1 vs scroll as much

337
00:24:40,350 --> 00:24:41,650
as one.

338
00:24:41,880 --> 00:24:47,950
If the next page is three if you scroll as much as trivets And that's exactly what we need it to do.

339
00:24:48,150 --> 00:24:53,880
So the only thing that is missing in here is that it's seeing the next page is actually a an integer

340
00:24:53,880 --> 00:25:00,480
value what you need the float value someone is saying give me a C.G. float value of the next page and

341
00:25:00,490 --> 00:25:02,310
multiply by derivate.

342
00:25:02,310 --> 00:25:06,800
So now we have the new frame that we know that the school you should go there.

343
00:25:06,960 --> 00:25:08,510
Tovey should also go there.

344
00:25:08,580 --> 00:25:18,770
So I'm going to say my scroll view dot is cruel next to a visible scroll it is this new frame.

345
00:25:18,960 --> 00:25:20,330
And is it animated.

346
00:25:20,370 --> 00:25:21,980
Yes.

347
00:25:22,050 --> 00:25:29,880
So you're scrolling the scroll view not manually by the user animating or or tapping right there by

348
00:25:29,880 --> 00:25:33,620
a problematic review or scrolling you to a certain place.

349
00:25:33,630 --> 00:25:38,080
Let's see if that's going to work the way I'm suggesting with more.

350
00:25:38,210 --> 00:25:43,790
So now that they have the simulator on I can do this just like before I can type in there and it will

351
00:25:43,870 --> 00:25:46,790
automatically scroll the scroll wheel.

352
00:25:47,450 --> 00:25:51,450
So every time I type it will go and find the current page in here.

353
00:25:51,470 --> 00:25:55,690
And based on that it will push the view to that particular offering.

354
00:25:56,000 --> 00:25:57,440
And that's all we have to do.

355
00:25:59,340 --> 00:26:05,930
Now you might notice a little error in here and that is when I type it tries to go to the next stage

356
00:26:06,380 --> 00:26:13,580
then switches back and then goes and that's simply because when I tap on the page or by default it wants

357
00:26:13,580 --> 00:26:14,880
to jump to the next one.

358
00:26:15,070 --> 00:26:20,480
And it does that for a split site and pay attention to this really quickly it goes there.

359
00:26:20,480 --> 00:26:27,020
But then it comes back and that's simply because as it goes to the next page it says that the way a

360
00:26:27,020 --> 00:26:33,640
scroll of you did scroll is actually trying to force it to be in a different place because when we tap

361
00:26:33,640 --> 00:26:38,980
in here and the animation of the school view begins this thing is also happening.

362
00:26:38,990 --> 00:26:44,930
A school of view is a scrolling and based on somebody saying oh no you shouldn't be there just yet.

363
00:26:44,930 --> 00:26:46,690
You haven't reached halfway.

364
00:26:46,820 --> 00:26:50,570
So they're both essentially working against each other to fix that.

365
00:26:50,570 --> 00:26:56,900
I have a suggestion and my suggestion is that we find a way to know that if we are currently using the

366
00:26:56,900 --> 00:27:01,660
paging we are animating manually this thing shouldn't happen.

367
00:27:01,670 --> 00:27:09,230
So once again if you're animating using this school view animation we shouldn't be accounting for this

368
00:27:09,230 --> 00:27:09,860
thing.

369
00:27:10,010 --> 00:27:12,530
So let's go ahead and write that in code.

370
00:27:12,530 --> 00:27:20,300
I'm going to go up in here on the new value about the value of man animating which is by default false

371
00:27:20,330 --> 00:27:25,230
because we are not animating by default by default scrolling manually.

372
00:27:25,490 --> 00:27:31,630
So I'm going to go in here and say this entire thing should only happen if we are not animating.

373
00:27:31,640 --> 00:27:38,840
So if not animating which is the default mode all of these things should happen.

374
00:27:38,840 --> 00:27:42,950
Which is exactly what we have been doing up until this point.

375
00:27:43,040 --> 00:27:46,170
All of these are happening because we were not animating.

376
00:27:46,370 --> 00:27:47,490
Let's run this now.

377
00:27:49,240 --> 00:27:51,790
And now everything is working the way we wanted it.

378
00:27:51,800 --> 00:27:57,740
We still have the same problem that the dots on the page controller they turn on momentarily and then

379
00:27:57,740 --> 00:27:59,790
they turn off from time to time.

380
00:27:59,870 --> 00:28:01,230
So we have to address that.

381
00:28:01,270 --> 00:28:07,420
So I'm going to come in and say everything that views the page everything that we do that go ahead and

382
00:28:07,420 --> 00:28:10,440
make the animating become truth.

383
00:28:10,460 --> 00:28:14,000
So we are constantly animating using this guy.

384
00:28:14,240 --> 00:28:15,890
So let's see how that works.

385
00:28:17,920 --> 00:28:22,670
So now when I start they go perfectly from one to another to another to another.

386
00:28:22,800 --> 00:28:26,290
And none of those things that we were experiencing before happened.

387
00:28:26,830 --> 00:28:33,040
But you can imagine that now we have a different problem and that different problem is the animating

388
00:28:33,040 --> 00:28:34,540
is set to true.

389
00:28:34,570 --> 00:28:41,260
And if I do this it won't have any impact on the page control anymore simply because anything is not

390
00:28:41,350 --> 00:28:42,490
always true.

391
00:28:42,580 --> 00:28:47,300
So we have to find a way to make the animating actually false from time to time.

392
00:28:47,440 --> 00:28:50,050
And then we have to set the animating to false.

393
00:28:50,070 --> 00:28:56,320
Again that is Vendy is clearly always Isabel has finished and there is an actual delegate method for

394
00:28:56,320 --> 00:28:56,580
that.

395
00:28:56,580 --> 00:29:01,240
And that's the one I showed you a few lessons ago and I told you I even tried to embedded in one of

396
00:29:01,240 --> 00:29:05,880
the future lessons Previously I used to solve this problem in a different way.

397
00:29:06,010 --> 00:29:08,680
But now I thought that I could show you that method as well.

398
00:29:08,740 --> 00:29:11,580
So it's got to a school of your delegates.

399
00:29:12,010 --> 00:29:15,090
If it does show me some it plays a trick on me.

400
00:29:15,100 --> 00:29:22,710
So jump to the definition and there is something called escrowed view of end and scrolling animation.

401
00:29:22,720 --> 00:29:24,440
So that's the one that they need.

402
00:29:24,690 --> 00:29:28,600
It's going you say right after this one

403
00:29:31,390 --> 00:29:33,040
and animating.

404
00:29:33,390 --> 00:29:37,360
So a school of you did an animation so I know animate thing.

405
00:29:37,600 --> 00:29:40,500
So everything does and animation.

406
00:29:40,570 --> 00:29:46,620
I want to say animating because once again because it's not animating anymore.

407
00:29:46,870 --> 00:29:50,230
So let's go ahead and run this again.

408
00:29:50,270 --> 00:29:56,510
So now I have my simulator up I can scroll on I see them they happening and I can tap on those and they

409
00:29:56,510 --> 00:29:58,990
perfectly work the way I expected them.

410
00:29:59,000 --> 00:30:04,220
You don't have that little glitch happening anymore because the value of the animating gets to be true

411
00:30:04,220 --> 00:30:11,330
every time that we are animating using the PH controller and every time that we scroll we see them jumping

412
00:30:11,330 --> 00:30:17,030
from one point to the other one depending on the location of the offset which is exactly what we were

413
00:30:17,030 --> 00:30:18,070
hoping to see.

414
00:30:18,350 --> 00:30:19,670
So that's about it.

415
00:30:19,670 --> 00:30:22,760
A very long exercise I must say.

416
00:30:22,760 --> 00:30:30,170
We covered a lot of cons from doing the kind of strains from using a cross-train as an outlet to changing

417
00:30:30,170 --> 00:30:37,310
the values of the different you know views and placing them in different spots in the SQL view to finally

418
00:30:37,310 --> 00:30:44,090
getting this core view content of set value within the school view the school and then eventually adding

419
00:30:44,090 --> 00:30:47,890
a page function to our page control.

420
00:30:48,110 --> 00:30:52,200
So let's keep it up to here and move on to our next lesson.