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Welcome back, so we can select the date now, and that works.

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But now let's actually calculate how much time has passed ever since.

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So let's go back to coding.

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So we have the date now, and this is just using this simple date format that we have prepared.

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And it's parsing that into the data variable.

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But I wants to know the selected state in minutes.

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So today that we're getting there is not giving us.

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So the selected date in minutes, so how much time has passed ever since and minutes?

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So what I want to use for that is going to be a variable that will be called selected date in minutes.

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And in order to get that, I can use to date variable here and get its time property and then divide

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that by 60000.

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So why would I divide it by 60000?

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Because date so the date property for look at it here gives us the details and to time that has passed

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ever since a given moment, so here does get time.

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Method, for example, gives us the number of milliseconds to January the 1st 1970 at midnight.

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Okay, so when you use get time, you get a super long value.

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This is a long data type.

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It's a very long value.

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And if you want to get minutes instead of milliseconds, you, first of all, have to divide by thousand

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to get two seconds and then another time by 60 in order to get from seconds to minutes.

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So if you do both in one step, you divide by 60000 and then you get the time that has passed since

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1970 in minutes.

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And this time property is the same thing as if we were asking for get time.

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So it's the same as if I would use get time here, for example.

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Like So but this is this great time is the old fashioned way we can just get this time by using the

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property.

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Access syntax does time, as you can see here.

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So now we have the selected date, and we need to calculate how much time has passed between the selected

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date and the current date.

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So let's get to current date.

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Current date is going to use to SDF pass.

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And here we need to use the format, so we could, of course, create the format object here and so

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forth, but I'm just going to do it in one step as the format where I use system that current millis.

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So what this will do is it will give me the time that has passed since the 1st of January 1970 in milliseconds.

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That's how I can basically use this approach here.

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Here we get how much time has passed since the ball between the selected date and 1970 1st of January.

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And here we get the current time.

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So how much time has passed between now and 1970?

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Okay, so that's the current date that we get.

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And now we need to calculate the difference in minutes.

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OK, so let's get the current date.

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And we need to calculate that in minutes, actually.

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So let's create a vault current date in minutes.

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Which will be the current date time divided by 60000.

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And now we can use the current date in minutes minus the selected date in minutes.

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And this will give us how much time is between those two time points.

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So between the selected and the current date?

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OK, so now we can use this difference in minutes and actually assign it to our text view that wants

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to know about it, and it's this text view here which currently doesn't have an ID, so let's give it

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an ID.

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You probably know how to do it.

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You just use this Android ID at plus ID slash, or you could have used a designer to find ID here or

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here directly.

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OK, well, I'm going to show you how to do it in the code.

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It's called a TV age in minutes.

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OK, so now let's access this text view in our code, and therefore we need to create another variable

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up here.

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So private VAR and I'm going to call the TV age in minutes, which will also be a text you optional.

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I'm going to set it to null and then I can initialize it here in my own create.

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Method, and I will find it by its side, which is our Dart ID, dot tbe h in minutes.

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OK, so here we are signing the text use and this age in minutes is this text view here, by the way,

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you can get there by holding the control key, clicking into it and you see which text you.

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It is in the split view.

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You can click into here and you will see that it's this one here.

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What currently says 14 million?

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So that's the one that I want to overwrite.

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OK.

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So in the main activity, now we have access to this TV age in minutes and we can actually assign it.

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So here TV age in minutes.

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That text should now be the difference in minutes.

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Now, unfortunately, the difference in minutes is of type along, so we need to convert it into a string

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for this to work.

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And TV age in minutes here, because it's another bill, we need to add the question mark here for type

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safety.

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OK, so at this point, let's actually test us.

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So let's test once again.

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And that selected date, let's select between.

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Yesterday and today, it's not yesterday, but it's a little longer, so you see here, 14, 40 minutes

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have passed.

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Ever since that day that I've selected and no.

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So let me select the first of September ever since 20 minutes have passed, but me select the date in

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the future because today's the 21st.

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So let me select the 22nd.

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And you see, it's some sometime in the past, even though for some reason my phone thinks it's a different

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date, I believe it thinks that it's September the 15th, so definitely something wrong with my phone

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here and still stuck at the 15th and thinks the current date is 15th, even though it's the 21st.

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But if I were to test this on a real phone, this would work.

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So how can I limit the selection to dates in the past because they cannot be born in the future, right?

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Well, that is something that we can do with a neat little trick.

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So instead of showing this date picker dialogue here directly, what we can do is we can put this entire

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date picker dialogue, which is all of this code.

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This is all of the code that this part of our date picker dialogue, so we can put that into a variable

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so I can call the DPD, for example, and paste all of that in there.

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So this DPD value more variable will now be our data picker dialog.

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So let me shrink it down.

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And now, while in here with this minus, I can collapse the code.

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You see, all of this code now is going to be reduced, at least from a visible point of view.

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And now we can show the date picker dialog.

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Let's just test if the date picker dialog will still appear as we wanted it so we can see it's the works.

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Let me select the date here.

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OK, that still works.

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And now, instead of just showing it, I want to add another property to it.

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And here I can set the date picker property.

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To be set to a specific max date, so here does this mix date, and I can assign he makes date to it.

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And here, in order to set the max date to be yesterday, I can just go ahead and set it to a system

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that current time in milliseconds minus eighty six four zero zero, so 86 million, 400000 milliseconds.

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So there are 3.6 million milliseconds in one hour.

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So multiply that by 24 and you get eighty six point four million milliseconds.

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So let's test that once again, and I'll select the date in the future.

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While you can see I cannot select dates in the future anymore, I can only select dates in the past.

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So, for example, one day in the past and you can see now it's 14 40, that's how many minutes I'm

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old.

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If I'm one day old.

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Exactly.

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OK, so now we can make a couple of changes here to our code.

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Because we are using to date here.

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And now, if you look at our code, you will see that there are some parts of the code marked, OK,

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so this dead date, for example, is highlighted or has a background color here, and that is because

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we're not using type safety.

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So what you can do here instead, is you can make it null safe by using the following approach by basically

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creating this selected date in minutes.

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If the date is not empty, so here's the date question mark.

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Don't let.

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And now do all of this part here inside of it.

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OK, so only if the date is not empty, then run this code.

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The same goes for the current date.

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So here we can use current date.

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Question mark.

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Don't let.

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And then execute the rest only if current date is not empty.

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So this date let is just an approach to make sure that you we only execute this code if the date is

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in fact not empty.

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If the date is empty for some reason, then we will not execute the code.

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So this way we're making sure that our code is not crashing.

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And this is just null safety that we are implementing here.

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And then another thing that we can optimize is that we can make sure that this click data picker is

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private as well, so we can make it private so that it will only be accessible from this class and from

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the other class, which may totally make sense for our particular case.

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So if we ever want to use this method from somewhere else, we would just have to make it public again

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and then we can access it from the other classes.

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But in our case, as this is never going to be required for now, we can replace that.

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And another thing you see here, this view is never used, so we can basically just replace it with

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an underscore and the code will work exactly as it did before.

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OK, so that's the highly optimized code that we have here and now we can feel confident when we published

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this application.

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So in the next lecture, I have a little challenge for you where I would like you to rebuild this application,

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not displaying the age in minutes, but actually the age and hours.

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So good luck with that and see you in the next.