Last time we started working on the module
13 doing textile and XNA so here's a reminder of the learning
objectives for the module. We did the keyboard input last time so
that we could use the keyboard to control the
player. Of course we can use keyboard input for
lots of other things as well, letting the player
enter their gamer tag into a text box and so on, but we kept it pretty simple for what we're doing
in this course. In this lecture we're going to talk about
how we can provide text output in our XNA
games. Obviously when we had a console application we could just use
console.rightline to output stuff but in our XNA games we can't use that
approach. We have to do something slightly more
complicated and so that's what we're going to cover
today. The first thing we need to know is to
actually display text in our XNA game we need a special kind of content
that we haven't used yet. So I'm going to go over to the content.
Project in my solution that I obviously just blasted over to and opened
up, and I'm going to add a new item. And when I say I want to add a new item, I
get a number of different choices. I can add an XML file which can be really
useful for saving. Level design information into XML files but we're not going to do that in
this course. I could save an effect file. But I'm going to create a new SpriteFont.
So a SpriteFont, and let me just call this [SOUND] Arial. A SpriteFont is a font that will get used
within our game. In fact, what we do is, we specify a
particular font name here, and this font needs to be installed on
your computer so that when it's time to build, it can turn this SpriteFont into an
XNB file. Which is compiled XNA content. If you're a MonoGame user, you're not
going to be doing any of this. You can't add a SpriteFont, you can't
build a SpriteFont. There's no content pipeline in MonoGame at
this time. So for this particular lecture I will be
providing you with a compiled XNB file for this SpriteFont we're building.
But you should understand you can't do it. Right?
You have to, you have to build a content pipeline some other way, at this point, within
MonoGame. But if you're using Visual Studio and XNA,
then you do what I'm showing you here. And you pick the font name, and you can
pick a size. And you can do there's lots of stuff you
can do. You can make 'em bold or italic. All kinds of things that you can do to
specify what this font will look like when you display it in your
XNA game. All I wanted to do is change it to Arial
so I will Ctrl+s. And I'm going to actually build right now because this would be the point at which,
if you said, you know, you had a misspelling, and you said Arialiosity or something like
that, then. It would blow up because it can't build
the font because it doesn't have it installed on your computer. Okay, so now I have this piece of content
that I've built but I still need to, you know, have a variable
that holds it and load it and so on. So I'm going to, just as before, I have
some commented out stuff that I'm going to uncomment to sort of
reveal our solution as we go. So the first thing that we will do is, uncomment this Sprite font
field and I will also send you to an in-lecture
quiz about. Wow, I don't want to give away the answer.
So about content for fonts. So go take that in-lecture quiz.
Okay, so I've got this SpriteFont object that was the right answer
SpriteFont. I've got this SpriteFont variable or field
that I've declared. And I want to come down here and I want to
make sure I load it. So that I have that content loaded just
like we've loaded texture 2Ds, just like we've
loaded sound effects. This time of course, we're loading something different, we're loading a
SpriteFont. At this point though, I'm not drawing
anything. And so we should now add the rest of the
code we need to draw stuff. So, I'll start by showing you a, a sub-optimal way to
draw. And then we'll fix it. So, this is not the sub-optimal part.
This is a good idea. So we're going to have some position at
which we are going to draw the score. And at this point, that position will be WINDOW_WIDTH over 12, and WINDOW_HEIGHT
over 12. And I shouldn't have said at this point. Throughout this entire game, that's where
it's going to get drawn. So instead of using a draw_rectangle, For
the text we're going to draw, we're going to tell it
where to draw it. And, and XNA will take it from there when
we go to draw it. So let's actually go to draw it. This will be less exciting because I can't
actually score at this point, but at least I can draw a
string. So I'm going to instead of just uncommenting
that because this is the commented code is the better way to do it, lets say I
decide to do this, [SOUND] so basically every time I'm here notice
I'm doing this slightly differently. Instead of doing a SpriteBatch draw which
was for texture 2D's I'm doing a SpriteBatch draw string which is for, not
surprisingly, drawing strings. And I can provide it there are a bunch of
overloads. I see I'm going to have to open up my
declaration of the score variable, so I'll fix that in a moment. I have some overloads, but they're all
going to require me to pass in the SpriteFont, because it can't draw it
if it doesn't know what font to use. And then I pass it the string, then I pass
it where I want it drawn, and then I pass it
to color. In this particular overload of draw string
just as SpriteBatch draw. Has a lot of overline, overloads. SpriteBatch draw string has a lot of overloads as well.
All right. I'm going to get rid of this compilation
error here. So I will go up to the top, and start
adding a little bit of score support, we're not all
the way there yet. So if I F6, I get a build succeeded. If I F5 you can see up here in the upper
left hand corner it's hard for, because the mouse is
invisible nor should it be because I'm not using the mouse in this
game but you can see that its now displaying the score for me
in the upper left hand corner. The reason I said this was sub-optimal is
because I am creating, remember, because strings are immutable, down here
in the draw method, I am creating a new string 60
times a second, and using it for a sixtieth of a second and throwing it away and creating
an new one. And that's really not the kind of inefficiency that we should add to our
code. So let's optimize that part and then we'll
actually add some real scoring. So instead of doing it that way, I want a field called scoreString, way back up at
the top. I want a field called scoreString that
will hold the current score string and that string will only change
when the player scores points. And that way we're not creating new
strings 60 times a second, we're only creating new strings
each time the player scores. When I did that, I discovered that here in
load content I needed to initialize it, and of course now
I get a compilation error because it says I
don't know what this get score string thing is, because I need
to come uncomment this private method that I wrote that gets
the score string. So you pass in a score, and it returns a
string that includes the prefix concantonated with the actual score. Let me Ctrl+Z a little bit there, there we
go, concantonated with the actual score. I wrote this method because we'll see in a
couple of moments that I need to do this multiple
times in my code. And as soon as you start thinking copy and paste, stop yourself and think private
method instead. Alright, so now when I F5, you're not going to see any difference in program
behavior. It still looks exactly the same way it did
before. This is an example of re-factoring to fix
the quality of the code without actually
changing its performance. We might have seen some performance hits
later on if we had lots of objects and suddenly creating 60 new
strings a second caused problems for us. So we just fixed it now and did it in a
much more appropriate way. This idea, by the way, is very similar to
when I said you shouldn't be creating a new draw
rectangle. On every call to draw for the same exact
reason. We don't want to create a whole bunch of
extra objects that we use very, very briefly and then let the
garbage collector go get 'em. Alright, so the only other thing I
actually need in this game is to be able to score and so I'll uncomment these two lines of
code so this is where the bear collides with
the fish. So I'm going to add some score to my current score and this is the
point at which I now need to go get a new
string. And so I call that get scoreString method
that I showed you moments ago. I need to uncomment. My bear score constant that I had
commented out up to this point, now I can F6. Now I can F5 and we'll see that if I run
into bears I actually get scores so now you
know you can play the game and build up your score and try to get on the leader boards for this amazing almost commercial quality
but not quite game. So what we didn't do was the other
in-lecture quiz where you go tell me how you actually draw
a string. So you should go do that now. And that's it for today. So, as a recap, we learned how we use
SpriteFonts as content so that we can do XNA text
output and we learned how to actually do that
text output by calling the drawstring method on the
sprite brat, SpriteBatch [LAUGH]. That's the end of this module and that's
the end of all the formal modules in the course.
There is one more week. And that week is for you to do the
optional project, if you choose to do so. For you to study for, if you decide you
want to, the final exam. And for you to take the final exam. So, even though there's no sort of official formal lectures with new material nor are
there assignments due, you do, next week, need to do your peer evaluation of project
increment five for everyone and I'll post some lectures talking about the optional
project talking about sort of the core ideas that you should
carry with you into the final exam. And closing out the course with some final
thoughts.