Android Application Development Tutorial - 65 - Animating a Bitmap Video

what's up guys welcome your 65th Android
tutorial for the new Boston again it's
me Travis we're going to do is do like a
you know simple animation and adding a
few other things that we can do with
this canvas here so let's first do our
animation and now we're going to do that
is just basically set up an int let's do
a float yeah float that's something new
and we're just going to call this
changing Y yeah
changing Y sounds good and basically
within our constructor because again
this is going to be called because
that's just how things work I guess
changing Y we're going to set it equal
to B 0 now what we can do is instead of
having this 0 here we can put in a
variable such as our changing Y and at
the moment it's still 0 so it's not
going to change anything but what we can
do is we can now add change because
basically this on draw is going to be
looping so we can say changing Y
actually let's do if changing Y is less
than a canvas dot get height then we're
going to add to it so it's going to get
bigger and bigger until it gets to you
know the size of our canvas so we're
going to add like what 10 10 pixels or
something and if that's not the case if
it's bigger than the canvas and we're
going to say else we're just going to
start it over changing Y is equal to 0
so it's basically going to start it over
and now if we run this as well because
basically this on draw thing is going to
be called over and over and over or
actually right now it's not I'm sorry we
need to do one last thing so within our
on draw we need to do one method called
invalidate
and basically it's kind of like check
its gonna go through this on draw it's
gonna be like hey man you draw the
background white it's gonna be like yeah
it's like hey man do you you put the
ball on there yeah
hey man do you change the change in Y
variable yeah I think we're done for the
day and then like the boss is like
invalidated do it over again that's
that's not the case just restart it so
that's going to cause it go into a loop
of some sort so you have to have that
invalidate method we're just going to
save that and run it now and you know
this is going to be our first simple
animation because you know our changing
Y is zero and then it's going to go
through and paint everything and then
it's going to invalidate so it's going
to start over but our changing Y
variable will now be 10 which will make
it go a little bit lower on the campus
until it gets to the point that the
number is so high it's the same or
bigger a greater value than the height
of our canvas and then it's going to you
know start back at zero so I mean it's
not that cool of an animation but there
we go as something simple now let's add
something else to our screen here so
after we've changed our value let's
let's add a box or a rectangle so what
we're going to do is we're going to say
rec this is a class name basically
referring to a rectangle class we're
going to say middle rec for like the
because we're going to put this
rectangle in the middle for the most
part so we need to import a rectangle
and what we're going to do we're going
to say new rec and that's method
basically that's just like what we did
with our you know our graphics class
except this time we were passing
anything in so the constructor of the
rect class is going to have nothing
within its parameters so hopefully
you're kind of getting this constructor
and this new business going on so
basically we set up a new rectangular
and now we're just going to kind of
define the rectangle so what we can do
is say middle rectangle
and we say dot set and as you can see we
have a left top right bottom so let's do
our left as zero our rights going to be
canvas dot get wit and then our height
let's say just guess on this let's just
do like four hundred and four bottom
again this is the top of the rectangle
and this is the bottom so we're going to
say five hundred so it's going to be
just like let's do five fifty so there
we go we kind of set up the dimensions
of the rectangle now and now let's also
set up a certain color so what we can do
is something like a paint which is going
to be a paint variable we're going to
say our blue obviously could we could
refer to the color class and then do
blue because I'm sure they have that
we're going to do it a little different
my way just be you know teaching guys
something new
so we have our paint our blue and now
we're going to say you know what new
paint I'm sorry space out there paint
and then we can say our blue dot set set
color to again color dot blue
and let's let's say let's just keep it
at that for now I'll show you guys some
other stuff in the next tutorial because
this one's getting kind of lengthy but
all we have to do now is we got to paint
them onto our canvas so we need to refer
to our canvas and say dot draw rec and
then it takes a rectangle and a paint
within its parameters so we're going to
say a rectangle which we just created
was middle rectangle or middle rect and
our paint was called our blue so our
blue and let's see how that looks so I'm
just gonna save this and run this as
well
none of those tutorials getting kind of
long and then we'll probably do maybe
one more tutorial before we actually get
into the way that you guys want to do it
because right now we're extending the
view class and you that's not
necessarily the way you want to do
animations and such so I'll probably do
one more just hit you guys familiar with
how to draw rectangles or bitmaps onto
some kind of a canvas so let's open this
up and there we go this is 400 down and
this is 550 pixels down as you can see
the ball goes behind the rectangle
because within our code we painted the
ball first and then we painted our
rectangle after that onto our canvas
here so the ball is being painted and
then you know that the rectangle is
being painted on top of that so
hopefully you guys get some information
out of this tutorial and I'll catch you
guys in the next one peace