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Creating the Adapter
12:17In this video I create a custom adapter for my ListView and then set that adapter as MainActivity's ListAdapter.
Now that we have our holes object,
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we can use it in a list adapter which
we're going to need for our list view.
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So, let's create it.
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I'm going to call my adapter ListAdapter.
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And it will extend BaseAdapter.
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Then I'll use Alt+Enter
to implement methods.
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From previous adapters, I know that I'm
going to need a context at some point.
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Also, for this specific adapter,
I'm going to need the holes.
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So let's create a constructor
to get both of those.
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Then I'm going to use the n prefix
to let Android Studio know that I'd
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like fields to be created.
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Then i'll use Alt+Enter
to create the fields.
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And delete this space
because I don't like it.
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All right.
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Now that we have access to our holes,
we can update some of these functions.
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For example, get count,
should now return mholes.length,
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get item at position should
return mholes of index position.
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getItemId.
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We won't implement.
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And then getView which is the tricky one.
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Before we get into getView, recall
that we're going to need a ViewHolder.
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So let's type private static class
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ViewHolder and
now we have our view holder class.
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The ViewHolder class just holds the views,
so
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all it needs is variables for
each of the views we'd like it to hold.
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In this case, it's each of
the views from out listitem.xml, so
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we're going to need one TextView,
two TextViews, one, two buttons.
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So two TextViews and two buttons.
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Go back to list adapter,
and let's make a TextView.
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And It will be called HoleLabel
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cause that's the first TextView and
another TextView called strokeCount
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and then the two buttons,
removeStrokeButton then
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Alt+Enter to import the button,
and addStrokeButton.
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All right,
now that we have our view holder,
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we can get back into getView.
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The first thing I'm going to do is
declare a ViewHolder variable, and
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I'm going to declare this final.
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The upcoming if block,
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which is going to be if
convertView is null,
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and else needs to be able
to handle the view holder.
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So we'll set it here, or here.
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So, if convert view is null,
then we needed to set it to a view.
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Which will be layout inflator.from, and
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this is where we needed
the context then .inflate.
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And we wanna send it our list_item and
a null for the theme.
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Now that we have our convertView,
we need to create our ViewHolder and
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add it to that convert view as a tag,
so holder = new
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ViewHolder() and then we need to set each
of the properties of our view holder so
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holder.holeLabel = (TextView).
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And we want to textView
from the convertView, so
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we'll do
convertView.findViewById(R.Id.holeLabel);
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Looks good,
then I'm going to use the Cmd or
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Ctrl+D shortcut to duplicate
this line three times.
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Then I'm going to copy this up to here,
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This to here,
addStrokeButton is going to go up to here.
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These two need to be buttons, And
we'll need to change these ids as well.
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All right, now that we've done that,
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all that's left is to set
the convertViews tag to our holder.
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So we'll set the tag to our holder object.
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So on the flipside,
if convertView isn't null,
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all we need to do is get
the holder from our convertView.
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So holder equals,
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we're going to cast it as a ViewHolder,
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and convertView.getTag.
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All right?
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Now that we definitely have our holder
variable, regardless of if convertView is
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null or not, we can use it to set
the properties of our list_item.xml.
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So holder.holeLabel.setText, and
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we want to set it to (mHoles[position])
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to get the hole that we're currently
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getting the view for .getLabel.
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And we want to do something similar for
the strokeCount.
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SetText(mHoles[position].getStrokeCount,
perfect.
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Then we also want to set
the onclicklisteners for
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our buttons to make sure that they
are updating the correct view.
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.setonclickListener, then we'll type new,
capital O,
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tab and that willl make that
all automatically appear.
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And when we click on
the remove stroke button,
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what we want to happen is we want
the stroke to decrement by one.
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So let's create a updated new stroke
count variable to handle that, int
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updatedStrokeCount and
we'll set it equal to
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mholes position dot get
stroke count minus one.
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There's a pretty clear bug here
that we need to handle and
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that's what happens when they're already
at zero strokes and we put minus one.
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We'd show a minus one on the screen,
which is impossible in golf, so
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we should handle that.
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So if updated stroke count is less than
zero, updated stroke count should be zero.
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And you can omit brackets for your if
statements if it's all on one line, and
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there's only one statement.
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Now that we have our updated stroke count,
which is definitely valid,
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we can use it to set the text.
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So we'll start by setting this hole's
stroke count To the updatedStrokeCount,
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and then setting the strokeCount on
the screen to the new strokeCount as well.
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And this reminds me that we'll want to add
this plus empty string right here as well.
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When we pass an integer to the setText
function, it's going to look for
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a resource with that integer.
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But we don't want it to look for
a resource.
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We're passing in what we
want it to take as a string.
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So to make this a string,
we'll just add an empty string to it.
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All right.
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Now let's do the add stroke button.
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Set on click listener,
new, capital O, tab.
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And then this is very similar to before.
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Updated stroke count
equals mHoles position.
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Plus one this time.
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mHoles position.getstrokecount.
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And we don't need to any special check for
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this stroke count because your
stroke can go as high as it can.
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So, mholes, position, set the stroke
count for the whole object here.
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And then we'll set the text
on the screen as well
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Looks good.
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Now the last thing we need to
do is change this return null.
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We should be returning a view which
Technically null works for that, but
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we don't wanna return a null view for
our whole list, we wouldn't see anything.
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So let's change this to convert view.
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All right, I think we're done
with the list adapter class.
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The last thing we need to do with our
list adapter is set it in main activity.
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We'll want to set it,
after we initialize the holes,
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because we need to pass
them into the constructor.
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We'll also want our list
adapter to be a field.
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So I'll start it with an m prefix, to
let Android studio generate that for me.
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For the context we can either pass N,
get application context or just this,
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which is main activity.Both are context so
either works.
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And then we need the holes variable.
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And Alt+Enter to create
our list adapter field.
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And then we just need to set
the list adapter to m list adapter.
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All right, that looks good.
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Let's see what happens when we run it.
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All right,
here we've got all our holes, and
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when we hit the plus button,
the score goes up.
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When we hit the minus button,
it goes down.
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Let's give him a hole in one on Hole 1.
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And if we scroll to the bottom,
18 holes, just like we would expect.
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But if we leave the app and
come back to it, the scores are all zero.
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It completely forgot what the score was.
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How useless.
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Let's fix that.
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