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Let's make our first attempt at running the application on older devices and see what looks the same and what looks different. We'll also explore potential crashes and their fixes that we’ll have to keep in mind when backporting our visual look and feel of our app. AppCompat is our friend here, and we'll introduce you to grabbing the bits for that library in this video.
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It's great that we've reduced some of
the code related to styling our views.
0:00
But we still haven't made our managers
happy by allowing our app to be run on
0:03
devices all the way back to KitKat.
0:06
Let's make our first
attempt at fixing that.
0:08
I'm in the apps build back creative file
where I'll change the minSdkVersion to 19,
0:10
which corresponds to Android 4.4 KitKat.
0:14
Let's sync Gradle and run the app on our
emulator with KitKat to see what happens.
0:18
Well, the toolbar shouldn't be there but
0:23
everything else looks good in the album
list activity and album details activity.
0:25
What about in the play back activity?
0:29
Whoops, there's a crash.
0:32
Turns out that there's an image view
that's attempting to use a resource that
0:34
isn't available on versions of
Android before Lollipop or API 21.
0:37
I'll show you how to fix that crash and
0:41
other issues of backwards
compatibility now.
0:43
First, we need to grab the Android
support library called AppCompat
0:45
that I mentioned earlier.
0:49
To get the most recent
version of AppCompat,
0:51
just perform a Google search for
support library packages Android.
0:53
Click the link titled
Support Library Packages and
0:56
then click v7 AppCompat
library from the sidebar.
0:59
The most recent version
will be listed below.
1:03
Copy that and paste it into your app's
build.gradle file along with a compile
1:06
statement and some single quotes.
1:09
Then when Gradle ask you to sync,
go ahead and do so.
1:11
Now that we've added AppCompat,
1:17
we can begin to fix the errors that
were plaguing our application.
1:18
The first change we'll make is removing
the android:namespace declaration
1:21
from the android:background attribute
1:25
of the image view in our song playback
activity layout that is causing the crash.
1:27
The reason the crash was happening here is
that on Android version 19, Android can't
1:31
find the resource specified by
?:attr/SelectableItemBackgroundBorderless.
1:35
That resource simply wasn't
available back at that time, so
1:42
by removing the add Android we tell
the system to look up this value,
1:46
selectableItemBackgroundBorderless, within
the current theme.
1:49
In our case, since we're now going to be
using AppCompat, the system can find that
1:53
resource and we're good to
continue our hunt for errors.
1:56
Let's check and fix any issues
with our styles.xml file first.
1:59
When we first look at this file, we'll
see that there's some red error markers.
2:04
However, I wanna drive home
this point a little further.
2:07
So bear with me as I perform
a quick little hack to bring these
2:10
errors into more focus.
2:12
In order to see more obviously what
attributes were available in KitKat,
2:14
the version that we're targeting,
2:17
I'm gonna go into my app's
build.grade file again and
2:19
temporarily change the compileSdkVersion
to 19 to match my minSdkVersion.
2:21
Now I'll go back into styles.xml and
sync the Gradle files.
2:26
If you're following along and
you get an error message about failing to
2:31
find target with hashstring Android 19,
just click Install Missing Platforms and
2:34
Sync Project and
Android Studio will do the rest.
2:39
After verifying you have the older
version of the Android SDK installed and
2:43
successfully synced Gradle, a bunch of
errors will pop up and that makes sense.
2:46
We just told Android to use an older
version of the platform so it can't find
2:51
the resources it needs for the material
theme that's currently applied to our app.
2:54
It's safe to ignore these errors for now,
though, as we're only temporarily lowering
2:58
the compile list decay to perform
some maintenance for the app.
3:01
When I synced my Gradle files,
a file called
3:04
ldltr-v21/values/ltltr-v21.xml pops up,
and I get an error message.
3:07
It's safe to close the file and
navigate back to the styles.xml file now.
3:14
Now the errors in the styles.xml file
are lit up like a Christmas tree and
3:18
they are much easier to spot.
3:22
What we are going to do now is replace
the previous attributes from the Android
3:23
platform with the attributes
from the AppCompat library.
3:27
First, we will change the theme to inherit
from theme.appcompat.NoActionBar for
3:30
both the app theme and the settings theme.
3:34
To select the next occurrence of
the highlighted text, click Ctrl+G.
3:36
I find that's an incredibly
useful trick in any IDE.
3:40
Then we'll need to change
android:colorAccent,
3:43
which sets the accent color for
the android:theme.material themes,
3:46
to set the accent color for
the Theme.AppCompat themes by removing
3:50
the android:namespace before
the words colorAccent.
3:54
You may notice that we
still use the @android for
3:57
setting the color itself to
@android:color/darker_gray.
3:59
We can do this because the color darker
gray still exists on the platform on older
4:03
versions.
4:07
However, it's the color accent property
that did not exist back on API 19.
4:08
Next we'll remove the android:
in our playback button style,
4:12
as well as in our settings toolbar style,
and that should do it for our styles file.
4:15
It is now backwards compatible.
4:23
However, there is still some work
to do to complete the process.
4:25
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