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So I just made an intentional but

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00:00:02,590 --> 00:00:07,560
very common mistake where I mistyped the
name that we used in the other activity.

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00:00:07,560 --> 00:00:12,480
So if we run the app now it starts up and
everything seems fine.

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00:00:12,480 --> 00:00:13,905
But if we type our name.

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00:00:16,959 --> 00:00:20,233
And start our adventure, we get an error.

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00:00:20,233 --> 00:00:22,530
Let's investigate and see what happened.

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00:00:22,530 --> 00:00:26,550
Here I want to bring up the Android
monitor which again has our log cat view.

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00:00:26,550 --> 00:00:29,660
This is a lot of information and
it's sometimes hard to see.

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00:00:29,660 --> 00:00:31,890
There's a button here that can
change at the line breaks.

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00:00:31,890 --> 00:00:33,870
But I like to have it here and
scroll over.

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00:00:33,870 --> 00:00:36,600
By the way you can see the error,
it's nice and obvious.

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00:00:36,600 --> 00:00:39,780
It's highlighted in red whereas the rest
of the stuff was black and blue.

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00:00:41,290 --> 00:00:43,100
I'm going to scroll over a little bit and

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00:00:43,100 --> 00:00:44,980
take a better look at
the exception itself.

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00:00:46,010 --> 00:00:47,520
So let's unpack this a little bit.

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00:00:47,520 --> 00:00:50,880
We have a fatal exception
in our main thread.

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00:00:50,880 --> 00:00:56,080
It's in our app interactive story and
it is a java.lang.runtime exception.

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00:00:56,080 --> 00:00:59,620
Says it was unable to start the activity
and it gives some details about it.

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00:00:59,620 --> 00:01:02,950
And this is called a stack
trace because it traces through

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00:01:02,950 --> 00:01:07,430
the stack of method calls where the error
handled and then was bubbled up.

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00:01:07,430 --> 00:01:10,740
So if we scroll down a little bit we can
see that it was originally caused by

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00:01:10,740 --> 00:01:15,680
a NullPointerException where it
says print line needs a message.

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00:01:15,680 --> 00:01:17,580
And if we dig back a little bit further,

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00:01:17,580 --> 00:01:19,540
we can see that it's
from our log statement.

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00:01:19,540 --> 00:01:23,220
And sure enough we get to
a line in StoryActivity

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00:01:23,220 --> 00:01:25,460
inside of our onCreate method,
and it's clickable.

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00:01:25,460 --> 00:01:26,390
If we click on it,

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00:01:26,390 --> 00:01:31,290
we can see the offending line that
threw the initial NullPointerException.

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00:01:31,290 --> 00:01:34,210
Our app crashed because we
didn't handle that error.

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00:01:34,210 --> 00:01:38,210
The first thing we can do is avoid
a hard crash by adding a null check

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00:01:38,210 --> 00:01:39,820
around this code.

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00:01:39,820 --> 00:01:42,540
This is good practice whenever we're
getting data from an intent or

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00:01:42,540 --> 00:01:43,710
anywhere really.

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00:01:43,710 --> 00:01:47,001
We know in this simple app that we
will always start StoryActivity from

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00:01:47,001 --> 00:01:47,870
MainActivity.

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00:01:47,870 --> 00:01:51,720
But in a more complex app we might be
starting activities from multiple places.

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00:01:51,720 --> 00:01:55,940
And if we're not careful, we might not
have the same exact intents from each one.

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00:01:55,940 --> 00:01:57,770
So let's reduce this Android monitor.

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00:01:57,770 --> 00:02:01,240
And we can still set
the name variable here.

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00:02:01,240 --> 00:02:04,518
But after the fact,
we want to add a new if statement.

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00:02:04,518 --> 00:02:11,400
if name = null then we should give
the name some kind of default value.

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00:02:11,400 --> 00:02:15,521
Let's set name = Friend instead.

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00:02:16,740 --> 00:02:19,990
So now, no matter what,
our name variable will have a value.

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00:02:19,990 --> 00:02:23,280
Well, that's not totally true, what
happens if the user doesn't type anything?

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00:02:23,280 --> 00:02:25,110
In that case,
it would have a blank string.

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00:02:25,110 --> 00:02:25,910
It would just be blank.

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00:02:25,910 --> 00:02:28,500
That would affect how our story will look,
so

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00:02:28,500 --> 00:02:32,850
we should also supply a default
value if there is a blank string.

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00:02:32,850 --> 00:02:35,550
We can do that with another check here.

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00:02:35,550 --> 00:02:39,177
So if name is null or if name is empty,

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00:02:39,177 --> 00:02:42,520
name.isEmpty, we'll check
if it's an empty string.

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00:02:44,000 --> 00:02:49,824
So first let's run this and see if it
catches the exception for the wrong key.

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00:02:49,824 --> 00:02:55,185
And we can type the name, start the
adventure and it didn't crash this time.

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00:02:55,185 --> 00:03:00,130
And if we go to log we should be able to
find yep, there it is, Friend was used.

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00:03:00,130 --> 00:03:03,900
Now let's fix the typo with the key,
change this to a lowercase n, and

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00:03:03,900 --> 00:03:04,420
run it again.

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00:03:06,290 --> 00:03:09,570
This time I'm not going to type anything,
just click on the button.

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00:03:09,570 --> 00:03:12,792
And if we go back to the log,
same thing, there we go.

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00:03:12,792 --> 00:03:15,450
A new string with the word Friend in it.

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00:03:15,450 --> 00:03:19,660
In the next video, we will address the key
name by setting it in one master location,

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the string resource file.