Verify Array Elements with Log Messages Udacity English English (auto-generated)

Verify Array Elements with Log MessagesYouTube↗ IA↗(long shot)
Education 35.6K views 9 likes 0 dislikes 11 May 2016

Udacity 651K subscribers United States YouTube↗

Click to Play Video

So far you've practiced creating an array and initializing the array.

so far if practice creating an array and initializing the array and now your

And now you'll practice writing code to access elements of the array.

practice writing code to access elements

And knowing this,

of the array and knowing this you can

you can use the value of an array index to set the text on text view.

use the value of an array index to set the text on textview so for now you'll

So for now you'll access elements of an array

access elements of an array by printing

by printing the value to the Android logs.

the value to the android logs so

So remember you can access the logcat manager from this button here.

remember you can access the logcat washer from this button here so given

So given the code that we have now, nothing shows up on the screen just yet.

the code that we have now nothing shows up on the screen just yet

And remember that we introduced logging back in the Android for

remember that we introduced logging back

Beginners course.

into android for beginners course so

So there we learned that Android keeps a system log of what is

there we learned that Android keeps the

happening on the device.

system log of what is happening on the

It's a running log of messages from the system.

device it's a running log of messages

You can think of it as a diary that includes the time something happened and

from the system you couldn't think of it as a diary that includes the time

the description of what happened.

something happened and the description

These system messages are helpful for

of what happened these system messages

debugging and we could check the logs to go back in time

are helpful for debugging and we could check the logs to go back in time to

to figure out what's happening in the device before the problem occurred.

figure out what's happening on the device before the problem occurred you

You witness this firsthand when we were building the just Java app

witnessed this firsthand when we were

back in the Android for Beginners course.

building the just Java app back in the Android for beginners course when an app

When an app crashed,

crashed we could see the error messages

we could see the error messages in the logs to help us debug the problems.

in the logs to help us debug the

Remember in Android Studio that the messages appear in the logcat Window.

problems remember an Android studio that the messages appear in the logcat window

Now in addition to using the log to view errors,

now in addition to using the log to view

we as developers can also write messages to the log.

errors we as developers can also write

And we call this process of writing to a log, logging.

messages to the log and we call this process of writing to the log logging

This can help us temporarily debug our app or

this can help us temporarily debug our

just double-check the state of our app while it's running.

app or just double check the state of our app while it's running so it's

So it's similar to using the debug tool where we can add breakpoints

similar to using the debug tool where we

to check the state of different variables in our app and

can add breakpoints to check the state of different variables in our app and

this allows us to write the value of certain variables to the logs.

this allows us to write the value of certain variables to the logs but

But personally, I like using logging statements because they're quicker.

personally I like using logging

So instead of manually stepping through each line of code in the app,

statements because they're quicker so instead of manually stepping through

you just let the app run as normal and log messages get printed along the way.

each line of code in the app you just let the app run as normal and log messages get printed along the way so

So this is a helpful article on how to write log messages.

this is a helpful article on how to

You just need a single line of code for one log message.

write log messages you just need a single line of code for one log message

Notice that there are five different categories of log messages

notice that there are five different categories of log messages based on how

based on how severe or urgent the message is.

severe or urgent the message is so it

So it ranges from verbose messages,

ranges from verbose messages which are

which are just nice to know messages, all the way to error messages, which

just nice to know messages all the way

mean severe issues such as when your app is running into unexpected behavior.

to error messages which means severe issues such as when your app is running into unexpected behavior so for now

So for now, we're just going to practice writing verbose log messages

we're just gonna practice writing verbose log messages to help us check

to help us check the state of certain variables in our app.

the state of certain variables in our

Notice for all these log messages, they required two strings as inputs.

app notice for all these log messages they require two strings as inputs so

So clicking on this first Log.v method,

clicking on this first log dot V

we see that the first input parameter is a tag name.

then we see that the first input parameter is a tag name so anyone can

So anyone can print to the logs, the Android systems, or other apps.

print to the logs the Android systems or

So we use this tag to identify where the message is coming from.

other apps so we use this tag tied into five where the message is coming from

Often for the tag, we just use the name of the activity or

often for the tag we just use the name

class the logging statement is found in.

of the activity or class the logging

For example, we can have a log statement in the numbers activity and

statement is found in for example we can have a log statement and the numbers

we can make the tag just be the numbers activity string.

activity and we can make the tag just be the numbers activity string the second

The second parameter is message, and

parameter is message and this is just

this is just the message we'd see appear in the logs.

the message would see appear in the logs

And the second parameter is message, and this is just the message we'd

and the second parameter is message and

see appear in the logs, and it can be whatever you'd like to be logged.

this is just the message would see appear in the logs and it can be whatever you'd like to be logged so

So going back to that main article, we see an example down here.

going back to that main article we see

It's a Log.I method call, which we know from here is an information log.

an example down here it's a log dot I method call which we know from here is

We see that the tag name here is main activity and the message is here.

an information log we see that the tag name here is main activity and the

So in our message parameter, we use the plus operator to concatenate strings.

message is here so in our message parameter we use the LES operator to

So string concatenation is a fancy way to say, string addition.

concatenate strings so string concatenation is a fancy way to say string addition similar to how we add

Similar to how we add numbers together,

numbers together we can merge strings

we can merge strings with the plus operator.

with the plus operator in this case

In this case, we're merging this string with this position variable to create

we're merging this string with this position variable to create a much

a much longer string.

longer string it's on the lock cat

So in the logcat, you'll see MyActivity as the tag name.

you'll see my activity as the tag name

And then the message MyClass.View- get item number 1.

and then the message my class dot view - get item number one and this is assuming

And this is assuming that the value of the position variable is 1.

that the value of the position variable

Here's an example in our NumbersActivity.

is one here's an example in our numbers

So I added these two log messages at the bottom of our onCreate method.

activity so I added these two log messages at the bottom of our on create

Now I'm going to run the app on my device.

method now I'm gonna run the app on my

device now with the app running I'm

Now with the app running, I'm going to navigate to the numbers activity and

going to navigate to the numbers

notice that these two messages in the log output appear.

activity and notice that these two messages in the log output appear so we

So we get the statements the word at index 0 is one and

get the statements the word at index 0

the word at index 1 is two.

is 1 and the word at index 1 is 2 now

Now notice two things here.

notice two things here first we need to

First, we need to add a buffer space after the colon, so

add a buffer space after the colon so

that all this text isn't all scrunched up together.

that all this text isn't all scrunched

And secondly, we didn't put this

up together and secondly we didn't put

words[0] in quotations because we

this words bracket 0 closing bracket in quotations because we want the value at

want the value at this index, not the literal string with the brackets.

this index not the literal string with

So to summarize, printing out the log message is a really useful way

the brackets so to summarize printing out the log message is a really useful

to make sure that the variable has the expected value you expect it to.

way to make sure that the variable has the expected value you expect it to

So these log messages will be temporary and we'll remove them later on.

so these log messages will be temporary and we'll remove them later on now let's

Now let's put logging to practice in your Miwok app.

put logging to practice and your me walk

Take the time to log messages in your code so

out take this time to log messages in

that you can see the value of each element in the words array.

your code so that you can see the value of each element in the words array and

And so this is the expected output in the logs and go ahead and

so this is the expected output in the

check this box when you're done.

logs and go ahead and check this box when you're done

Similar videos:

Multiple_Constructors_for_Word_Class
Udacity
39.7K views 21 likes 0 dislikes 22 Apr 201630% match

Use_the_For_Loop
Udacity
30.1K views 9 likes 0 dislikes 21 Apr 201628% match

Working with an ArrayList
Udacity
43.6K views 15 likes 7 dislikes 11 May 201628% match

Fix_Phrases_Activity_to_Hide_Images
Udacity
28.2K views 9 likes 1 dislikes 22 Apr 201628% match

Working with an Array
Udacity
34.8K views 8 likes 2 dislikes 11 May 201627% match

Blocos Try/Catch/Finally
Udacity
1.2K views 6 likes 1 dislikes 08 Aug 201627% match

Programming with Go 04 | Structures and Pointers
Programming Tutorials
1.6K views 21 likes 3 dislikes 07 Sep 201626% match

Untitled
Udacity
37.9K views 8 likes 2 dislikes 04 May 201626% match

Variables
CS50
47.3K views 0 likes 0 dislikes 16 Sep 201226% match

Music Player App
Udacity
904 views 11 likes 2 dislikes 06 May 201626% match

When to Create a Custom Class
Udacity
62.1K views 14 likes 4 dislikes 11 May 201626% match

Play Correct Audio File Per Word
Udacity
827 views 11 likes 6 dislikes 06 May 201626% match

When to use Arrays
Udacity
76.4K views 25 likes 0 dislikes 21 Apr 201625% match

Example Dagger2 Using Advanced | Dependency injection 08
Programming Tutorials
1.8K views 32 likes 0 dislikes 21 Aug 201625% match

08 Java course | Loop for
Programming Tutorials
7.1K views 46 likes 2 dislikes 08 Jun 201525% match

Fix_Phrases_Activity_to_Hide_Images
Udacity
901 views 14 likes 6 dislikes 22 Apr 201625% match

Functions
CS50
90.9K views 0 likes 0 dislikes 26 Sep 201225% match

Libgdx for Android | Tutorial 40 | Game Menu | How to make Android games
Programming Tutorials
9.4K views 70 likes 2 dislikes 16 Oct 201525% match

Settings Privacy About Contact Donate