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Cleaning Up the Date and Time
8:22We have valid data in our app, but not all of it is useful in its current form. Let's see how to convert a UNIX timestamp into a more meaningful time string.
The data model for
our app is coming along quite nicely.
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We've accomplished a lot those far,
with parsing
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the days on formatted weather data, and
getting it into our current weather model.
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However, if you recall from our
time value, it was a bit unwieldly.
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Let's take another look at
the documentation for our API,
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and see what we can discover.
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If we go back to the dark
sky documentation, and
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click on the response format link,
we see a list of the various object,
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and their properties that
are returned from the API call.
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We're working in the currently object.
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So let's click on this data point
link here for additional information.
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If we scroll down a bit,
we see the time property.
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It says that this is the Unix time
where this data point begins.
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What is UNIX time though?
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UNIX time is a system for describing time,
you find is the number of seconds
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that have elapsed since
coordinated universal time, UTC.
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UTC started on Thursday,
January 1st, 1970.
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You may also hear this referred to,
as the UNIX Epoch.
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I know.
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Leave it to developers to
represent time in a crazy fashion.
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But, this is a very standard way
of handling time on UNIX systems.
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And fortunately, there are several
built-in methods to handle this format.
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Our mock-up calls for the time to be
displayed in an easily readable format.
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Right now however,
our time is in a huge number of seconds.
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We'll need to convert that into
a more human readable format, and
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put that time string into a text view.
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Notice too that we're just wanting
the time portion of the time since
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the UNIX Epoch,
we're not concerned about the date.
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Let's add a new method to the current
weather class called, getFormattedTime.
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We can use the simple date
format class to help us out.
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Looking through the documentation for
a simple date format, we see that it can
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take in date and time values in
different formats, including UNIX time.
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It can then convert them
into local specific time.
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This is exactly what we're looking to do.
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The way this works, is that we create and
configure a formatter object.
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Then use it to format a date value.
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There's a list here of all the different
format symbols we can use.
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Recall from our mock-up, if we want
the time to be in the format of hours
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without a leading zero
if it's a single digit.
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Then minutes, and then AM or PM.
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Let's head back to current weather,
and create our formatter, and
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set our time value.
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So back here in CurrentWeather,
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let's add a getFormattedTime method,
under getTime
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public, will return a String, called
getFormattedTime.
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Inside here, we'll put SimpleDateFormat
to use and build our formatter.
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SimpleDateFormat, call it formatter.
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Be a new SimpleDateFormat,
hours without a leading zero, minutes,
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including that leading zero, and then a,
which will give us our AM or PM.
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We're getting the time value from the
forecast, from the location we specified.
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In our case, that's Alcatraz Island,
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which resides in the San Francisco Bay
of California, in the United States.
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And, it's in the Pacific Time Zone.
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Therefore, we need to set the time
appropriately with the time zone in mind.
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So we can do formatter.setTimeZone.
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For our parameter in here, we can use
a helper from the Java TimeZone class.
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TimeZone, getTimeZone, in here,
we need a time zone code as a string.
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Seems like we've seen
that somewhere before.
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Let's look at getCurrentDetails
over in main activity.
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There it is.
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We're logging it here
in getCurrentDetails.
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Let's add it to our data model,
so we can use it.
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Make it a private, String, timeZone.
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Now back in MainActivity,
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we can set our timezone using
the timezone variable we already have.
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CurrentWeather, setTimeZone,
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Passing time zone.
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And it looks like we need to go back, and
generate our getter and setter for that.
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So Code, Generate, Getter and
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Setter for timezone, great.
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No more error there,
if we go back to CurrentWeather.
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And we can use that timezone, in here.
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Our formatter is ready.
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We just need to return it.
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Return, formatter.format().
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Now here's the tricky part.
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Working with dates can be a challenge,
it can require a lot of trial and
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error in readings or documentation.
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We need to pass in
a Java Date object here, so
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let's look at the Date documentation.
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We look here in the Constructor Summary,
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there's a constructor here that
takes a time value as a long.
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Nice.
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That's what we're already have.
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Well, wait a second.
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It says here that it needs
to be in milliseconds.
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Our time value is currently in seconds.
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So we need to make that conversion first.
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This can be super frustrating, and
cause lots of headaches, if you don't
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realize that the time needs to be in
milliseconds, and you pass in seconds.
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Fortunately, it's an easy fix.
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We simply need to multiply
our seconds by 1,000,
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since there are 1,000
milliseconds in a second.
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So we'll do Date dateTime, do our import.
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We want the java.util.
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Date (time * 1000),
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I forgot an equal sign,
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that would be good to have.
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Now we can pass this into
our time string formatter.
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All right, let's test this out
by calling this new method, and
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logging it in MainActivity in
the getCurrentDetails method.
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So MainActivity,
getCurrentDetails, down here.
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Log.d, our TAG,
currentWeather.getFormattedTime().
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And let's remove this breakpoint, since we
won't be using a debugger at the moment.
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And we'll run our app.
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And look in the Logcat.
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And there it is, our formatted time,
very cool, this will be ready for us,
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when we get to working
on the user interface.
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