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Let's see how to send complex data from one app to another. We'll need to create a custom intent and a custom intent filter in a second app.
We've already seen how
to bundle up a song and
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send it by an intent from
one activity to another.
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We'll do the same thing here to
send it from one app to another but
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we need to create a custom intent and
a custom intent filter in a second app.
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Let's do this from detail activity, where
we already have a specific song chosen.
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I already created a menu option for us.
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So, all we need to do is
define our new intent and
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share it when that menu option is tapped.
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First we need a song though.
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Right now it's only available
here in the onCreate method
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because that's the only
place we are using it.
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I've also already seated these starter
files with a member variable mSong.
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So let's just switch that.
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So we'll change song to mSong, and
we'll do the same thing down here,
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mSong, and over here, msong.
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Okay, now let's scroll down
to the methods for the menu.
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First is the create method, and
then we have the onOptionsItemSelected,
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which is called when
a menu item is Selected.
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Now it's good practice to check the item
id and then perform actions on it,
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we only have one item id but let's follow
the best practice and check it, so
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if we expand menu and look at the detail
XML, we see that the id is action_ share.
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Let's go back here at a test,
if ItemID = r.id.action_share.
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Then we want to share the data.
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Let's play it safe in here and add a check
to make sure that our song isn't null so
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if Msong does not equal
null then we will continue.
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Let's create a custom intent
CustomIntent equals a new Intent.
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What we really need is a custom action.
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It's just a string value, but we want it
to be unique so that it doesn't collide
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with any other custom actions that any
other developers might have made up.
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Common practice when we
need to use unique values
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is to prefix them with the package name.
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So let's create a constant
to use down here.
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Up at the top let's add
public static final string.
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And let's call this share_song.
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Let's set this equal to the Packers name,
come.teamtreehouse.
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And then I'll follow
the intent.ActionPattern used by Android.
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We'll finish with .SHARE_SONG.
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Let's go back down and
use this in our constructor.
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So now we pass in SHARE_SONG.
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And now we can add the song as
an extra since it's parsable.
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customIntent.putExtra(mSong).
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Whoops I forgot to pass in a key.
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Let's add that.
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We'll use the same one as before,
MainActivity.EXTRA_SONG, mSong.
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There we go.
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Finally lets start the activity.
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But rather than just calling
regular old startActivity
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let's follow another best practice and
use an activity chooser.
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Let's revisit our handy intense and
filters page.
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And now we wanna look at
Forcing an app chooser.
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The app chooser is a nice feature because
it allows the user to pick a specific app
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and even make that app the default for
that action for
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given app We just need to create
a second intent to create a chooser for
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the actual intent, which we see down here.
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So before we call this,
let's create a second intent called intent
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chooser equals intent.createchooser.
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Then we pass in our custom intent and
a title for the chooser dialog.
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Let's say Share song, and now we can
pass in chooser to start activity.
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Now we can't try this yet because we don't
have anything that can receive it, but
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still let's take a look.
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So let's pick one of
the songs in our list and.
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We got an error.
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Let's take a look and see.
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So, here in the stack trace we see
that it is a NullPointerException and
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it links to the offending line and
I see what it is.
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This is a common mistake I made it before.
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We want to call the .equals method and
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the Intent.ACTION said I want
to switch it around the order.
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Now right now get action might be N o and
it's giving us a No pointer.
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So instead we say intent.
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ACTION_SEND.equals And
then we pass in intent.getAction.
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There that's better let's try this again.
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So, now if we click on a song
we're taken to the detail view.
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And if we try the menu we
can click on share song.
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But now it's hard to see it says
no apps can perform this action.
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One of the good things about using
a chooser like this is that we avoid
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a runtime exception.
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If we weren't using a chooser we would
need to add another check like we did
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before by calling result activity and
checking the package manager for handlers.
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