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Android Android Lists and Adapters Displaying Lists of Data Creating a Custom Layout

Posted by Tomás Borges
Tomás Borges
4,394 Points

Problems understanding the xml code

Hi, I don't understand the usage of <data> , <variable> and the line "android:text="@{String.valueOf(hour.time)}" " in the xml code, could you please help me? Perhaps provide me some links, thanks!

1 Answer

Tonnie Fanadez
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Tonnie Fanadez
UX Design Techdegree Graduate 22,796 Points
Tonnie Fanadez
.a{fill-rule:evenodd;}techdegree seal-36
Tonnie Fanadez
UX Design Techdegree Graduate 22,796 Points

Tomás Borges sorry for the late reply.

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>
        <variable
            name="hour"
            type="com.androidshowtime.stormy.weather.Hour" />
    </data>

    <RelativeLayout>

        <TextView
            android:id="@+id/timeLabel"
            android:text="@{String.valueOf(hour.time)}"
            android:textSize="24sp" />

Data Binding enables you to bind UI elements in your layouts to data sources in your app using a declarative style rather than programmatically. data-binding xml layout files are slightly different and must start with a root tag of layout followed by a <data> element and a view root element in this case it is the Relative Layout. 

<data>
        <variable name="hour"
           type="com.androidshowtime.stormy.weather.Hour" />
    </data>

The hour variable declared within data tag describes the property to be used within this layout. 

<TextView
            android:id="@+id/timeLabel"
            android:text="@{String.valueOf(hour.time)}"
            android:textSize="24sp" />

If you want to use expressions inside your layout, you can call attribute properties using the ** “ @{}" ** syntax. In the example above, the TextView text is set to the time property of the hour variable

I trust this clarifies.

Thanks,

Tonnie