tools:text for RecyclerView items

Question

I know that when you set

tools:text="Sample text"

within a TextView, you'll see the sample text in Preview mode in Android Studio, but not within the actual app. I'd like to do this for items in a RecyclerView, but I can't seem to be able to. Here's what I've done so far:

In the RecyclerView (named content_feed):

tools:listitem="@layout/cell_feed"

In the cell (name cell_feed):

tools:showIn="@layout/content_feed"

Here are the xml files:

cell_feed.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="@dimen/height_feed_cell"
    android:layout_marginLeft="@dimen/margin_feed_cell"
    android:layout_marginRight="@dimen/margin_feed_cell"
    android:orientation="horizontal"
    tools:showIn="@layout/content_feed">

    <LinearLayout
        android:id="@+id/timeLayouts"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_centerVertical="true"
        android:orientation="vertical">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:alpha="@dimen/alpha_feed_secondary_text"
            android:textSize="@dimen/size_feed_secondary_text"
            android:id="@+id/startTimeText"
            tools:text="8:00 AM"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:alpha="@dimen/alpha_feed_secondary_text"
            android:textSize="@dimen/size_feed_secondary_text"
            android:id="@+id/endTimeText"
            tools:text="10:00 AM"/>
    </LinearLayout>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="@dimen/margin_feed_cell_text"
        android:layout_toRightOf="@+id/timeLayouts"
        android:layout_centerVertical="true"
        android:orientation="vertical">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginBottom="@dimen/margin_bottom_feed_cell_title"
            android:textSize="@dimen/size_feed_cell_title"
            android:textStyle="bold"
            android:id="@+id/titleText"
            tools:text="Event title"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:alpha="@dimen/alpha_feed_secondary_text"
            android:textSize="@dimen/size_feed_secondary_text"
            android:id="@+id/captionText"
            tools:text="Event caption"/>
    </LinearLayout>

    <CheckBox
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        android:layout_marginLeft="@dimen/margin_feed_cell_text"
        tools:text=""/>
</RelativeLayout>

content_feed.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.RecyclerView
    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"
    android:id="@+id/feedRecycler"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:listitem="@layout/cell_feed"
    tools:showIn="@layout/activity_feed"/>

Answer 1

The feature you want is called "Support for sample data" and was recently announced in Google I/O 2017 event. This is a direct link to the exact minute where Tor Norbye introduces the new feature.

For example, applying following to the layout item:

tools:text="@tools:sample/lorem"

will result in following output in Preview window:

Applying this:

tools:text="@tools:sample/date_day_of_week"

will result in this output in Preview window:

You can also populate it with your custom data. This blog post demonstrates a full example of how to do that. First, you right click on your app module and choose New | Sample Data directory.

Then you would create for example an activity_log.json file in the sampledata directory with following content:

{
    "activities" : [
     {
       "icon": "@sample/activity_icons[ic_biking.png]",
       "description": "Biking",
       "location" : "Pleasant Hill, CA",
       "distance": "48 miles",
       "date": "Yesterday"
     },
     // other items here
    ]
}

Then you can apply this data to your layout this way:

tools:src="@sample/activity_log.json/activities/icon"
tools:src="@sample/activity_log.json/activities/distance"

This will result in following output in Preview window:

For more details on the topic have a look at "Tool Time" series of posts by Mark Allison.