Preview layout with merge root tag in Intellij IDEA/Android Studio

Question

Let\'s imagine we are developing compound component based on LinearLayout. So, we create class like this:

public class SomeView extends LinearLayout {
    public         


        

Answer 1

There is a new parentTag tools attribute (added in Android Studio 2.2) that you can use to specify the layout type for a merge tag, which will make the layout render correctly in the layout editor preview.

So using your example:

<merge xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:parentTag="LinearLayout"
    tools:orientation="horizontal">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Some text"
        android:textSize="20sp"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Some other text"/>
</merge>

Note: Both android:layout_width and android:layout_height must be specified in order for the layout to display properly in the editor.

Answer 2

Is also possible use custom class as parent instead of merge like

<com.mycompany.SomeView xmlns:android="http://schemas.android.com/apk/res/android">
...
</com.mycompany.SomeView>

And then directly inflate this layout and cast result view to SomeView. Android studio will directly check parent class of SomeView and handle preview like LinerLayout. You can use onFinishInflate() method in the SomeView to bind views by findViewById(). Benefit of this solution is that you can put all layout definitions or style definition directly to the layout file, you can't use method like setOrientation() in code.

Answer 3

Edit: Outdated answer. See answer by starkej2.

---

Android Studio 0.5.8 added support for tools:showIn. By using it it is possible to preview < merge > layouts.

http://tools.android.com/recent/androidstudio058released

layout/layout_merge.xml with tools:showIn:

<merge xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:custom="http://schemas.android.com/apk/res-auto"
   xmlns:tools="http://schemas.android.com/tools"
   tools:showIn="@layout/simple_relativelayout">

......

</merge>

layout/simple_relativelayout.xml with include:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <include layout="@layout/layout_merge"/>

</RelativeLayout>