Properties requiring higher API than minSdkVersion allowed as layout properties, but not as style items

Question

My app's minSdkVersion is < 17. I want to change position and direction of a LinearLayout programmatically instead of defining two different LinearLayouts.

Old solution:

<LinearLayout
    android:visibility="gone"
    android:id="@+id/toolbar_vertical_outside"
    ...
    android:layout_height="wrap_content"
    android:layout_width="wrap_content"
    android:orientation="vertical"
    android:layout_alignTop="@id/aView"
    android:layout_toEndOf="@id/aView"
    android:layout_toRightOf="@id/aView">
    ...

<LinearLayout
    android:visibility="gone"
    android:id="@+id/toolbar_horizontal_inside"
    android:layout_height="wrap_content"
    android:layout_width="wrap_content"
    android:orientation="horizontal"
    android:layout_alignEnd="@id/aView"
    android:layout_alignRight="@id/aView"
    android:layout_alignBottom="@id/aView">
    ...

New solution:

<LinearLayout
    android:id="@+id/toolbar"
    ...
    android:layout_height="wrap_content"
    android:layout_width="wrap_content"
    style="@style/Toolbar_VerticalOutside">
    ...

... including new styles:

<style name="Toolbar_VerticalOutside">
    <item name="android:orientation">vertical</item>
    <item name="android:layout_alignTop">@id/aView</item>
    <item name="android:layout_toEndOf">@id/aView</item>
    <item name="android:layout_toRightOf">@id/aView</item>
</style>

<style name="Toolbar_HorizontalInside">
    <item name="android:orientation">horizontal</item>
    <item name="android:layout_alignEnd">@id/aView</item>
    <item name="android:layout_alignRight">@id/aView</item>
    <item name="android:layout_alignBottom">@id/aView</item>
</style>

Problem: For the new solution, Android Studio complains about name="android:layout_toEndOf" and name="android:layout_alignEnd": "... requires API level 17 (current min is 14)". But it didn't complain about the same properties when they were used in a layout file. Why is Android Studio more tolerant about new properties in a layout than in styles? I want to use new properties in styles, too.

score 1 · Accepted Answer · answered Jul 24 '17 at 22:16

This is just a quirk of how the Android Studio linter works.

In your layout, you've included

    android:layout_alignEnd="@id/aView"
    android:layout_alignRight="@id/aView"

And you get no warnings/errors. That is because you have both defined. If you delete just alignEnd, the linter will warn that you should add alignEnd to support right-to-left layouts. If you delete just alignRight, the linter will warn that you should add alignRight to support pre-17 API levels.

In styles, this "check if both are present" behavior isn't there. The linter just checks each <item> separately, so it warns that alignEnd requires API 17. However, this won't prevent your app from compiling/running.

If you really wanted to be a good citizen, you'd define two separate styles within two resource directories.

In /res/values/styles.xml:

<style name="Toolbar_HorizontalInside">
    <item name="android:orientation">horizontal</item>
    <item name="android:layout_alignRight">@id/aView</item>
    <item name="android:layout_alignBottom">@id/aView</item>
</style>

In /res/values-v17/styles.xml:

<style name="Toolbar_HorizontalInside">
    <item name="android:orientation">horizontal</item>
    <item name="android:layout_alignEnd">@id/aView</item>
    <item name="android:layout_alignBottom">@id/aView</item>
</style>

Thanks for your answer! The first part was already clear to me. I won't be a good citizen - now I set all those params programmatically in my code because I cannot change a style directly: https://stackoverflow.com/questions/11723881/android-set-view-style-programmatically — Andi, Jul 25 '17 at 02:13

Properties requiring higher API than minSdkVersion allowed as layout properties, but not as style items

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