Hiding views declaratively based on screen size in Android

Question

In android xml:ish

Is there any way to change a visibility attribute based on the layout size/orientation in the xml directly?

I have a button in a fragment that should be visible for small screens sizes only. On larger sizes, let's say layout-large, I want it to be hidden.

Sure, I can write code for this without any problem but for academic reasons I would like to know it it's possible to do something like this.

<Button
     android:id="@+id/btn_check_availability"
     style="@style/product_info_footer_button"
     android:layout_width="fill_parent"
     android:layout_height="35dp"
     android:text="@string/check_availability"
     android:visibility="<magic expression here>" />

Thanks

// Johan

Answer 1

This answer is based off the explanation provided here by Flávio Faria.

The visible, gone, etc can be values mapped to their corresponding enum values in a string resource - which means you can create a visibilty.xml with string resources for each layout you want, and Android will automatically resolve the one you want for each screen type.

I'd recommend the following:

/res/values/visibilty.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!-- Enum values pulled from Android source -->
    <string name="visibility_visible">0</string>
    <string name="visibility_invisible">1</string>
    <string name="visibility_gone">2</string>

    <string name="product_info_footer_button_visibility">@string/visibility_visible</string>
</resources>

/res/values-large/visibilty.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="product_info_footer_button_visibility">@string/visibility_invisible</string>
</resources>

And then you can reference the visibility as follows for your button:

<Button
     android:id="@+id/btn_check_availability"
     style="@style/product_info_footer_button"
     android:layout_width="fill_parent"
     android:layout_height="35dp"
     android:text="@string/check_availability"
     android:visibility="@string/product_info_footer_button_visibility" />

Warning: This depends on the device having the same enum values for visibility (0/1/2) as defined in the AOSP source. Device manufacturers and custom ROM creators can change these values, in which case this code will likely not work as desired.

Answer 2

The android:visibility attribute is an int (like many attributes) so you can do the following :

Define a resource file named visibility.xml in values-port and values-land resource directories. The content of this file is like this :

values-port/visibility.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <integer name="buttonvisibility">0</integer> <!-- 0 is the value for android:visible -->
</resources>

values-land/visibility.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <integer name="buttonvisibility">1</integer> <!-- 1 is the value for android:invisible -->
</resources>

and in your layout.xml :

<Button
 android:id="@+id/btn_check_availability"
 style="@style/product_info_footer_button"
 android:layout_width="fill_parent"
 android:layout_height="35dp"
 android:text="@string/check_availability"
 android:visibility="@integer/buttonvisibility" />

It works : btn_check_availability is visible in portrait and invisible in landscape.

Note : this example use layout orientation as discriminator, but you can of course do it with any resource qualifier (like dimension, density, ...)

Answer 3

There is no magic expressions available in XML. If only.

There are two approaches to this problem:

a/ use the drawable folder system. Drawable folders can be copied and named to be DPI aware following the conventions dictated here: Supporting Multiple Screens.

b/ Do it programmatically. On runtime check for screen DPI and show/hide view accordingly.