Avoid numbers in Android layouts?

Question

Is it possible to design an Android layout (LinearLayout or RelativeLayout) without specifying any dp, px or any other units? Maybe using percentages? layout_weight is an option. But still what about margins and paddings? Can we completely avoid magic numbers from a layout?

Answer 1

There is the Percent Support Library with its PercentFrameLayout and PercentRelativeLayout where you can specify any layout dimensions (i.e. size, position and margins) with percentages instead of absolute values:

<android.support.percent.PercentRelativeLayout
         xmlns:android="http://schemas.android.com/apk/res/android"
         xmlns:app="http://schemas.android.com/apk/res-auto"
         android:layout_width="match_parent"
         android:layout_height="match_parent">

     <ImageView
         app:layout_widthPercent="50%"
         app:layout_heightPercent="50%"
         app:layout_marginTopPercent="25%"
         app:layout_marginLeftPercent="25%"/>

</android.support.percent.PercentRelativeLayout>

Answer 2

You can always define and use dimension variable to remove magic number from layouts i.e.:

<ImageView 
  layout_width="@dimen/large_photo_size"
  layout_height="@dimen/large_photo_size"
/>

Where @dimen/large_photo_size is defined inside dimens.xml resource file i.e.:

<resources>
    <dimen name="large_photo_size">25dp</dimen>
</resources>

Yet another alternative would be to extract width and height settings into styles i.e.:

<style name="Thumbnail">
    <item name="android:layout_width">25dp</item>
    <item name="android:layout_height">25dp</item>
</style>

and use it i.e. <ImageView style="@style/PopupMenu" ... />

With themes you can apply certain styles globally.