Great question! Handling dimension scaling across different screen sizes is key to building a natural, user-friendly Android UI. Let’s break this down into actionable steps, starting with how these folders work, then moving to practical allocation strategies.

First, let’s clarify the basics: Android’s size-based values folders trigger based on a device’s minimum screen dimension (width or height) in dp (not physical inches). Here’s the standard breakdown of each folder and the devices they target:

• values-small: For devices with a minimum dimension under ~320dp (think older small-screen phones)
• values-normal: The baseline for most standard phones, covering devices with min dimensions between 320dp and 479dp
• values-large: For larger devices like phablets or small tablets, with min dimensions from 480dp to 719dp
• values-xlarge: For full-size tablets (7"+) with min dimensions 720dp and above

Core Strategy for Allocating Dimensions #

The goal is to adjust sizes so your UI feels proportional on every screen—no cramped text on small phones, no tiny interactive elements on big tablets. Here’s a practical approach:

1. Set your baseline in values-normal
   This should be your primary dimension set, optimized for the most common phone sizes (5"-6" screens). Define all core dimensions here: font sizes, button heights, margins, padding, etc. This acts as the fallback if a dimension isn’t defined in a size-specific folder.

2. Tweak values-small for tight spaces
   Small screens have limited real estate, so shrink non-critical sizes to avoid overflow:

   • Reduce title font sizes by 2-4sp (e.g., 20sp → 18sp)
   • Compress horizontal/vertical margins by 4dp (e.g., 16dp → 12dp)
   • Shrink button heights slightly (48dp → 44dp) to save space without hurting usability

3. Expand values-large for more breathing room
   Larger screens can handle more space and slightly bigger interactive elements:

   • Increase title font sizes by 2sp (20sp → 22sp)
   • Widen margins by 4dp (16dp → 20dp)
   • Make buttons taller (48dp → 52dp) for easier tapping

4. Optimize values-xlarge for tablets
   On big tablets, you can go further to make elements feel proportional, especially if you’re using tablet-specific layouts (like two-pane views):

   • Boost title font sizes by 4sp (20sp → 24sp)
   • Increase margins to 24dp for a spacious, uncluttered layout
   • Enlarge buttons to 56dp for better touch targets
   • Adjust card padding to give content more room

Example Dimension Structure #

Suppose your base dimens.xml in values-normal looks like this:

<resources>
    <dimen name="text_size_title">20sp</dimen>
    <dimen name="text_size_body">16sp</dimen>
    <dimen name="button_height">48dp</dimen>
    <dimen name="margin_horizontal">16dp</dimen>
    <dimen name="padding_card">12dp</dimen>
</resources>

Your size-specific folders only need to override values that need scaling:

values-small/dimens.xml #

<resources>
    <dimen name="text_size_title">18sp</dimen>
    <dimen name="margin_horizontal">12dp</dimen>
    <dimen name="button_height">44dp</dimen>
</resources>

values-large/dimens.xml #

<resources>
    <dimen name="text_size_title">22sp</dimen>
    <dimen name="margin_horizontal">20dp</dimen>
    <dimen name="button_height">52dp</dimen>
</resources>

values-xlarge/dimens.xml #

<resources>
    <dimen name="text_size_title">24sp</dimen>
    <dimen name="margin_horizontal">24dp</dimen>
    <dimen name="button_height">56dp</dimen>
    <dimen name="padding_card">16dp</dimen>
</resources>

Pro Tips #

• Don’t repeat everything: Android automatically falls back to the nearest matching folder (or the default values folder) for any dimension you don’t override. Only adjust values that actually need scaling.
• Use sw<N>dp for precision: If you want more control than the broad small/normal/large/xlarge categories, use values-sw320dp, values-sw600dp, etc. These target devices with a minimum width of exactly <N> dp, which is more flexible for modern device sizes.
• Test on real devices/emulators: Always verify your adjustments—what looks good on paper might need tweaks once you see it on actual hardware.

内容的提问来源于stack exchange，提问作者Rahul pal