Open Source & Free  

Customizing Themes Of Codename One Apps

Customizing Themes Of Codename One Apps

Recipes to customize the look and feel of Codename One apps using Themes, CSS, Styles, etc.

Jump To Topic

The following recipes include tips on customizing the look and feel of Codename one apps using themes, CSS, styles, etc.

Platform-Specific Styling


You have used CSS to style your app, and it looks great on some devices but not on others. You want to change the font size of some styles, but only on specific devices.


Use CSS media queries to target styles at a specific device (e.g. desktop, tablet, or phone), platform (e.g. Android, iOS, Mac, Windows, etc…​), or device densities (e.g. low, medium, high, very high, etc..).

Example: A media query to override Label color on iOS only

					@media platform-ios {
    Label {
        color: red;

Media queries will allow you to target devices based on three axes: Platform, Device, and Density

Table 1. Platform Queries

Value Description
Apply only on iOS
Apply only on Android
Apply only on Mac desktop
Apply only on Windows desktop

Table 2. Device Queries

Value Description
Apply only on desktop
Apply only on tablet
Apply only on phone

Table 3. Density Queries

Value Description
Very low density 176x220 and smaller
Low density up to 240x320
Medium density up to 360x480
High density up to 480x854
Very high density up to 1440x720
HD up to 1920x1080
Intermediate density for screens between HD to 2HD
Double the HD level density
4K level density

You can combine media queries to increase the specificity.

Example: Targeting only 4k Android tablets

					@media platform-and, device-tablet, density-4k {
    Label {
        font-size: 5mm;

You can also combine more than one query of the same type to broaden the range of the query.

For example, targeting only HD, 2HD, and 4K Android tablets:

					@media platform-and, device-tablet, density-4k, density-2hd, density-hd {
    Label {
        font-size: 5mm;

Further Reading:

Platform-Specific Font Scaling


Your app looks great except that on desktop, the fonts are a little too small. If you could only scale the fonts to be 25% larger on the desktop, your app would be perfect.


You can use font-scaling constants to scale all of the fonts in your stylesheet by a constant factor. You can use a “media-query-like” syntax to apply this scaling only on particular platforms, devices, or densities.

Example: Scaling Fonts to be 25% larger on desktop

					#Constants {
    device-desktop-font-scale: "1.25";


In most cases it is better to use standard media queries to apply styles which target specific platforms in a more fine-grained manner.

Further Reading:


  • ThomasH99 says:

    Great addition, really useful. Thanks!

  • Javier Anton says:

    Thanks, I rely on themes at the moment and kind of dread migrating to CSS. I know the clock is ticking and you will switch off support for themes at some point, so resources like these are great

    • ThomasH99 says:

      Javier, I’m using CSS since quite some time, I found it easy to get started, and it’s a really nice way of working, especially with the live update (the simulator is updated as soon as you save the CSS file). This has made the workflow a LOT faster. The only slight concern I’ve come across is that since the CSS conversion creates every possible variation of the UIIDs (pressed ect), my generated .res becomes very big (280 uiids gives a .res of 400kb, no pictures). I define UIIDs for most of the individual elements based on their semantics and that might not be the best solution, but it makes it easy to tune individual styles whenever needed.

Leave a Reply