仅定义单种屏幕密度限定符？values-hdpi下dimens.xml适配规则

Hey there! Let's walk through your questions about Android screen density resource qualifiers step by step:

1. What happens if only one screen density qualifier is defined? #

When you only set up one density-specific resource directory (like values-hdpi for dimensions), here's how Android handles different devices:

• For lower-density devices (e.g., mdpi): The system will automatically scale down the dimension values from your single density directory to fit the lower-resolution screen. This can lead to blurry UI elements or misaligned layouts, since scaling down from a higher density doesn't always preserve sharpness.
• For higher-density devices (e.g., xhdpi, xxhdpi): The system will scale up the values from your single directory to match the higher screen density. This often results in oversized UI elements, and stretching can make text or graphics look pixelated or out of proportion.
• If you don't also have a default values directory (without any density qualifier), you run a higher risk of severe layout glitches on devices with densities far from your defined one. It breaks Android's recommended resource adaptation workflow.

2. When only values (default) and values-hdpi have dimens.xml, which one do higher-density devices use? #

Great question—higher-density devices (like xhdpi/xxhdpi) will use the values-hdpi file, then scale its values up to fit their screen density, not the default values directory.

Here's the logic behind it: Android's resource matching system first looks for a directory that exactly matches the device's density. If there's no exact match, it picks the closest lower-density qualifier available and scales those resources up. Since hdpi is the closest lower density to xhdpi/xxhdpi, it prioritizes values-hdpi over the default values folder. The default directory only gets used when there are no density-specific directories at all.

内容的提问来源于stack exchange，提问作者y.allam