What is the Difference Between "px", "dip", "dp" and "sp" in Android?

In Android, when specifying dimensions or typography sizes, it's essential to use the correct units to ensure that your UI looks consistent across various devices with different screen sizes and densities. Here's the breakdown of the different units:

px (Pixels):
- It represents actual pixels on the screen.
- It's a dot on the physical screen.
- Using px can lead to inconsistent UI on different devices because the density of screens can vary, meaning the same pixel count can look larger on a low-density screen and tiny on a high-density one.
dp or dip (Density-independent Pixels):
- This unit abstracts away the density of the device and provides a consistent way to define layout measurements.
- It is a virtual pixel unit that's roughly equivalent to one pixel on a medium-density screen (160dpi; the baseline density).
- Android will automatically scale dp measurements for screens with higher or lower densities.
- It ensures that the UI is consistent across various screen densities.
- dp and dip are the same. The former is just a shorthand for the latter.
sp (Scale-independent Pixels):
- This is similar to dp, but it also factors in the user's font size preference.
- It's primarily used for text sizes.
- If a user has set a larger font size in their device settings, sp will scale appropriately. So, if you've set a text size to be 16sp and the user has their font size setting at "Large," the text might appear to be equivalent to, say, 20sp or 24sp.
- Using sp for typography ensures that your text respects the user preferences and accessibility settings.

Recommendations:

For layout dimensions: Always use dp (or dip, though dp is more common). It ensures consistent sizing across different screen densities.
For text sizes: Always use sp to make sure text size respects user settings and is accessible.
Avoid using px: Since this doesn't adjust for screen density, it can lead to inconsistent appearances across devices.

In essence, while designing and developing for Android, it's crucial to be aware of these units to create a consistent and accessible user interface across the diverse Android device ecosystem.

How to Convert px to dp in Android:

Use the formula: dp = px / (dpi / 160).

Example:

int pxValue = 100;
float scale = getResources().getDisplayMetrics().density;
int dpValue = (int) (pxValue / scale);

Scaling Text with sp in Android:
- Use sp for text size to ensure it scales based on both screen density and user font size preferences.
- Example:
```
<TextView
    android:textSize="18sp"
    ... />
```