Density of pixels in android

Question

If I have android device with 5 inches diagonal screen size and 2.3 inches screen width and its screen supports 1080*1920 pixels what is the nearest type of its screen density? How can solve this question?

Answer 1

You should use sp for font sizes and dp for anything else. See this SO post regarding screen density, terminology, and proper uses: Difference between px, dp, dip and sp in Android?

Also, here is a link to the android developer's API guide for supporting multiple screens in your applications: http://developer.android.com/guide/practices/screens_support.html

Answer 2

You can find out device display info reading DisplayMetrics from Activity

DisplayMetrics dm = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(dm);

int dpi = dm.densityDpi;

dm.densityDpi will give you device dpi bucket expressed in dots-per-inch

You can also get other display metrics like:

float density       - The logical density of the display - scaling factor
float scaledDensity - A scaling factor for fonts displayed on the display.
int widthPixels     - The absolute width of the display in pixels.
int heightPixels    - The absolute height of the display in pixels.
float xdpi          - Physical pixels per inch of the screen in the X dimension.
float ydpi          - Physical pixels per inch of the screen in the Y dimension.

However, for some devices xdpi and ydpi metrics are returning wrong numbers and you cannot rely on them. Since API 17 you can also use getRealMetrics(). It should give you accurate values for xdpi and ydpi.

DisplayMetrics dm = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getRealMetrics(dm);