Comparison of pixel units DP, PX, PT, SP in Android

DP (DIP): device independent pixels (unit independent pixels). Different devices have different display effects, this is related to the device hardware, generally we support WVGA, HVGA and QVGA recommend this, do not rely on pixels.
Px:pixels (pixels). Different devices show the same effect, generally we hvga represent 320x480 pixels, this use more.
Pt:point, is a standard length unit, 1pt=1/72 inches, for the printing industry, very simple to use;
sp:scaled pixels (enlarge pixels). Mainly used for font display of best for textsize.
Thus, according to Google's suggestion, TextView's font size is best to use SP to do units, and view the source of TextView know that Android by default using the SP as the font size units.

Also, the Google code inside the units used in the PX as the default unit.

APK resource Bundle, when the screen density=240 use the hdpi tag resource

Resources that use MDPI tags when the screen is density=160

When the screen density=120, use the ldpi tag resource.

1DP = 1px on a monitor 160 dots per inch.

Here are several different units that convert each other.

public static int dip2px (context context, float Dipvalue) {
Final float scale = context.getresources (). Getdisplaymetrics (). density;
return (int) (Dipvalue * scale + 0.5f);
}
public static int Px2dip (context context, float Pxvalue) {
Final float scale = Context.getresource (). Getdisplaymetrics (). density;
return (int) (Pxvalue/scale + 0.5f);
}
public static int dip2px (context context, float Dipvalue) {
Final float scale = context.getresources (). Getdisplaymetrics (). density;
return (int) (Dipvalue * scale + 0.5f);
}
public static int Px2dip (context context, float Pxvalue) {
Final float scale = Context.getresource (). Getdisplaymetrics (). density;
return (int) (Pxvalue/scale + 0.5f);
}

Here's how to get the resolution:

In an activity's OnCreate method, write the following code:
Displaymetrics metric = new Displaymetrics ();
Getwindowmanager (). Getdefaultdisplay (). Getmetrics (Metric);
int width = metric.widthpixels; Screen width (pixels)
int height = metric.heightpixels; Screen height (pixels)
float density = metric.density; Screen Density (0.75/1.0/1.5)
int densitydpi = metric.densitydpi; Screen density dpi (120/160/240)

In Android, 1pt is roughly equal to 2.22SP.

For reference, if the UI can provide the best design in SP, if there is no concept of SP in the design, the developer can also take approximate values by appropriate conversion.
In the past, programmers typically designed computer user interfaces in pixels. For example, you define a form field with a width of 300 pixels, a space between columns of 5 pixels, an icon size of 16x16 pixels, and so on. The problem with this approach is that if you run the program on a new monitor with a higher dots per inch (dpi), the user interface will appear small. In some cases, the user interface may be too small to see the content. Resolution-independent units of measure can solve this problem.

Android supports all of the following units.
PX (pixels): The point on the screen.
In (inches): unit of length.
MM (mm): unit of length.
PT (lb): 1/72 inches.
DP (density-independent pixels): An abstract unit based on screen density. 1DP = 1px on a monitor 160 dots per inch.
Dip: Same as DP, more for android/ophone example.
SP (scale independent pixels): Similar to DP, but can be scaled based on the user's font size preference.

Comparison of pixel units DP, PX, PT, SP in Android