What are the differences between DIP, PX, PT, and SP for beginners of Android?

Display Unit: pixel, dip, and SP

Dip: Device Independent pixels (device independent pixel ). different devices have different display effects, which are related to the hardware of the device. We recommend that you use this function to support WVGA, hvga, and qvga without pixels.

Px: pixels (pixels). Different devices have the same display effect. Generally, we use hvga to represent 320x480 pixels, which is usually used.

PT: point, a standard unit of length, 1pt = 1/72 inch, used in the printing industry, very easy to use;

SP: scaled pixels (zoom in pixels). It is mainly used to display the best for textsize in fonts.

Therefore, according to Google's suggestion, it is best to use SP as the unit for textview font size and view
Textview
Android uses SP as the font size unit by default.

Conversion (using SP and Pt as an example)
View the source code of textview and other classes. We can see that:

Case complex_unit_px:
Return value;
Case complex_unit_sp:
Return Value * metrics. scaleddensity;
Case complex_unit_pt:
Return Value * metrics. xdpi * (1.0f/72 );

--------------------------
Scaleddensity = density_device/(float) density_default;
Xdpi = density_device;

--------------------------
Density_default = density_medium = 160;

========================================================== ====
Therefore, if PT and SP take the same value of 1, the coefficient between 1pt and 1sp can be set to X,

1 * density_device/72 = x * 1 * density_device/160 = & gt;
X = 160/72 = 2.2222

That is to say, in Android, 1pt is roughly equal to 2.22sp

The above is for reference. If the UI can provide the best design in SP units, if there is no SP in the Design
Then, developers can take an approximate value by appropriate conversion.

Reprinted content: http://hi.baidu.com/lfcaolibin/blog/item/f3f60d1e438deefee0fe0bae.html
What are dip and SP?

In the past, programmers often designed computer user interfaces in pixels. For example, define a form field with a width of 300 pixels. the spacing between columns is 5 pixels, And the Icon size is 16 × 16 pixels. The problem with this processing is that if you run the program on a new display with a dot (DPI) higher per inch, the user interface will look small. In some cases, the user interface may be small to difficult to see the content.

The measurement units irrelevant to resolution can solve this problem. Android supports all of the following units.

Px (pixel): the point on the screen.

In (INCHES): the unit of length.

Mm (mm): the unit of length.

Pt (lbs): 1/72 inch.

DP (density-independent pixels): An abstract unit based on screen density. 1dp = 1px on a display at 160 o'clock per inch.

Dip: it is the same as DP and is mostly used in Android/ophone examples.

SP (pixels irrelevant to the scale): similar to DP, but can be scaled based on the user's font size preferences.

To enable normal display of the current and future display types on the user interface, we recommend that you always use SP as the unit of text size and dip as the unit of other elements. Of course, you can also consider using a vector image instead of a bitmap.