Andorid system layout, values, drawable adaptation

andorid Screen adaptation

Density type	Represents the resolution of （px）	Screen density （dpi）	conversion （px/dp）	The proportion
Low density （ldpi）	240x320	120	1dp=0.75px	3
Medium density （mdpi）	320x480	160	1dp=1px	4
high-density （hdpi）	480x800	240	1dp=1.5px	6
Ultra high density （xhdpi）	720x1280	320	1dp=2px	8
Ultra high density （xxhdpi）	1080x1920	480	1dp=3px	12

stay Android in , It is stipulated that 160dpi（ That is, the screen resolution is 320x480） Benchmarking ：1dp=1px

The preferred smallestWidth  

smallestWidth Qualifiers fit

• The screen resolution qualifier is adapted according to the screen resolution ,Android The device resolution is a lot , But also consider the virtual keyboard , This requires a lot of dimens.xml file . Because no matter how many pixels the phone screen is , What is the density ,90% The minimum width of all mobile phones is 360dp, So using smallestWidth Qualifier adaptation requires only a small amount dimens.xml File can .
• The screen resolution qualifier adapts to px Company , and smallestWidth The unit of qualifier adaptation is dp and sp,dp and sp yes google Recommended unit of measurement . Because many applications require the font size to change with the system , So font units use sp And more flexible .
• Screen resolution qualifier adaptation requires device resolution and values-xx Only when the folders are completely matched can the adaptation be achieved , and smallestWidth Qualifier adaptation search dimens.xml The principle of documents is to look from big to small , For example, the minimum width of the equipment is 360dp, They'll look for it first values-360dp, If you don't find it, you will look down values-320dp, If you still don't have one, just find the default one values Under the demens.xml file , So even if there is no perfect match, it can achieve a good adaptation effect .
• Whether it's width or height , Which side is considered to be “ Minimum width ”

 

• Qualifier type ：
• Size （size） qualifiers
• Minimum width （Smallest-width） qualifiers
• Layout alias
• Screen orientation （Orientation） qualifiers

Width and height qualifiers fit   This practice is not recommended , such as 1920x1080 Your cell phone must be found 1920x1080 Qualifier for , Otherwise, you can only use the unified default dimens The file . If you use the default size ,UI It's likely to deform , In short , The fault tolerance mechanism is very poor .

1.layout-sw500dp
    there sw representative smallwidth It means , When the absolute width of your screen is greater than 500dp when , The screen will automatically call layout-sw500dp The layout in the folder .

    Be careful ： The absolute width here refers to the actual width of the mobile phone , It has nothing to do with the horizontal and vertical screen of the mobile phone .

2.layout-w500dp
   When the relative width of your screen is greater than 500dp when , The screen will automatically call layout-w500dp The layout in the folder .

   Be careful ： The relative width here refers to the relative width of the mobile phone ; That is, when the mobile phone vertical screen , Is the length of the smaller side ; When the phone is horizontal , Is the length of the longer side .

3.layout-h500dp
And layout-w500dp It's the same with , It just refers to the relative height .

Be careful ： The relative height here refers to the relative height of the mobile phone ; That is, when the mobile phone vertical screen , Is the length of the longer side ; When the phone is horizontal , Is the length of the smaller side . But this approach is rarely used , Because the screen is at a relative height , That is, it can usually roll in the longitudinal direction, resulting in length change , Instead of being basically fixed in the horizontal direction , Therefore, this method has poor flexibility ,google Official documents suggest using this method as much as possible .

 

 

example ： The density is 240  Size is ：1280x720 and 1920x1080 Under which adapter folder should it be placed

 Android in , It is stipulated that 160dpi（ That is, the screen resolution is 320x480） Benchmarking

The corresponding density ratio is ：

160  1
240  1.5
320  2

Use the minimum as the width ：1280x720 yes 720,1920x1080 yes 1080
720/1.5 =480
1080/1.5 =720
sw480dp
sw720dp

layout Namely layout-sw720dp , yes values Namely values-sw720dp

Reference resources ：

https://www.jianshu.com/p/1302ad5a4b04

https://www.sohu.com/a/169423446_468731