ScreenCompatibility

Android屏幕的一些技巧

官网适配方案

https://developer.android.com/training/basics/supporting-devices/index.html
https://developer.android.com/training/multiscreen/screensizes.html

资源图片适配

Provide alternative bitmaps

To provide good graphical qualities on devices with different pixel densities, you should provide multiple versions of each bitmap in your app—one for each density bucket, at a corresponding resolution. Otherwise, Android must scale your bitmap so it occupies the same visible space on each screen, resulting in scaling artifacts such as blurring.

Figure 2. Relative sizes for bitmaps at different density sizes

There are several density buckets available for use in your apps. Table 1 describes the different configuration qualifiers available and what screen types they apply to.

Table 1. Configuration qualifiers for different pixel densities.

Density qualifier	Description
`ldpi`	Resources for low-density (ldpi) screens (~120dpi).
`mdpi`	Resources for medium-density (mdpi) screens (~160dpi). (This is the baseline density.)
`hdpi`	Resources for high-density (hdpi) screens (~240dpi).
`xhdpi`	Resources for extra-high-density (xhdpi) screens (~320dpi).
`xxhdpi`	Resources for extra-extra-high-density (xxhdpi) screens (~480dpi).
`xxxhdpi`	Resources for extra-extra-extra-high-density (xxxhdpi) uses (~640dpi).
`nodpi`	Resources for all densities. These are density-independent resources. The system does not scale resources tagged with this qualifier, regardless of the current screen’s density.
`tvdpi`	Resources for screens somewhere between mdpi and hdpi; approximately 213dpi. This is not considered a “primary” density group. It is mostly intended for televisions and most apps shouldn’t need it—providing mdpi and hdpi resources is sufficient for most apps and the system will scale them as appropriate. If you find it necessary to provide tvdpi resources, you should size them at a factor of 1.33*mdpi. For example, a 100px x 100px image for mdpi screens should be 133px x 133px for tvdpi.

To create alternative bitmap drawables for different densities, you should follow the 3:4:6:8:12:16 scaling ratio between the six primary densities. For example, if you have a bitmap drawable that’s 48x48 pixels for medium-density screens, all the different sizes should be:

36x36 (0.75x) for low-density (ldpi)
48x48 (1.0x baseline) for medium-density (mdpi)
72x72 (1.5x) for high-density (hdpi)
96x96 (2.0x) for extra-high-density (xhdpi)
144x144 (3.0x) for extra-extra-high-density (xxhdpi)
192x192 (4.0x) for extra-extra-extra-high-density (xxxhdpi)

Then, place the generated image files in the appropriate subdirectory under res/ and the system will pick the correct one automatically based on the pixel density of the device your app is running on:

res/
  drawable-xxxhdpi/
    awesome-image.png
  drawable-xxhdpi/
    awesome-image.png
  drawable-xhdpi/
    awesome-image.png
  drawable-hdpi/
    awesome-image.png
  drawable-mdpi/
    awesome-image.png

Then, any time you reference @drawable/awesomeimage, the system selects the appropriate bitmap based on the screen’s dpi. If you don’t provide a density-specific resource for that density, the system picks the next best match and scales it to fit the screen.

This means that if you generate a 200x200 image for xhdpi devices, you should generate the same resource in 150x150 for hdpi, 100x100 for mdpi, and 75x75 for ldpi devices.
而UI问我们需要多少大小的图，如果效果图根据750*1334的话，可以告诉他，不过PS有个叫
cutterman的工具可以自动生成不同分辨率的图片