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118 lines
3.2 KiB
Markdown
118 lines
3.2 KiB
Markdown
---
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title: Display density on Android
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language: en
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layout: default
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created: 2015-12-02 17:19:42 +0200
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updated: 2015-12-02 17:19:42 +0200
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toc: false
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tags:
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- know-how
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- hacking
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- android
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- display
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- resolution
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- lcd
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---
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Methods
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=======
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Android supports changing the display resolution in 2 different ways.
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wm density
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----------
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This method works without root and changes the density of the *window manager*.
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You can call this command only from the adb shell.
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The syntax is:
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wm density [ppi]
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E.g. the Nexus 9 has a real display density of 288ppi, so you would run:
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wm density 288
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To reset the value to the factory setting (for the N9 that is 320), just run:
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wm density reset
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build.prop
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----------
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The other way to change the display density is to edit the `build.prop`. This
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only works with root access.
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To edit the file, first make the `system` partition writable by remounting it.
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Then find the file `/system/build.prop` and open it in a text editor. I use
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my favourite file manager [FX File Explorer](https://play.google.com/store/apps/details?id=nextapp.fx)
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with its integrated editor for that.
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Find the following line (Example from Nexus 9 with currently 320ppi):
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ro.sf.lcd_density=320
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And change the number to your desired value. BE SURE TO NOT CHANGE ANYTHING ELSE.
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Save the file and reboot your device.
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Advantages
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==========
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Setting the correct density value makes the display appear sharper and it may
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even make your device run better.
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Android knows different *densities* and if an app supplies graphics in different
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qualities, it loads them according to the detected density. This means: The
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higher the density, the larger graphics Android has to load and keep in
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memory. So reducing the density (to the real value) can make Android load
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a bit less detailed graphics and thus save RAM.
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Android knows these quality classes:
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| Class | PPI |
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|------:|:-------:|
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| ldpi | 100-140 |
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| mdpi | 141-199 |
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| hdpi | 200-319 |
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| xhdpi | 320-340 |
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| xxhdpi| ~480 |
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|xxxhdpi| ~640 |
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As you can see, the 320ppi of the Nexus 9 makes Android use *xhdpi* resources.
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If you change the density to 318, you won't notice anything, but Android will
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suddenly use the *hdpi* resources and save memory when running apps.
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Problems
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========
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If you don't have root access and try to change the density using the `wm density`
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command only, it might seem to work on the first glance, but you will notice
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strange effects.
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If you're using SwiftKey, you'll notice it right away:
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Other problems are more subtle (Nexus 9 at 288ppi):
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Compare this to the same screen at the original 320ppi:
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(If you're still searching: Notice the huge "chevron" icon after the
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developer's name. And also the **huge** background image.)
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<p><div class="noteimportant" markdown="1">
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These problems only occur if you use only one method to change the density. If
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you use **both** methods and set them to the same value, everything will look
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just fine.
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</div></p>
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More info at the [xda forum](http://forum.xda-developers.com/nexus-9/general/guide-little-trick-improvimg-nexus-9-t3224931).
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