6336e641f4
Summary: When some drawing attributes of a view changes how it measures, we need to be able to relayout it correctly. This adds method `invalidate(View)` to `YogaLayout` which will flag the corresponding node as dirty and requiring layout again. Reviewed By: emilsjolander Differential Revision: D4634563 fbshipit-source-id: af7f47dce00a31414d0987a58307c5d44c1bcf20
2.5 KiB
docid, title, layout, permalink
| docid | title | layout | permalink |
|---|---|---|---|
| android | Android | docs | /docs/api/android/ |
There is an easy interface to Yoga called YogaLayout. This is a view group that lays out its children using Yoga. We recommend looking at the sample app for details on its usage. However, as an overview you can simply define XML layouts such as
Note that there are some caveats, such as requiring the custom YogaLayoutViewFactory in order to have tags YogaLayout instead of com.facebook.samples.yoga.YogaLayout.
layout_width and layout_height
If either are set to an actual size (in px or dp etc) then this is taken as a default for yoga:height or yoga:width. Otherwise they are ignored.
VirtualYogaLayout
Sometimes you will nest YogaLayouts within YogaLayouts in order to get your layout to be perfect, but some of the YogaLayouts are just there to control position: they don't render or anything. If so, then they are unnecessary (since Yoga stores the view hierarchy itself) and VirtualYogaLayout is a ViewGroup that fixes this. It will never get drawn, but all its children will be placed appropriately.
RTL locales
RTL locales are supported by default. That is, unless you explicitly set the yoga:direction="ltr|rtl|inherit" attribute on a view, it will obtain the locale direction at runtime. This means that the layout will rearrange properly, even if the locale changes while your app is running!
Attributes
The list of all attributes can be found in attrs.xml, but logically map from the Yoga properties.
Auto margins
You can specify margin_left="auto" (or margin_right etc.) for auto values. This is in addition to the dimensions you can speicfy, such as margin_left="20dp".
Invalidation (temporary)
If you change any attribute of a view that will change its measure size, you must invalidate it. Do this by calling YogaLayout#invalidate(View) on any YogaLayout further up the tree. Obviously it is most efficient to call it on the view's parent (if it is a YogaLayout, but in case this is impractical, you can call it on the root of the tree.
This is a temporary solution. Ideally, the view should invalidate itself whenever an attribute (text, font etc.) that will alter its size changes. This will be automatic once we find a good way to hook into the Android invalidation system.