It's currently not possible to use the "React" tab in the devtools to inspect app widgets. This is due to a change in how the application scripts are evaluated in the devtools plugin; they are now run inside a Web Worker, and the plugin is unaware of this and so unable to communicate properly with React Native.
However, you can still use the Console feature of the devtools, and debugging JavaScript with breakpoints works too. To use the console, make sure to select the ⚙debuggerWorker.js entry in the devtools dropdown that by default is set to <top frame>.
This is an initial release of React Native Android and therefore not all of the views present on iOS are released on Android. We are very much interested in the communities' feedback on the next set of modules and views for Open Source. Not all native views between iOS and Android have a 100% equivalent representation, here it will be necessary to use a counterpart eg using ProgressBar on Android in place of ActivityIndicator on iOS.
Our provisional plan for common views and modules includes:
There are properties that work on one platform only, either because they can inherently only be supported on that platform or because they haven't been implemented on the other platforms yet. All of these are annotated with @platform in JS docs and have a small badge next to them on the website. See e.g. Image.
There are known cases where the APIs could be made more consistent across iOS and Android:
<SwitchAndroid> and <SwitchIOS> are very similar and should be unified to a single <Switch> component.<AndroidViewPager> (to be open sourced soon) and <ScrollView pagingEnabled={true}> on iOS do a similar thing. We might want to unify them to <ViewPager>.alert() needs Android support (once the Dialogs module is open sourced)LinkingIOS and IntentAndroid (to be open sourced) closer together.ActivityIndicator could render a native spinning indicator on both platforms (currently this is done using ActivityIndicatorIOS on iOS and ProgressBarAndroid on Android).ProgressBar could render a horizontal progress bar on both platforms (currently only supported on iOS via ProgressViewIOS).There is currently no easy way of publishing custom native modules on Android. Smooth work flow for contributors is important and this will be looked at very closely after the initial Open Source release. Of course the aim will be to streamline and optimize the process between iOS and Android as much as possible.
overflow style property defaults to hidden and cannot be changed on Android #This is a result of how Android rendering works. This feature is not being worked on as it would be a significant undertaking and there are many more important tasks.
We don't support shadows on Android currently. These are notoriously hard to implement as they require drawing outside of a view's bounds and Android's invalidation logic has a hard time with that. A possible solution is to use elevation, but more experimentation will be required.
An optimization feature of the Android version of React Native is for views which only contribute to the layout to not have a native view, only their layout properties are propagated to their children views. This optimization is to provide stability in deep view hierarchies for React Native and is therefore enabled by default. Should you depend on a view being present or internal tests incorrectly detect a view is layout only it will be necessary to turn off this behavior. To do this, set collapsable to false as in this example:
React Native Android depends on Fresco for loading and displaying images. Currently we have disabled downsampling because it is experimental, so you may run into memory issues when loading large PNG images.
Try running react-native init with --verbose and see #2797 for common causes.
The text input has by default a border at the bottom of its view. This border has its padding set by the background image provided by the system, and it cannot be changed. Solutions to avoid this is to either not set height explicitly, case in which the system will take care of displaying the border in the correct position, or to not display the border by setting underlineColor to transparent.