Android Plugin Architecture at Mobel

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Android Plugin Architecture

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Cross-app communication

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Cross-app communication • Intent and BroadcastReceiver • ContentResolver and ContentProvider • Services  …

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Android Plugin Architecture

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Android Plugin Architecture • Why? • User Plugin Discovery • Host App Plugin Discovery • Plugin Communication

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App Examples

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DashClock Widget

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DashClock Widget

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Muzei Live Wallpaper

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Muzei Live Wallpaper

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Why?

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Ecosystem-based marketing • Don’t create all your own plugins • Open up an API to extend your app • Indirectly promoting your app

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Business Model • Free app with basic functionality • Paid plugins

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Permission Mitigation • Standard Android is all or nothing • People might not install your permission rich app • Provide core app with less permissions • User can choose permissions by installing plugins (Before Android 6)

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User Plugin Discovery

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User Plugin Discovery • Hardcode references in core app • Link to a search term on Play Store • Download a JSON • Use a WebView • …

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App Plugin Discovery

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BroadcastReceiver Host app Plugin app BroadcastReceiver BroadcastReceiver Are there any plugins? Plugin app BroadcastReceiver

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BroadcastReceiver Host app Plugin app BroadcastReceiver BroadcastReceiver Yea, I’m a plugin! Plugin app BroadcastReceiver Yea, I’m a plugin!

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BroadcastReceiver • Not recommended • It wakes up every plugin app • Not sure when every plugin app responded

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PackageManager • Every plugin implements a custom intent action • PackageManager queries for every component using that custom action • Easily get metadata of that component

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Package Broadcasts • Android system sends package broadcasts • Host app checks if we are interested  in that package change • Host app can update a live list of plugins

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Package Broadcasts Host app BroadcastReceiver ListView Android System App installs App replaces App deletes

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Package Broadcasts Host app BroadcastReceiver ListView Android System App installs App replaces App deletes PACKAGE_ADDED  PACKAGE_REPLACED PACKAGE_REMOVED

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Package Broadcasts Host app ListView Android System App installs App replaces App deletes PACKAGE_ADDED  PACKAGE_REPLACED PACKAGE_REMOVED Update

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Plugin Communication

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MetaData Great for getting static data • Plugin name • Plugin icon • Plugin api level

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Coding Example MetaData Using resources from other app PackageManager manager = getPackageManager(); Resources pluginResources = manager.getResourcesForApplication("com.example.pluginapp"); int drawableResID = pluginResources.getIdentifier("app_icon", "drawable", "com.example.pluginapp"); Drawable drawable = pluginResources.getDrawable(drawableResID);

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BroadcastReceiver Host app Plugin app BroadcastReceiver BroadcastReceiver Provide me data

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BroadcastReceiver Host app Plugin app BroadcastReceiver BroadcastReceiver Here’s my data

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Remote Service Binding • Preferred way • Remote services found with PackageManager • Communication protocol using AIDL • Callback with Messenger for delayed responses

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Remote Service Binding - AIDL • All primitive types • int • long • char • … • String • Charsequence • List (ArrayList) • Map (HashMap) • Parcelable

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Remote Service Binding Host app Plugin app AIDL Compile Stub Stub Build

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Remote Service Binding Host app Plugin app Stub Stub Impl Impl Build

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Remote Service Binding Host app Plugin app Stub Stub Impl Impl Bind Run

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Remote Service Binding Host app Plugin app Stub Stub Impl Impl IPC Run

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GUI Plugins

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WebViews • Plugin provides data • Static URI using MetaData • Dynamic URI using IPC • Host has a WebView that loads the data • Easy • Not native • Security issues (javascript)

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RemoteViews • Native • Homescreen widgets • Lockscreen widgets • Notiﬁcations • Only basic View Widgets • Parcelable!

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Roll Your Own Parcelable • More ﬂexible • A lot more work • Need to version your view building

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Some extra tips

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Some Extra Tips • Think about your versioning • Abstract to a library for distribution • Input validation in host • Make sure it’s secure • Don’t leak data  →using signature level permissions

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Questions? Siebe Sysmans Consultant at AppFoundry [email protected] @ThisIsSiebe