marcshilling marcshilling - 4 months ago 222
Android Question

How to access Activity from a React Native Android module?

I'm attempting to bridge over the Android functionality of keeping the screen on to React Native. I figured I could do this with a simple module, however I don't know how to get access to the current Android Activity from said module.

I need the Activity reference so I can call

.getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
on it

I tried to get the activity via casting like so
((Activity)getReactApplicationContext().getBaseContext())
, but this throws a "cannot be cast to Android.app.Activity" error

Answer

CustomReactPackage.java:

public class CustomReactPackage implements ReactPackage {

    private Activity mActivity = null;

    public CustomReactPackage(Activity activity) {
        mActivity = activity;
    }

    @Override
    public List<NativeModule> createNativeModules(ReactApplicationContext reactContext) {
        List<NativeModule> modules = new ArrayList<>();
        // Add native modules here
        return modules;
    }

    public List<Class<? extends JavaScriptModule>> createJSModules() {
        return Collections.emptyList();
    }

    public List<ViewManager> createViewManagers(ReactApplicationContext reactContext) {
        List<ViewManager> modules = new ArrayList<>();
        // Add native UI components here
        modules.add(new LSPlayerManager(mActivity));
        return modules;
    }
}

LSPlayerManager is my native UI component. I define a constructor so that I can pass in the activity:

public LSPlayerManager(Activity activity) {
    mActivity = activity;
}

And finally in MainActivity.java where the ReactInstanceManager is defined, we can pass the activity to our custom React package:

mReactInstanceManager = ReactInstanceManager.builder()
        .setApplication(getApplication())
        .setBundleAssetName("index.android.bundle")
        .setJSMainModuleName("src/index.android")
        .addPackage(new MainReactPackage())
        .addPackage(new CustomReactPackage(this)) // <--- LIKE THIS!
        .setUseDeveloperSupport(BuildConfig.DEBUG)
        .setInitialLifecycleState(LifecycleState.RESUMED)
        .build();

UPDATE FOR REACT NATIVE 0.29.0

This is no longer how you access activity in a native module. See https://github.com/facebook/react-native/releases/tag/v0.29.0 for migration instructions

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