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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Sharing members between an activity and its fragment(s)","articleBody":"Hello,\n\nas it is, the communication between `Activity` and `Fragment` classes is a little bit complicated.\nBundle and intents work only for simple data. But at the moment there is no easy way to pass \"_real objects_\" onto activities (like DbHelper, or image downloaders...). \n\nWhat I propose a new annotation _@Shared_\n\n``` java\n@EActivity(R.layout.activity_main)\npublic class MainActivity extends Activity {\n\n    @Shared\n    String param1 = \"string from the activity\";\n\n    @Shared\n    Bundle param2;\n\n    @Shared\n    @Bean\n    MyBean bean;\n\n    @AfterInject\n    void initInject() {\n                // You can do custom member initialisation here\n        param2 = new Bundle();\n        param2.putString(\"are we\", \"done?\");\n    }\n}\n\n```\n\nAnd \n\n``` java\n@EFragment(R.layout.fragment_main)\npublic class MainFragment extends Fragment {\n\n    @Shared\n    String param1 = \"string from the fragment\";\n\n    @Shared\n    Bundle param2;\n\n    @Shared\n    MyBean bean;\n\n    @AfterViews\n    void init() {\n        // All the members are initialized and ready !\n    }\n}\n\n```\n\nI did a little mockup to validate the idea and it works nicely.\n\nHere is the generated code \n\n``` java\npublic final class MainFragment_ extends MainFragment ... {\n\n    @Override\n    public void onViewChanged(HasViews hasViews) {\n        ...\n        initShared_();\n        ...\n    }\n\n    private void initShared_() {\n        if (getActivity() instanceof SharingActivity_) {\n            SharingActivity_ act = (SharingActivity_) getActivity();\n            param1 = (String) act.getSharedObject_(\"param1\");\n            param2 = (Bundle) act.getSharedObject_(\"param2\");\n            bean = (MyBean) act.getSharedObject_(\"bean\");\n        }\n    }\n\n        // Reset the shared members to prevent memory leaks\n    private void resetShared_() {\n        param1 = null ;\n        param2 = null ;\n        bean = null ;\n    }\n\n    public void onDestroyView () {\n        resetShared_() ; \n        super.onDestroyView() ;\n    }\n\n```\n\nThe parent activity implements `SharingActivity_` if it exposes shared members.\n\n``` java\npublic interface SharingActivity_ {\n\n    Object getSharedObject_(String name);\n\n}\n```\n\n``` java\npublic final class MainActivity_ extends MainActivity implements\n        ... SharingActivity_ {\n\n    @Override\n    public Object getSharedObject_(String name) {\n        if (\"param1\".equals(name))\n            return param1;\n        if (\"param2\".equals(name))\n            return param2;\n        if (\"bean\".equals(name))\n            return bean;\n        Log.d( \"TAG\", \"The member '+name +\"' is not declared by the activity 'MainActivity' or is not annotated with @Share\" ) ;\n        return null;\n    }\n\n```\n\nThe `getSharedObject_` method returns something only for shared members.\n\nI think that along with [Otto](http://square.github.io/otto/) that could really ease the development with `Fragment`.\n\n**edit**: reset shared variables to prevent memory leaks\n","author":{"url":"https://github.com/PerfectCarl","@type":"Person","name":"PerfectCarl"},"datePublished":"2014-01-02T11:16:52.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":18},"url":"https://github.com/854/androidannotations/issues/854"}