从另一个Activity调用方法（调用Fragment）

Question

I have called method:

protected void ask(){

        Fragment newContent = new QuestionsFragment();
        ((MainActivity) getActivity()).switchContent(newContent, R.string.questions, MenuFragment.questions_id, BottomActionBarMode.QUESTIONS);
}

MainActivity: https://docs.google.com/file/d/0B30eXgoSJlFsczNSdkE5Qnc5eG8/edit?usp=sharing

Error:

08-21 17:16:28.574: E/AndroidRuntime(26360): FATAL EXCEPTION: main 08-21 17:16:28.574: E/AndroidRuntime(26360): java.lang.ClassCastException: com.chiv.successteritory.activities.AskLikeQuestionDetailsActivity cannot be cast to com.chiv.successteritory.activities.MainActivity

how to call? thanks in advance

Answer 1

If you are on MainActivity and starts the AskLikeQuestionDetailsActivity , it's not guaranteed that MainActivity is still there, as the OS can garbage collect any Activities on background.

If you want change a Fragment on MainActivity after the ask() method is called on AskLikeQuestionDetailsActivity , I would suggest you to do the following:

On MainActivity , instead of calling startActivity to start AskLikeQuestionDetailsActivity , call startActivityForResult and override the onActivityResult method to change the Fragment depending on the result received.

On AskLikeQuestionDetailsActivity 's ask() , call setResult with Activity.RESULT_OK and a configured Intent to send some information back to MainActivity , then call finish() (if you have to exit the AskLikeQuestionDetailsActivity Activity right away).

Is it clear? Hope it helps.

Answer 2

In ask() AskLikeQuestionDetailsActivity:

Intent intent = new Intent(getActivity(), MainActivity.class);
        int condition = 1;
        intent.putExtra("condition", condition);
        startActivity(intent);

In onCreate() MainActivity.class:

Bundle extras = getIntent().getExtras();
    if (extras != null) {
        showQuestions();
    }