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I am new to Android and this is my second app. I am creating a tabbed activity where the first fragment has a form to create a new task, the second fragment has the list of all the saved tasks, and the third fragment will show the comments on a task when selected from the list in the second fragment. The third fragment is also supposed to act like a chat activity which posts comments when you type them in and tap the send button. When I implement this chat activity from a separate Activity (CommentsActivity.java in the GitHub branch in the link below), the app runs absolutely as it is supposed to. However, when I try to implement the same code from the third Fragment, I have the following problems:

  • I have to tap the list item (in TasksFragment.java) twice before the CommentsFragment is launched.

  • The fragment remains blank and shows no details or comments.

  • The title bar is messed up. It does set the title correctly when CommentsFragment is launched for the first time. However, it becomes blank subsequently, when I swipe between the fragments . Sometimes it even shows the title of the last open fragment instead of the one currently open.

You can find all my code here: https://github.com/geekskool/android-teamwork/tree/only_fragments

Other details: I am passing the data between the TasksFragment and the CommentsFragment with fragment interaction methods that interact with the main activity--AddTask.java. This is the only way I know of. If there is a better way, please let me know.

Ishita Sinha
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1 Answers1

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I saw your branch and noticed that you are using a ViewPager and trying to use FragmentTransaction to update the fragments inside the ViewPager. This does not work as the fragments will already have been created when the ViewPagerAdapter is created and cannot be attached to the ViewPager through a FragmentTransaction.

Here is how I solved it. Since I was using a ViewPager, using FragmentTransaction as below did not work:

Wrong way:

FragmentManager fm = getSupportFragmentManager();
android.support.v4.app.FragmentTransaction ft = fm.beginTransaction();
CommentsFragment commentsFragment = CommentsFragment.newInstance(mTaskId, mTaskName);
ft.replace(R.id.container, commentsFragment);
ft.addToBackStack(null);
ft.commit();

With the ViewPager, I had to update the adapter populating it and then set it to the correct fragment. This is what I did:

Right way:

In the onListItemClick() in the TasksFragment, call this interface method onFragmentInteraction. And then in the main activity AddTask, implement it as below:

@Override
public void onFragmentInteraction(String taskId, String taskName, String assigneeRef) { 
    CommentsFragment commentsFragment = CommentsFragment.newInstance(taskId, taskName);
    mSectionsPagerAdapter.fragmentList.remove(2);
    mSectionsPagerAdapter.fragmentList.add(commentsFragment);
    mSectionsPagerAdapter.notifyDataSetChanged();
    mViewPager.setCurrentItem(2);
}

Hope this helps you and someone else who faces a problem with updating Fragments inside a ViewPager.