How to pre-load a fragment before showing?

问题

In my activity I have several fullscreen fragments, each of them downloads some data from web (using an async task) and shows them to the user. The fragments are showed one at a time.

To be more specific, each of the fragment readings some urls from a sqlite database, and fetch the content before showing them in a list, if that matters. The data loading tasks can be done in the OnCreate() function.

I would like to preload all the fragment (at least starting the downloading), when I show a splash screen. Pretty much like a viewpager preload its fragments.

I am wondering how to achieve this? I tried initialize/create all the fragments in the OnCreate() function of my activity, hoping the OnCreate() of fragments could be called earlier, but the OnCreate() and OnCreateView() function of the fragments are not called until a fragment is about to show to the user.

回答1:

It sounds like you need to separate your model (the data which is downloaded) from your view (the fragments). One way to do this is to start the downloading AsyncTasks in your activity, rather than starting them in each fragment. Then when the fragments are eventually displayed they can show the data which has been downloaded (or a spinner or some other indication that the download process is still executing).

回答2:

Fragment's onActivityCreated(Bundle) tells the fragment that its activity has completed its own Activity.onCreate().

So your solution to this problem is initialize or create or do your stuffs which you want to preload before fragments are created, inside your Fragment's onActivityCreated(Bundle)

see documents for fragment's lifecyle

回答3:

The earliest pace you can start loading is either in a static singleton or in the Application Class

回答4:

What I end up doing is the following, (1) add all the fragments into the container. So they (and their view) will be created and initialized. (2) hide those not in use and only show the one I would like the user to see. (3) use FragmentTrasaction.show()/FragmentTrasaction.hide() to manipulate the visibility instead of FragmentTrasaction.add() or FragmentTrasaction.replace().

If you following this approach, be warn that all the fragments will be cached in memory. But the benefit is the switch between fragment will be fast and efficient.

回答5:

I was facing the same problem and then I used this method, suppose we are having an EditText in the fragment, then we can use codes like this

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {

    //this method allows you to input or instantiate fragments before showing this to an activity conidering id is "editTextEditProfileFirstName"
    EditText firstName = (EditText) getActivity().findViewById(R.id.editTextEditProfileFirstName);

    firstName.setText("This is my first name", TextView.BufferType.EDITABLE);
    super.onViewCreated(view, savedInstanceState);
}

来源：https://stackoverflow.com/questions/25634709/how-to-pre-load-a-fragment-before-showing

标签

android

fragment