Fragment is transparent and shows Activity below

问题:

My Android application launches into BeginActivity which is a subclass of SherlockFragmentActivity and shows it's first view using:

@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        if (getSupportFragmentManager().findFragmentById(android.R.id.content) == null) {
            Fragment f = LoginFragment.newInstance();

            getSupportFragmentManager()
                    .beginTransaction()
                    .add(android.R.id.content, f, "loginfragment")
                    .attach(f)
                    .commit();
        }
}

LoginFragment shows a view like this:

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        super.onCreateView(inflater, container, savedInstanceState);
        // Inflate the layout for this fragment
        View v = inflater.inflate(R.layout.login, container, false);

        // Get pointers to text views
        usernameField = (EditText) v.findViewById(R.id.usernameLog);
        passwordField = (EditText) v.findViewById(R.id.passwordLog);
        progressBar = (ProgressBar) v.findViewById(R.id.progressBarLog);
        // Set button click listeners for both buttons
        Button b = (Button) v.findViewById(R.id.loginButton);
        b.setOnClickListener(this);

        return v;
    }

when clicking login I show a list view like this:

BeginActivity top = (BeginActivity) getActivity();
Fragment f = OfferListFragment.newInstance();
        top.getSupportFragmentManager()
                .beginTransaction()
                .add(android.R.id.content, f, "offerList")
                .addToBackStack(f.getClass().getSimpleName())
                .commit();

and finally, OfferListFragment displays its view like this:

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View v = inflater.inflate(R.layout.offers, container, false);

        return v;
    }

Now the problem I am having, is that the final OfferListFragment seems to be transparent and I can see the login screen below it. I am using Theme.Sherlock that has a black background. Should I be manually setting the views backgrounds to black also? Or would the black in the theme be customisable by the user on the system? (I'm not an Android user).

Thanks

回答1:

Try using FragmentTransaction class to replace the fragments instead of just adding.

Explanation:

Each transaction is a set of changes that you want to perform at the same time. You can set up all the changes you want to perform for a given transaction using methods such as add(), remove(), and replace(). Then, to apply the transaction to the activity, you must call commit().

Before you call commit(), however, you might want to call addToBackStack(), in order to add the transaction to a back stack of fragment transactions. This back stack is managed by the activity and allows the user to return to the previous fragment state, by pressing the Back button.

For example, here's how you can replace one fragment with another, and preserve the previous state in the back stack:

Example:

// Create new fragment and transaction
Fragment newFragment = new ExampleFragment();
FragmentTransaction transaction = getFragmentManager().beginTransaction();

// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack
transaction.replace(R.id.fragment_container, newFragment);
transaction.addToBackStack(null);

// Commit the transaction
transaction.commit();

Reference: Please have a look at Managing Fragments

I hope it will be helpful !!

回答2:

IMHO I do not agree with this answer.

You may want to replace your fragment or you may want to add it.

For example let's say that you are in a fragment that is a list retrieved by a network request, if you replace the fragment with let's say the detailFragment and you add it to backStack.

When you go back your fragment will redo the network query, of course you can cache it but why? It is a back to a previous state, so with add the last fragment will be in exactly the same status with no code whatsoever.

Fragments are transparent backgrounded by default because they can be used to paint only a small portion of the screen but if your fragment is match_parent then just set its background to a color and keep using add on the fragmentTransaction.

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/scrollView1"
android:background="@android:color/white"
android:layout_width="match_parent"
android:layout_height="wrap_content" >

That will be your root element on the fragment layout XML, could be linear, etc etc and the transaction code is:

YourFragment detail = YourFragment.newInstance(Id);
ft.add(R.id.contentHolder, detail);
ft.addToBackStack(TAG);
ft.commit();

Hope this helps someone that wants to know how to see a solid background without changing the add to replace which is usually not the best case.

Regards

回答3:

i used many techniques but no gain Finally i fixed it by adding background of the container or the fragment layout like this

android:background="@android:color/white"    

you just need to add in your Layout or the container view of you Fragment Hope it will help