Android片段显示和隐藏

Question

I tried to create a ProgressFragment to be used in the whole application:

public class ProgressFragment extends Fragment {
    private static final String KEY = "info";
    private CustomProgressView mProgress;


    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View root = inflater.inflate(...);
        mProgress = (CustomProgressView) root.findViewById(...);
        mProgress.start();
        if (getArguments() != null) {
            mProgress.setText(getArguments().getString(KEY, ""));
        }
        return root;
    }

    public void setInformation(String text) {
        if (mProgress != null) {
            if (this.isHidden()) {
                show(getActivity().getSupportFragmentManager());
            }
            mProgress.setText(text);
        } else {
            Bundle b = new Bundle();
            b.putString(KEY, text);
            setArguments(b);
        }
    }

    public void hide(FragmentManager fm) {
        FragmentTransaction ft = fm.beginTransaction();
        ft.hide(this);
        ft.commit();
    }
    private void show(FragmentManager fm) {
        FragmentTransaction ft = fm.beginTransaction();
        ft.show(this);
        ft.commit();
    }
}

The ProgressFragment is expected to attached(added) to the activity once, and there should be only one instance, then the client should only update its' information or hide it.

Usage in client(activity):

class MainActivity...{
    ProgressFragment mFragment;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mFragment = ProgressFragment.newInstance(null);
        FragmentTransaction fs = getSupportFragmentManager().beginTransaction();
        fs.add(id, mFragment);
        fs.commit();
    }

    //close the progress
    mFragment.hide()


    //show the progress 
    mFragment.setInformation("..")
}

However it does not worked as expected, sometime the progress view will show only at the first call or it does not even show.

Did I miss anything?

Answer 1

• Don't set your onCreateView as @Nullable ;
• Use commitAllowingStateLoss() ;

• Instead of just add() , use addToBackStack() . When you want to close it, just use the FragmentManager popBackStack() :

   getActivity().getSupportFragmentManager().popBackStack();