Question

默认情况下，listview片段将在我的活动中显示为第一个

这是我的活动：

public class SecondActivity extends FragmentActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        FragmentManager manager = getFragmentManager();
        FragmentTransaction tran = manager.beginTransaction();
        ListViewFragment fr = new ListViewFragment();
        Bundle bundle = new Bundle();
        bundle.putParcelable("Object", getIntent().getParcelableExtra("ObjectFromCategory"));
        fr.setArguments(bundle);
        tran.addToBackStack(null);
        tran.replace(R.id.places_fragment_cointainer, fr, "ListView");
        tran.commit();
        //handleFragmentCycle();
    }

然后在ListviewFragment中我得到参数：

public class ListViewFragment extends Fragment implements OnClickListener {
    private TextView mTxtMapView;
    private Category mObject;


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        View v = inflater.inflate(R.layout.fragment_places_listview, container,false);
        mTxtMapView = (TextView)v.findViewById(R.id.txt_mapview);
        mObject = getArguments().getParcelable("Object");
        Toast.makeText(getActivity(), mObject.getText(), Toast.LENGTH_LONG).show();
        mTxtMapView.setOnClickListener(this);
        return v;
    }

这是我的MapViewFragment：

public class MapViewFragment extends Fragment implements OnClickListener {

    TextView txtListView;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        View v = inflater.inflate(R.layout.fragment_places_mapview, container, false);
        FragmentManager fm = getChildFragmentManager();
        MapFragment supportMapFragment = MapFragment.newInstance();
        fm.beginTransaction().replace(R.id.mapwhere, supportMapFragment).commit();
        txtListView = (TextView) v.findViewById(R.id.txt_listview);
        txtListView.setOnClickListener(this);
        return v;

    }

第一次创建ListViewFragment时，我可以成功获取参数，但是当我更改为MapViewFragment然后更改回ListViewFragment时我得到null。我找出了一个解决方案，我应该在bundle中传递一个int值来检测ListViewFragment是从Activity还是MapViewFragment创建的。但我不认为这是一个很好的解决方案因为我仍然想要获得类别目标，所以我想听听是否有人有更好的解决方案。谢谢！

Answer 1

您可以使用活动中的gjson将对象存储到SharePreference 然后在Fragment中，您从SharePreference检索对象。之后，您永远不会在null

中获得Fragment个对象

===
这是从SharePreference中保存和检索对象的方法的创建

SharedPreferences mPrefs = getPreferences(MODE_PRIVATE);//Creating shared preference

对于保存对象

Editor prefsEditor = mPrefs.edit(); Gson gson = new Gson(); String json = gson.toJson(myObject); // myObject - instance of MyObject prefsEditor.putString("Object", json); prefsEditor.commit();

用于检索对象

Gson gson = new Gson(); String json = mPrefs.getString("Object", ""); MyObject obj = gson.fromJson(json, MyObject.class);

当片段创建视图第二次时，getArgument得到nullexception

1 个答案: