我在主要 Activity 中创建了一个方法，该方法将 ArrayList Bundle 发送到我的 Fragment 类，但是当我尝试在 Fragment 中获取预期值时，我的 fragment 中声明的 ArrayList 为 null。有人可以帮我 checkin 我的代码吗？
主要 Activity .java: sendBundleData() 是 MainActivity 中用于将 ArrayList 包发送到 fragment 的方法
public class MainActivity extends AppCompatActivity {
private ActionBarDrawerToggle toggle;
private DrawerLayout drawerLayout;
private ListView lv;
private String[] arrValues;
private ArrayAdapter<String> adapter;
DBHelper helper;
public ArrayList<Bible> _bibleValues;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
/** Instance of DBHelper */
helper = new DBHelper(MainActivity.this);
/** Getting arraylist values from the DBHelper */
try {
_bibleValues=helper.queryData();
} catch (SQLException e) {
e.printStackTrace();
}
/** Initialize drawer layout */
drawerLayout= (DrawerLayout) findViewById(R.id.drawerLayout_bibledashboard);
//Getting the values of the String resources to the array
arrValues=getApplicationContext().getResources().getStringArray(R.array.verse_chapter);
//Setting the needed parameters in an Array Adapter
adapter= new ArrayAdapter<>(this,android.R.layout.simple_list_item_1,arrValues);
lv= (ListView) findViewById(R.id.listview_verseTitle);
lv.setAdapter(adapter);
//Specify the OnItemCLick listener in the Listview
lv.setOnItemClickListener(new DrawerItemClickListener());
if (savedInstanceState == null){
selectItem(0);
}
/** CHeck if we can createDatabase */
try {
helper.createDatabase();
}catch (IOException e) {
e.printStackTrace();
throw new Error("Unable to Create Database");
}
/** CHeck to open the database created */
try {
helper.openDatabase();
}catch (SQLException e) {
e.printStackTrace();
throw new Error("Unable to open Database");
}
Log.d("Database Creation","Success");
/** Display Sample Data Query in DATABASE
try {
verseList=helper.queryData();
verseAdapter= new VerseAdapter(this,verseList);
} catch (SQLException e) {
e.printStackTrace();
} */
/** Setting up DrawerToggle */
toggle= new ActionBarDrawerToggle(this,drawerLayout,R.string.drawer_opened,R.string.drawer_closed) {
@Override
public void onDrawerOpened(View drawerView) {
super.onDrawerOpened(drawerView);
invalidateOptionsMenu();
}
@Override
public void onDrawerClosed(View drawerView) {
super.onDrawerClosed(drawerView);
invalidateOptionsMenu(); /** ENd of Coding */
}
}; //end of toggle '}'
drawerLayout.addDrawerListener(toggle);
/** Enabling ActionbarDrawer toggle */
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
} /** End of OnCreate */
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
toggle.onConfigurationChanged(newConfig);
}
@Override
protected void onPostCreate(@Nullable Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
toggle.syncState();
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (toggle.onOptionsItemSelected(item)) {
}
return true;
}
/** Method for sending Bundle of arraylist to the Fragments*/
public void sendBundleData() {
GenesisFragment gFragment= new GenesisFragment();
Bundle args= new Bundle();
args.putParcelableArrayList("verseValues",_bibleValues); /** Make the Object class Parcelable 1st */
gFragment.setArguments(args);
}
private class DrawerItemClickListener implements ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectItem(position);
}
}
private void setActionBarTitles(int position) {
String title;
if (position==0) {
title="Genesis";
}else {
title=arrValues[position];
}
getSupportActionBar().setTitle(title);
}
private void selectItem(int position) {
Fragment fragment;
switch (position) {
case 0:
fragment= new GenesisFragment();
sendBundleData();
break;
default:
fragment=new GenesisFragment();
break;
}
FragmentTransaction ft= getFragmentManager().beginTransaction();
ft.replace(R.id.bible_screenlayout,fragment);
ft.addToBackStack(null);
ft.commit();
setActionBarTitles(position);
drawerLayout.closeDrawer(lv);
}
我的 fragment 类: 在 fragment 的 onCreate 方法中，我尝试检索包
public class GenesisFragment extends Fragment {
ListView lv;
ArrayList<Bible> verseList;
VerseAdapter verseAdapter;
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
Log.d("ON ATTACH","onAttache method!");
}
/** @Override */
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d("ON CREATE","onCreate");
Bundle bundle=getArguments();
verseList= new ArrayList<>();
verseList=bundle.getParcelableArrayList("verseValues"); //retrieving bundles in the MainActivity
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
verseAdapter= new VerseAdapter(getActivity(),verseList);
// Inflate the layout for this fragment
View v= inflater.inflate(R.layout.fragment_genesis, container, false);
return v;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
lv=(ListView)getActivity().findViewById(R.id.listview_genesis);
lv.setAdapter(verseAdapter);
verseAdapter.notifyDataSetChanged();
}
}
最佳答案
这是因为您在 sendBundleData() 中将参数设置为不同的 fragment 实例并替换了一个单独的实例
将 fragment 作为参数传递给方法
public void sendBundleData(Fragment fragment) {
Bundle args= new Bundle();
args.putParcelableArrayList("verseValues",_bibleValues); /** Make the Object class Parcelable 1st */
fragment.setArguments(args);
}
你的 switch case 看起来像
switch (position) {
case 0:
fragment= new GenesisFragment();
sendBundleData(fragment);
break;
default:
fragment=new GenesisFragment();
break;
}
关于java - fragment 中传递的 Arraylist 为空，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/38700042/