我有一个具有相当标准片段布局的应用程序。左侧的可扩展列表视图片段和右侧的面板用于不同的事情，具体取决于用户选择对左侧列表执行的操作（显示数据、添加新数据等）。
我将 LoaderManager（第一次使用加载器）与 CommonWare 的loaderex库一起使用，因为我不需要或不希望为我的数据库创建内容提供程序，这样我就可以使用标准的 CursorLoader。此设置非常适合显示我的列表。
我遇到的问题是当我使用第二个片段将数据添加到数据库时。我无法弄清楚如何在第一个片段中触发重新加载列表。对于我的一生，我无法弄清楚如何从第二个片段的第一个片段中获取加载器，以便它知道需要再次提取数据，我似乎也无法弄清楚如何手动触发重新加载.
由于这是我第一次尝试使用 Loaders，如果我做的不正确，我很乐意（温和地）重新引导到更好的道路上。
片段 1
public class StudentListFragment extends ListFragment implements
LoaderManager.LoaderCallbacks<Cursor> {
private TAOpenHelper mDbHelper = null;
private MyExpandableListAdapter mAdapter = null;
private ExpandableListView lv = null;
private Button addStudentButton;
public static long mRowId = 0;
public SQLiteCursorLoader studentLoader=null;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.leftlistfragment_entry, container,
false);
return v;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
addStudentButton = (Button) getActivity().findViewById(R.id.AddButton);
addStudentButton.setText(getResources().getString(
R.string.button_add_student));
addStudentButton.setOnClickListener(addStudentButtonHandler);
lv = (ExpandableListView) getListView();
mDbHelper = TAOpenHelper.getInstance(getActivity());
fillData();
getLoaderManager().getLoader(-1);
if (studentLoader != null && !studentLoader.isReset()) {
getLoaderManager().restartLoader(-1, null, this);
} else {
getLoaderManager().initLoader(-1, null, this);
}
}
private void fillData() {
mAdapter = new MyExpandableListAdapter(getActivity(), this,
R.layout.listlayout_exp_double_group,
R.layout.listlayout_exp_double_child,
new String[] { TeacherAidDB.STUDENT_FIRST,
TeacherAidDB.STUDENT_LAST }, new int[] {
R.id.ListItem1, R.id.ListItem2 }, new String[] {
TeacherAidDB.CLASS_NAME, TeacherAidDB.CLASS_LEVEL },
new int[] { R.id.ListItem1, R.id.ListItem2 });
lv.setAdapter(mAdapter);
}
public class MyExpandableListAdapter extends SimpleCursorTreeAdapter {
protected final SparseIntArray mGroupMap;
private StudentListFragment mFragment;
public MyExpandableListAdapter(Context context,
StudentListFragment clf, int groupLayout, int childLayout,
String[] groupFrom, int[] groupTo, String[] childrenFrom,
int[] childrenTo) {
super(context, null, groupLayout, groupFrom, groupTo, childLayout,
childrenFrom, childrenTo);
mFragment = clf;
mGroupMap = new SparseIntArray();
}
@Override
protected Cursor getChildrenCursor(Cursor groupCursor) {
int groupPos = groupCursor.getPosition();
int groupId = groupCursor.getInt(groupCursor
.getColumnIndex(TeacherAidDB.CLASS_ROWID));
mGroupMap.put(groupId, groupPos);
Loader<Cursor> loader = getActivity().getLoaderManager().getLoader(
groupId);
if (loader != null && !loader.isReset()) {
getActivity().getLoaderManager().restartLoader(groupId, null,
mFragment);
} else {
getActivity().getLoaderManager().initLoader(groupId, null,
mFragment);
}
return null;
}
public SparseIntArray getGroupMap() {
return mGroupMap;
}
}
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
if (id != -1) { // Child Cursor
studentLoader = new SQLiteCursorLoader(getActivity(), mDbHelper,
TeacherAidDB.STUDENT_LIST_CLASS_QUERY + id, null);
} else { // Group Cursor
studentLoader = new SQLiteCursorLoader(getActivity(), mDbHelper,
TeacherAidDB.STUDENT_LIST_QUERY, null);
}
return studentLoader;
}
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
int id = loader.getId();
if (id != -1) { // Child cursor
if (!data.isClosed()) {
SparseIntArray groupMap = mAdapter.getGroupMap();
int groupPos = groupMap.get(id);
mAdapter.setChildrenCursor(groupPos, data);
}
} else { // Groups cursor
mAdapter.setGroupCursor(data);
}
}
@Override
public void onLoaderReset(Loader<Cursor> arg0) {
mAdapter.changeCursor(null);
}
View.OnClickListener addStudentButtonHandler = new View.OnClickListener() {
public void onClick(View v) {
AddPerson personadd = AddPerson.newInstance(AddPerson.STUDENT, AddPerson.CREATE, mRowId);
getFragmentManager().beginTransaction()
.replace(R.id.rightpane, personadd).commit();
}
};
}
片段 2
public class AddPerson extends Fragment {
public static int STUDENT = 0;
public static int TEACHER = 1;
public static int CREATE = 0;
public static int EDIT = 1;
private int mRowId;
private TAOpenHelper mDbHelper;
private Cursor personedit;
private Button commit;
private Button cancel;
int who;
int what;
long rowId;
static AddPerson newInstance(int type, int action, long rowid) {
AddPerson f = new AddPerson();
Bundle args = new Bundle();
args.putInt("type", type);
args.putInt("action", action);
args.putLong("rowid", rowid);
f.setArguments(args);
return f;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
who = getArguments().getInt("type");
what = getArguments().getInt("action");
rowId = getArguments().getInt("rowid");
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.dialog_person_add, container, false);
mDbHelper = TAOpenHelper.getInstance(getActivity());
if (what == EDIT) {
if (who == STUDENT) {
// Student Edit stuff here
} else {
// Teacher Edit stuff here
}
} else {
if (who == STUDENT) {
// Student Create stuff here
} else {
// Teacher Create stuff here
}
}
// Code to gather data from user goes here
commit = (Button) v.findViewById(R.id.commitbutton);
commit.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
first = firstTxt.getText().toString();
last = lastTxt.getText().toString();
street = streetTxt.getText().toString();
city = cityTxt.getText().toString();
zip = zipTxt.getText().toString();
phone = phoneTxt.getText().toString();
email = emailTxt.getText().toString();
if (what == CREATE) {
processAdd(who);
} else {
processUpdate(who);
}
}
});
cancel = (Button) v.findViewById(R.id.cancelbutton);
cancel.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Fragment check = getFragmentManager().findFragmentById(
R.id.rightpane);
getFragmentManager().beginTransaction().remove(check).commit();
}
});
return v;
}
private void processAdd(int who) {
ContentValues initialValues = new ContentValues();
if (who == STUDENT) {
initialValues.put(TeacherAidDB.STUDENT_FIRST, first);
initialValues.put(TeacherAidDB.STUDENT_LAST, last);
initialValues.put(TeacherAidDB.STUDENT_STREET, street);
initialValues.put(TeacherAidDB.STUDENT_CITY, city);
initialValues.put(TeacherAidDB.STUDENT_STATE, state);
initialValues.put(TeacherAidDB.STUDENT_ZIP, zip);
initialValues.put(TeacherAidDB.STUDENT_PHONE, phone);
initialValues.put(TeacherAidDB.STUDENT_EMAIL, email);
initialValues.put(TeacherAidDB.STUDENT_BDAY, birthday);
// How to get studentLoader from fragment 1?
//studentLoader.insert(TeacherAidDB.STUDENT_TABLE, null, initialValues);
}
}
}