如何在Android中使用两个游标和CursorJoiner在LoaderManager [英] How to use two Cursors and CursorJoiner in LoaderManager in android

问题描述

我有一个 的ContentProvider ，它有两个表1 OnlineContacts 2 AllContacts 。然后，我有一个方法，其中我查询两个表和分别得到他们得到的游标。然后加入他们使用的 CursorJoiner 并制作的 联系人列表 。通过这个列表，我的 CustomAdapter扩大BaseAdapter ，我填充我的列表视图。像：

I have a ContentProvider, it's having two tables 1. OnlineContacts 2. AllContacts. Then i have a method in which i am querying both the tables and getting their resultant cursors separately. And then joining them using CursorJoiner and making a list of Contacts. Passing this list to my CustomAdapter extending BaseAdapter, i am populating my listview. Like :

public static List<Contact> getContacts(Context context){
    List<Contact> contactList = new ArrayList<Contact>(); 

// Getting First Cursor
    String URL = xyz;
    Uri baseUri1 = Uri.parse(URL);
    String[] select = xyz; 
    String where =xyz; 
    Cursor cursor =  context.getContentResolver().query(baseUri1, select, where, null, "pid");

// Getting 2nd Cursor
    Uri baseUri = xyz; 
    String[] projection =xyz; 
    String selection =xyz; 
    String[] selectionArgs = null;
    String sortOrder = xyz; 

    Cursor mCursor= context.getContentResolver().query(baseUri, projection, selection, selectionArgs, sortOrder);

    // Joinging Both Cursors

    CursorJoiner joiner = new CursorJoiner(cursor, new String[] {MyContentProvider.PHONE_ID} , mCursor, new String[] {MyContentProvider.Phone._ID});
    for (CursorJoiner.Result joinerResult : joiner) {
        Contact cont = new Contact();

        switch (joinerResult) {
        case LEFT:
            // handle case where a row in cursorA is unique
            break;
        case RIGHT:
            // handle case where a row in cursorB is unique

        case BOTH:
            // handle case where a row with the same key is in both cursors
            cont.setID(xyz);
            cont.setName(xyz);
            cont.setPhoneNumber(xyz);
            cont.setStatus("0");
            contactList.add(cont);
            break;
        }
    }
    mCursor.close();
    cursor.close();
    return contactList;
}   

和这里是我的 CustomAdapter

private class CustomAdapter extends BaseAdapter {

        List<Contact> contactsList ;
        public CustomAdapter(List<Contact> contactsList){
            this.contactsList = contactsList;
        }

        public List<Contact> contacts() {
            return this.contactsList;    
        }

        @Override
        public int getCount() {
            return contactsList.size();
        }

        @Override
        public Contact getItem(int arg0) {
            return contactsList.get(arg0);
        }

        @Override
        public long getItemId(int arg0) {
            return arg0;
        }

        @Override
        public View getView(int position, View view, ViewGroup viewGroup) {

            SimpleViewHolder viewHolder;
            if(view==null)
            {
                LayoutInflater inflater = (LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                view = inflater.inflate(R.layout.list_item, viewGroup,false);
                viewHolder = new SimpleViewHolder(view);
                view.setTag(viewHolder);
            }

            viewHolder = (SimpleViewHolder) view.getTag();

            TextView contName = (TextView) viewHolder.get(R.id.nameText);
            ImageView image = (ImageView) viewHolder.get(R.id.contact_image);

            Contact contact = contactsList.get(position);
            image.setBackgroundResource(R.drawable.person_empty_offline);

            contName.setText(contact.getName());
            return view;
        }

    }   

现在，我需要用做 LoaderManager 。我知道，在一定程度上，它的实施。我知道，在 onCreateLoader 行为，如：

Now , i need to do it using LoaderManager. I know , to some extent, the implementation of it. I know , the onCreateLoader acts like:

    public Loader<Cursor> onCreateLoader(int id, Bundle args) {

        Uri baseUri = xyz;
        String[] projection =  xyz;
        String selection =  xyz;
        String[] selectionArgs = null;
        String sortOrder =  xyz;
        return  new CursorLoader(getActivity(), baseUri, projection, selection, selectionArgs, sortOrder);
}

而在的OnCreate ，如果我使用 MyCursorAdapter延伸的CursorAdapter ，我们做的事这样的：

And in OnCreate , if i use MyCursorAdapter extending CursorAdapter, we do something like :

mAdapter = new MyCursorAdapter(getActivity(), null, 0);
        setListAdapter(mAdapter);
        getLoaderManager().initLoader(0, null, this);

现在，我需要做的是利用我怎么能achive上述实施 LoaderManager 。我不知道该怎么问这就是为什么它太解释。

Now, i need to do is how can i achive the above implementation using LoaderManager. I didn't know how to ask thats why its too explanatory.

推荐答案

用两个装载机，每个光标。当一方完成装载，调用另一个方法是将加入他们，如果双方都加载。

Use two loaders, one for each cursor. When either one finishes loading, call another method that will join them if both have loaded.

// Loader IDs. You could also generate unique R.id values via XML
private static final int LOADER_ID_CURSOR_1 = 1;
private static final int LOADER_ID_CURSOR_2 = 2;

private Cursor cursor1 = null;
private Cursor cursor2 = null;

// return loader for cursor 1
private CusorLoader getCursor1Loader() {
    Uri uri = Uri.parse(abc);
    String[] select = abc; 
    String where = abc;
    String[] whereArgs = abc;
    String sortOrder = abc;
    return new CursorLoader(uri, select, where, whereArgs, sortOrder);
}

// return loader for cursor 2
private CusorLoader getCursor2Loader() {
    // same as above but with different values
    return new CursorLoader(uri, select, where, whereArgs, sortOrder);
}

// to start loading, ...
LoaderManager lm = getLoaderManager();
lm.initLoader(LOADER_ID_CURSOR_1, null, this);
lm.initLoader(LOADER_ID_CURSOR_2, null, this);

// LoaderCallbacks implementations
@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    switch(id) {
    case LOADER_ID_CURSOR_1:
        return getCursor1Loader();
    case LOADER_ID_CURSOR_2:
        return getCursor2Loader();
    }
}

@override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
    switch(loader.getId()) {
    case LOADER_ID_CURSOR_1:
        cursor1 = data;
        joinCursors();
        break;
    case LOADER_ID_CURSOR_2:
        cursor2 = data;
        joinCursors();
        break;
    }
}

private void joinCursors() {
    if (cursor1 != null && cursor2 != null) {
        // use CursorJoiner here
    }
}

这篇关于如何在Android中使用两个游标和CursorJoiner在LoaderManager的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！