使用notifyDataSetChanged（）

Question

从Fragment呼叫Activity，我正在显示ListView个Buttons。当我点击menu_item（即在线显示）时，我正在更新数据，因此ListView。现在我需要反映更新的数据。单击“在线显示”后，如何刷新Fragment。直到现在，我使用了以下代码：

Intent intent = getIntent();
Intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
finish();
startActivity(intent);

但这会重新启动整个Activity。我只需要刷新当前Fragment。

enter image description here

已编辑：已添加代码

ACTIVITY CLASS

    public class ContactListActivity extends ActionBarActivity {

    ListView listView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        final ActionBar actionBar = getActionBar();
        MenuButtonUtil.enableMenuButton(this);

        FragmentManager fragmentManager = getFragmentManager();

        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

        MyContactsFragment contactListFragment = new MyContactsFragment ();
        fragmentTransaction.replace(android.R.id.content, contactListFragment);
        fragmentTransaction.commit();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == R.id.show_online) {
            ContentValues values = new ContentValues();
            String where = "((" + ContactsContentProvider.PHONE_ID + " NOTNULL) AND ((" +
                       ContactsContentProvider.PHONE_ID+ " = 17486 )OR (" +
                       ContactsContentProvider.PHONE_ID+ " = 17494 )))";

            values.put(ContactsContentProvider.STATUS, true);
            this.getContentResolver().update(ContactsContentProvider.CONTENT_URI, values, where, null);

            listView = (ListView) this.findViewById(android.R.id.list);
            ((BaseAdapter) listView.getAdapter()).notifyDataSetChanged();

            return true;
        }
        return super.onOptionsItemSelected(item);
    }

}

片段

public class MyContactsFragment extends ListFragment{

Button allContactsBtn;
Button neeoContactsBtn;
ListView listView;
CustomAdapterForAllContacts adapterForAllContacts;
CustomAdapterForNeeoContacts adapterForNeeoContacts;

@Override
public void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    final ActionBar actionBar = getActivity().getActionBar();
    MenuButtonUtil.enableMenuButton(getActivity());
    adapterForNeeoContacts = new CustomAdapterForNeeoContacts();
    adapterForAllContacts = new CustomAdapterForAllContacts();
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {

    View view = inflater.inflate(R.layout.contactsfragment, container,false);

    allContactsBtn = (Button) view.findViewById(R.id.allContactsButton);
    neeoContactsBtn = (Button) view.findViewById(R.id.neeoContactsButton);
    listView = (ListView) view.findViewById(android.R.id.list);


    // ==================== Neeo Contacts ============================
    neeoContactsBtn.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            listView.setAdapter(adapterForNeeoContacts);

        }
    });

    // ====================== All Contacts =============================

    allContactsBtn.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            listView.setAdapter(adapterForAllContacts);
        }
    });

    return view;
}

适配器：

private class CustomAdapterForAllContacts extends BaseAdapter {

public CustomAdapterForAllContacts(){

}
    List<Contact> contactsList = getAllContacts();
    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return contactsList.size();
    }

    @Override
    public Contact getItem(int arg0) {
        // TODO Auto-generated method stub
        return contactsList.get(arg0);
    }

    @Override
    public long getItemId(int arg0) {
        // TODO Auto-generated method stub
        return arg0;
    }

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

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

        TextView contName = (TextView)view.findViewById(R.id.nameText);
        TextView contNumber = (TextView)view.findViewById(R.id.numberText);
        ImageView image = (ImageView)view.findViewById(R.id.contact_image);

        Contact contact = contactsList.get(position);

        String status = contact.getStatus();

        if(contact.getStatus().equals("1")){
            image.setBackgroundResource(com.example.mycontentprovider.R.drawable.person_empty_online);
        }else{
            image.setBackgroundResource(com.example.mycontentprovider.R.drawable.person_empty_offline);
        }

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

    public Contact getContactPosition(int position)
    {
        return contactsList.get(position);
    }
    public List<Contact> getAllContacts(){

        List<Contact> contactList = new ArrayList<Contact>(); 

        String URL = "content://com.example.provider.Contacts/contacts";
        Uri baseUri1 = Uri.parse(URL);
        String[] select = {ContactsContentProvider.PHONE_ID, ContactsContentProvider.STATUS};

        String where = "((" + ContactsContentProvider.NEEO_USER + " NOTNULL) AND (" +
                                                   ContactsContentProvider.NEEO_USER+ " = 1 )AND (" +
                                                   ContactsContentProvider.STATUS+ " = 1 ))";

        Cursor cursor =  getActivity().getContentResolver().query(baseUri1, select, where, null, "pid");

        for(cursor.moveToFirst(); cursor.moveToNext(); cursor.isAfterLast()) {
            Log.w("Filtered IDS",""+ cursor.getString(cursor.getColumnIndex(ContactsContentProvider.PHONE_ID))+
                    ""+ cursor.getString(cursor.getColumnIndex(ContactsContentProvider.STATUS)));
        }


        Uri baseUri = ContactsContract.CommonDataKinds.Phone.CONTENT_URI;

        String[] projection = new String[] {
                ContactsContract.CommonDataKinds.Phone._ID,
                ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME,
                ContactsContract.CommonDataKinds.Phone.NUMBER};

        String selection = "((" + 
                ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME + " NOTNULL) AND (" +
                ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME + " != ' ' ))";

        String[] selectionArgs = null;
        String sortOrder = ContactsContract.CommonDataKinds.Phone._ID + " COLLATE LOCALIZED ASC";

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

        // Joinging Both Cursors
                CursorJoiner joiner = new CursorJoiner(cursor, new String[] {ContactsContentProvider.PHONE_ID} , mCursor, new String[] {ContactsContract.CommonDataKinds.Phone._ID});
                for (CursorJoiner.Result joinerResult : joiner) {
                    Contact cont = new Contact();
                    Log.e("Result", joinerResult.toString());
                    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
                        cont.setID(mCursor.getString(mCursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone._ID)));
                        cont.setName(mCursor.getString(mCursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME)));
                        cont.setPhoneNumber(mCursor.getString(mCursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER)));
                        cont.setStatus("0");
                        contactList.add(cont);
                        break;
                    case BOTH:
                        // handle case where a row with the same key is in both cursors
                        cont.setID(mCursor.getString(mCursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone._ID)));
                        cont.setName(mCursor.getString(mCursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME)));
                        cont.setPhoneNumber(mCursor.getString(mCursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER)));
                        cont.setStatus(cursor.getString(cursor.getColumnIndex(ContactsContentProvider.STATUS)));
                        contactList.add(cont);
                        break;
                    }
                }
                mCursor.close();
                cursor.close();
        return contactList;
    }
}

Answer 1

根据您ListView和Adapter的具体实施方式，您有多种方法可以解决此问题。

致电notifyDataSetChanged()
重置Adapter

使用notifyDataSetChanged（）

这是最佳解决方案，但您需要修改List正在使用的Adapter才能生效。例如，如果您使用ArrayAdapter，请执行以下操作：

String[] dataSource = new String[] {
    "A", "B", "C", ...
};

ArrayAdapter<String> adapter = new ArrayAdapter<String>(context, R.layout.example, dataSource);

正如您所看到的，String[]是Adapter的dataSource。我们可以像这样修改数组，但这些更改不会立即反映在ListView：

dataSource[0] = "some new String value";

只有在我们致电notifyDataSetChanged()后，ListView才会更新：

adapter.notifyDataSetChanged();

来自documentation：

public void notifyDataSetChanged（）

通知附加的观察者基础数据已经存在   已更改，任何反映数据集的视图都应自行刷新。

但是不要将notifyDataSetChanged()与notifyDataSetInvalidated()混淆，因为notifyDataSetInvalidated()做了一些完全不同的事情，只会弄乱你的ListView。

来自documentation：

public void notifyDataSetInvalidated（）

通知附加的观察者不再有基础数据   有效或可用。一旦被调用，该适配器就不再有效了   不应该报告进一步的数据集更改。

通过重置`Adapter`

这很简单。每次设置新Adapter时，ListView都会自行更新。如果您出于某种原因无法使用notifyDataSetChanged()，那么您必须这样做。每次要更新Adapter时，只需创建一个新的ListView：

ArrayAdapter<String> adapter = new ArrayAdapter<String>(context, R.layout.example, newData);

并使用setAdapter()将其设置为ListView：

listView.setAdapter(adapter);

这将始终更新ListView，但此解决方案存在一些问题。首先，每当您以这种方式更新ListView时，它会滚动回到顶部，当频繁更新或ListView中有大量内容时，这可能非常烦人。

修改

您的代码中有一些不太理想的东西。首先，您的Adapter不应包含下载联系人的代码。它不属于那里，Adapter的唯一责任应该是他从给定的数据源创建Views。首先，您应该将getAllContacts()方法移到Adapter之外。我建议你为此创建静态帮助方法，我冒昧地相应地修改你的代码：

public class ContactsHelper { public static List<Contact> getAllContacts(Context context) { List<Contact> contactList = new ArrayList<Contact>(); String URL = "content://com.example.provider.Contacts/contacts"; Uri baseUri1 = Uri.parse(URL); String[] select = {ContactsContentProvider.PHONE_ID, ContactsContentProvider.STATUS}; String where = "((" + ContactsContentProvider.NEEO_USER + " NOTNULL) AND (" + ContactsContentProvider.NEEO_USER + " = 1 )AND (" + ContactsContentProvider.STATUS + " = 1 ))"; Cursor cursor = context.getContentResolver().query(baseUri1, select, where, null, "pid"); for (cursor.moveToFirst(); cursor.moveToNext(); cursor.isAfterLast()) { Log.w("Filtered IDS", "" + cursor.getString(cursor.getColumnIndex(ContactsContentProvider.PHONE_ID)) + "" + cursor.getString(cursor.getColumnIndex(ContactsContentProvider.STATUS))); } Uri baseUri = ContactsContract.CommonDataKinds.Phone.CONTENT_URI; String[] projection = new String[]{ ContactsContract.CommonDataKinds.Phone._ID, ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME, ContactsContract.CommonDataKinds.Phone.NUMBER}; String selection = "((" + ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME + " NOTNULL) AND (" + ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME + " != ' ' ))"; String[] selectionArgs = null; String sortOrder = ContactsContract.CommonDataKinds.Phone._ID + " COLLATE LOCALIZED ASC"; Cursor mCursor = context.getContentResolver().query(baseUri, projection, selection, selectionArgs, sortOrder); // Joinging Both Cursors CursorJoiner joiner = new CursorJoiner(cursor, new String[]{ContactsContentProvider.PHONE_ID}, mCursor, new String[]{ContactsContract.CommonDataKinds.Phone._ID}); for (CursorJoiner.Result joinerResult : joiner) { Contact cont = new Contact(); Log.e("Result", joinerResult.toString()); 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 cont.setID(mCursor.getString(mCursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone._ID))); cont.setName(mCursor.getString(mCursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME))); cont.setPhoneNumber(mCursor.getString(mCursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER))); cont.setStatus("0"); contactList.add(cont); break; case BOTH: // handle case where a row with the same key is in both cursors cont.setID(mCursor.getString(mCursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone._ID))); cont.setName(mCursor.getString(mCursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME))); cont.setPhoneNumber(mCursor.getString(mCursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER))); cont.setStatus(cursor.getString(cursor.getColumnIndex(ContactsContentProvider.STATUS))); contactList.add(cont); break; } } mCursor.close(); cursor.close(); return contactList; } }

使用此代码，您可以获得以下所有联系人：

List<Contact> contacts = ContactsHelper.getAllContacts(getActivity());

在此之后，我们需要修改您的Adapter，以便notifyDateSetChanged()能够正常工作：

private class CustomAdapterForAllContacts extends BaseAdapter { private final List<Contact> contactsList; private final LayoutInflater inflater; public CustomAdapterForAllContacts(Context context, List<Contact> contacts) { this.inflater = LayoutInflater.from(context); this.contactsList = contacts; } @Override public int getCount() { return contactsList.size(); } @Override public Contact getItem(int position) { return contactsList.get(position); } @Override public long getItemId(int position) { return position; } // We expose the List so we can modify it from outside public List<Contact> contacts() { return this.contactsList; } private class SimpleViewHolder { private final SparseArray<View> viewArray = new SparseArray<View>(); private final View convertView; public SimpleViewHolder(View convertView) { this.convertView = convertView; } public View get(int id) { View view = this.viewArray.get(id, null); if(view == null) { view = this.convertView.findViewById(id); this.viewArray.put(id, view); } return view; } } @Override public View getView(int position, View convertView, ViewGroup viewGroup) { // By implementing the view holder pattern you only need to perform // findViewById() once. This will improve the performance of `ListView` // and reduce lag. SimpleViewHolder viewHolder; if (convertView == null) { convertView = this.inflater.inflate(R.layout.list_item, viewGroup, false); viewHolder = new SimpleViewHolder(convertView); convertView.setTag(viewHolder); } viewHolder = (SimpleViewHolder) convertView.getTag(); TextView contName = (TextView) viewHolder.get(R.id.nameText); TextView contNumber = (TextView) viewHolder.get(R.id.numberText); ImageView image = (ImageView) viewHolder.get(R.id.contact_image); Contact contact = getItem(position); String status = contact.getStatus(); if (contact.getStatus().equals("1")) { image.setBackgroundResource(com.example.mycontentprovider.R.drawable.person_empty_online); } else { image.setBackgroundResource(com.example.mycontentprovider.R.drawable.person_empty_offline); } contName.setText(contact.getName()); contNumber.setText(contact.getPhoneNumber()); return view; } }

我已在此Adapter中更改了多项内容。首先，List的{{1}}现在是最终的，我添加了一个方法Contacts来公开contacts()，以便我们可以修改List中的数据外。我还实现了视图持有者模式，因此您的Adapter滚动更快更顺畅！

我希望我没有忘记任何事情，但这应该是你需要的所有改变。您可以像这样使用新的ListView：

Adapter

如果您想稍后更新List<Contact> contacts = ContactsHelper.getAllContacts(getActivity()); CustomAdapterForAllContacts adapter = new CustomAdapterForAllContacts(getActivity(), contacts); listView.setAdapter(adapter);，则需要修改ListView内的List，如下所示：

Adapter

我希望我能帮到你，如果你有任何其他问题，请随时提出来！

Answer 2

如果你在片段中，那么你可以做

// code for fetching the data
// ...
// ...
((BaseAdapter) yourlistview.getAdapter()).notifyDataSetChanged();

刷新当前片段（ListView数据）保留在同一活动中

2 个答案:

使用notifyDataSetChanged（）

通过重置`Adapter`

刷新当前片段（ListView数据）保留在同一活动中

2 个答案:

使用notifyDataSetChanged（）

通过重置Adapter

通过重置`Adapter`