关于 NotifyDataSetChanged答案

【问题标题】：About NotifyDataSetChanged关于 NotifyDataSetChanged
【发布时间】：2017-09-08 04:49:25
【问题描述】：

我一直在研究适配器并尝试使用 notifydatasetchanged 对其进行更新。但我面临的问题是，在我成功更新适配器后，我可以看到在列表视图中进行了更改，然后在我从其他片段返回后，它将更改回以前的数据。我听说适配器将使用导致问题的相同数据重用转换视图，但我不知道如何解决这个问题。我已经搜索了答案，但找不到任何类似的答案，因为大多数答案都是关于声明一个新的适配器。以下是我的部分代码：

1.fragment中的刷新方法

public void toggleRefreshInBackground(ArrayList<HashMap<String, Object>> list) {
    dialog_list.clear();
    dialog_list.addAll(list);
    adapter.update(list);
}

2.getView() 我的适配器

public class DialogListAdapter extends BaseAdapter {
Context context;
private ImageLoader imageLoader;
private static LayoutInflater inflater;
private ArrayList<HashMap<String, Object>> member_list;
private ArrayList<HashMap<String, Object>> member_list2;
private SparseBooleanArray mSelectedItemsIds;
private ArrayList<Integer> selectedItemPosition;
//private static final int droidGreen = Color.parseColor("#A4C639");
//private BadgeView badge;
Resources res;
String sorting;

public DialogListAdapter(Context c,
                         ArrayList<HashMap<String, Object>>content, String temp_sorting) {

    inflater=(LayoutInflater)c.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    this.context=c;
    this.member_list = content;

    this.member_list2 = new ArrayList<>();
    this.member_list2.addAll(this.member_list);

    res=c.getResources();

    this.sorting = temp_sorting;
    mSelectedItemsIds = new SparseBooleanArray();
    selectedItemPosition = new ArrayList<>();

}

@Override
public int getCount() {
    // TODO Auto-generated method stub
    return member_list.size();
}

@Override
public HashMap<String, Object> getItem(int position) {
    // TODO Auto-generated method stub
    return member_list.get(position);
}

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

public void update(ArrayList<HashMap<String,Object>> obj) {
    member_list2.clear();
    member_list2.addAll(obj);
    notifyDataSetChanged();
}

public final class DialogListItem{ // view holder
    public TextView read_count;
    public TextView nameView;
    public TextView numberView;
    public TextView statusView;
    public ImageView thumb_image;
    public TextView timeView;
    public TextView senderView;
    public ImageView tick;
    //public BadgeView badge;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    int index;

    if(sorting.equals("D")){
        index = member_list.size()-position-1;
    }else{
        index = position;
    }

    View row = convertView;
    DialogListItem dialogItem=null;
    String textbuff_time = null;
    String textbuff_mess = null;
    String textbuff_sender = null;
    if (convertView==null){
        row=inflater.inflate(R.layout.dialog_list_single, null);
        dialogItem=new DialogListItem();
        dialogItem.read_count=(TextView)row.findViewById(R.id.readcount);
        dialogItem.nameView=(TextView)row.findViewById(R.id.member_name);
        dialogItem.numberView=(TextView)row.findViewById(R.id.tab2number);
        dialogItem.statusView=(TextView)row.findViewById(R.id.tab2status);
        dialogItem.thumb_image=(ImageView)row.findViewById(R.id.tab2image);
        dialogItem.timeView=(TextView) row.findViewById(R.id.tab2date);
        dialogItem.senderView=(TextView) row.findViewById(R.id.tab2sender);
        dialogItem.tick = (ImageView) row.findViewById(R.id.tick);
        row.setTag(dialogItem);
    }
    else{
        dialogItem=(DialogListItem) row.getTag();
    }

    if (mSelectedItemsIds.get(position)) {
        row.setBackgroundColor(context.getResources().getColor(R.color.item_selected));
    } else {
        row.setBackgroundColor(context.getResources().getColor(R.color.item_unselected));
    }

    HashMap<String,Object>items;
    items=member_list.get(index);
    dialogItem.nameView.setText((String)items.get(DBhelper.MEMBER_NAME));
    dialogItem.nameView.setTypeface(null,Typeface.BOLD);
    dialogItem.nameView.setSingleLine(true);
    dialogItem.nameView.setMaxLines(1);
    dialogItem.nameView.setEms(13);
    dialogItem.nameView.setEllipsize(TruncateAt.END);
    dialogItem.numberView.setText((String)items.get(DBhelper.MEMBER_NUMBER));
    String textbuff=(String)items.get(DBhelper.MEMBER_LMESSAGE);
    if (!TextUtils.isEmpty(textbuff)){
        textbuff_time=textbuff.substring(0, 19);
        textbuff_mess=textbuff.substring(20);
        int bound=textbuff_mess.indexOf("½");
        if(bound!=-1){
            textbuff_sender=textbuff_mess.substring(0,bound);
            textbuff_mess=textbuff_mess.substring(bound+2);
        }
        else
            textbuff_sender="";

        dialogItem.statusView.setText(textbuff_mess);

        if (textbuff_sender.equals(context.getResources().getString(R.string.myself))) {
            dialogItem.senderView.setVisibility(View.GONE);
            dialogItem.tick.setVisibility(View.VISIBLE);
        } else {
            textbuff_sender = textbuff_sender + ": ";
            dialogItem.senderView.setVisibility(View.VISIBLE);
            dialogItem.senderView.setText(textbuff_sender);
            dialogItem.tick.setVisibility(View.GONE);
        }

        try {
            dialogItem.timeView.setText(Utility.relativeTime(row.getContext(), textbuff_time));
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
    else{
        dialogItem.statusView.setText("");
        dialogItem.senderView.setText("");
        dialogItem.timeView.setText("---");
    }

    dialogItem.statusView.setTextColor(Color.GRAY);
    dialogItem.statusView.setTypeface(null,Typeface.NORMAL);
    dialogItem.timeView.setTextColor(Color.GRAY);
    dialogItem.timeView.setTypeface(null,Typeface.NORMAL);
    dialogItem.senderView.setTextColor(Color.GRAY);
    dialogItem.senderView.setTypeface(null,Typeface.NORMAL);
    dialogItem.senderView.getPaint().setTextSkewX(-0.25f);

    String sformat=" "+String.valueOf(items.get(DBhelper.MEMBER_SIZE))+" ";
    dialogItem.read_count.setText(sformat);
    int badge_number=(Integer)items.get(DBhelper.MEMBER_SIZE);
    if(badge_number>0){

        dialogItem.read_count.setVisibility(View.VISIBLE);
        dialogItem.statusView.setTextColor(Color.BLACK);
        dialogItem.statusView.setTypeface(null,Typeface.BOLD);
        dialogItem.timeView.setTextColor(Color.BLACK);
        dialogItem.timeView.setTypeface(null,Typeface.BOLD);
        dialogItem.senderView.setTextColor(Color.BLACK);
        dialogItem.senderView.setTypeface(null,Typeface.BOLD);
        dialogItem.senderView.getPaint().setTextSkewX(-0.25f);
    }
    else{
        dialogItem.read_count.setVisibility(View.GONE);
    }

    StringBuffer link=new StringBuffer(Register.get_current_server_address());
    if(items.get(DBhelper.MEMBER_TYPE).equals(res.getString(R.string.broadcast_chat))){
        dialogItem.nameView.setTextColor(row.getResources().getColor(R.color.tab4_title));
        link.append("uniappSystemFile.asp");
        link.append("?file=").append("broadcast.png");
        //imageLoader.DisplayImage(link.toString(), dialogItem.thumb_image);
        Picasso.with(context).load(link.toString()).transform(new CircleTransform()).resize(200,200).into(dialogItem.thumb_image);
        dialogItem.read_count.setVisibility(View.GONE); // disable broadcast badge
    }
            Picasso.with(context).load(R.drawable.ic_contact).resize(200,200).into(dialogItem.thumb_image);
            Picasso.with(context).load(R.drawable.ic_notif).resize(200, 200).into(dialogItem.thumb_image);
        }else{
            link2 = new IMService(context.getApplicationContext()).group_image_thumb_get(tab2.myphone, (String) items.get(DBhelper.MEMBER_NUMBER));
            dialogItem.nameView.setTextColor(row.getResources().getColor(R.color.tab3_title));
            //imageLoader.DisplayImage(link2, dialogItem.thumb_image);
            Picasso.with(context).load(link2).transform(new CircleTransform()).resize(200, 200).placeholder(R.drawable.ic_group_circle_black_48dp).error(R.drawable.ic_group_circle_black_48dp).into(dialogItem.thumb_image);
        }
    }

public void setSearchPattern(String pattern) {
    filterListByPattern(pattern.trim());
    this.notifyDataSetChanged();
}

private void filterListByPattern(String searchPattern) {

    member_list.clear();
    for (HashMap<String,Object> info : member_list2) {
        boolean add = true;
        do {
            if (searchPattern == null || searchPattern.equals("")) {
                break;
            }
            if (info.get(DBhelper.MEMBER_NAME).toString().toLowerCase().contains(searchPattern)) {
                break;
            }
            add = false;
        } while (false);
        if (add) {
            member_list.add(info);
        }
    }
}

public void resetList() {
    this.member_list2 = new ArrayList<HashMap<String,Object>>();
    this.member_list2.addAll(this.member_list);
    this.notifyDataSetChanged();
}

public void remove(Object object) {
    member_list.remove(object);
    notifyDataSetChanged();
}

public void toggleSelection(int position) {
    selectView(position, !mSelectedItemsIds.get(position));
}

public void removeSelection() {
    mSelectedItemsIds = new SparseBooleanArray();
    selectedItemPosition = new ArrayList<>();
    notifyDataSetChanged();
}

public void selectView(int position, boolean value) {
    if (value) {
        mSelectedItemsIds.put(position, value);
        selectedItemPosition.add(position);
    } else {
        mSelectedItemsIds.delete(position);
        selectedItemPosition.remove(selectedItemPosition.indexOf(position));
    }
    notifyDataSetChanged();
}

public int getSelectedCount() {
    return mSelectedItemsIds.size();
}

public SparseBooleanArray getSelectedIds() {
    return mSelectedItemsIds;
}

public ArrayList<Integer> getItemPosition() {
    return selectedItemPosition;
}

}

所以，我的问题是为什么我的适配器和列表视图会在我从其他片段返回到这个片段后显示旧数据，以及如何解决这个问题？

附：请不要告诉我像这样声明一个新的适配器

adapter = new MyAdapter(list);
adapter.notifyDataSetChanged();

我知道它可以工作，但它不是一个好的和合适的方法，因为它是一个繁重的操作，你甚至不需要在声明一个新的适配器后使用 notifyDataSetChanged。

非常感谢

【问题讨论】：

为什么不试试回收站视图而不是列表视图？
@Anonymous 但是 recyclerview 和列表视图有什么区别？我仍然需要一个适配器并对其进行更改
我认为 recyclerview 中的视图持有人是对列表视图的重大增强。任何方式都可以发布您的整个适配器编号。分析代码将很容易
@Anonymous 我现在很喜欢。大约半小时后我会发布整个适配器。
@Harris.C stackoverflow.com/a/29078116/3395198

标签： android listview android-fragments android-adapter

【解决方案1】：

试试把setRetainInstance(true); 在你的片段中。

如果上述方法不起作用，请尝试以下onSaveInstanceState() -

在顶部声明，Parcelable state;

保存列表视图状态，state = listview.onSaveInstanceState(); 在片段的 onpause() 内或在更改片段时手动保存。然后在 onCreateView 检查 state 是否为空。如果为null则设置适配器/获取数据，如果不是则设置

listview.onRestoreInstanceState(state);

另一方面，每次加载片段时，ArrayList 都会从空开始。所以你需要小心保存数据。

【讨论】：