Question

我在列表视图中实现了延迟加载。当我向下滚动列表并且它成功追加时，我在列表视图中追加10行。但是在这里，在追加后，列表会滚动到第一个位置。我希望列表与追加之前的位置相同。您能否请看下面的代码并帮助我。谢谢。

package com.example.abe;

import java.util.ArrayList;
import android.annotation.TargetApi;
import android.app.Activity;
import android.content.Context;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public class Tab1Fragment extends ListFragment {
    ListView lv;
    Activity act = this.getActivity();
    Context ct = this.getActivity();
    XMLGettersSetters data;
    boolean loadingMore = false;
    String abc[] = new String[50];
    static int count = 0;
    final int itemsPerPage = 10;
    ArrayList<String> myListItems;
    ArrayList<String> myListItems2;
    ArrayAdapter<String> adapter;
    static int size = 0;
    int position;

    @SuppressWarnings("unused")
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        if (container == null) {
            return null;
        }
        myListItems2 = new ArrayList<String>();
        adapter = new ArrayAdapter<String>(getActivity().getBaseContext(),
                android.R.layout.simple_list_item_1, myListItems2);
        View root = inflater.inflate(R.layout.tab_frag1_layout, container,
                false);
        lv = (ListView) root.findViewById(android.R.id.list);
        lv.setAdapter(adapter);
        return root;
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        myListItems = new ArrayList<String>();
        View footerView = ((LayoutInflater) this.getActivity()
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(
                R.layout.listfooter, null, false);
        this.getListView().addFooterView(footerView);
        this.setListAdapter(adapter);
        for (int i = 0; i < 50; i++) {
            abc[i] = "ab" + i;
        }
        this.getListView().setOnScrollListener(new OnScrollListener() {
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
            }

            @Override
            public void onScroll(AbsListView view, int firstVisibleItem,
                    int visibleItemCount, int totalItemCount) {
                System.out.println(abc.length);
                System.out.println(count);
                System.out.println("First" + firstVisibleItem);
                System.out.println("Vis" + visibleItemCount);

                int lastInScreen = firstVisibleItem + visibleItemCount;
                System.out.println("Last" + lastInScreen);
                System.out.println("Total" + totalItemCount);
                if ((lastInScreen == totalItemCount) && !(loadingMore)) {
                    if (count < size) {
                        try {
                            Thread thread = new Thread(null, loadMoreListItems);
                            thread.start();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }

                    }

                    else {
                        Toast.makeText(getActivity().getApplicationContext(),
                                "DATA =)", Toast.LENGTH_LONG).show();
                    }
                }
            }
        });
        try {
            Thread thread = new Thread(null, loadMoreListItems);
            thread.start();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private Runnable loadMoreListItems = new Runnable() {
        @Override
        public void run() {
            loadingMore = true;
            myListItems = new ArrayList<String>();
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
            }
            size = abc.length;
            for (int i = 0; i < itemsPerPage; i++) {
                if (count < size) {
                    myListItems.add(abc[count].toString());
                    count = count + 1;
                } else {
                    break;
                }
            }
            Log.i("a", "b");
            try {
                getActivity().runOnUiThread(returnRes);
            } catch (Exception e) {
                e.printStackTrace();
            }
            Log.i("a", "b");
        }
    };
    private Runnable returnRes = new Runnable() {
        @Override
        public void run() {
            if (myListItems != null && myListItems.size() > 0) {
                for (int i = 0; i < myListItems.size(); i++)
                    adapter.add(myListItems.get(i));
            }
            setListAdapter(adapter);
            Log.i("a", "b");
            adapter.notifyDataSetChanged();
            lv.setSelection(position);
            lv.setSelectionFromTop(position, 0);
            Log.i("a", "b");
            getActivity().setTitle(
                    "Neverending List with "
                            + String.valueOf(adapter.getCount()) + " items");
            loadingMore = false;
        }
    };
}

Answer 1

这是因为以下几行：

lv.setSelection(position);
lv.setSelectionFromTop(position, 0);

并且无法看到位置设置在任何地方。只是评论它们。

附加数据后的动态列表视图位置

1 个答案: