Android ListView在更新其数据时重置滚动状态
我尝试根据listview滚动更新数据。数据更新良好。但在更新数据之后,listview进入顶部。我需要保持原样。我从stockoverflow试了很多。没什么帮助。我想我的密码错了。请帮我解决这个问题 我的代码是:Android ListView在更新其数据时重置滚动状态,android,listview,Android,Listview,我尝试根据listview滚动更新数据。数据更新良好。但在更新数据之后,listview进入顶部。我需要保持原样。我从stockoverflow试了很多。没什么帮助。我想我的密码错了。请帮我解决这个问题 我的代码是: public class ViewAll extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCrea
public class ViewAll extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_all);
new GetMessage().execute();
FinalMessage = new ArrayList<HashMap<String, String>>();
ProgressBar footer = new ProgressBar(this);
ListView lv = (ListView) findViewById(listView);
lv.addFooterView(footer);
}
private void getMessageFromUrl()
{
new GetMessage().execute();
}
private class GetMessage extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
......
}
@Override
protected Void doInBackground(Void... arg0)
{
ServiceHandler sh = new ServiceHandler();
nameValuePairs = new ArrayList<NameValuePair>(1);
nameValuePairs.add(new BasicNameValuePair("page",String.valueOf(page)));
String jsonStr = sh.makeServiceCall(url, ServiceHandler.POST, nameValuePairs);
Log.d("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
......
}
}
catch (JSONException e)
{
e.printStackTrace();
}
}
else
{
Log.e("SericeHandler","Couldn't get any data from url");
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
runOnUiThread(new Runnable() {
public void run() {
if(dorefresh==1)
{
ListView lv = (ListView) findViewById(listView);
Customlistadapter adapter = new Customlistadapter(ViewAll.this, title1, msg1);
lv.setAdapter(adapter);
int index = lv.getFirstVisiblePosition();
View v = lv.getChildAt(0);
int top = (v == null) ? 0 : v.getTop();
lv.setSelectionFromTop(index, top);
page = page + 1;
lv.setOnScrollListener(new AbsListView.OnScrollListener() {
int currentVisibleItemCount;
int currentScrollState;
int currentFirstVisibleItem;
int totalItem;
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// TODO Auto-generated method stub
this.currentScrollState = scrollState;
this.isScrollCompleted();
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
// TODO Auto-generated method stub
this.currentFirstVisibleItem = firstVisibleItem;
this.currentVisibleItemCount = visibleItemCount;
this.totalItem = totalItemCount;
}
private void isScrollCompleted() {
if (totalItem - currentFirstVisibleItem == currentVisibleItemCount
&& this.currentScrollState == SCROLL_STATE_IDLE) {
getMessageFromUrl();
}
}
});
Toast.makeText(ViewAll.this, "Updated", Toast.LENGTH_SHORT).show();
}
else
{
Toast.makeText(ViewAll.this, "No More Messages", Toast.LENGTH_SHORT).show();
}
}
});
}
}
}
public类ViewAll扩展了appcompative活动{
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity\u view\u all);
新建GetMessage().execute();
FinalMessage=newarraylist();
ProgressBar页脚=新的ProgressBar(此);
ListView lv=(ListView)findViewById(ListView);
lv.addFooterView(页脚);
}
私有void getMessageFromUrl()
{
新建GetMessage().execute();
}
私有类GetMessage扩展了异步任务{
@凌驾
受保护的void onPreExecute(){
super.onPreExecute();
......
}
@凌驾
受保护的Void doInBackground(Void…arg0)
{
ServiceHandler sh=新的ServiceHandler();
nameValuePairs=新的ArrayList(1);
添加(新的BasicNameValuePair(“页面”,String.valueOf(页面));
字符串jsonStr=sh.makeServiceCall(url、ServiceHandler.POST、nameValuePairs);
Log.d(“响应:”、“>”+jsonStr);
if(jsonStr!=null){
试一试{
......
}
}
捕获(JSONException e)
{
e、 printStackTrace();
}
}
其他的
{
Log.e(“SerieHandler”,“无法从url获取任何数据”);
}
返回null;
}
@凌驾
受保护的void onPostExecute(void结果){
super.onPostExecute(结果);
runOnUiThread(新的Runnable(){
公开募捐{
if(dorefresh==1)
{
ListView lv=(ListView)findViewById(ListView);
Customlistadapter=新的Customlistadapter(ViewAll.this,title1,msg1);
低压设置适配器(适配器);
int index=lv.getFirstVisiblePosition();
视图v=lv.getChildAt(0);
int top=(v==null)?0:v.getTop();
lv.设置从顶部选择(索引,顶部);
页码=页码+1;
lv.setOnScrollListener(新的AbsListView.OnScrollListener(){
int currentVisibleItemCount;
int当前状态;
int currentFirstVisibleItem;
整数项目;
@凌驾
公共无效onScrollStateChanged(AbsListView视图,int scrollState){
//TODO自动生成的方法存根
this.currentScrollState=scrollState;
这个.isScrollCompleted();
}
@凌驾
public void onScroll(AbsListView视图,int firstVisibleItem,
int visibleItemCount,int totalItemCount){
//TODO自动生成的方法存根
this.currentFirstVisibleItem=firstVisibleItem;
this.currentVisibleItemCount=visibleItemCount;
this.totalItem=totalItemCount;
}
私有无效IsCrollCompleted(){
如果(totalItem-currentFirstVisibleItem==currentVisibleItemCount
&&this.currentScrollState==SCROLL\u STATE\u IDLE){
getMessageFromUrl();
}
}
});
Toast.makeText(ViewAll.this,“Updated”,Toast.LENGTH_SHORT.show();
}
其他的
{
Toast.makeText(ViewAll.this,“无更多消息”,Toast.LENGTH_SHORT.show();
}
}
});
}
}
}
CustomlistAdapter.java
public class Customlistadapter extends ArrayAdapter<String> {
ArrayList<String> title;
ArrayList<String> msg;
Context context;
public Customlistadapter(Activity context, ArrayList<String> text, ArrayList<String> msgView) {
super(context, R.layout.list_row, text);
// TODO Auto-generated constructor stub
this.title = text;
this.msg = msgView;
this.context = context;
}
public View getView(final int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
LayoutInflater inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View single_row = inflater.inflate(R.layout.list_row, null,
true);
TextView textView = (TextView) single_row.findViewById(R.id.title);
TextView msgView = (TextView) single_row.findViewById(R.id.msgView);
textView.setText(title.get(position));
msgView.setText(msg.get(position));
return single_row;
}
}
公共类Customlistadapter扩展了ArrayAdapter{
ArrayList标题;
ArrayList味精;
语境;
公共Customlistadapter(活动上下文、ArrayList文本、ArrayList msgView){
super(上下文、R.layout.list_行、文本);
//TODO自动生成的构造函数存根
this.title=文本;
this.msg=msgView;
this.context=上下文;
}
公共视图getView(最终整数位置、视图转换视图、视图组父视图){
//TODO自动生成的方法存根
LayoutFlater充气器=(LayoutFlater)上下文
.getSystemService(上下文布局\充气机\服务);
查看单行=充气机。充气(R.layout.list行,空,
正确的);
TextView TextView=(TextView)单行.findViewById(R.id.title);
TextView msgView=(TextView)单行.findViewById(R.id.msgView);
setText(title.get(position));
msgView.setText(msg.get(position));
返回单_行;
}
}
您的问题是每次更新数据时都会创建一个新的Customlistadapter
。如果希望ListView
保持滚动状态,则必须重用适配器。只需更改适配器中的数据并调用myAdapter.notifyDataSetChanged()
例如,如果您的适配器是ArrayAdapt
ArrayAdapter adapter = (ArrayAdapter)listView.getAdapter();
adapter.clear();
adapter.addAll(newData);
adapter.notifyDataSetChanged();