我在片段中使用ListView。我有一个asynctask从远程服务器下载json数据。我尝试在onPostExecute函数中以编程方式刷新我显示的适配器/列表视图，但它对我不起作用。
我的主要活动有三个片段，三个listview，三个适配器和一个异步任务。
public class ContactsActivity extends ActionBarActivity implements ActionBar.TabListener {
SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;
private static List<Item> BackList = new ArrayList<Item>();
private static List<Item> BackList2 = new ArrayList<Item>();
private static List<Item> BackList3 = new ArrayList<Item>();
private static ListView ListView;
private static Context activity;
public static String HASH;
private static final String[] timestamp = {"0"};
private static WeatherAdapter adapter;
private static int fragment;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.contacts);
Intent myIntent= getIntent();
HASH = myIntent.getStringExtra("HASH");
Log.d("Intent - contactActivity", HASH);
final ActionBar actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
actionBar.addTab(
actionBar.newTab()
.setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
(new PrefetchData()).execute();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.contacts, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
mViewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
return PlaceholderFragment.newInstance(position + 1);
}
@Override
public int getCount() {
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
fragment = position;
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
case 2:
return getString(R.string.title_section3).toUpperCase(l);
}
return null;
}
}
public static Bitmap getBitmapFromURL(String src) {
try {
URL url = new URL(src);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setDoInput(true);
connection.connect();
InputStream input = connection.getInputStream();
Bitmap myBitmap = BitmapFactory.decodeStream(input);
return myBitmap;
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
public static class PlaceholderFragment extends Fragment {
private static final String ARG_SECTION_NUMBER = "section_number";
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
int index = getArguments().getInt(ARG_SECTION_NUMBER);
fragment = index;
activity = getActivity();
ListView listview1 = (ListView) rootView.findViewById(R.id.listView);
switch(fragment){
case 1:
adapter = new WeatherAdapter(activity, R.layout.listview_item_row, BackList);
listview1.setOnItemClickListener(new ListView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> a, View v, int i, long l) {
Intent rozmowa = new Intent(getActivity(), Incotalk.class);
rozmowa.putExtra("HASH", HASH);
startActivity(rozmowa);
}
});
break;
case 2:
adapter = new WeatherAdapter(activity, R.layout.listview_item_row2, BackList2);
break;
case 3:
adapter = new WeatherAdapter(activity, R.layout.listview_item_row3, BackList3);
break;
}
listview1.setAdapter(adapter);
ListView = listview1;
return rootView;
}
}
/**
* Async Task to make http call
*/
private class PrefetchData extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// before making http calls
}
@Override
protected Void doInBackground(Void... arg0) {
final String id = HASH;
final String url = "http://freshfrog.pl/projects/talk.php?user="+id+"&t=" + timestamp[0];
Log.d("BBB","start");
try {
String page = new Communicator().executeHttpGet(url);
JSONObject jsonObject = new JSONObject(page);
timestamp[0] = jsonObject.getString("t");
HASH = jsonObject.getJSONObject("s").getString("hash");
JSONArray oczekujacy = jsonObject.getJSONArray("m");
// wiadomosci
BackList.clear(); // czyści przed odświerzeniem
BackList2.clear();
BackList3.clear();
for (int i=oczekujacy.length()-1; i>0; i--) {
JSONObject actor = oczekujacy.getJSONObject(i);
String message = actor.getString("m");
String hash = actor.getString("n");
String t = actor.getString("t");
int l = BackList.size();
Boolean jest = false;
for(int j=0; j<l; j++){
Item item = BackList.get(j);
if(!item.isSection()){
ContactItem contactItem= (ContactItem) item;
if( (contactItem.hash).equals(hash) ){
jest = true;
break;
}
}
//Log.d("bbb", BackList.get(j).hash);
}
if(!jest && !hash.equals(id)) BackList.add(
new ContactItem(BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher),
message,
hash));
}
// znajomi
BackList2.add(new SectionItem("Otrzymane zaproszenia"));
oczekujacy = jsonObject.getJSONObject("f").getJSONObject("p").getJSONArray("sending");
for (int i=0; i<oczekujacy.length(); i++) {
JSONObject actor = oczekujacy.getJSONObject(i);
String name = actor.getString("name");
String hash = actor.getString("hash");
String avatar = actor.getString("avatar");
BackList2.add(new ContactItem(getBitmapFromURL(avatar) , name, hash) );
}
// szukaj
BackList3.add(new SectionItem("Znajomi"));
Cursor phones = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null,null,null, null);
while (phones.moveToNext())
{
String name= phones.getString(phones.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
String phoneNumber = phones.getString(phones.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));
BackList3.add(new ContactItem(
BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher),
name,
phoneNumber) );
}
} catch (Exception e) {
Log.d("BBB", e.toString());
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
/* gdy skończy */
adapter.notifyDataSetChanged();
ListView listview2 = (ListView) findViewById(R.id.listView);
listview2.invalidateViews();
//Toast.makeText(ContactsActivity.this, "coś przyszło", Toast.LENGTH_SHORT).show();
Log.d("BBB", "powinno sie odswieżyc");
new PrefetchData().execute();
}
}
}
我的自定义适配器
public class WeatherAdapter extends ArrayAdapter<Item> {
Context context;
int layoutResourceId;
List<Item> data = null;
private LayoutInflater vi;
public WeatherAdapter(Context context, int layoutResourceId, List<Item> data) {
super(context, layoutResourceId, data);
this.layoutResourceId = layoutResourceId;
this.context = context;
this.data = data;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View row = convertView;
WeatherHolder holder = null;
SectionHolder holder2 = null;
LayoutInflater inflater = ((Activity)context).getLayoutInflater();
Item i = data.get(position);
if(row == null){
if(!i.isSection()){
row = inflater.inflate(layoutResourceId, parent, false);
holder = new WeatherHolder();
holder.imgIcon = (ImageView)row.findViewById(R.id.imgIcon);
holder.txtTitle = (TextView)row.findViewById(R.id.txtTitle);
row.setTag(holder);
ContactItem contactItem = (ContactItem)i;
holder.txtTitle.setText(contactItem.title);
holder.imgIcon.setImageBitmap(contactItem.icon);
}else{
row = inflater.inflate(R.layout.listview_header_row, parent, false);
holder2 = new SectionHolder();
holder2.txtTitle = (TextView)row.findViewById(R.id.txtTitle);
row.setTag(holder2);
SectionItem sectionItem = (SectionItem)i;
holder2.txtTitle.setText(sectionItem.title);
}
}
else
{
if(!i.isSection()){
//holder = (WeatherHolder) row.getTag();
}else{
//holder2 = (SectionHolder) row.getTag();
}
}
return row;
}
public void update(List<Item> newlist) {
Log.d("bbb","aktualizacja listview");
data.clear();
data.addAll(newlist);
this.notifyDataSetChanged();
}
@Override
public void notifyDataSetChanged() // Create this function in your adapter class
{
//notifySetDataChanged()
super.notifyDataSetChanged();
}
static class WeatherHolder
{
ImageView imgIcon;
TextView txtTitle;
}
static class SectionHolder
{
TextView txtTitle;
}
}
答案 0 :(得分：1)
“if（row == null）{”的部分应该只包含视图和viewHolders的初始化。
它不应包含对视图的任何数据设置。
在此部分之后（在“else {...}”之后），您应该使用新数据更新视图。
这是我对你的代码的修复（看起来很丑，但应该有效）：
...
int type=getViewType();
switch(type)
{
case 0:
if(row == null)
{
row = inflater.inflate(layoutResourceId, parent, false);
holder = new WeatherHolder();
holder.imgIcon = (ImageView)row.findViewById(R.id.imgIcon);
holder.txtTitle = (TextView)row.findViewById(R.id.txtTitle);
row.setTag(holder);
}
else
holder = (WeatherHolder) row.getTag();
ContactItem contactItem = (ContactItem)i;
holder.txtTitle.setText(contactItem.title);
holder.imgIcon.setImageBitmap(contactItem.icon);
break;
case 1:
if(row == null)
{
row = inflater.inflate(R.layout.listview_header_row, parent, false);
holder2 = new SectionHolder();
holder2.txtTitle = (TextView)row.findViewById(R.id.txtTitle);
row.setTag(holder2);
}
else
holder2 = (SectionHolder) row.getTag();
SectionItem sectionItem = (SectionItem)i;
holder2.txtTitle.setText(sectionItem.title);
break;
}
return row;
...
... int getViewType(...) {... return i.isSection()? 1:0;}
... int getViewTypeCount(){return 2;}
例如，您可以使用getViewTypeCount，getViewType，getItem，如the API所示。
答案 1 :(得分：-1)
查看您的代码我发现您已经在postExcecute
上再次启动了异步执行 @Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
/* gdy skończy */
adapter.notifyDataSetChanged();
ListView listview2 = (ListView) findViewById(R.id.listView);
listview2.invalidateViews();
//Toast.makeText(ContactsActivity.this, "coś przyszło", Toast.LENGTH_SHORT).show();
Log.d("BBB", "powinno sie odswieżyc");
new PrefetchData().execute();
}
还清除doBackground中的数据
要更改您的数据，您不应该清除您的数据只是获取更新记录并通知您的adapeter
答案 2 :(得分：-1)
尝试使用addall（newlist，data）更改方法data.addAll（newlist）; 在addall方法里面逐个添加元素列表。这样它应该可以工作。
我有同样的问题，我按照我解释的方式纠正。