我的一个片段中有一个列表视图，当我离开该片段时它会清空。
为什么会这样？
那个片段：
public class ListActivity extends ListFragment {
public void ToastLoadShout(String msg) {
Toast.makeText(getActivity(), msg.toString(), Toast.LENGTH_LONG).show();
}
private static View View;
HttpClient client;
HttpPost httppost;
HttpGet httpget;
JSONObject json;
List<List<String>> items;
List<item> markers = new ArrayList<item>();
MobileArrayAdapter adapter;
ListView list;
ProgressBar listload;
Button relist;
Preferences pref;
String datadata = "";
String savedlat="0.0";
String savedlon="0.0";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.activity_list, container, false);
}
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setRetainInstance(true);
try {
pref = new Preferences(getActivity());
list = (ListView) getView().findViewById(android.R.id.list);
listload = (ProgressBar) getView().findViewById(R.id.listload);
HashMap<String, String> loc = pref.getData();
ToastLoadShout(loc.get(Preferences.LAT) + ","
+ loc.get(Preferences.LON));
if (loc.get(Preferences.LAT) != "0.0" && loc.get(Preferences.LAT) != null)
{
//adapter.deleteList();
//list.destroyDrawingCache();
if (loc.get(Preferences.LAT) != savedlat && loc.get(Preferences.LON)!=savedlon){
new Load().execute();
savedlat=loc.get(Preferences.LAT);
savedlon=loc.get(Preferences.LON);
}
}
else
ToastLoadShout("Get Location First.");
relist = (Button) getView().findViewById(R.id.relist);
relist.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
listload.setVisibility(View.INVISIBLE);
HashMap<String, String> loc = pref.getData();
ToastLoadShout(loc.get(Preferences.LAT) + ","
+ loc.get(Preferences.LON));
if (loc.get(Preferences.LAT) != "0.0" && loc.get(Preferences.LAT) != null){
adapter.deleteList();
list.destroyDrawingCache();
new Load().execute();}
else
ToastLoadShout("Get Location First.");
}});
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
// get selected items
//String selectedValue = (String) getListAdapter().getItem(position);
String selectedValue = markers.get(position).getTitle();
Toast.makeText(getActivity(), selectedValue, Toast.LENGTH_SHORT).show();
}
}
以及保存片段的主活动：
public class Fragments extends FragmentActivity {
Fragment newFragment;
Button Add;
public void ToastLoadShout(String msg) {
Toast.makeText(this, msg.toString(), Toast.LENGTH_SHORT).show();
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fragments);
//Set Custom actionBar<
getActionBar().setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM);
getActionBar().setCustomView(R.layout.titlebar);
getActionBar().setHomeButtonEnabled(true);
getActionBar().setDisplayHomeAsUpEnabled(true);
//Set Custom actionBar>
ListActivity fragment = new ListActivity();
FragmentTransaction transaction = getSupportFragmentManager()
.beginTransaction();
transaction.add(R.id.fragment_place, fragment,"Nearby");
transaction.commit();
turnGPSOn();
Add = (Button)findViewById(R.id.add);
Add.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Intent Intent = new Intent(Fragments.this,Add.class);
Bundle bndlanimation =
ActivityOptions.makeCustomAnimation(getApplicationContext(),
R.anim.animation,R.anim.animation2).toBundle();
startActivity(Intent, bndlanimation);
}
});
/* For putting commas in attractin's checkIns
String number = "1345";
int amount = Integer.parseInt(number);
DecimalFormat formatter = new DecimalFormat("#,###");
ToastLoadShout(formatter.format(amount));*/
}
public void onSelectFragment(View view) {
String fragTag="";
boolean needNew=false;
if (view == findViewById(R.id.map))
{
Fragment f = getSupportFragmentManager().findFragmentByTag("Map");
if (f==null){
newFragment = new MainActivity();
needNew=true;
fragTag="Map";
}
else{
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragment_place, f, "Map"); //or whatever other string you want to use
transaction.addToBackStack(null);
transaction.commit();
}
}
else if (view == findViewById(R.id.nearby))
{
Fragment f = getSupportFragmentManager().findFragmentByTag("Nearby");
if (f==null){
newFragment = new ListActivity();
needNew=true;
fragTag="Nearby";
}
else{
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragment_place, f, "Nearby"); //or whatever other string you want to use
transaction.addToBackStack(null);
transaction.commit();
}
}
if (needNew) {
FragmentTransaction transaction = getSupportFragmentManager()
.beginTransaction();
transaction.replace(R.id.fragment_place, newFragment, fragTag);
transaction.addToBackStack(null);
transaction.commit();
}
}
}
已经尝试在OnCreate上加载列表。根本不起作用。
感谢您的帮助。
编辑：
负载类：
class Load extends AsyncTask<String, Integer, Boolean> {
@Override
protected void onPreExecute() {
listload.setVisibility(View.VISIBLE);
}
@Override
protected Boolean doInBackground(String... params) {
try {
items = DownloadList();
if (items != null)
return true;
} catch (Exception e) {
e.printStackTrace();
return false;
}
return false;
}
@Override
protected void onPostExecute(Boolean res) {
// TODO Auto-generated method stub
if (res) {
ArrangePutMarkers();
adapter=new MobileArrayAdapter(getActivity(), markers);
list.setAdapter(adapter);
} else {
ToastLoadShout("Error");
ToastLoadShout(datadata);
}
listload.setVisibility(View.INVISIBLE);
}
}
正如我所看到的，每次显示片段时您都会重新创建 loc 对象。它显然会让您分段以重新加载数据。
将适配器作为字段保持在活动中。当你离开碎片时，摧毁它中的所有东西是很正常的事情。 setRetainInstance()仅适用于配置更改，例如屏幕旋转。每次返回片段时重新创建列表（例如，在onActivityCreated()中，就像您知道的那样），并为其提供存储的适配器，其中包含保存的数据。您可以访问片段内的活动，例如，通过强制转换 (MainActivity)getActivity() ，因为在这种情况下传递给此片段的Activity实际上是您的活动。