问题
I have a listview which is fetching data from sqlite database by Json.
I want to turn it into dynamic listview that at the end of scroll, a \"load more items\" appears in the footer of the list while loading more items and adding them to the adapter (for example 10 items each time). I have problem in implementing this feature. Please help me with it. Thanks.
public class AllProductsActivity extends Activity {
... defining variables...;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
new LoadAllProducts().execute();
}
class LoadAllProducts extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
... progress dialog...
}
protected String doInBackground(String... args) {
countryList = new ArrayList<Country>();
List<NameValuePair> params = new ArrayList<NameValuePair>();
JSONObject json = jParser.makeHttpRequest(url_all_products, \"GET\", params);
Log.d(\"All Products: \", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// products found
// Getting Array of Products
products = json.getJSONArray(TAG_PRODUCTS);
// looping through All Products
for (int i = 0; i < products.length(); i++) {
JSONObject c = products.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_PID);
String name = c.getString(TAG_NAME);
String description = c.getString(TAG_DESCRIPTION);
String due_date = c.getString(TAG_DUE_DATE);
String staff = c.getString(TAG_STAFF);
String status = c.getString(TAG_STATUS);
country = new Country(id,name,description,
due_date, staff, status);
countryList.add(country);
}
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(String file_url) {
pDialog.dismiss();
runOnUiThread(new Runnable() {
public void run() {
displayListView();
}
});
}
}
private void displayListView() {
dataAdapter = new MyCustomAdapter(this,
R.layout.country_info, countryList);
ListView listView = (ListView) findViewById(R.id.listView1);
listView.setAdapter(dataAdapter);
}
private class MyCustomAdapter extends ArrayAdapter<Country> {
... blah blah blah ...
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
Log.v(\"ConvertView\", String.valueOf(position));
if (convertView == null) {
... blah blah blah ...
}
return convertView;
}
}
}
回答1:
you try the following code
list.setOnScrollListener(new OnScrollListener() {
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
if(firstVisibleItem+visibleItemCount == totalItemCount && totalItemCount!=0)
{
if(flag_loading == false)
{
flag_loading = true;
additems();
}
}
}
});
in the additem() add the next 10 items to array list and set the flag_loading as false. and call notifydatasetchanged. it should work.
回答2:
There is the solution, Activity has to implement interface AbsListView.OnScrollListener
In Activity:
int currentFirstVisibleItem = 0;
int currentVisibleItemCount = 0;
int totalItemCount = 0;
int currentScrollState = 0;
boolean loadingMore = false;
Long startIndex = 0L;
Long offset = 10L;
View footerView;
@Override
public void onScroll(AbsListView absListView, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
this.currentFirstVisibleItem = firstVisibleItem;
this.currentVisibleItemCount = visibleItemCount;
this.totalItemCount = totalItemCount;
}
@Override
public void onScrollStateChanged(AbsListView absListView, int scrollState) {
this.currentScrollState = scrollState;
this.isScrollCompleted();
}
private void isScrollCompleted() {
if (this.currentVisibleItemCount > 0 && this.currentScrollState == SCROLL_STATE_IDLE && this.totalItemCount == (currentFirstVisibleItem + currentVisibleItemCount)) {
/*** In this way I detect if there's been a scroll which has completed ***/
/*** do the work for load more date! ***/
if (!loadingMore) {
loadingMore = true;
new LoadMoreItemsTask(this).execute();
}
}
}
private class LoadMoreItemsTask extends AsyncTask<Void, Void, List<ListItem>> {
private Activity activity;
private View footer;
private LoadMoreItemsTask(Activity activity) {
this.activity = activity;
loadingMore = true;
footer = activity.getLayoutInflater().inflate(R.layout.base_list_item_loading_footer, null);
}
@Override
protected void onPreExecute() {
list.addFooterView(footer);
list.setAdapter(adapter);
super.onPreExecute();
}
@Override
protected List<ListItem> doInBackground(Void... voids) {
return getNextItems(startIndex, offset);
}
@Override
protected void onPostExecute(List<ListItem> listItems) {
if (footer != null) {
list.removeFooterView(footer);
}
list.setAdapter(adapter);
loadingMore = false;
if (listItems.size() > 0) {
startIndex = startIndex + listItems.size();
setItems(listItems);
}
super.onPostExecute(listItems);
}
}
Oncreate:
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.base_list);
list = (ListView) findViewById(R.id.list);
list.setOnItemClickListener(this);
list.setOnScrollListener(this);
footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.base_list_item_loading_footer, null, false);
initAdapter();
new LoadMoreItemsTask(this).execute();
}
base_list_item_loading_footer.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/list_item_footer"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical"
android:padding="15dp" >
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:orientation="horizontal" >
<ProgressBar
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
</ProgressBar>
<TextView
style="@style/ItemHeadTextStyle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="@string/loading_list_items" />
</LinearLayout>
</RelativeLayout>
I hope , it helps.
回答3:
Best way to implement Dynamic Expandaple LW with footer explained below:
private int firstVisibleItem, visibleItemCount,totalItemCount;
expandapleListView.setOnScrollListener(new AbsListView.OnScrollListener() {
@Override
public void onScroll(AbsListView view,
int firstVisibleItemm, int visibleItemCountt,
int totalItemCountt) {
firstVisibleItem = firstVisibleItemm;
visibleItemCount = visibleItemCountt;
totalItemCount = totalItemCountt;
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
final int lastItem = firstVisibleItem + visibleItemCount;
if (lastItem == totalItemCount && scrollState == SCROLL_STATE_IDLE) {
expandapleInt++;
new AsyncTask().execute();
//get next 10-20 items(your choice)items
}
}
});
Footer implementation:
Given below xml code, should be in bottom of Layout that your ListView inside it...
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="45dp"
android:layout_gravity="center"
android:id="@+id/footer">
<ProgressBar
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_toLeftOf="@+id/textView3"
android:layout_toStartOf="@+id/textView3">
</ProgressBar>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Loading"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true"
android:id="@+id/textView3" />
Bind it in your activity
footer = (RelativeLayout) findViewById(R.id.footer);
footer.setVisibility(View.GONE);
onPreExecute
footer.setVisibility(View.VISIBLE);
onPostExecute
footer.setVisibility(View.GONE);
来源：https://stackoverflow.com/questions/16398921/dynamic-listview-adding-load-more-items-at-the-end-of-scroll