以下代码用于在列表视图的滚动中从json获取新数据。但是在获得新的json后，它不会从json添加新的json，而是采用第一个json中的相同数据。
请帮我解决这个问题。
我的活动。
public class ProductView extends AppCompatActivity {
ListView list_product;
String json;
ProgressActivity loadingview;
int current_page = 1;
int totalPage = 1;
int Pagecount = 1;
Toolbar toolbar;
GetProductAdapter productAdapter;
List<BeanGetProducts> beanGetProductses = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_product_view);
toolbar = (Toolbar) findViewById(R.id.back_toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
onBackPressed();
}
});
ImageView img_home = (ImageView) findViewById(R.id.dr_image_home);
img_home.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(ProductView.this, AdminAccess.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
finish();
}
});
list_product = (ListView) findViewById(R.id.list_products);
productAdapter = new GetProductAdapter(beanGetProductses, ProductView.this, getApplicationContext());
list_product.setOnScrollListener(new AbsListView.OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView absListView, int i) {
}
@Override
public void onScroll(AbsListView absListView, int firstItem, int visibleItemCount, int totalItem) {
int total = firstItem + visibleItemCount;
if (Pagecount < totalPage) {
if (total == totalItem) {
Pagecount++;
new getProducts(Pagecount).execute();
productAdapter.notifyDataSetChanged();
list_product.setAdapter(productAdapter);
}
}
}
});
new getProducts(current_page).execute();
}
public class getProducts extends AsyncTask<Void, Void, String> {
int pageNo;
public getProducts(int pageNo) {
this.pageNo = pageNo;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
try {
loadingview = new ProgressActivity(ProductView.this, "");
loadingview.setCancelable(false);
loadingview.show();
} catch (Exception e) {
}
}
@Override
protected String doInBackground(Void... voids) {
List<NameValuePair> pairs = new ArrayList<>();
pairs.add(new BasicNameValuePair("", String.valueOf(pageNo)));
json = new ServiceHandler().makeServiceCall(GlobalLinks.mainLink + GlobalLinks.productDetails, ServiceHandler.POST, pairs);
Log.e("Parameters", "" + pairs);
return json;
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
loadingview.dismiss();
System.out.println(s);
try {
if (!Internet.isConnectingToInternet(getApplicationContext())) {
Internet.noInternet(getApplicationContext());
} else {
if (s.equalsIgnoreCase(null) || s.equalsIgnoreCase("") || s.equalsIgnoreCase("null") || s.length() == 0) {
GlobalUse.nullJSON(getApplicationContext());
} else {
JSONObject mainObject = new JSONObject(s);
boolean status = mainObject.getBoolean("status");
String message = mainObject.getString("message");
totalPage = mainObject.getInt("total_page");
Log.e("total_page", "" + totalPage);
Toast.makeText(getApplicationContext(), "" + message, Toast.LENGTH_LONG).show();
if (status == true) {
JSONArray dataArray = mainObject.getJSONArray("data");
for (int i = 0; i < dataArray.length(); i++) {
JSONObject object = dataArray.getJSONObject(i);
JSONObject getProductObject = object.getJSONObject("GetProduct");
BeanGetProducts getProducts = new BeanGetProducts();
getProducts.setProduct_id(getProductObject.getString("product_id"));
getProducts.setImage(getProductObject.getString("image"));
getProducts.setSku(getProductObject.getString("sku"));
getProducts.setQuantity(getProductObject.getString("quantity"));
getProducts.setPrice(getProductObject.getString("price"));
getProducts.setStock_status_id(getProductObject.getString("stock_status_id"));
JSONObject product_description = object.getJSONObject("Product_Description");
getProducts.setName(product_description.getString("name"));
getProducts.setDescription(product_description.getString("description"));
JSONObject SpecialPrice = object.getJSONObject("SpecialPrice");
getProducts.setSpecialPrice(SpecialPrice.getString("price"));
beanGetProductses.add(getProducts);
}
// productAdapter = new GetProductAdapter(beanGetProductses, ProductView.this, getApplicationContext());
productAdapter.notifyDataSetChanged();
list_product.setAdapter(productAdapter);
}
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
public void onBackPressed() {
Intent intent = new Intent(getApplicationContext(), AdminAccess.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);
finish();
}
}
答案 0 :(得分：0)
创建一个名为EndlessScrollListener
的新类import android.widget.AbsListView;
public abstract class EndlessScrollListener implements AbsListView.OnScrollListener {
// The minimum number of items to have below your current scroll position
// before loading more.
private int visibleThreshold = 5;
// The current offset index of data you have loaded
private int currentPage = 0;
// The total number of items in the dataset after the last load
private int previousTotalItemCount = 0;
// True if we are still waiting for the last set of data to load.
private boolean loading = true;
// Sets the starting page index
private int startingPageIndex = 0;
public EndlessScrollListener() {
}
public EndlessScrollListener(int visibleThreshold) {
this.visibleThreshold = visibleThreshold;
}
public EndlessScrollListener(int visibleThreshold, int startPage) {
this.visibleThreshold = visibleThreshold;
this.startingPageIndex = startPage;
this.currentPage = startPage;
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount)
{
// If the total item count is zero and the previous isn't, assume the
// list is invalidated and should be reset back to initial state
if (totalItemCount < previousTotalItemCount) {
this.currentPage = this.startingPageIndex;
this.previousTotalItemCount = totalItemCount;
if (totalItemCount == 0) { this.loading = true; }
}
// If it's still loading, we check to see if the dataset count has
// changed, if so we conclude it has finished loading and update the current page
// number and total item count.
if (loading && (totalItemCount > previousTotalItemCount)) {
loading = false;
previousTotalItemCount = totalItemCount;
currentPage++;
}
// If it isn't currently loading, we check to see if we have breached
// the visibleThreshold and need to reload more data.
// If we do need to reload some more data, we execute onLoadMore to fetch the data.
if (!loading && (firstVisibleItem + visibleItemCount + visibleThreshold) >= totalItemCount ) {
loading = onLoadMore(currentPage + 1, totalItemCount);
}
}
// Defines the process for actually loading more data based on page
// Returns true if more data is being loaded; returns false if there is no more data to load.
public abstract boolean onLoadMore(int page, int totalItemsCount);
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// Don't take any action on changed
}
}
然后按以下方式更改您的代码。
您在asynctask中传递的页面数实际上是列表的大小。因此，您可以在从网络传输数据后更新此变量。
public class ProductView extends AppCompatActivity {
ListView list_product;
String json;
ProgressActivity loadingview;
int Pagecount = 0
Toolbar toolbar;
GetProductAdapter productAdapter;
List<BeanGetProducts> beanGetProductses = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_product_view);
toolbar = (Toolbar) findViewById(R.id.back_toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
onBackPressed();
}
});
ImageView img_home = (ImageView) findViewById(R.id.dr_image_home);
img_home.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(ProductView.this, AdminAccess.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
finish();
}
});
list_product = (ListView) findViewById(R.id.list_products);
productAdapter = new GetProductAdapter(beanGetProductses, ProductView.this, getApplicationContext());
// Load first time data and insert into list.
new getProducts(Pagecount).execute();
list_product.setOnScrollListener(new EndlessScrollListener() {
@Override
public boolean onLoadMore(int page, int totalItemsCount) {
// Triggered only when new data needs to be appended to the list
// Add whatever code is needed to append new items to your AdapterView
new getProducts(Pagecount).execute();
// or loadNextDataFromApi(totalItemsCount);
return true; // ONLY if more data is actually being loaded; false otherwise.
}
});
}
public class getProducts extends AsyncTask<Void, Void, String> {
int pageNo;
public getProducts(int pageNo) {
this.pageNo = pageNo;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
try {
loadingv
iew = new ProgressActivity(ProductView.this, "");
loadingview.setCancelable(false);
loadingview.show();
} catch (Exception e) {
}
}
@Override
protected String doInBackground(Void... voids) {
List<NameValuePair> pairs = new ArrayList<>();
pairs.add(new BasicNameValuePair("", String.valueOf(pageNo)));
json = new ServiceHandler().makeServiceCall(GlobalLinks.mainLink + GlobalLinks.productDetails, ServiceHandler.POST, pairs);
Log.e("Parameters", "" + pairs);
return json;
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
loadingview.dismiss();
System.out.println(s);
try {
if (!Internet.isConnectingToInternet(getApplicationContext())) {
Internet.noInternet(getApplicationContext());
} else {
if (s.equalsIgnoreCase(null) || s.equalsIgnoreCase("") || s.equalsIgnoreCase("null") || s.length() == 0) {
GlobalUse.nullJSON(getApplicationContext());
} else {
JSONObject mainObject = new JSONObject(s);
boolean status = mainObject.getBoolean("status");
String message = mainObject.getString("message");
totalPage = mainObject.getInt("total_page");
Log.e("total_page", "" + totalPage);
Toast.makeText(getApplicationContext(), "" + message, Toast.LENGTH_LONG).show();
if (status == true) {
JSONArray dataArray = mainObject.getJSONArray("data");
// Update Pagecount here
Pagecount = Pagecount + dataArray.length();
for (int i = 0; i < dataArray.length(); i++) {
JSONObject object = dataArray.getJSONObject(i);
JSONObject getProductObject = object.getJSONObject("GetProduct");
BeanGetProducts getProducts = new BeanGetProducts();
getProducts.setProduct_id(getProductObject.getString("product_id"));
getProducts.setImage(getProductObject.getString("image"));
getProducts.setSku(getProductObject.getString("sku"));
getProducts.setQuantity(getProductObject.getString("quantity"));
getProducts.setPrice(getProductObject.getString("price"));
getProducts.setStock_status_id(getProductObject.getString("stock_status_id"));
JSONObject product_description = object.getJSONObject("Product_Description");
getProducts.setName(product_description.getString("name"));
getProducts.setDescription(product_description.getString("description"));
JSONObject SpecialPrice = object.getJSONObject("SpecialPrice");
getProducts.setSpecialPrice(SpecialPrice.getString("price"));
beanGetProductses.add(getProducts);
productAdapter.notifyDataSetChanged();
}
}
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
public void onBackPressed() {
Intent intent = new Intent(getApplicationContext(), AdminAccess.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);
finish();
}
}