在android中向下滾動時，加載更多項目並在列表底部添加底部
[英]Load more items and add bottom to the list when scroll down in android
問題描述
我嘗試實現向適配器添加更多項的功能，但是每次刷新都會刷新，而不是將新項添加到列表的底部。
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Calendar;
public class MainActivity extends AppCompatActivity {
private DataListAdapter dataListAdapter;
Activity _activity;
ArrayList<DataObject> dataArrayList;
private ListView lv;
private String jsonResult;
boolean loadingMore = false;
private DataObject dataObject;
private static final String TAG = MainActivity.class.getSimpleName();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
_activity = this;
lv = (ListView) findViewById(R.id.listView1);
View footerView = ((LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.loading_view, null, false);
this.lv.addFooterView(footerView);
if (isOnline(_activity)) {
new LoadJsonData().execute();
scrollNotifyChange();
}
}
private void scrollNotifyChange() {
lv.setOnScrollListener(new AbsListView.OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
//what is the bottom item that is visible
int lastInScreen = firstVisibleItem + visibleItemCount;
//is the bottom item visible & not loading more already? Load more!
if ((lastInScreen == totalItemCount) && !(loadingMore)) {
// //start a new thread for loading the items in the list
Thread thread = new Thread(null, loadMoreListItems);
thread.start();
}
}
});
}
private Runnable loadMoreListItems = new Runnable() {
@Override
public void run() {
//Set flag so we cant load new items 2 at the same time
loadingMore = true;
//Reset the array that holds the new items
//Simulate a delay, delete this on a production environment!
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
}
jsonResult = doInBackground();
runOnUiThread(returnRes);
}
};
private Runnable returnRes = new Runnable() {
@Override
public void run() {
onPostExecute(jsonResult);
loadingMore = false;
}
};
public String doInBackground() {
String jsonResult = "";
// jsonResult=get("https://datatables.net/examples/server_side/scripts/server_processing.php");
// return jsonResult;
InputStream inputStream = null;
String result = "";
try {
HttpClient httpclient = new DefaultHttpClient();
HttpGet request = new HttpGet("https://datatables.net/examples/server_side/scripts/server_processing.php");
HttpResponse httpResponse = httpclient.execute(request);
inputStream = httpResponse.getEntity().getContent();
if (inputStream != null) {
jsonResult = convertInputStreamToString(inputStream);
} else {
jsonResult = "Did not work!";
}
} catch (Exception e) {
Log.e(TAG, "GET failed", e);
}
return jsonResult;
}
public void onPostExecute(String result) {
try {
// progress.dismiss();
dataArrayList = new ArrayList<DataObject>();
JSONObject dataJsontObject = new JSONObject(result);
JSONArray dataJsonArray = dataJsontObject.getJSONArray("data");
for (int i = 0; i < dataJsonArray.length(); i++) {
JSONArray dataSubArray = dataJsonArray.getJSONArray(i);
dataObject = new DataObject();
dataObject.setName((String) dataSubArray.get(0));
dataObject.setType((String) dataSubArray.get(1));
dataObject.setProfession((String) dataSubArray.get(2));
dataObject.setCountry((String) dataSubArray.get(3));
dataObject.setCurrency((String) dataSubArray.get(5));
dataArrayList.add(dataObject);
}
dataListAdapter = new DataListAdapter(dataArrayList);
dataListAdapter.add(dataObject);
// lv.setAdapter(dataListAdapter);
// dataListAdapter.add(dataObject);
dataListAdapter.notifyDataSetChanged();
lv.setAdapter(dataListAdapter);
lv.smoothScrollToPosition(dataListAdapter.getCount());
} catch (JSONException e) {
e.printStackTrace();
}
}
public static boolean isOnline(Context context) {
ConnectivityManager cm =
(ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
return netInfo != null && netInfo.isConnectedOrConnecting();
}
private class LoadJsonData extends AsyncTask<Void, Void, String> {
ProgressDialog progress;
@Override
protected void onPreExecute() {
super.onPreExecute();
progress = ProgressDialog.show(_activity, "Progress",
"Please wait", true);
}
@Override
protected String doInBackground(Void... params) {
String jsonResult = "";
// jsonResult=get("https://datatables.net/examples/server_side/scripts/server_processing.php");
// return jsonResult;
InputStream inputStream = null;
String result = "";
try {
HttpClient httpclient = new DefaultHttpClient();
HttpGet request = new HttpGet("https://datatables.net/examples/server_side/scripts/server_processing.php");
HttpResponse httpResponse = httpclient.execute(request);
inputStream = httpResponse.getEntity().getContent();
if (inputStream != null) {
jsonResult = convertInputStreamToString(inputStream);
} else {
jsonResult = "Did not work!";
}
} catch (Exception e) {
Log.e(TAG, "GET failed", e);
}
return jsonResult;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
try {
progress.dismiss();
if(loadingMore)
{
// listViwe.removeFooterView(loadingFooter);
loadingMore = false;
}
dataArrayList = new ArrayList<DataObject>();
JSONObject dataJsontObject = new JSONObject(result);
JSONArray dataJsonArray = dataJsontObject.getJSONArray("data");
for (int i = 0; i < dataJsonArray.length(); i++) {
JSONArray dataSubArray = dataJsonArray.getJSONArray(i);
DataObject dataObject = new DataObject();
dataObject.setName((String) dataSubArray.get(0));
dataObject.setType((String) dataSubArray.get(1));
dataObject.setProfession((String) dataSubArray.get(2));
dataObject.setCountry((String) dataSubArray.get(3));
dataObject.setCurrency((String) dataSubArray.get(5));
dataArrayList.add(dataObject);
}
dataListAdapter = new DataListAdapter(dataArrayList);
lv.setAdapter(dataListAdapter);
dataListAdapter.notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
if(loadingMore)
{
// listViwe.removeFooterView(loadingFooter);
loadingMore = false;
}
}
}
}
public class DataListAdapter extends BaseAdapter {
ArrayList<DataObject> dataListObject = new ArrayList<DataObject>();
public DataListAdapter(ArrayList<DataObject> dataListObject) {
this.dataListObject = dataListObject;
}
@Override
public int getCount() {
return dataListObject.size();
}
@Override
public Object getItem(int position) {
return dataListObject.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
public void add(DataObject dataObject){
// Log.v("AddView", country.getCode());
this.dataListObject.add(dataObject);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
if (convertView == null) {
LayoutInflater inflater = LayoutInflater.from(_activity);
convertView = inflater.inflate(R.layout.single_row, null);
holder = new ViewHolder();
holder.name = (TextView) convertView.findViewById(R.id.name);
holder.type = (TextView) convertView.findViewById(R.id.type);
holder.profession = (TextView) convertView.findViewById(R.id.profession);
holder.country = (TextView) convertView.findViewById(R.id.country);
holder.currency = (TextView) convertView.findViewById(R.id.currecy);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
final DataObject current = dataListObject.get(position);
holder.name.setText("Name--" + current.getName());
holder.type.setText("Type--" + current.getType());
holder.profession.setText("Professoion--" + current.getProfession());
holder.country.setText("Country--" + current.getCountry());
holder.currency.setText("Currency--" + current.getCurrency());
return convertView;
}
}
static class ViewHolder {
TextView name;
TextView type;
TextView profession;
TextView country;
TextView currency;
}
public static String convertInputStreamToString(InputStream inputStream) throws IOException {
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
String line = "";
String result = "";
while ((line = bufferedReader.readLine()) != null) {
result += line;
}
inputStream.close();
return result;
}
}
2 個解決方案
解決方案1
0 2016-06-30 05:20:58
AsyncTask自己產生一個新的智能線程，在后台運行事物，並在onPostExecute方法中發布UI線程的結果。
您不應自己調用AsyncTask的方法。 Android自行完成。 而不是在scrollchangelistener中調用新線程，例如：
Thread thread = new Thread(null, loadMoreListItems);
呼叫
new LoadJsonData().execute();
您不需要兩個Runnable線程即可完成asyncTask要做的同一件事。
問題是您的這段代碼：
dataListAdapter = new DataListAdapter(dataArrayList);
lv.setAdapter(dataListAdapter);
每次滾動結束時，它最終都會調用onPostExecute方法將結果發布到UI上。 但是在這里，您正在使用新的數據集進行新的Adapter eveytime，這就是為什么它總是刷新整個列表的原因。
刪除此部分並將其設置在Activity的onCreate中。在onPostExecute中將新值添加到適配器的數據列表中。 然后，只需在AsyncTask的onPostExecute內執行notifyDataSetChanged即可。
解決方案2
0 已采納 2016-06-30 05:26:04
您需要在onCreate方法中創建一個適配器
像這樣：
ArrayList<DataObject> list;
onCreate() {
list=new ArrayList();
ListAdapter dataListAdapter =new ListAdapter(list) // creating an adapter with empty list of data
listView.setAdpater(adpater);
}
然后，在onPostExceute（）方法中：將數據添加到ArrayList中，並像這樣通知適配器：
onPostExecute(){
....
.....
list.add(dataObject); //here you can add 'n' number of object to the list
dataListAdapter.notifyDataSetChanged(); // notify the adapter to update the listview
.....
}
編輯：我根據@ user3422948請求更新了此答案
DataListAdapter dataListAdapter;
ArrayList<DataObject> dataArrayList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
_activity = this;
//edit: declare your arraylist and adapter here
dataArrayList = new ArrayList<DataObject>();
dataListAdapter = new DataListAdapter(dataArrayList);
lv = (ListView) findViewById(R.id.listView1);
View footerView = ((LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.loading_view, null, false);
this.lv.addFooterView(footerView);
if (isOnline(_activity)) {
new LoadJsonData().execute();
scrollNotifyChange();
}
}
......
.......
public void onPostExecute(String result) {
try {
// progress.dismiss();
//dataArrayList = new ArrayList<DataObject>(); //edit
JSONObject dataJsontObject = new JSONObject(result);
JSONArray dataJsonArray = dataJsontObject.getJSONArray("data");
for (int i = 0; i < dataJsonArray.length(); i++) {
JSONArray dataSubArray = dataJsonArray.getJSONArray(i);
dataObject = new DataObject();
dataObject.setName((String) dataSubArray.get(0));
dataObject.setType((String) dataSubArray.get(1));
dataObject.setProfession((String) dataSubArray.get(2));
dataObject.setCountry((String) dataSubArray.get(3));
dataObject.setCurrency((String) dataSubArray.get(5));
dataArrayList.add(dataObject);
}
//edit: your creating new adapter for every execution
//dataListAdapter = new DataListAdapter(dataArrayList);
//dataListAdapter.add(dataObject);
// lv.setAdapter(dataListAdapter);
// dataListAdapter.add(dataObject);
dataListAdapter.notifyDataSetChanged();
//lv.setAdapter(dataListAdapter);
lv.smoothScrollToPosition(dataListAdapter.getCount());
} catch (JSONException e) {
e.printStackTrace();
}
}
問題是您要創建新適配器的每次執行
當用戶嘗試向下滾動時，如何在列表底部實現刷新？
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