我知道这次被问过几次，但我无法弄清楚如何将更多数据加载到我的列表视图中。
我正在使用这个代码来调用listview的第一个数据，没关系，在加载数据之后我显示了一个按钮来加载更多结果但是没有向listview显示任何新内容：
编辑：现在它正在从服务器加载数据，但它没有将它附加到列表视图，它正在用新的内容替换内容，我该如何覆盖它？编辑2：我添加了ListViewAdapter的代码。感谢@aegean
public class DownloadJSON extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Create a progressdialog
mProgressDialog = new ProgressDialog(MainActivity.this);
// Set progressdialog title
mProgressDialog.setTitle("Cargando reportes en tiempo real");
// Set progressdialog message
mProgressDialog.setMessage("Por favor espere");
mProgressDialog.setIndeterminate(false);
// Show progressdialog
mProgressDialog.show();
}
@Override
protected Void doInBackground(Void... params) {
// Create an array
arraylist = new ArrayList<HashMap<String, String>>();
// Retrieve JSON Objects from the given URL address
jsonobject = JSONfunctions
.getJSONfromURL("http://www.videotrafico.com/api/timeline.php?page=1");
try {
// Locate the array name in JSON
jsonarray = jsonobject.getJSONArray("datos");
for (int i = 0; i < jsonarray.length(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
jsonobject = jsonarray.getJSONObject(i);
jsonobject1 = jsonobject.getJSONObject("reporte");
// Retrive JSON Objects
map.put("imagen", jsonobject.getString("imagen"));
map.put("quien", jsonobject.getString("quien"));
map.put("fecha", jsonobject.getString("fecha"));
map.put("reporte", jsonobject.getString("reporte"));
map.put("contenidopost", jsonobject1.getString("contenidopost"));
map.put("imgs", jsonobject1.getString("imgs"));
map.put("video", jsonobject1.getString("video"));
// Set the JSON Objects into the array
arraylist.add(map);
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void args) {
// Locate the listview in listview_main.xml
listview = (ListView) findViewById(R.id.listview);
// Pass the results into ListViewAdapter.java
adapter = new ListViewAdapter(MainActivity.this, arraylist);
Button btnLoadMore = new Button(MainActivity.this);
btnLoadMore.setText("Cargar m‡s reportes");
// Adding Load More button to lisview at bottom
listview.addFooterView(btnLoadMore);
// Set the adapter to the ListView
listview.setAdapter(adapter);
//LoadMore button
/**
* Listening to Load More button click event
* */
btnLoadMore.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// Starting a new async task
new loadMoreListView().execute();
}
});
// Close the progressdialog
mProgressDialog.dismiss();
}
}
这是loadmore按钮的类：
public class loadMoreListView extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
// Showing progress dialog before sending http request
mProgressDialog = new ProgressDialog(
MainActivity.this);
mProgressDialog.setMessage("Cargando más reportes");
mProgressDialog.setIndeterminate(true);
mProgressDialog.setCancelable(false);
mProgressDialog.show();
}
protected Void doInBackground(Void... unused) {
// increment current page
current_page += 1;
arraylist = new ArrayList<HashMap<String, String>>();
// Retrieve JSON Objects from the given URL address
jsonobject = JSONfunctions
.getJSONfromURL("http://www.videotrafico.com/api/timeline.php?page="+current_page);
try {
// Locate the array name in JSON
jsonarray = jsonobject.getJSONArray("datos");
for (int i = 0; i < jsonarray.length(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
jsonobject = jsonarray.getJSONObject(i);
jsonobject1 = jsonobject.getJSONObject("reporte");
// Retrive JSON Objects
map.put("imagen", jsonobject.getString("imagen"));
map.put("quien", jsonobject.getString("quien"));
map.put("fecha", jsonobject.getString("fecha"));
map.put("reporte", jsonobject.getString("reporte"));
map.put("contenidopost", jsonobject1.getString("contenidopost"));
map.put("imgs", jsonobject1.getString("imgs"));
map.put("video", jsonobject1.getString("video"));
// Set the JSON Objects into the array
arraylist.add(map);
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return (null);
}
protected void onPostExecute(Void unused) {
listview = (ListView) findViewById(R.id.listview);
// closing progress dialog
// get listview current position - used to maintain scroll position
int currentPosition = listview.getFirstVisiblePosition();
// Appending new data to menuItems ArrayList
/*adapter = new ListViewAdapter(
MainActivity.this,
arraylist);
listview.setAdapter(adapter);
*/
ListViewAdapter myExistingAdapter = null;
if(listview.getAdapter() instanceof WrapperListAdapter) {
myExistingAdapter = (ListViewAdapter)((WrapperListAdapter)listview.getAdapter()).getWrappedAdapter();
} else if (listview.getAdapter() instanceof ListViewAdapter) {
myExistingAdapter = (ListViewAdapter)listview.getAdapter();
}
myExistingAdapter.setItems();
myExistingAdapter.notifyDataSetChanged();
// Setting new scroll position
listview.setSelectionFromTop(currentPosition + 1, 0);
mProgressDialog.dismiss();
}
}
public class ListViewAdapter extends BaseAdapter {
// Declare Variables
Context context;
LayoutInflater inflater;
ArrayList<HashMap<String, String>> data;
ImageLoader imageLoader;
HashMap<String, String> resultp = new HashMap<String, String>();
String coment;
public String img;
public int imga;
public ListViewAdapter(Context context,
ArrayList<HashMap<String, String>> arraylist) {
this.context = context;
data = arraylist;
imageLoader = new ImageLoader(context);
}
@Override
public int getCount() {
return data.size();
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
public View getView(final int position, View convertView, ViewGroup parent) {
// Declare Variables
TextView quien;
ImageView imagen;
TextView reporte;
TextView fecha;
VideoView video;
ImageView imgs;
inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View itemView = inflater.inflate(R.layout.listview_item, parent, false);
// Get the position
resultp = data.get(position);
// Locate the TextViews in listview_item.xml
// Locate the ImageView in listview_item.xml
imagen = (ImageView) itemView.findViewById(R.id.imagen);
fecha = (TextView) itemView.findViewById(R.id.fecha);
quien = (TextView) itemView.findViewById(R.id.quien);
reporte = (TextView) itemView.findViewById(R.id.reporte);
video = (VideoView) itemView.findViewById(R.id.videos);
imgs = (ImageView) itemView.findViewById(R.id.imgs);
// Capture position and set results to the TextViews
// Capture position and set results to the ImageView
// Passes flag images URL into ImageLoader.class
imageLoader.DisplayImage(resultp.get(MainActivity.IMAGEN), imagen);
fecha.setText(resultp.get(MainActivity.FECHA));
reporte.setText(resultp.get(MainActivity.CONTENIDOPOST));
quien.setText(resultp.get(MainActivity.QUIEN));
if (resultp.get(MainActivity.VIDEO).length() != 0){
imageLoader.DisplayImage(resultp.get(MainActivity.IMGS), imgs);
final String videoplayer = resultp.get(MainActivity.VIDEO);
if (resultp.get(MainActivity.CONTENIDOPOST).length() == 0){
reporte.setVisibility(View.GONE);
}
imgs.setVisibility(View.VISIBLE);
imgs.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(videoplayer));
context.startActivity(intent);
}
});
}
if (resultp.get(MainActivity.IMGS).length() != 0 && resultp.get(MainActivity.VIDEO).length() <= 5){
imageLoader.DisplayImage(resultp.get(MainActivity.IMGS), imgs);
final String imagenview = resultp.get(MainActivity.IMGS);
imgs.setVisibility(View.VISIBLE);
if (resultp.get(MainActivity.CONTENIDOPOST).length() == 0){
reporte.setVisibility(View.GONE);
}
imgs.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
/*
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.setDataAndType(Uri.parse(imagenview), "image/*");
context.startActivity(intent);
*/
Intent intentBrowseFiles = new Intent(Intent.ACTION_VIEW);
intentBrowseFiles.setDataAndType(Uri.parse(imagenview), "image/*");
//intentBrowseFiles.setFlag(Intent.FLAG_ACTIVITY_NEW_TASK);
context.startActivity(intentBrowseFiles);
}
});
}
return itemView;
}
}
我做错了什么？提前谢谢！
答案 0 :(得分：3)
现在它正在从服务器加载数据，但它没有附加它 对于listview，它正在用新的内容替换内容，怎么可能 我重写了吗？
因为您正在创建新的适配器：
adapter = new ListViewAdapter(MainActivity.this, arraylist);
尝试将新项目添加到现有适配器。
listview = (ListView) findViewById(R.id.listview);
ListViewAdapter myExistingAdapter = null
if(listview.getAdapter() instanceof WrapperListAdapter) {
myExistingAdapter = (ListViewAdapter)((WrapperListAdapter)listview.getAdapter()).getWrappedAdapter();
} else if (listview.getAdapter() instanceof ListViewAdapter) {
myExistingAdapter = (ListViewAdapter)listview.getAdapter();
}
myExistingAdapter.addItems(items);
myExistingAdapter.notifyDataSetChanged();
注意：要使用类似setItems（）方法的东西，我假设你有一个方法来设置数组适配器的项目。
在ListViewAdapter类下，编写一个方法来更新适配器中的项目：
public void addItems(ArrayList itemToAdd) {
if(data != null) {
data.addAll(itemToAdd);
} else {
data = itemToAdd;
}
}
BTW我建议你阅读更多关于listView和适配器的信息。因为你的实现不太好。你必须重新使用你的观点。 See an example here