我正在学习如何使用onscrolllistner
RecyclerOkHttpHandler类将从服务器执行基数为0且限制为5的select。我想要的是再次执行RecyclerOkHttpHandler以获取新数据，对于基础5的限制10.但在onscrolllistner上添加以下内容
handler.execute().get();
我收到了这个错误：
Cannot execute task: the task has already been executed (a task can be executed only once)
好吧，我明白我不能再执行任务了，但我应该如何过去和限制？
这（它正在工作）将执行一个将从服务器获取图像的类，但是我需要传递基数0和限制5
final RecyclerOkHttpHandler handler = new RecyclerOkHttpHandler( this, new RecyclerOkHttpHandler.MyInterface() {
@Override
public void myMethod(ArrayList result) {
mAdapter_first = new MyAdapter(result,SearchActivity.this);
mAdapter_first.notifyDataSetChanged();
mRecyclerView_first.setAdapter(mAdapter_first);
}
},"girls",base,limit);
try {
handler.execute().get();
} catch (Exception e) {
Log.d("SearchActivity error", "error in mRecyclerView_first");
e.printStackTrace();
}
这是addOnScrollListener，
mRecyclerView_first.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
visibleItemCount = mRecyclerView_first.getChildCount();
totalItemCount = mLayoutManager.getItemCount();
firstVisibleItem = mLayoutManager.findFirstVisibleItemPosition();
if (loading) {
if (totalItemCount > previousTotal) {
loading = false;
previousTotal = totalItemCount;
System.out.println("previousTotal:" + previousTotal);
System.out.println("totalItemCount:" + totalItemCount);
System.out.println("visibleItemCount:" + visibleItemCount);
}
}
if (!loading && (totalItemCount - visibleItemCount)
<= (firstVisibleItem + visibleThreshold)) {
// End has been reached
System.out.println(totalItemCount);
Log.i("Yaeye!", "end called");
// base =String.valueOf(firstVisibleItem);
// limit=String.valueOf(visibleItemCount);
// Do something
try {
handler.execute().get();
} catch (Exception e) {
Log.d("SearchActivity error", "error in mRecyclerView_first");
e.printStackTrace();
}
loading = true;
}
}
});
这是RecyclerOkHttpHandler类
public class RecyclerOkHttpHandler extends AsyncTask<String, Void, String> {
private Context mContext;
private MyInterface mListener;
public String category;
public String basestart;
public String limitend;
public RecyclerOkHttpHandler(Context context, MyInterface mListener, String categ, String base, String limit){
mContext = context;
this.mListener = mListener;
category=categ;
basestart=base;
limitend=limit;
}
public interface MyInterface {
public void myMethod(ArrayList result);
}
private final String Fetch_URL = "http://justedhak.com/old-files/Recyclerview_data.php";
// ArrayList<Listitem> Listitem;
ArrayList<CategoryList> Listitem;
int resulta;
OkHttpClient httpClient = new OkHttpClient();
ListView list;
String myJSON;
JSONArray peoples = null;
InputStream inputStream = null;
@Override
protected String doInBackground(String... params) {
Log.d("okhttp Fetch_URL", Fetch_URL);
RequestBody formBody = new FormEncodingBuilder()
.add("category", category)
.add("base", basestart)
.add("limit", limitend)
.build();
Request request = new Request.Builder()
.url(Fetch_URL)
.post(formBody)
.build();
String result = null;
try {
Response response = httpClient.newCall(request).execute();
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
inputStream = response.body().byteStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null)
{
sb.append(line + "\n");
}
result = sb.toString();
resulta = 1; //"Success
// return response.body().bytes();
} catch (Exception e) {
Toast.makeText(mContext, "Connection failed, check your connection",
Toast.LENGTH_LONG).show();
e.printStackTrace(); }
finally {
try{if(inputStream != null)inputStream.close();}catch(Exception squish){}
}
return result;
}
@Override
protected void onPostExecute(String result){
if( resulta ==1){
myJSON=result;
Log.e("result",result);
showList();
}
else{
Log.e("d","there is an error on postexecute in okhhttphandler.java");
}
}
protected void showList(){
try {
JSONObject jsonObj = new JSONObject(myJSON);
peoples = jsonObj.getJSONArray("result");
System.out.println("Length:"+peoples.length());
int J_length=peoples.length()-1;
//JSONObject maxj = peoples.getJSONObject(peoples.length() - 1);
// max of arrray
jsonObj= peoples.getJSONObject(J_length);
String j_id= jsonObj.getString("id");
int _id = Integer.parseInt(j_id);
System.out.println(j_id);
//max of
DatabaseHandler db = new DatabaseHandler(mContext);
String db_id="";
db_id = db.getmax();
if (db_id== null)
{
db_id="0";
}
int d_id = Integer.parseInt(db_id);
Log.e("db_id", db_id);
Log.e("j_id",j_id);
// if (_id < d_id) {
System.out.println("Getting json result ");
Listitem = new ArrayList<CategoryList>();
for (int i = 0; i < peoples.length(); i++) {
JSONObject c = peoples.getJSONObject(i);
String id = c.getString("id");
String url = c.getString("url");
Listitem.add(new CategoryList(id, url));
}
if (mListener != null)
mListener.myMethod(Listitem);
} catch (JSONException e) {
e.printStackTrace();
}
}
}
答案 0 :(得分：0)
我再次阅读了您的问题，解决方案可能只是每次都创建一个新的RecyclerOkHttpHandler。这就是错误消息所说的内容以及AsyncTasks的工作方式。如果在无法再次调用它时调用.execute（），则必须创建一个新对象。
仍然应该覆盖onPostExecute（），否则你阻止了UI线程。看看AsyncTask。 我需要RecyclerOkHttpHandler的代码来说更多......