使用AsyncTasks作为单独的公开课 [英] Using AsyncTasks as separate public classes
问题描述
这个问题是什么，我都问orginally <延续href=\"http://stackoverflow.com/questions/9690055/type-mismatch-cannot-convert-from-asynctask\">here
我试图找到一种更好的方式来传递从的AsyncTask ArrayList中的活动（任何活动调用AsyncTask的），所以在我的情况，我有一个 SongsManager.java 延伸到的AsyncTask ，你可以看到下面。
我的问题是，它不返回我的0 songsList 我得到大小...任何想法我失踪或者我需要调整或增加任何code再？
SongsManager.java
公共类SongsManager扩展的AsyncTask＆LT;无效，无效的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;＆GT; { 公共接口SongsMasterCallback {
无效showSongList（列表＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;结果）;
} 私人SongsMasterCallback mCallback;
公共SongsManager（SongsMasterCallback回调）
{
mCallback =回调;
} //构造
//公共SongsManager（）{}
ArrayList的＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT; songsList =新的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;（）;
@覆盖
保护的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT; doInBackground（虚空...... PARAMS）
{
//填充所有数据....
HashMap的＆LT;字符串，字符串＆GT;地图=新的HashMap＆LT;字符串，字符串＆GT;（）;
// .........
songsList.add（地图）;
} 返回songsList;
} @覆盖
保护无效onPostExecute（ArrayList的＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;的结果）{
// TODO自动生成方法存根
//super.onPostExecute(result）;
mCallback.showSongList（结果）;
}
}
main.java
公共类主要活动扩展实现SongsMasterCallback {公共无效showSongList（列表＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;结果）
{
this.songsList =（ArrayList的＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;）的结果;
//然后做一些与此列表
}@覆盖
公共无效的onCreate（捆绑savedInstanceState）{ 新SongsManager（本）.execute（）;
Log.d（songsSize，字符串：+ songsList.size（））; //它显示0？}}
试试这个
公共类SongsManager扩展的AsyncTask＆LT;无效，无效的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;＆GT; { 公共接口SongsMasterCallback {
无效showSongList（列表＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;结果）;
} 私人SongsMasterCallback mCallback;
公共SongsManager（SongsMasterCallback回调）
{
mCallback =回调;
} //构造
//公共SongsManager（）{}
@覆盖
保护的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT; doInBackground（虚空...... PARAMS）
{
ArrayList的＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT; songsList =新的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;（）;
//填充所有数据....
HashMap的＆LT;字符串，字符串＆GT;地图=新的HashMap＆LT;字符串，字符串＆GT;（）;
// ......... 返回地图;
} @覆盖
保护无效onPostExecute（ArrayList的＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;的结果）{
// TODO自动生成方法存根
//super.onPostExecute(result）;
songsList.add（结果）;
mCallback.showSongList（结果）;
}
这是发生，因为你是在UI线程创建songsList的对象，并在后台线程中添加数据。
this question is a continuation of what i have asked orginally here
i am trying to find a better way to pass the ArrayList from AsyncTask to the Activity (any activity that calls the AsyncTask) so in my situation i have a SongsManager.java which extends to AsyncTask as you can see below.
my question is, It does not returning me the songsList i am getting size of 0... any idea what i am missing or do i need to tweak or add any code further?
SongsManager.java
public class SongsManager extends AsyncTask<Void, Void, ArrayList<HashMap<String, String>>> {
public interface SongsMasterCallback {
void showSongList(List<HashMap<String, String>> result);
}
private SongsMasterCallback mCallback;
public SongsManager (SongsMasterCallback callback)
{
mCallback = callback;
}
// Constructor
//public SongsManager(){ }
ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
@Override
protected ArrayList<HashMap<String, String>> doInBackground(Void... params)
{
//populating all the data....
HashMap<String, String> map = new HashMap<String, String>();
//.........
songsList.add(map);
}
return songsList;
}
@Override
protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
// TODO Auto-generated method stub
//super.onPostExecute(result);
mCallback.showSongList(result);
}
}
main.java
public class Main extends Activity implements SongsMasterCallback {
public void showSongList(List<HashMap<String, String>> result)
{
this.songsList = (ArrayList<HashMap<String, String>>) result;
// then do something with the list here
}
@Override
public void onCreate(Bundle savedInstanceState) {
new SongsManager(this).execute();
Log.d("songsSize", "string : "+songsList.size()); //it shows 0 ???
}
}
Try this
public class SongsManager extends AsyncTask<Void, Void, ArrayList<HashMap<String, String>>> {
public interface SongsMasterCallback {
void showSongList(List<HashMap<String, String>> result);
}
private SongsMasterCallback mCallback;
public SongsManager (SongsMasterCallback callback)
{
mCallback = callback;
}
// Constructor
//public SongsManager(){ }
@Override
protected ArrayList<HashMap<String, String>> doInBackground(Void... params)
{
ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
//populating all the data....
HashMap<String, String> map = new HashMap<String, String>();
//.........
return map;
}
@Override
protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
// TODO Auto-generated method stub
//super.onPostExecute(result);
songsList.add(result);
mCallback.showSongList(result);
}
This is happening because you are creating object of songsList in UI thread and adding data in background thread.
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