更新UI线程的AsyncTask在公共类 [英] Updating UI Thread from AsyncTask in public class
问题描述
我想一些的AsyncTask类剥离到公共（单独）功能，因此我并没有改写了这么多code。我几乎有它，除了一个非常重要的方面。该AsyncTask的函数编译一个ArrayList通过PHP调用服务器。当这个名单是完整的，我需要更新主UI线程上的微调。我发现了一个非常好的答案<一href="http://stackoverflow.com/questions/13815807/return-value-from-asynctask-class-onpostexecute-method">here但我有一点点困难，使其正常工作。
下面是什么，我有一个缩小版本：（请注意，在这一点上，所有我想要做的是叫吐司消息证明往返正）
下面是调用活动：
公共类MyActivity扩展活动实现OnTaskCompleted {
@覆盖
保护无效的onCreate（包savedInstanceState）{
super.onCreate（savedInstanceState）;
sg_list =新的ArrayList＆LT;字符串＆GT;（）;
新GetSuperGroups（UpdateAffiliations preferences.this，语境，检索组列表...）执行（）。
}
公共无效onTaskCompleted（ArrayList中＆LT;字符串＆GT;列表）{
Toast.makeText（getApplicationContext（），你好，从异步，Toast.LENGTH_SHORT）.show（）;
}
}
这是界面：
公共接口OnTaskCompleted {
无效onTaskCompleted（ArrayList中＆LT;字符串＆GT;清单）;
}
最后，这里是的AsyncTask 。请注意，这是一个公共类：
公共类GetSuperGroups延伸的AsyncTask＆LT;字符串，字符串，ArrayList的＆LT;字符串＆GT;＆GT; {
私人活动的活动;
私人上下文的背景下;
私人字符串progressMsg;
私人ProgressDialog pDialog;
私人的ArrayList＆LT;字符串＆GT; sg_list;
私人OnTaskCompleted监听;
公共GetSuperGroups（活动活动，上下文的背景下，字符串progressMsg）{
this.activity =活动;
this.context =背景;
this.progressMsg = progressMsg;
}
公共无效setSuperGroupList（OnTaskCompleted监听器）{
this.listener =侦听器;
}
@覆盖
在preExecute保护无效（）{
super.on preExecute（）;
pDialog =新ProgressDialog（上下文）;
pDialog.setMessage（progressMsg）;
pDialog.setIndeterminate（假）;
pDialog.setCancelable（真正的）;
pDialog.show（）;
}
@覆盖
受保护的ArrayList＆LT;字符串＆GT; doInBackground（字符串参数... args）{
sg_list =新的ArrayList＆LT;字符串＆GT;（）;
//使PHP调用，编译的ArrayList
返回sg_list;
}
保护无效onPostExecute（ArrayList中＆LT;字符串＆GT; sg_list）{
pDialog.dismiss（）;
//这下一行导致空指针错误
//注意，我扔掉了数组列表现在
//我想要做的就是证明我可以调用吐司回调用活动
listener.onTaskCompleted（新的ArrayList＆其中;字符串＆GT;（））;
}
}
就在你的的AsyncTask OnTaskCompleted监听器参数> 构造 GetSuperGroups 。然后通过这当您执行的AsyncTask 。
公共类MyActivity扩展活动实现OnTaskCompleted {
@覆盖
保护无效的onCreate（包savedInstanceState）{
super.onCreate（savedInstanceState）;
sg_list =新的ArrayList＆LT;字符串＆GT;（）;
新GetSuperGroups（UpdateAffiliations preferences.this，语境，检索组列表...，这一点）.execute（）;
}
公共无效onTaskCompleted（ArrayList中＆LT;字符串＆GT;列表）{
Toast.makeText（getApplicationContext（），你好，从异步，Toast.LENGTH_SHORT）.show（）;
}
}
和
公共类GetSuperGroups延伸的AsyncTask＆LT;字符串，字符串，ArrayList的＆LT;字符串＆GT;＆GT; {
私人活动的活动;
私人上下文的背景下;
私人字符串progressMsg;
私人ProgressDialog pDialog;
私人的ArrayList＆LT;字符串＆GT; sg_list;
私人OnTaskCompleted监听;
公共GetSuperGroups（活动活动，上下文的背景下，字符串progressMsg，OnTaskCompleted监听器）{
this.activity =活动;
this.context =背景;
this.progressMsg = progressMsg;
this.listener =侦听器;
}
I'm trying to split off some AsyncTask classes into public (separate) functions so that I'm not having to rewrite so much code. I almost have it, except for one very important aspect. The AsyncTask function compiles an ArrayList by making php calls to a server. When this list is complete, I need to update a spinner on the main UI thread. I found a really nice answer here but I'm having a little difficulty making it work.
Here is a scaled down version of what I have: (note that at this point, all I am trying to do is to call a Toast message to prove that the round trip is working)
Here is the calling Activity:
public class MyActivity extends Activity implements OnTaskCompleted {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
sg_list = new ArrayList<String>();
new GetSuperGroups(UpdateAffiliationsPreferences.this, context, "Retrieving Group List...").execute();
}
public void onTaskCompleted(ArrayList<String> list) {
Toast.makeText(getApplicationContext(), "hello from async", Toast.LENGTH_SHORT).show();
}
}
This is the interface:
public interface OnTaskCompleted {
void onTaskCompleted(ArrayList<String> list);
}
And finally, here is the AsyncTask. Note that it is a Public class:
public class GetSuperGroups extends AsyncTask<String, String, ArrayList<String>> {
private Activity activity;
private Context context;
private String progressMsg;
private ProgressDialog pDialog;
private ArrayList<String> sg_list;
private OnTaskCompleted listener;
public GetSuperGroups(Activity activity, Context context, String progressMsg) {
this.activity = activity;
this.context = context;
this.progressMsg = progressMsg;
}
public void setSuperGroupList (OnTaskCompleted listener){
this.listener = listener;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(context);
pDialog.setMessage(progressMsg);
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected ArrayList<String> doInBackground(String... args) {
sg_list = new ArrayList<String>();
//make a php call, compile the ArrayList
return sg_list;
}
protected void onPostExecute(ArrayList<String> sg_list) {
pDialog.dismiss();
//this next line causes a null pointer error
//note that I am throwing away the array list for now
//all I want to do is prove that I can call the Toast back in the calling Activity
listener.onTaskCompleted(new ArrayList<String>());
}
}
Just add OnTaskCompleted listener parameter in your asyncTask constructor GetSuperGroups. Then pass this when you execute your asyncTask.
public class MyActivity extends Activity implements OnTaskCompleted {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
sg_list = new ArrayList<String>();
new GetSuperGroups(UpdateAffiliationsPreferences.this, context, "Retrieving Group List...", this).execute();
}
public void onTaskCompleted(ArrayList<String> list) {
Toast.makeText(getApplicationContext(), "hello from async", Toast.LENGTH_SHORT).show();
}
}
and
public class GetSuperGroups extends AsyncTask<String, String, ArrayList<String>> {
private Activity activity;
private Context context;
private String progressMsg;
private ProgressDialog pDialog;
private ArrayList<String> sg_list;
private OnTaskCompleted listener;
public GetSuperGroups(Activity activity, Context context, String progressMsg, OnTaskCompleted listener) {
this.activity = activity;
this.context = context;
this.progressMsg = progressMsg;
this.listener = listener;
}
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