我需要知道如何从该活动启动的服务启动我原始活动中的AsyncTask。它可以获取音乐并在服务中播放它，我希望它在完成之后抓住下一首歌：
mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener()
{
public void onCompletion(MediaPlayer mp)
{
if (MainMenu.radioFlag == 1) {
// Start new asynctask
} else {
stopSelf();
}
}
});
下面是我的Radio.class中的AsyncTask。我不知道如何通过引用Radio.this使其静态，我也在startService（i）和stopService（i）上遇到错误。我非常感谢你的帮助，谢谢。
private class LoadList extends AsyncTask<String, UserRecord, JSONArray> {
String result = null;
InputStream is = null;
StringBuilder sb = null;
JSONArray jArray;
@Override
protected void onCancelled() {
Toast toast = Toast.makeText(getApplicationContext(), "Loading failed, trying again", Toast.LENGTH_LONG);
toast.show();
new LoadList().execute(linkurl);
}
protected JSONArray doInBackground(String... link) {
linkurl = link[0];
URI uri = null;
try {
uri = new URI(link[0]);
} catch (URISyntaxException e2) {
// TODO Auto-generated catch block
e2.printStackTrace();
}
//http post
try{
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(uri);
//httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
}catch(Exception e){
Log.e("log_tag", "Error in http connection"+e.toString());
}
//convert response to string
try{
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"UTF8"),8);
sb = new StringBuilder();
sb.append(reader.readLine() + "\n");
String line="0";
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result=sb.toString();
}catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
}
if (result == null) {
linkurl = link[0];
cancel(true);
} else {
try{
jArray = new JSONArray(result);
JSONObject json_data=null;
displayname = new String[jArray.length()];
song_name = new String[jArray.length()];
artist = new String[jArray.length()];
description = new String[jArray.length()];
genre = new String[jArray.length()];
custom_genre = new String[jArray.length()];
album = new String[jArray.length()];
timestamp = new String[jArray.length()];
song_id = new String[jArray.length()];
avatar = new String[jArray.length()];
test_rating = new Float[jArray.length()];
songurl = new String[jArray.length()];
viewss = new String[jArray.length()];
section = new String[jArray.length()];
plays = new String[jArray.length()];
downloads = new String[jArray.length()];
ratingcount = new String[jArray.length()];
commentcount = new String[jArray.length()];
dlFlag = new int[jArray.length()];
link1 = new String[jArray.length()];
link2 = new String[jArray.length()];
link3 = new String[jArray.length()];
link4 = new String[jArray.length()];
link5 = new String[jArray.length()];
for(int i=0;i<jArray.length();i++){
json_data = jArray.getJSONObject(i);
song_id[i]=json_data.getString("id");
song_name[i]=json_data.getString("songname");
artist[i]=json_data.getString("artist");
displayname[i]=json_data.getString("displayname");
description[i]=json_data.getString("description");
genre[i]=json_data.getString("genre");
custom_genre[i]=json_data.getString("customgenre");
album[i]=json_data.getString("album");
timestamp[i]=json_data.getString("format");
avatar[i]=json_data.getString("image_url");
songurl[i]=json_data.getString("song_url");
test_rating[i] = (float) json_data.getDouble("rating");
viewss[i] = json_data.getString("views");
section[i] = json_data.getString("section");
plays[i] = json_data.getString("plays");
downloads[i] = json_data.getString("downloads");
ratingcount[i] = json_data.getString("rating_count");
commentcount[i] = json_data.getString("comments");
dlFlag[i] = json_data.getInt("downloadflag");
link1[i] = json_data.getString("link1");
link2[i] = json_data.getString("link2");
link3[i] = json_data.getString("link3");
link4[i] = json_data.getString("link4");
link5[i] = json_data.getString("link5");
}
}
catch(JSONException e1){
e1.printStackTrace();
} catch (ParseException e1) {
e1.printStackTrace();
}
}
return null;
}
protected void onProgressUpdate(UserRecord... progress) {
}
protected void onPostExecute(JSONArray jArray) {
i.putExtra("songURL", songurl[0]);
i.putExtra("songNAME", displayname[0]);
MainMenu.radioFlag = 1;
ratingBar.setRating(0);
tvTrack.setText(displayname[0]);
if(dialog.isShowing()) {
dialog.dismiss();
}
if(MainMenu.serviceRunning == 1) {
stopService(i);
startService(i);
} else {
startService(i);
}
tvTime.setText(timestamp[0]);
tvViews.setText(viewss[0]);
tvComments.setText(commentcount[0]);
tvRatings.setText(ratingcount[0]);
tvPlays.setText(plays[0]);
tvDownloads.setText(downloads[0]);
if(description[0] == "null" || description[0] == ""){
viewDesc.setVisibility(View.GONE);
viewDesc2.setVisibility(View.GONE);
descriptionTitle.setVisibility(View.GONE);
tvDescription.setVisibility(View.GONE);
} else {
viewDesc.setVisibility(View.VISIBLE);
descriptionTitle.setVisibility(View.VISIBLE);
tvDescription.setVisibility(View.VISIBLE);
tvDescription.setText(description[0]);
viewDesc2.setVisibility(View.VISIBLE);
}
}
protected void onPreExecute(){
dialog = ProgressDialog.show(Radio.this, "",
"Loading. Please wait...", true);
}
}
答案 0 :(得分：2)
即使可以，也不想让AsyncTask静态。每个实例都适合一次拍摄，永远不能再次运行。
您Activity和Service之间似乎有一些沟通。在这种情况下，你应该研究binding the service to your activity。您可以轻松地来回调用方法，也可以设置Message和Handler频道，如果您想要异步执行。
答案 1 :(得分：1)
您可以轻松地将其声明为静态。
您只需要传递对Activity的引用，以便访问其成员。
通过使其成为静态，您将失去对外部类实例成员的访问权限，因此只需通过将其传递给AsyncTask的构造函数，然后在访问它之前将其检查为null来维护对活动的引用。
我还建议将其设为WeakReference ：
可辩论的好处是AsyncTask不会持有引用 回到它的父Activity（java中的内部类得到一个强大的ref 回到父母，除非他们是静止的）。
这将允许在用户使用时进行GC（垃圾收集）活动 切换屏幕。
这是一个代码示例
private static class StatusLoader extends AsyncTask <Boolean, Void, ServiceStatus> {
WeakReference<StatusActivity> _act;
StatusLoader(StatusActivity pActivity) {
_act = new WeakReference<StatusActivity>(pActivity);
}
@Override
protected ServiceStatus doInBackground(Boolean... params) {
ServiceStatus retval = null;
boolean bUseCache = params[0];
retval = StatusMgr.getStatus(bUseCache); // do work...
return retval;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
StatusActivity act = _act.get();
if (act != null) {
act._mData.showProgress(U.getStringRes(R.string.progress_msg_status_update));
}
}
@Override
protected void onPostExecute(ServiceStatus pResult) {
super.onPostExecute(pResult);
StatusActivity act = _act.get();
if (act != null) { // <-- in case activty is no longer alive
act._dsStatus = pResult;
act._mData.hideProgress();
act._mData.bindStatusData(StatusMgr.getResultMode());
}
}
}