我遇到了在单独的类中从asyncTask获取结果的问题。我在这里听到了类似的问题答案，但我不知道我哪里出错了。
我的AsyncTask位于一个单独的类中，方便调用，我需要能够注意到asyntask已经完成，然后开始下一个活动。
我会欢迎任何帮助，因为我不确定我哪里出错了。
public class StartScreen extends Activity{
ProgressDialog pd;
CountDownTimer waitTimer;
public static final String APP_PREFERENCES = "AppPrefs";
SharedPreferences settings;
SharedPreferences.Editor prefEditor;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start_screen);
settings = getSharedPreferences(APP_PREFERENCES, MODE_PRIVATE);
// getPreferences();
// prefEditor = settings.edit();
waitTimer = new CountDownTimer(2000, 300) {
public void onTick(long millisUntilFinished) {
//called every 300 milliseconds, which could be used to
//send messages or some other action
}
public void onFinish() {
//After 2000 milliseconds (2 sec) finish current
//if you would like to execute something when time finishes
pd = ProgressDialog.show(StartScreen.this,"Title","Detail text",true,false,null);
getPreferences();
}
}.start();
}
private void getPreferences() {
String UserName = settings.getString("UserName", null);
if (UserName != null) {
// the key does not exist
Intent intent=new Intent(StartScreen.this,InitialPreferences.class);
startActivity(intent);
} else{
//if (UserName.equals(UserName)){
// handle the value
dataTask();
//pd.dismiss();
}
}
private void dataTask() {
// TODO Auto-generated method stub
new DATATask(this).execute(new FragmentCallback(){
@Override
public void onTaskDone() {
startMainAct();
}
});
}
private void startMainAct() {
Intent intent=new Intent(StartScreen.this,MainActivity.class);
startActivity(intent);
}
public interface FragmentCallback {
public void onTaskDone();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.start_screen, menu);
return true;
}
}
的AsyncTask：
public class DATATask extends AsyncTask<Void, Void, ArrayList<String>> {
private FragmentCallback mFragmentCallback;
public void execute(FragmentCallback fragmentCallback) {
mFragmentCallback = fragmentCallback;
}
ArrayList<String> arr_data=new ArrayList<String>();
private Context context;
public DATATask(Context context)
{
this.context = context;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected ArrayList<String> doInBackground(Void... params) {
Document docVts, docTide;
String shippingList, tideTimes;
try {
docVts = Jsoup.connect("https://vts.mhpa.co.uk/main_movelistb.asp").timeout(600000).get();
Elements tableRows = docVts.select("table.dynlist td:eq(0),td:eq(1),td:eq(3),td:eq(4),td:eq(7),td:eq(8)");
tableRows.size();
for(int i = 1; i < 80; i++){//only allows x results from vts list, from 1 not 0. 0 produces needless results
shippingList = tableRows.get(i).text().replaceAll(" | ", "") +"\n";
arr_data.add(shippingList);// add value to ArrayList
System.out.println(shippingList);
};
docTide = Jsoup.connect("http://www.mhpa.co.uk/search-tide-times/").timeout(600000).get();
Elements tideTimeOdd = docTide.select("div.tide_row.odd div:eq(0)");
Elements tideTimeEven = docTide.select("div.tide_row.even div:eq(0)");
Elements tideHightOdd = docTide.select("div.tide_row.odd div:eq(2)");
Elements tideHightEven = docTide.select("div.tide_row.even div:eq(2)");
Element firstTideTime = tideTimeOdd.first();
Element secondTideTime = tideTimeEven.first();
Element thirdTideTime = tideTimeOdd.get(1);
Element fourthTideTime = tideTimeEven.get(1);
Element firstTideHight = tideHightOdd.first();
Element secondTideHight = tideHightEven.first();
Element thirdTideHight = tideHightOdd.get(1);
Element fourthTideHight = tideHightEven.get(1);
System.out.println("first tide time: " + firstTideTime.text() + " " + firstTideHight.text());
System.out.println("second tide time: " + secondTideTime.text() + " " + secondTideHight.text() );
System.out.println("third tide time: " + thirdTideTime.text() + " " + thirdTideHight.text());
System.out.println("fourth tide time: " + fourthTideTime.text() + " " + fourthTideHight.text());
{
/*
Work with data - all is OK
*/
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return arr_data;//<< return ArrayList from here
}
@Override
protected void onPostExecute(ArrayList<String> result) {
mFragmentCallback.onTaskDone();
}
}
感谢您的帮助。
答案 0 :(得分：2)
您没有调用正确的AsyncTask.execute（）。正确的执行将调用onPreExecute（）然后调用doInBackground（）然后调用onPostExecute（）。
new DATATask(this).execute(new FragmentCallback(){
@Override
public void onTaskDone() {
startMainAct();
}
});
}
将调用此方法（错误的方法）：
public void execute(FragmentCallback fragmentCallback) {
mFragmentCallback = fragmentCallback;
}
您要做的是将此方法更改为 - setFragmentCallBack(FragmentCallback);
然后在OnPostExecute（）中添加：startMainAct();
而不是这样做：
@Override
public void onTaskDone() {
startMainAct();
}
完成此操作后，请致电new DATATask(this).execute();
它将调用preExecute（），doInbackground和PostExecute（）
您正在做的是将FragCallback添加到DataTask而不是调用正确的执行函数。
我希望这会有所帮助。
答案 1 :(得分：0)
实际上你没有执行你的AsyncTask。你应该调用“super.execute（Params ... params）;”在你重载的execute（FragmentCallback）方法。
答案 2 :(得分：0)
在您的活动中： DataTask dataTask = new DataTask（）; dataTask.execute（）;
在AsyncTask类中： onPostExecute（）{ //表达你的意图，开始活动或完成后你想做的任何事情 }
我认为这比制作它简单得多。希望有所帮助。另请参阅AsyncTask Android example
答案 3 :(得分：0)
您没有执行AsyncTask。调用DATATask.execute(FragmentCallback)只会将回调分配给您的任务。您需要拨打AsyncTask#execute(Runnable)，AsyncTask#execute(Params...)或AsyncTask#executeOnExecutor(Executor exec, Params... params)。
另外，我会通过构造函数或setter将回调传递给DATATask，而不是创建新的重载execute(FragmentCallback)方法。它很容易让人迷惑。