Question

我试图通过从网站上删除数据来填充 RecyclerView 。问题是getData() {model}的SearchCards.java方法在 AsyncTask 完成执行之前返回String（pageTitle），导致空String。这是我的代码

FragmentOne.java

 mAdapter = new SearchAdapter(SearchCards.getData(),this,recyclerView);
 recyclerView.setAdapter(mAdapter);

SearchCards.java

public static ArrayList<SearchCards> getData() {

    ArrayList<SearchCards> datatList = new ArrayList<SearchCards>();

    String pageTitle = new Scrapping().scrapSubs(); //scrapSubs contains AsynTask                     
    String[] yearArr = setYearArr();

    for (int i = 0; i < yearArr.length; i++) {
        SearchCards searchCard = new SearchCards();
        searchCard.setYear(yearArr[i]);
        searchCard.setTitle(pageTitle); //same pagetitle for every year
        datatList.add(searchCard);             
    }      

    return dataList;
}

Scrapping.java

public String ScrapSubs(){
    JsoupAsyncTask jsoupAsyncTask = new JsoupAsyncTask();
    jsoupAsyncTask.execute();
    return pageTitle;
}

private class JsoupAsyncTask extends AsyncTask<Void, Void, Void> {
    @Override
        protected Void doInBackground(Void... params) {
            try {
                htmlDocument = Jsoup.connect(htmlPageUrl).get();
                pageTitle = htmlDocument.title();
                Log.i(TAG,"PAGETITLE"+pageTitle);
            } catch (IOException e) {
                e.printStackTrace();
            }
            return null;
        }

    @Override
        protected void onPostExecute(Void result) {
        //do something
        }
}

如何在Scrapping.java中执行返回pageTitle之类的操作仅在AsyncTask执行完成后执行。我尝试了这个但是没有用：

if(jsoupAsyncTask.getStatus() == AsyncTask.Status.FINISHED){
     return pageTitle;
}

修改可能这不是一个研究得很好的问题。在这里，我找到了我要找的东西：http://stacktips.com/tutorials/android/android-recyclerview-example 我所要做的就是在onPostExecute（）中移动SearchAdapter初始化。

Answer 1

private class JsoupAsyncTask extends AsyncTask<Void, Void, You Result Data Type> {
        @Override
        protected You Result Data Type doInBackground(Void... params) {
            try {
                htmlDocument = Jsoup.connect(htmlPageUrl).get();
                pageTitle = htmlDocument.title();
                Log.i(TAG,"PAGETITLE"+pageTitle);
            } catch (IOException e) {
                e.printStackTrace();
            }
            return Your Execution Result;
        }

        @Override
        protected void onPostExecute(You Result Data Type Your Execution Result)           {
        //Do Rest of Your Program
        }
}

Answer 2

创建intarface：

private class JsoupAsyncTask extends AsyncTask<Void, Void, Void> {

    public interface FinishListener {
        void processFinish(Boolean isFinish);
    }

    FinishListener finishListener = null;

    public JsoupAsyncTask(FinishListener  finishListener) {
        this.finishListener = finishListener;
    }

    @Override
    protected Void doInBackground(Void... params) {
        try {
            htmlDocument = Jsoup.connect(htmlPageUrl).get();
            pageTitle = htmlDocument.title();
            Log.i(TAG, "PAGETITLE" + pageTitle);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        finishListener.processFinish(true);
        //do something
    }
}

听众：

new JsoupAsyncTask(new JsoupAsyncTask.FinishListener() {
@Override
public void processFinish(Boolean isFinish) {
        // do somthing  }
        }).execute();

Answer 3

如果您希望代码同步运行，那么您根本不需要使用AsyncTask - 只需创建一个可以满足您需要的方法并调用它。然而，这在UI线程中不起作用 - UI线程方法必须快速返回，否则整个应用程序停止。您可能需要重新考虑您的设计。一种方法是显示某种“等待ui”，微调器，进度条等，而AsyncTask在后台运行，只有当你有数据移动并显示它时。

如何在AsyncTask的onPostExecute（）执行后返回值？

3 个答案: