AsyncTask不会更新Viewpager中的First片段内的TextView

Question

我已经开始为Android编程（来自iOS），当我在新项目向导中选择Activity + Scrollable tabs选项时，我正在使用ADT为我生成的样板代码。在下面的代码中，我在评论中标记了相同的内容。

场景是我在editText中输入文本，按下按钮并从Web服务中获取一些数据。我希望将这些数据放在视图寻呼机内的相应片段（有3个片段）中。我正在获取数据，当我滑动时，我能够在Fragment 2和Fragment 3上设置它，但是一旦AsycTask完成，与Fragment 1相关的数据就不会被设置。但是，在刷到片段3后，当我回到片段1时，数据就在那里。

这是我的代码：

活动

public class XXXX extends FragmentActivity {

SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;

//My additions to the boiler plate source generated by ADT
public ArrayList<String> p1T,p2T,p3T,p4T;
private EditText editText;
private Button button;
private boolean flag;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.konjugation);
    mSectionsPagerAdapter = new SectionsPagerAdapter (getSupportFragmentManager());
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mSectionsPagerAdapter);

    //My additions to the boiler plate source below
    flag=false;
    p1T = new ArrayList<String>(6); 
    p2T = new ArrayList<String>(6); 
    p3T = new ArrayList<String>(6); 
    p4T = new ArrayList<String>(6); 

    editText = (EditText) findViewById(R.id.editText1);
    button = (Button) findViewById(R.id.button1);

    button.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            String url = editText.getText().toString();
            if(!url.isEmpty()) {
                url="http://.../?q="+editText.getText().toString();
                PAsyncTask task = new PAsyncTask();
                task.execute(url);
            }

    mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener(){
        @Override
        public void onPageSelected(int pos) {
            if(flag==true) {
                if(pos==0) DummySectionFragment.setText(p4T,p1T);
                if(pos==1) DummySectionFragment.setText(p4T,p2T);
                if(pos==2) DummySectionFragment.setText(p4T,p3T);
            }
            else {
                Log.d("ts","data not arrived");
            }
        }
    });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.konjugation, menu);
    return true;
}

PagerAdapter

    public class SectionsPagerAdapter extends FragmentStatePagerAdapter {
    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        Fragment fragment = new DummySectionFragment();
        return fragment;
    }

    @Override
    public int getCount() {
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        switch (position) {
        case 0:
            return getString(R.string.title_section1);
        case 1:
            return getString(R.string.title_section2);
        case 2:
            return getString(R.string.title_section3);
        }
        return null;
    }

    @Override
    public void notifyDataSetChanged() {
        int pos = mViewPager.getCurrentItem();
        if(pos==0) DummySectionFragment.setText(p4T,p1T);
        else if(pos==1) DummySectionFragment.setText(p4T,p2T);
        else if(pos==2) DummySectionFragment.setText(p4T,p3T);
    }

}

的AsyncTask

private class PAsyncTask extends AsyncTask<String, Void, String> {
    @Override
    protected String doInBackground(String... params) 
    {
        String response = "";
        for (String url : params) {
            DefaultHttpClient client = new DefaultHttpClient();
            HttpGet httpGet = new HttpGet(url);
            try {
                HttpResponse execute = client.execute(httpGet);
                InputStream content = execute.getEntity().getContent();
                BufferedReader buffer = new BufferedReader(new InputStreamReader(content));
                String s = "";
                while ((s = buffer.readLine()) != null) {
                    response += s;
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return response;
    }

    protected void onPostExecute(String result) 
    {
        try {
            p1T.clear();
            p2T.clear();
            p3T.clear();

            //do something very important with the result here

             flag=true;
            //hoping that somehow the viewpager adapter will refresh the view
            mSectionsPagerAdapter.notifyDataSetChanged();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Viewpager的片段

public static class DummySectionFragment extends Fragment {
    private static TextView dummyTextView;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_konjugation_dummy, container, false);
        dummyTextView = (TextView) rootView.findViewById(R.id.section_label);
        return rootView;
    }

    public static void setText(ArrayList<String> s, ArrayList<String> t) {
        try {
            DummySectionFragment.dummyTextView.setText("");
            for(int i=0;i<s.size();i++) {
                DummySectionFragment.dummyTextView.append(s.get(i)+" "+t.get(i)+"\n\n");
            }
        } catch(NullPointerException e) {
            e.printStackTrace();
        }
    }
}
}

在看完这里的一些帖子之后，我觉得有点失落。请帮忙： - （

Answer 1

你应该在runOnUiThread（）方法中更新它，它将一个runnable对象作为参数，所以你可以在其中传递你的实现。