Android片段上的"内容视图尚未创建"

Question

我正在使用Android Fragments viewpager设置.基本上有5个标签可以刷卡.

5个中的4个包含ListFragments由MySQL表填充的内容; 这是在一个内部完成的AsyncTask.当我快速滑动时,我有时会收到此错误:

09-01 07:54:01.243: E/AndroidRuntime(19706): FATAL EXCEPTION: main
09-01 07:54:01.243: E/AndroidRuntime(19706): java.lang.IllegalStateException: Content view not yet created
09-01 07:54:01.243: E/AndroidRuntime(19706):    at android.support.v4.app.ListFragment.ensureList(ListFragment.java:328)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at android.support.v4.app.ListFragment.getListView(ListFragment.java:222)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at com.---.---.MasterCat$TopFrag$TopTask.onPostExecute(MasterCat.java:570)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at com.---.---.MasterCat$TopFrag$TopTask.onPostExecute(MasterCat.java:1)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at android.os.AsyncTask.finish(AsyncTask.java:631)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at android.os.AsyncTask.access$600(AsyncTask.java:177)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at android.os.Handler.dispatchMessage(Handler.java:99)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at android.os.Looper.loop(Looper.java:137)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at android.app.ActivityThread.main(ActivityThread.java:4928)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at java.lang.reflect.Method.invokeNative(Native Method)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at java.lang.reflect.Method.invoke(Method.java:511)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:558)
09-01 07:54:01.243: E/AndroidRuntime(19706):    at dalvik.system.NativeStart.main(Native Method)

我故意不使用a,ProgressDialog因为它会使刷卡口吃得相当多.

所以我有两个选择,我需要帮助:

1. 如何防止此错误并在刷卡时保持列表刷新.

2. 或者一旦加载了5个片段,关闭"刷卡时刷新".换句话说,除非您退出活动并返回,否则列表将保持不变.

我更喜欢选项#1.请告诉我您需要查看的代码:

@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_layout);


        mSectionsPagerAdapter = new SectionsPagerAdapter(
                getSupportFragmentManager());

        final ActionBar actionBar = getActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        mViewPager = (ViewPager) findViewById(R.id.viewpager);
        mViewPager.setAdapter(mSectionsPagerAdapter);

        mViewPager
                .setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
                    @Override
                    public void onPageSelected(int position) {
                        actionBar.setSelectedNavigationItem(position);

                    }
                });

        for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
            actionBar.addTab(actionBar.newTab()
                    .setText(mSectionsPagerAdapter.getPageTitle(i))
                    .setTabListener(this));
        }




    }

    public void onTabUnselected(ActionBar.Tab tab,
            FragmentTransaction fragmentTransaction) {

    }

    @Override
    public void onSaveInstanceState(Bundle savedInstanceState) {
            super.onSaveInstanceState(savedInstanceState);
        }

    @Override
    public void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);

    }

    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
        mViewPager.setCurrentItem(tab.getPosition());
    }

    public void onTabReselected(ActionBar.Tab tab,
            FragmentTransaction fragmentTransaction) {
    }

    public class SectionsPagerAdapter extends FragmentPagerAdapter {

        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            Fragment f = null;
            switch (position) {
            case 0: {
                f = new MasterFrag();
                Bundle args = new Bundle();

                f.setArguments(args);
                break;
            }
            case 1: {
                f = new FeaturedFrag();
                Bundle args = new Bundle();

                f.setArguments(args);
                break;
            }
            case 4: {
                f = new TopFrag();
                Bundle args = new Bundle();

                f.setArguments(args);
                break;
            }
            case 3: {
                f = new NewFrag();
                Bundle args = new Bundle();

                f.setArguments(args);
                break;
            }
            case 2: {
                f = new TrendFrag();
                Bundle args = new Bundle();

                f.setArguments(args);
                break;
            }
            default:
                throw new IllegalArgumentException("not this many fragments: "
                        + position);
            }

            return f;

        }

此外,LogCat中引用的第570行属于AsyncTask内部的getListView(),它位于上面未显示的ListFragment内部.

编辑:

添加5个片段中的一个 - 在LogCat中引用的片段 - "TopFrag"

class TopTask extends AsyncTask<String, String, Void> {
        InputStream is = null;
        String result = "";

        @Override
        protected Void doInBackground(String... params) {
            String url_select = "http://www.---.com/---/---.php";

            HttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url_select);
            ArrayList<NameValuePair> param = new ArrayList<NameValuePair>();
            param.add(new BasicNameValuePair("Top", "Top"));

            try {
                httpPost.setEntity(new UrlEncodedFormEntity(param));
                HttpResponse httpResponse = httpClient.execute(httpPost);
                HttpEntity httpEntity = httpResponse.getEntity();

                // read content
                is = httpEntity.getContent();

            } catch (Exception e) {

                Log.e("log_tag", "Error in http connection " + e.toString());
            }
            try {
                BufferedReader br = new BufferedReader(
                        new InputStreamReader(is));
                StringBuilder sb = new StringBuilder();
                String line = "";
                while ((line = br.readLine()) != null) {
                    sb.append(line + "\n");
                }
                is.close();
                result = sb.toString();

            } catch (Exception e) {
                // TODO: handle exception
                Log.e("log_tag", "Error converting result " + e.toString());
            }

            return null;

        }

        protected void onPostExecute(Void v) {

            String item, cat;
            try {
                JSONArray jArray = new JSONArray(result);
                JSONObject json_data = null;
                for (int i = 0; i < jArray.length(); i++) {
                    json_data = jArray.getJSONObject(i);
                    item = json_data.getString("item");
                    cat = json_data.getString("category");


                    items.add(item);
                    cats.add(cat);



                }
            } catch (JSONException e1) {
                Toast.makeText(getActivity(), "No Top Items Found",
                        Toast.LENGTH_LONG).show();
            } catch (ParseException e1) {
                e1.printStackTrace();
            }

            ListView listView;
            listView = getListView();
            listView.setTextFilterEnabled(true);

            listView.setOnItemClickListener(new OnItemClickListener() {

                public void onItemClick(AdapterView<?> arg0, View arg1,
                        int arg2, long id) {
           // edit

                }
            });

            MasterCatObject[] mco = new MasterCatObject[items.size()];
            int index = 0;

            for (@SuppressWarnings("unused")
            String i : items) {
                mco[index] = new MasterCatObject(items.get(index),
                        cats.get(index));
                index++;
            }

            adapter = new AllTimeAdapter(getActivity(), mco);
            setListAdapter(adapter);

        }
    }

}

Answer 1

at android.support.v4.app.ListFragment.getListView(ListFragment.java:222)
at com.---.---.MasterCat$TopFrag$TopTask.onPostExecute(MasterCat.java:570)

TopTask.onPostExecute()当片段尚未(之前onCreateView)/不再显示(之后onDestroyView)时,您不得触摸UI .根本没有ListView你能得到的.

你可以在这里做的是更新所使用的数据结构,ListView以便下次绘制列表时包含新数据.