Question

正如我在问题标题中所说的那样，我正在尝试用我的mysql数据库中的项目填充我的Home Activity操作栏微调器......我正在调整我的私有GetFeeds类（AsyncTask扩展类）来获得我想要的东西来自活动的onCreate方法中的数据库..我正确地得到了结果，但随后应用停止并关闭，我甚至看不到手机中的活动......

我的HomeActivity：

public class HomeActivity extends ActionBarActivity implements
    ActionBar.OnNavigationListener {

InternetConnectivityManager icm;
ProgressDialog pDialog;
BDFunctions bdfunctions;

String[] feeds;

/**
 * The serialization (saved instance state) Bundle key representing the
 * current dropdown position.
 */
private static final String STATE_SELECTED_NAVIGATION_ITEM = "selected_navigation_item";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_home);

    // Set up the action bar to show a dropdown list.
    final ActionBar actionBar = getSupportActionBar();
    actionBar.setDisplayShowTitleEnabled(false);
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);

    icm = new InternetConnectivityManager(getApplicationContext());

    new GetFeeds().execute();

    // Set up the dropdown list navigation in the action bar.
    actionBar.setListNavigationCallbacks(
    // Specify a SpinnerAdapter to populate the dropdown list.
            new ArrayAdapter<String>(actionBar.getThemedContext(),
                    android.R.layout.simple_list_item_1,
                    android.R.id.text1, feeds), this);
}

private class GetFeeds extends AsyncTask<Void, Void, JSONObject> {

    @Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();
        pDialog = new ProgressDialog(HomeActivity.this);
        pDialog.setMessage("A vrificar os grupos onde estas inserido...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();
    }

    protected JSONObject doInBackground(Void... arg0) {
        bdfunctions = new BDFunctions(getApplicationContext());
        JSONObject json = bdfunctions.getFeeds();
        return json;
    }

    protected void onPostExecute(JSONObject json) {
        // dismiss the dialog after getting the result
        pDialog.dismiss();
        if(json != null) {

            try {
                if (json.getString(JSONKeys.KEY_SUCCESS) != null) {
                    String res = json.getString(JSONKeys.KEY_SUCCESS); 
                    if(Integer.parseInt(res) == 1){

                        JSONArray jsonFeeds = json.getJSONArray("feeds");
                        feeds = new String[jsonFeeds.length()];
                        for(int i=0; i<jsonFeeds.length(); i++) {
                            JSONObject feedOBJ = (JSONObject) jsonFeeds.get(i);
                            feeds[i] = feedOBJ.getString("descricao");
                        }

                    }else{

                        Toast.makeText(getApplicationContext(), json.getString(JSONKeys.KEY_ERROR_MSG), Toast.LENGTH_LONG).show();
                    }
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        } else {
            Toast.makeText(getApplicationContext(), "Ocorreu um erro com o servidor", Toast.LENGTH_LONG).show();
        }
    }
}

@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
    // Restore the previously serialized current dropdown position.
    if (savedInstanceState.containsKey(STATE_SELECTED_NAVIGATION_ITEM)) {
        getSupportActionBar().setSelectedNavigationItem(
                savedInstanceState.getInt(STATE_SELECTED_NAVIGATION_ITEM));
    }
}

@Override
public void onSaveInstanceState(Bundle outState) {
    // Serialize the current dropdown position.
    outState.putInt(STATE_SELECTED_NAVIGATION_ITEM, getSupportActionBar()
            .getSelectedNavigationIndex());
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.home, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

@Override
public boolean onNavigationItemSelected(int position, long id) {
    // When the given dropdown item is selected, show its contents in the
    // container view.
    getSupportFragmentManager()
            .beginTransaction()
            .replace(R.id.container,
                    PlaceholderFragment.newInstance(position + 1)).commit();
    return true;
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    private static final String ARG_SECTION_NUMBER = "section_number";

    /**
     * Returns a new instance of this fragment for the given section number.
     */
    public static PlaceholderFragment newInstance(int sectionNumber) {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        return fragment;
    }

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_home, container,
                false);
        TextView textView = (TextView) rootView
                .findViewById(R.id.section_label);
        textView.setText(Integer.toString(getArguments().getInt(
                ARG_SECTION_NUMBER)));
        return rootView;
    }
}

}

Logcat说错误是由此行的java.lan.NullPointerException引起的：

new ArrayAdapter<String>(actionBar.getThemedContext(),
                    android.R.layout.simple_list_item_1,
                    android.R.id.text1, feeds), this);

我试图将setListNavigationCallbacks方法及其内部的所有内容从我的私有类移到onPostExecute方法中，所以我只在填充结果时填充微调器..但它给了我一个错误，我不能把setListNavigationCallbacks放在那里..我该怎么做？

由于

Answer 1

GetFeeds任务以异步方式执行。这意味着在完成之前无法创建ArrayAdapter（或者feeds数组将为null，因此异常）。

您应该将对setListNavigationCallbacks()的调用移至任务的onPostExecute()方法。

Android：从Mysql填充操作栏微调器

1 个答案: