错误commit()在onCreate方法的Fragments中

Question

所以，这里是myActivity.java

基本上，当我尝试使用commit（）时，onCreate方法中出现了一个错误所以，只是不确定为什么会这样。可能需要一些指导。谢谢

此外，作为一个碎片的初学者，我有时会有点困惑。

它告诉我它"无法解析方法commit（）"。

public class MyActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);
        if (savedInstanceState == null) {
            getFragmentManager().beginTransaction()
                    .add(R.id.container, new ForecastFragment()
                            .commit();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.my, 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);
    }
    /**
     * A Forecast fragment containing a simple view.
     */
    public static class ForecastFragment extends Fragment {
        private ArrayAdapter<String> mForecastAdapter;
        public ForecastFragment() {
        }
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_my, container, false);
            String[] forecastArray={
                    "Right Now - Hot. Grab a Lemonade!",
                    "Today -  Boiling! Feels more like a Heat Furnace!",
                    "Tomorrow - Rains! Carry an Umbrella!",
                    "Tuesday - Hailstones!",
                    "Wednesday - Stormy",
                    "Thursday - Snowfall!",
                    "Friday - Rebecca Black",
                    "Saturday - Thunder!",
                    "Sunday - Just right." };
            List<String>weekForecast=new ArrayList<String>(Arrays.asList(forecastArray));
             mForecastAdapter = new ArrayAdapter<String>(
                    getActivity(),
                    R.layout.list_item_forecast,
                    R.id.list_item_forecast_textview,
                    weekForecast);
            ListView listView=(ListView) rootView.findViewById(R.id.listview_forecast);
            listView.setAdapter(mForecastAdapter);

            return rootView;
        }

    }
}

Answer 1

这是错误的

    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new ForecastFragment().
                        commit()); //<-----
    }

commit()是FragmentTransaction上的方法，而不是Fragment上的方法。因此，将您的代码更改为：

    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new ForecastFragment())
                .commit();
    }

Answer 2

如果你对混淆的片段感到困惑，你不应该将所有这些东西串联起来，在单独的行中进行，直到你完全舒服为止：

   getFragmentManager().beginTransaction()
                  .add(R.id.container, new ForecastFragment()
                        .commit();

成为

ForecastFragment newFragment = new ForecastFragment();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.add(R.id.container, newFragment );
transaction.addToBackStack(null);
transaction.commit();