为ListView设置片段中的适配器

Question

我是安卓系统的新手。试图将以前在主活动中控制的列表视图获取到片段中。

我的MainActivity扩展了FragmentActivity。我得到一个null指针，用于设置适配器和包含populateList()方法的行。

不确定解决方案是使用getActivity（）和/或我一直在阅读的setListAdapter()选项。我知道它正在从保存中查找项目，但我不确定如何更正此问题。如有任何见解，我们将不胜感激。

其他信息：我正在使用android.support.v4.app.FragmentActivity。FragmentS在public class TabbedActivity extends Fragment { 内

public static class FragmentS extends Fragment {

        public FragmentS() {
        }
        List<LiftSave> LiftSaves = new ArrayList<LiftSave>();
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.listview_s,
                    container, false);
            DatabaseHandler dbHandler;
            dbHandler = new DatabaseHandler (getActivity().getApplicationContext());
            if (dbHandler.getLiftSavesCount() != 0)
                LiftSaves.addAll(dbHandler.getAllLiftSaves());
            populateList();
            return rootView;
        }
        private void populateList() {
            ListView saveListView = (ListView)getActivity().findViewById(R.id.saveListView);
            ArrayAdapter<LiftSave> saveAdapter;
            saveAdapter = new SaveListAdapter();
            saveListView.setAdapter(saveAdapter);
        }
        public class SaveListAdapter extends ArrayAdapter<LiftSave> {
            public SaveListAdapter() {
                super(getActivity(), R.layout.listview_item, LiftSaves);
            }
            @Override
            public View getView(int position, View view, ViewGroup parent) {
                if (view == null)
                    view = getActivity().getLayoutInflater().inflate(R.layout.listview_item, parent, false);
                LiftSave currentLiftSave = LiftSaves.get(position);
                TextView liftName = (TextView) view.findViewById(R.id.liftName);
                liftName.setText(currentLiftSave.getLiftName());
                TextView maxValue = (TextView) view.findViewById(R.id.maxValue);
                maxValue.setText(currentLiftSave.getMaxValue());
                TextView weightAndReps = (TextView) view.findViewById(R.id.weightAndReps);
                weightAndReps.setText(currentLiftSave.getRepsAndWeight());
                TextView liftNotes = (TextView) view.findViewById(R.id.liftNotes);
                liftNotes.setText(currentLiftSave.getLiftNotes());
                TextView date = (TextView) view.findViewById(R.id.todayDate);
                date.setText(currentLiftSave.getTodayDate());
                return view;
            }
    }}

XML:

  <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".TabbedActivity$FragmentS"
    android:background="@android:color/holo_blue_dark">
<LinearLayout
android:id="@+id/tabSaveList"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
xmlns:android="http://schemas.android.com/apk/res/android">
<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:text="Saved Maxes"
    android:id="@+id/textView"
    android:layout_gravity="center"
    android:layout_marginTop="10dp"
    android:textColor="#fffaf4a1"
    android:textStyle="bold" />
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/saveListView" />

</LinearLayout>
</RelativeLayout>

Answer 1

我认为问题是，您在活动中搜索ListView，而不是在onCreateView（）中检索到的rootView

也许试试这个：

public static class FragmentS extends Fragment {
            private ListView saveListView;
            private List<LiftSave> LiftSaves = new ArrayList<LiftSave>();
            public FragmentS() {
            }
            @Override
            public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                     Bundle savedInstanceState) {
                View rootView = inflater.inflate(R.layout.listview_s,
                        container, false);
                saveListView = (ListView) rootView.findViewById(R.id.saveListView);
                DatabaseHandler dbHandler;
                dbHandler = new DatabaseHandler (getActivity().getApplicationContext());
                if (dbHandler.getLiftSavesCount() != 0)
                    LiftSaves.addAll(dbHandler.getAllLiftSaves());
                populateList();
                return rootView;
            }
            private void populateList() {
                ArrayAdapter<LiftSave> saveAdapter = new SaveListAdapter();
                saveListView.setAdapter(saveAdapter);
            }