Question

我试图将整个ListFragment类转换为添加了ListView的Fragment类。

将此类称为HomeworkListFragment。我将扩展名从ListFragment更改为Fragment：

结果我创建了以下内容：

public class HomeworkListFragment extends Fragment{

public static final String TAG = "HomeworkListFragment";

public ListView mListView;
public HomeworkAdapter mAdapter;

private ArrayList<HomeworkObject> mCrimes;


@Override
public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setHasOptionsMenu(true);

    getActivity().setTitle(R.string.homework_title);
    mCrimes = HomeworkLab.get(getActivity()).getHomework();

    mAdapter = new HomeworkAdapter(mCrimes);
    mListView.setAdapter(mAdapter);

    setRetainInstance(true);

}

@TargetApi(11)
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState){
    View v = super.onCreateView(inflater,parent,savedInstanceState);

    mListView = (ListView)v.findViewById(android.R.id.list);
    mListView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE_MODAL);

    mListView.setMultiChoiceModeListener(new MultiChoiceModeListener(){
        @Override
        public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
            switch (item.getItemId()){
                case R.id.menu_item_delete_homework:
                    HomeworkLab homeworkLab = HomeworkLab.get(getActivity());
                    for (int i = mAdapter.getCount() - 1;i>=0;i--){
                        //if (mListView.getListView().isItemChecked(i)){
                            //homeworkLab.deleteHomework(mAdapter.getItem(i));
                        //}
                    }
                    mode.finish();
                    mAdapter.notifyDataSetChanged();
                    return true;
                default:
                    return false;
            }
        }

        @Override
        public boolean onCreateActionMode(ActionMode mode, Menu menu) {
            //ActionMode.callback Methods
            MenuInflater inflater = mode.getMenuInflater();
            inflater.inflate(R.menu.homework_list_item_context, menu);
            return true;
        }

        @Override
        public void onDestroyActionMode(ActionMode arg0) {
            //not used here
        }

        @Override
        public boolean onPrepareActionMode(ActionMode arg0, Menu arg1) {
            //not used here
            return false;
        }

        @Override
        public void onItemCheckedStateChanged(ActionMode arg0,
                int arg1, long arg2, boolean arg3) {
            //not used here
        }

    });
    mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position,
                long id) {
            HomeworkObject c = mAdapter.getItem(position);
            //Start CrimeActivity
            //Intent i = new Intent(getActivity(), CrimeActivity.class);
            Intent i = new Intent(getActivity(), HomeworkPagerActivity.class);
            i.putExtra(HomeworkFragment.EXTRA_HOMEWORK_ID, c.getId());
            startActivity(i);               
        }

    });     
    return v;
}

@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater){
    super.onCreateOptionsMenu(menu,inflater);
    inflater.inflate(R.menu.fragment_homework_list, menu);
}

@TargetApi(11)
@Override
public boolean onOptionsItemSelected(MenuItem item){
    switch(item.getItemId()){
        case R.id.menu_item_new_homework:
            HomeworkObject homework = new HomeworkObject();
            homework.setTitle("");
            HomeworkLab.get(getActivity()).addHomework(homework);
            Intent i = new Intent(getActivity(),HomeworkPagerActivity.class);
            i.putExtra(HomeworkFragment.EXTRA_HOMEWORK_ID, homework.getId());
            startActivityForResult(i,0);
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
    getActivity().getMenuInflater().inflate(R.menu.homework_list_item_context, menu);
}

@Override
public boolean onContextItemSelected(MenuItem item) {
    AdapterContextMenuInfo info = (AdapterContextMenuInfo)item.getMenuInfo();
    int position = info.position;
    HomeworkObject h = mAdapter.getItem(position);

    switch (item.getItemId()) {
        case R.id.menu_item_delete_homework:
            HomeworkLab.get(getActivity()).deleteHomework(h);
            mAdapter.notifyDataSetChanged();
            return true;
    }
    return super.onContextItemSelected(item);
}


@Override
public void onResume() {
    super.onResume();
    mAdapter.notifyDataSetChanged();
    mCrimes = HomeworkLab.get(getActivity()).getHomework();//update list
}

@Override
public void onPause(){
    super.onPause();
    HomeworkLab.get(getActivity()).saveHomework();
}

/*@Override
public void onListItemClick(ListView l, View v, int position, long id){
    HomeworkObject c = ((HomeworkAdapter)getListAdapter()).getItem(position);
    //Start CrimeActivity
    //Intent i = new Intent(getActivity(), CrimeActivity.class);
    Intent i = new Intent(getActivity(), HomeworkPagerActivity.class);
    i.putExtra(HomeworkFragment.EXTRA_HOMEWORK_ID, c.getId());
    startActivity(i);
}*/

private class HomeworkAdapter extends ArrayAdapter<HomeworkObject>{
    public HomeworkAdapter(ArrayList<HomeworkObject> crimes){
        super(getActivity(), 0, crimes);
    }

    @SuppressLint("SimpleDateFormat")
    @Override
    public View getView(int position, View convertView, ViewGroup parent){
        if (convertView == null){
            convertView = getActivity().getLayoutInflater().inflate(R.layout.list_item_homework, null);
        }
        HomeworkObject c = getItem(position);

        TextView titleTextView = (TextView)convertView.findViewById(R.id.homework_list_item_titleTextView);
        titleTextView.setText(c.getTitle());
        TextView dateTextView = (TextView)convertView.findViewById(R.id.homework_list_item_dateTextView);

        DateFormat df = new SimpleDateFormat("EEEE, d MMMM yyyy");     
        String reportDate = df.format(c.getDate());
        dateTextView.setText(reportDate);
        //dateTextView.setText(c.getDate().toString());

        CheckBox solvedCheckBox = (CheckBox)convertView.findViewById(R.id.homework_list_item_solvedCheckBox);
        solvedCheckBox.setChecked(c.isSolved());

        return convertView;
    }
}

}

据我所知，onCreateView方法中存在一些错误，但是我无法解决此问题。

我最近在从iOS迁移后选择了Android，因此我对此非常陌生。任何解释都可以帮助很多！

Answer 1

请改用：

@TargetApi(11)
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState){
    super.onCreateView(inflater,parent,savedInstanceState);

    View v = inflater.inflate(R.layout.my_fragment_layout, parent, false);

    mListView = (ListView)v.findViewById(android.R.id.list);
    mListView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE_MODAL);

    mListView.setMultiChoiceModeListener(new MultiChoiceModeListener(){
        @Override
        public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
            switch (item.getItemId()){
                case R.id.menu_item_delete_homework:
                    HomeworkLab homeworkLab = HomeworkLab.get(getActivity());
                    for (int i = mAdapter.getCount() - 1;i>=0;i--){
                        //if (mListView.getListView().isItemChecked(i)){
                            //homeworkLab.deleteHomework(mAdapter.getItem(i));
                        //}
                    }
                    mode.finish();
                    mAdapter.notifyDataSetChanged();
                    return true;
                default:
                    return false;
            }
        }

        @Override
        public boolean onCreateActionMode(ActionMode mode, Menu menu) {
            //ActionMode.callback Methods
            MenuInflater inflater = mode.getMenuInflater();
            inflater.inflate(R.menu.homework_list_item_context, menu);
            return true;
        }

        @Override
        public void onDestroyActionMode(ActionMode arg0) {
            //not used here
        }

        @Override
        public boolean onPrepareActionMode(ActionMode arg0, Menu arg1) {
            //not used here
            return false;
        }

        @Override
        public void onItemCheckedStateChanged(ActionMode arg0,
                int arg1, long arg2, boolean arg3) {
            //not used here
        }

    });
    mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position,
                long id) {
            HomeworkObject c = mAdapter.getItem(position);
            //Start CrimeActivity
            //Intent i = new Intent(getActivity(), CrimeActivity.class);
            Intent i = new Intent(getActivity(), HomeworkPagerActivity.class);
            i.putExtra(HomeworkFragment.EXTRA_HOMEWORK_ID, c.getId());
            startActivity(i);               
        }

    });     
    return v;
}

Answer 2

<强>问题：

 mListView = (ListView)v.findViewById(android.R.id.list);

android.R.id.list仅限于ListFragment而非Fragment，这就是它为空的原因。

作为ListFragment的documentation：

ListFragment has a default layout that consists of a single list view. 
However, if you desire, you can customize the fragment layout by returning 
your own view hierarchy from onCreateView(LayoutInflater, ViewGroup, Bundle). 
To do this, your view hierarchy must contain a ListView object with the 
id "@android:id/list" (or list if it's in code)

<强>解决方案：

您需要在片段中为视图充气并使用ListView创建布局并使用创建的ListView ID而不是android.R.id.list

使用崩溃将ListView添加到片段

2 个答案: