android - 填充有 SQLite 数据库的 fragment 中的 Gridview - 如何实现对主要 Activity 的回调？

Question

我有一个扩展 FragmentActivity 的 MainActivity。有两个 fragment 。第一个包含一个 GridView，它由来自 SQLite 适配器类的 Cursor 填充。我已经分配了一个 onItemClick 事件来获取点击图 block 的数据。现在我需要将此数据从 fragment 传递到父 Activity ，以便在第二个 fragment 中使用它(根据 Android 开发最佳实践)。我看过几个实现回调的示例，并尝试将其编码到我的应用程序中，但我一定遗漏了一些非常明显的东西，因为我无法让它工作。这是第一个 fragment (我用/* */标签编辑了回调位):

public class TimetableFragment extends Fragment {

private MobileClassDbAdapter mDbHelper;
private Cursor mTimetableCursor;
private ActionMode mActionMode;
/*    OnItemClickListener mListener;

public interface OnItemClickListener {
    public void OnItemClick(AdapterView<?> parent, View v, int position, long id);
}

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    try {
        mListener = (OnItemClickListener) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString() + " must implement OnItemClickListener");
    }
}
*/    
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.timetable_fragment, container, false);

    GridView gridView = (GridView)view.findViewById(R.id.timetable_grid);
    fillTimetable(gridView);

    return view;
}

@SuppressWarnings("deprecation")
private void fillTimetable(GridView gridView) {
    mDbHelper = new MobileClassDbAdapter(getActivity().getApplicationContext());
    mDbHelper.open();
    // Get all of the rows from the database and create the item list
    mTimetableCursor = mDbHelper.fetchAllTimetableActivities();
    // check the length of the cursor
    int count = mTimetableCursor.getCount();
    int days = 5;
    int lessons = 9;
    int test = days * lessons;
    if (count < test) {
        Toast.makeText(getActivity(), "Not filled with timetable  activities", Toast.LENGTH_LONG).show();
        for (int i = 1; i <= days; i++) {
            for (int j = 1; j <= lessons; j++) {
                String day = Integer.toString(i);
                String lesson = Integer.toString(j);
                if (mDbHelper.findTimetableActivity(day, lesson, null, null) == false) {
                    mDbHelper.createTimetableActivity(day, lesson, null, null, null);
                }
            }
        mTimetableCursor = mDbHelper.fetchAllTimetableActivities();
        }
    }
    String[] from = new String[]{MobileClassDbAdapter.KEY_TIMETABLE_ACTIVITY,MobileClassDbAdapter.KEY_TIMETABLE_NOTE};

    int[] to = new int[]{R.id.timetable_text1,R.id.timetable_text2};

    // Now create a simple cursor adapter and set it to display
    final SimpleCursorAdapter timetable = new SimpleCursorAdapter(getActivity(), R.layout.timetable_card, mTimetableCursor, from, to);
    gridView.setAdapter(timetable);

    // create click listener
    gridView.setOnItemClickListener(new OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
            //JUST A TEST TO SEE IF THE ClickListener RETURNS THE CORRECT DATA
            Cursor item = (Cursor)timetable.getItem(position);
            String text = item.getString(item.getColumnIndexOrThrow(MobileClassDbAdapter.KEY_TIMETABLE_DAY))
                    + " " + item.getString(item.getColumnIndexOrThrow(MobileClassDbAdapter.KEY_TIMETABLE_LESSON))
                    + " (id: " + item.getString(item.getColumnIndexOrThrow(MobileClassDbAdapter.KEY_TIMETABLE_ID)) + ")";
            Toast.makeText(getActivity(), text, Toast.LENGTH_LONG).show();
            //END OF TEST...
/*              mListener.OnItemClick(parent, v, position, id);*/
        }
    });

}
}

这是 MainActivity:

public class MainActivity extends FragmentActivity {

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

}

我没有包括第二个 fragment ，因为我还没有开始编码 - 我首先需要将数据从 fragment 获取到父 Activity 。我真的需要一些建议...谢谢!

Answer 1

您的 MainActivity 需要实现 fragment 的接口(interface)。

无论如何，您应该在 Fragment 中处理 onItemClick，并且只将结果通知 Activity。在您的情况下，您将获得有关 AdapterView、项目的 View 和位置/id 的信息。但是您的 Activitiy 不知道 GridView...

在 Fragment 内部处理您的 onClick 并将所需结果传递给 Activity。

因此你应该添加一个像“itemClicked(InformationForActivity...)”这样的接口(interface)

试试这个:

public class TimetableFragment extends Fragment {
  ItemClickedListener mListener;

  public interface ItemClickedListener {
    public void onItemClicked(Item clickedItem);
  }

  @Override
  public void onAttach(Activity activity) {
     super.onAttach(activity);
     try {
        mListener = (CursorClickedListener ) activity;
     } catch (ClassCastException e) {
     throw new ClassCastException(activity.toString() 
     + " must implement CursorClickedListener ");
     }
   }

   @SuppressWarnings("deprecation")
   private void fillTimetable(GridView gridView) {
     ....
     Item item = ... ;// build your item
     mListener.onItemClick(item); //this informs the activity
   }
 }

Activity :

public class MainActivity extends FragmentActivity 
                      implements TimetableFragment.ItemClickedListener {

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

  @Override
  public void ItemClickedListener (Item clickedItem){
  //inform the other fragment here!
  }
}