Question

我有一个片段Movies，可以将数据库调整为列表视图。此片段类的辅助方法之一是swapCursor

public void swapCursor(final DatabaseAdapter myAdapter, final Cursor cursor){
    // Swap the cursor on the UI thread (prevents error: Only the original thread that created a view hierarchy can touch its views)
    getActivity().runOnUiThread(new Runnable() {
        @Override
        public void run() {
            myAdapter.swapCursor(cursor);
        }
    });
}

我需要能够从外部swapCursor类访问Movies方法。我无法swapCursor静态因为我无法拨打getActivity。

如何访问swapCursor？我是否需要获取片段类的实例并将swapCursor作为实例方法调用？我该怎么做？

修改

我想从另一个既不是片段也不是活动类的类中调用swapCursor，只是一个普通的Java类。我从这个方法调用的类是一个单例游标manger类。

修改

这是我的整个Movies课程，以使事情更清晰

public class Movies extends Fragment {

    static DatabaseAdapter myAdapter = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setRetainInstance(true);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_movies, container, false);
        myAdapter =  new DatabaseAdapter(getActivity(), null, 0);

        DatabaseHelper dbh = DatabaseHelper.getInstanceOf(getActivity());
        SQLiteDatabase db = dbh.getDatabase();

        String query = "SELECT 0 _id, * FROM Movies ORDER BY CAST(imdbVotes AS int) DESC";
        Cursor cursor = db.rawQuery(query, null);
        swapCursor(myAdapter, cursor);

        ListView listView = (ListView)  view.findViewById(R.id.listViewMovies);
        listView.setAdapter(myAdapter);

        return view;
    }

    public void swapCursor(final DatabaseAdapter myAdapter, final Cursor cursor){
        // Swap the cursor on the UI thread (prevents error: Only the original thread that created a view hierarchy can touch its views)
        getActivity().runOnUiThread(new Runnable() {
            @Override
            public void run() {
                myAdapter.swapCursor(cursor);
            }
        });
    }
}

Answer 1

如果您使用适配器进行片段（即视图寻呼机，标签适配器）//片段活动始终预先加载当前片段位置的+2。

Fragment fragment = (Fragment) pager.getAdapter().instantiateItem(pager, globalPosition);

    if (((FragmentDetail) fragment).getView() != null) {
                                   ((FragmentDetail) fragment).myMethod();
    }

Answer 2

我通过向片段类添加两个静态全局变量来解决这个问题

static DatabaseAdapter myAdapter = null;
static Activity activity = null;

在我的onCreateView查看方法中，我添加了以下行

activity = getActivity();

然后我将swapCursor设为静态并删除myAdapter参数

public static void swapCursor(final Cursor cursor){
    // Swap the cursor on the UI thread (prevents error: Only the original thread that created a view hierarchy can touch its views)
    activity.runOnUiThread(new Runnable() {
        @Override
        public void run() {
            myAdapter.swapCursor(cursor);
        }
    });
}

现在我可以从任何其他类中替换我的适配器中的光标=）

如何在片段类上调用实例方法？

2 个答案: