當列表不為空時，ListFragment顯示空文本

Question

我正在嘗試使LoaderManager列表向后兼容Android 2.1。 列表可以很好地加載，但是即使列表中明顯可見項目，也會顯示@ id / android：empty消息。

我在StackOverflow上查看了許多使用setEmptyView（）和setEmptyText（）的解決方案，但無法使它們正常工作。

這是ListFragment的代碼。 我一直在組合各種http://www.vogella.com/教程中的代碼。

package com.example.contentprov;

import android.support.v4.app.ListFragment;
import android.support.v4.app.LoaderManager;
import android.support.v4.content.CursorLoader;
import android.support.v4.content.Loader;
import android.support.v4.widget.SimpleCursorAdapter;
import android.content.Intent;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;

import com.example.contentprov.data.MyTodoContentProvider;
import com.example.contentprov.data.TodoTable;

/*
 * TodosOverviewActivity displays the existing todo items
 * in a list
 * 
 * You can create new ones via the ActionBar entry "Insert"
 * You can delete existing ones via a long press on the item
 */

public class TodoOverviewFragment extends ListFragment implements
LoaderManager.LoaderCallbacks<Cursor>, OnItemClickListener {
    private SimpleCursorAdapter adapter;

    /** Called when the activity is first created. */

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getActivity().setContentView(R.layout.todo_list);
        fillData();
    }

    // Opens the second activity if an entry is clicked
    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);
        Intent i = new Intent(getActivity(), TodoDetailActivity.class);
        Uri todoUri = Uri.parse(MyTodoContentProvider.CONTENT_URI + "/" + id);
        i.putExtra(MyTodoContentProvider.CONTENT_ITEM_TYPE, todoUri);
        startActivity(i);
    }

    private void fillData() {

        // Fields from the database (projection)
        // Must include the _id column for the adapter to work
        String[] from = new String[] { TodoTable.COLUMN_SUMMARY };
        // Fields on the UI to which we map
        int[] to = new int[] { R.id.label };

        getActivity().getSupportLoaderManager().initLoader(0, null, this);
        adapter = new SimpleCursorAdapter(getActivity(), R.layout.todo_row, null, from,
                to, 0);

        setListAdapter(adapter);
    }

    // Creates a new loader after the initLoader () call
    @Override
    public Loader<Cursor> onCreateLoader(int id, Bundle args) {
        String[] projection = { TodoTable.COLUMN_ID, TodoTable.COLUMN_SUMMARY };
        CursorLoader cursorLoader = new CursorLoader(getActivity(),
                MyTodoContentProvider.CONTENT_URI, projection, null, null, null);
        return cursorLoader;
    }

    @Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
        adapter.swapCursor(data);
    }

    @Override
    public void onLoaderReset(Loader<Cursor> loader) {
        // data is not available anymore, delete reference
        adapter.swapCursor(null);
    }

    @Override
    public void onItemClick(AdapterView<?> l, View v, int position, long id) {
        Intent i = new Intent(getActivity(), TodoDetailActivity.class);
        Uri todoUri = Uri.parse(MyTodoContentProvider.CONTENT_URI + "/" + id);
        i.putExtra(MyTodoContentProvider.CONTENT_ITEM_TYPE, todoUri);

        startActivity(i);
    }

} 

這是列表的XML文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ListView
        android:id="@id/android:list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </ListView>

    <TextView
        android:id="@id/android:empty"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/no_todos" />

</LinearLayout> 

編輯：解決方案是結合Eluvatar和dymmeh的答案。 這是ListFragment的新版本。

package com.example.contentprov;

import android.support.v4.app.ListFragment;
import android.support.v4.app.LoaderManager;
import android.support.v4.content.CursorLoader;
import android.support.v4.content.Loader;
import android.support.v4.widget.SimpleCursorAdapter;
import android.content.Intent;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;

import com.example.contentprov.data.MyTodoContentProvider;
import com.example.contentprov.data.TodoTable;

/*
 * TodosOverviewActivity displays the existing todo items
 * in a list
 * 
 * You can create new ones via the ActionBar entry "Insert"
 * You can delete existing ones via a long press on the item
 */

public class TodoOverviewFragment extends ListFragment implements
LoaderManager.LoaderCallbacks<Cursor>, OnItemClickListener {
    private SimpleCursorAdapter adapter;

    /** Called when the activity is first created. */

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        fillData();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.todo_list,
                container, false);
        return view;
    }

    // Opens the second activity if an entry is clicked
    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);
        Intent i = new Intent(getActivity(), TodoDetailActivity.class);
        Uri todoUri = Uri.parse(MyTodoContentProvider.CONTENT_URI + "/" + id);
        i.putExtra(MyTodoContentProvider.CONTENT_ITEM_TYPE, todoUri);
        startActivity(i);
    }

    private void fillData() {

        // Fields from the database (projection)
        // Must include the _id column for the adapter to work
        String[] from = new String[] { TodoTable.COLUMN_SUMMARY };
        // Fields on the UI to which we map
        int[] to = new int[] { R.id.label };

        getActivity().getSupportLoaderManager().initLoader(0, null, this);
        adapter = new SimpleCursorAdapter(getActivity(), R.layout.todo_row, null, from,
                to, 0);

        setListAdapter(adapter);
    }

    // Creates a new loader after the initLoader () call
    @Override
    public Loader<Cursor> onCreateLoader(int id, Bundle args) {
        String[] projection = { TodoTable.COLUMN_ID, TodoTable.COLUMN_SUMMARY };
        CursorLoader cursorLoader = new CursorLoader(getActivity(),
                MyTodoContentProvider.CONTENT_URI, projection, null, null, null);
        return cursorLoader;
    }

    @Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
        adapter.swapCursor(data);
    }

    @Override
    public void onLoaderReset(Loader<Cursor> loader) {
        // data is not available anymore, delete reference
        adapter.swapCursor(null);
    }

    @Override
    public void onItemClick(AdapterView<?> l, View v, int position, long id) {
        Intent i = new Intent(getActivity(), TodoDetailActivity.class);
        Uri todoUri = Uri.parse(MyTodoContentProvider.CONTENT_URI + "/" + id);
        i.putExtra(MyTodoContentProvider.CONTENT_ITEM_TYPE, todoUri);

        startActivity(i);
    }

} 

Answer 1

通過調用getActivity().setContentView(R.layout.todo_list); 您告訴活動顯示一個ListView和一個空的TextView 。 您的ListFragment已經包含一個ListView和一個空的TextView ，它會自動為您管理。 因此，您要做的是從todo_list布局中顯示一個單獨的ListView ，然后修改ListFragment包含的ListView （這就是為什么似乎沒有任何內容加載到ListView ）。 如果只刪除對getActivity().setContentView(R.layout.todo_list);的調用getActivity().setContentView(R.layout.todo_list); 只要您正確添加ListFragment它就應該起作用。