Question

我正在尝试使LoaderManager列表向后兼容Android 2.1。列表加载正常但@ id / android：empty消息显示即使列表中有明显可见的项目。

我已经在StackOverflow上查看了一些使用setEmptyView（）和setEmptyText（）但无法使它们工作的解决方案。

以下是ListFragment的代码。我一直在组合各种http://www.vogella.com/教程的代码。

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);
    }

}

以下是列表的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>

编辑：解决方案是结合Eluvatar和dymmeh的答案。这是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

致电getActivity().setContentView(R.layout.todo_list);，您告诉您的活动显示ListView和空TextView。您的ListFragment已包含自动管理的ListView和空TextView。所以你正在做的是从你的ListView布局中单独显示todo_list，然后修改ListView中包含的ListFragment（这就是为什么看起来没有任何内容被加载进入你的ListView）。如果您只是取消对getActivity().setContentView(R.layout.todo_list);的通话，只要您正确添加ListFragment，它就会有效。

当列表不为空时，ListFragment显示空文本

1 个答案: