Question

我正在更新Android 2.2应用程序以使用CursorLoader（使用v4兼容性库）而我正在试图理解当内容提供者通知更改时未调用onLoadFinished方法的原因在与CursorLoader查询关联的内容中。

CursorLoader正在查询客户内容提供商。我的提供者在其查询方法中设置通知URI：

cursor.setNotificationUri(getContext().getContentResolver(), uri);

并通知其插入/更新/删除方法的更改：

getContext().getContentResolver().notifyChange(uri, null);

在两种情况下，我都检查过URI是否相同。以前我使用的是同一内容提供商的ManagedQuery，并且查询的内容更新得很好，这让我觉得内容提供商可能没问题。

我查看了LoaderCursorSupport示例，有趣的是，当我在Nexus One上运行时，我看不到它反映了我对联系人名称所做的更改（在示例应用和联系人应用之间切换））。应该是？如果是这样，是否存在一些我不知道的潜在问题？

Answer 1

我终于明白了这一点，而且通常情况下，这对我来说是一个愚蠢的错误。我在我的onLoadFinished（）方法中调用cursor.close（） - 我使用返回的游标创建一个ArrayAdapter（我需要手动在列表顶部插入一个项目），并且光标关闭是使用ManagedQuery的剩余部分在迁移之前使用CursorLoader。

在找到这个的过程中，我创建了一个简单的测试类来显示书签列表并添加一个随机书签（使用选项菜单）。这样可以正常工作，即在添加项目后调用onLoadFinished（）。这是代码，以防它对其他人有用：

package com.test;

import android.content.ContentValues;
import android.database.Cursor;
import android.os.Bundle;
import android.provider.Browser;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
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.view.MenuItemCompat;
import android.support.v4.widget.SimpleCursorAdapter;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;

public class CursorLoaderTestActivity extends FragmentActivity 
{
    private static final String TAG = CursorLoaderTestActivity.class.getSimpleName();

    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);

        FragmentManager fm = getSupportFragmentManager();

        // Create the list fragment and add it as our sole content.
        if (fm.findFragmentById(android.R.id.content) == null) 
        {
            CursorLoaderListFragment list = new CursorLoaderListFragment();
            fm.beginTransaction().add(android.R.id.content, list).commit();
        }
    }


    public static class CursorLoaderListFragment extends ListFragment implements LoaderManager.LoaderCallbacks<Cursor> 
    {

        // This is the Adapter being used to display the list's data.
        SimpleCursorAdapter mAdapter;

        // If non-null, this is the current filter the user has provided.
        String mCurFilter;

        @Override public void onActivityCreated(Bundle savedInstanceState) 
        {
            super.onActivityCreated(savedInstanceState);

            // Give some text to display if there is no data.  In a real
            // application this would come from a resource.
            setEmptyText("No data");

            // We have a menu item to show in action bar.
            setHasOptionsMenu(true);

            // Create an empty adapter we will use to display the loaded data.
            mAdapter = new SimpleCursorAdapter(getActivity(),
                    android.R.layout.simple_list_item_1, null,
                    new String[] { Browser.BookmarkColumns.TITLE },
                    new int[] { android.R.id.text1}, 0);

            setListAdapter(mAdapter);

            // Start out with a progress indicator.
            setListShown(false);

            // Prepare the loader.  Either re-connect with an existing one,
            // or start a new one.
            getLoaderManager().initLoader(0, null, this);
        }

        //@Override 
        public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) 
        {
            // Place an action bar item for searching.
            MenuItem item = menu.add("Add Item");
            //item.setIcon(android.R.drawable.ic_menu_search);
            MenuItemCompat.setShowAsAction(item, MenuItemCompat.SHOW_AS_ACTION_ALWAYS);
        }

        @Override
        public boolean onOptionsItemSelected (MenuItem item)
        {
            ContentValues cv=new ContentValues();
            cv.put(Browser.BookmarkColumns.TITLE, "!AA " + System.currentTimeMillis());
            cv.put(Browser.BookmarkColumns.URL, "http://test/");
            cv.put(Browser.BookmarkColumns.BOOKMARK, 1);
            getActivity().getContentResolver().insert(Browser.BOOKMARKS_URI, cv);
            return true;
        }

       //columns to query
        static final String[] PROJECTION = new String[] { Browser.BookmarkColumns.TITLE };


        public Loader<Cursor> onCreateLoader(int id, Bundle args) 
        {
            Log.i(TAG, "onCreateLoader");

            return new CursorLoader(getActivity(), Browser.BOOKMARKS_URI,
                    PROJECTION, null, null,
                    Browser.BookmarkColumns.TITLE + " ASC");
        }

        public void onLoadFinished(Loader<Cursor> loader, Cursor data) 
        {
            Log.i(TAG, "onLoadFinished");

            // Swap the new cursor in.  (The framework will take care of closing the
            // old cursor once we return.)
            mAdapter.swapCursor(data);

            // The list should now be shown.
            if (isResumed()) 
                setListShown(true);
            else 
                setListShownNoAnimation(true);
        }

        public void onLoaderReset(Loader<Cursor> loader) 
        {
            // This is called when the last Cursor provided to onLoadFinished()
            // above is about to be closed.  We need to make sure we are no
            // longer using it.
            mAdapter.swapCursor(null);
        }
    }

}

Answer 2

也许您应该使用应用程序上下文：

getContext().getApplicationContext().getContentResolver().notifyChange(uri, null);

Android CursorLoader没有响应ContentProvider通知

2 个答案: