我正在 API Demo 中试用 LoaderCursor 示例：
package com.example.android.apis.app;
import android.app.Activity;
import android.app.FragmentManager;
import android.app.ListFragment;
import android.app.LoaderManager;
import android.content.CursorLoader;
import android.content.Loader;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.ContactsContract.Contacts;
import android.text.TextUtils;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.ListView;
import android.widget.SearchView;
import android.widget.SimpleCursorAdapter;
import android.widget.SearchView.OnQueryTextListener;
/**
* Demonstration of the use of a CursorLoader to load and display contacts
* data in a fragment.
*/
public class LoaderCursor extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FragmentManager fm = getFragmentManager();
// 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 OnQueryTextListener, 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 phone numbers");
// 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_2, null,
new String[] { Contacts.DISPLAY_NAME, Contacts.CONTACT_STATUS },
new int[] { android.R.id.text1, android.R.id.text2 }, 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("Search");
item.setIcon(android.R.drawable.ic_menu_search);
item.setShowAsAction(MenuItem.SHOW_AS_ACTION_IF_ROOM);
SearchView sv = new SearchView(getActivity());
sv.setOnQueryTextListener(this);
item.setActionView(sv);
}
public boolean onQueryTextChange(String newText) {
// Called when the action bar search text has changed. Update
// the search filter, and restart the loader to do a new query
// with this filter.
mCurFilter = !TextUtils.isEmpty(newText) ? newText : null;
getLoaderManager().restartLoader(0, null, this);
return true;
}
@Override public boolean onQueryTextSubmit(String query) {
// Don't care about this.
return true;
}
@Override public void onListItemClick(ListView l, View v, int position, long id) {
// Insert desired behavior here.
Log.i("FragmentComplexList", "Item clicked: " + id);
}
// These are the Contacts rows that we will retrieve.
static final String[] CONTACTS_SUMMARY_PROJECTION = new String[] {
Contacts._ID,
Contacts.DISPLAY_NAME,
Contacts.CONTACT_STATUS,
Contacts.CONTACT_PRESENCE,
Contacts.PHOTO_ID,
Contacts.LOOKUP_KEY,
};
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
// This is called when a new Loader needs to be created. This
// sample only has one Loader, so we don't care about the ID.
// First, pick the base URI to use depending on whether we are
// currently filtering.
Uri baseUri;
if (mCurFilter != null) {
baseUri = Uri.withAppendedPath(Contacts.CONTENT_FILTER_URI,
Uri.encode(mCurFilter));
} else {
baseUri = Contacts.CONTENT_URI;
}
// Now create and return a CursorLoader that will take care of
// creating a Cursor for the data being displayed.
String select = "((" + Contacts.DISPLAY_NAME + " NOTNULL) AND ("
+ Contacts.HAS_PHONE_NUMBER + "=1) AND ("
+ Contacts.DISPLAY_NAME + " != '' ))";
return new CursorLoader(getActivity(), baseUri,
CONTACTS_SUMMARY_PROJECTION, select, null,
Contacts.DISPLAY_NAME + " COLLATE LOCALIZED ASC");
}
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
// 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);
}
}
}
上面的代码尝试从“人”应用程序加载联系人信息。但是 LoaderCursor 在加载时停止：
06-16 01:07:30.270: E/AndroidRuntime(1331): FATAL EXCEPTION: AsyncTask #1
06-16 01:07:30.270: E/AndroidRuntime(1331): java.lang.RuntimeException: An error occured while executing doInBackground()
06-16 01:07:30.270: E/AndroidRuntime(1331): at android.os.AsyncTask$3.done(AsyncTask.java:278)
06-16 01:07:30.270: E/AndroidRuntime(1331): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
06-16 01:07:30.270: E/AndroidRuntime(1331): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
06-16 01:07:30.270: E/AndroidRuntime(1331): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
06-16 01:07:30.270: E/AndroidRuntime(1331): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
06-16 01:07:30.270: E/AndroidRuntime(1331): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
06-16 01:07:30.270: E/AndroidRuntime(1331): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
06-16 01:07:30.270: E/AndroidRuntime(1331): at java.lang.Thread.run(Thread.java:856)
06-16 01:07:30.270: E/AndroidRuntime(1331): Caused by: java.lang.SecurityException: Permission Denial: reading com.android.providers.contacts.ContactsProvider2 uri content://com.android.contacts/contacts from pid=1331, uid=10043 requires android.permission.READ_CONTACTS
06-16 01:07:30.270: E/AndroidRuntime(1331): at android.os.Parcel.readException(Parcel.java:1327)
06-16 01:07:30.270: E/AndroidRuntime(1331): at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:181)
06-16 01:07:30.270: E/AndroidRuntime(1331): at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:135)
06-16 01:07:30.270: E/AndroidRuntime(1331): at android.content.ContentProviderProxy.query(ContentProviderNative.java:358)
06-16 01:07:30.270: E/AndroidRuntime(1331): at android.content.ContentResolver.query(ContentResolver.java:310)
06-16 01:07:30.270: E/AndroidRuntime(1331): at android.content.CursorLoader.loadInBackground(CursorLoader.java:56)
06-16 01:07:30.270: E/AndroidRuntime(1331): at android.content.CursorLoader.loadInBackground(CursorLoader.java:42)
06-16 01:07:30.270: E/AndroidRuntime(1331): at android.content.AsyncTaskLoader.onLoadInBackground(AsyncTaskLoader.java:255)
06-16 01:07:30.270: E/AndroidRuntime(1331): at android.content.AsyncTaskLoader$LoadTask.doInBackground(AsyncTaskLoader.java:66)
06-16 01:07:30.270: E/AndroidRuntime(1331): at android.content.AsyncTaskLoader$LoadTask.doInBackground(AsyncTaskLoader.java:55)
06-16 01:07:30.270: E/AndroidRuntime(1331): at android.os.AsyncTask$2.call(AsyncTask.java:264)
06-16 01:07:30.270: E/AndroidRuntime(1331): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
06-16 01:07:30.270: E/AndroidRuntime(1331): ... 4 more
这是我第一次遇到 Loader 的问题，我不知道这里出了什么问题。那么可能是什么原因呢？