我有一个片段，可以将数据加载到列表适配器中以显示在屏幕上。当我的应用程序启动时，它会启动一项服务来查找新数据，如果找到任何数据，则需要显示该数据。目前，我的私人广播接收器实际上是主要活动 - 而不是片段。这对我来说似乎不对，但我看不出如何将通知从广播接收器传回到片段本身，而我读到的另一个问题是建议这种方法。
使用我在下面发布的代码，当我的广播接收器收到通知并在片段上调用updateConent时，我得到了以下错误：
10-26 20:31:21.328: E/AndroidRuntime(711): FATAL EXCEPTION: main
10-26 20:31:21.328: E/AndroidRuntime(711): java.lang.RuntimeException: Error receiving broadcast Intent { act=updatedata flg=0x10 (has extras) } in com.thedailydigi.dailydigi.Main$1@41458418
10-26 20:31:21.328: E/AndroidRuntime(711): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:765)
10-26 20:31:21.328: E/AndroidRuntime(711): at android.os.Handler.handleCallback(Handler.java:615)
10-26 20:31:21.328: E/AndroidRuntime(711): at android.os.Handler.dispatchMessage(Handler.java:92)
10-26 20:31:21.328: E/AndroidRuntime(711): at android.os.Looper.loop(Looper.java:137)
10-26 20:31:21.328: E/AndroidRuntime(711): at android.app.ActivityThread.main(ActivityThread.java:4745)
10-26 20:31:21.328: E/AndroidRuntime(711): at java.lang.reflect.Method.invokeNative(Native Method)
10-26 20:31:21.328: E/AndroidRuntime(711): at java.lang.reflect.Method.invoke(Method.java:511)
10-26 20:31:21.328: E/AndroidRuntime(711): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
10-26 20:31:21.328: E/AndroidRuntime(711): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-26 20:31:21.328: E/AndroidRuntime(711): at dalvik.system.NativeStart.main(Native Method)
10-26 20:31:21.328: E/AndroidRuntime(711): Caused by: java.lang.IllegalStateException: There is already a listener registered
10-26 20:31:21.328: E/AndroidRuntime(711): at android.support.v4.content.Loader.registerListener(Loader.java:130)
10-26 20:31:21.328: E/AndroidRuntime(711): at android.support.v4.app.LoaderManagerImpl$LoaderInfo.start(LoaderManager.java:260)
10-26 20:31:21.328: E/AndroidRuntime(711): at android.support.v4.app.LoaderManagerImpl.installLoader(LoaderManager.java:510)
10-26 20:31:21.328: E/AndroidRuntime(711): at android.support.v4.app.LoaderManagerImpl.createAndInstallLoader(LoaderManager.java:497)
10-26 20:31:21.328: E/AndroidRuntime(711): at android.support.v4.app.LoaderManagerImpl.restartLoader(LoaderManager.java:643)
10-26 20:31:21.328: E/AndroidRuntime(711): at com.thedailydigi.dailydigi.activity.HorizontalListFragment.updateContent(HorizontalListFragment.java:130)
10-26 20:31:21.328: E/AndroidRuntime(711): at com.thedailydigi.dailydigi.Main$1.onReceive(Main.java:36)
10-26 20:31:21.328: E/AndroidRuntime(711): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:755)
我收集'引起：java.lang.IllegalStateException：已经有一个已注册的监听器'是问题的关键但我没有注册的监听器？
任何人都可以了解一下 a）为什么我目前遇到上述错误并且 b）如果这是将额外数据加载到片段中的正确方法吗？
我的相关课程的完整代码如下。谢谢你的帮助。
Main.java
public class Main extends FragmentActivity {
private static final String LOG_TAG = "dd-Main";
private HorizontalListFragment mDailyDigiFragment;
private BroadcastReceiver myReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
//TODO go update the UI from the database
int newRecords = intent.getIntExtra(DownloadFeedService.DOWNLOADED,0);
long date = intent.getLongExtra(DownloadFeedService.BEGIN_DATE, DownloadFeedService.NULL_DATE);
Log.d(LOG_TAG, newRecords + " new records downloaded!");
if (intent.getStringExtra(DownloadFeedService.KEY).equals(getString(R.string.daily_digi_short))) {
mDailyDigiFragment.updateContent(newRecords, date);
} else {
//TODO add our other fragments here
}
}
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.v(LOG_TAG, "Main Activity started");
registerReceiver(myReceiver, new IntentFilter(DownloadFeedService.UPDATEDATA));
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
//mDailyDigiFragment = HorizontalListFragment.newInstance(getString(R.string.daily_digi_short), 10, R.drawable.banner_dailydigi, true);
mDailyDigiFragment = HorizontalListFragment.newInstance(getString(R.string.daily_digi_short), 10, R.drawable.banner_dailydigi, true);
FragmentTransaction dailyDigiTransaction = getSupportFragmentManager().beginTransaction();
dailyDigiTransaction.add(R.id.dailydigi, mDailyDigiFragment).commit();
//TODO instantiate our other fragments here
/*
Fragment digiShowFragment = HorizontalListFragment.newInstance(getString(R.string.digi_show_short), 10, R.drawable.banner_digishow, true);
FragmentTransaction digiShowTransaction = getSupportFragmentManager().beginTransaction();
digiShowTransaction.add(R.id.digishow, digiShowFragment).commit();*/
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
HorizontalListFragment.java
public class HorizontalListFragment extends Fragment
implements LoaderManager.LoaderCallbacks<ArrayList<RssFeed.Article>> {
private ArticleAdapter adapter ;
private static final String LOG_TAG = "dd-HorizontalListFragment";
private static String MAX_LOAD_KEY = "max";
private static String DATASOURCE_KEY = "key";
private static String IMAGE_SRC_KEY = "image";
private static String SHOW_TEXT_OVERLAY = "showOverlay";
private String mRssFeedKey = "";
private int mDefaultLoad;
private int mImageResource = 0;
//TODO do we want to toggle the overlay on the digishow feed?
private boolean mShowTextOverlay = true;
private HorizontalListView mListView;
ArticleLoader mLoader;
public static HorizontalListFragment newInstance(String key, int max, int img, boolean showOverlay) {
HorizontalListFragment myFragment = new HorizontalListFragment();
Bundle args = new Bundle();
args.putString(DATASOURCE_KEY, key);
args.putInt(MAX_LOAD_KEY, max);
args.putInt(IMAGE_SRC_KEY, img);
args.putBoolean(SHOW_TEXT_OVERLAY, showOverlay);
myFragment.setArguments(args);
return myFragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Bundle bundle = this.getArguments();
mRssFeedKey = bundle.getString(DATASOURCE_KEY);
mDefaultLoad = bundle.getInt(MAX_LOAD_KEY, getResources().getInteger(R.integer.default_display_max));
mImageResource = bundle.getInt(IMAGE_SRC_KEY, 0);
mShowTextOverlay = bundle.getBoolean(SHOW_TEXT_OVERLAY, true);
mLoader = new ArticleLoader(getActivity(), mRssFeedKey,mDefaultLoad);
getActivity().getSupportLoaderManager().initLoader(0, null, this);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.horizontal_list_section, container, false);
ImageView img = (ImageView) view.findViewById(R.id.Header_Image);
img.setImageResource(mImageResource);
mListView = (HorizontalListView) view.findViewById(R.id.hr_listview);
return view;
}
@Override
public Loader<ArrayList<RssFeed.Article>> onCreateLoader(int arg0, Bundle bundle) {
Log.d(LOG_TAG, "onCreateLoader: find " + mDefaultLoad + " articles from " + mRssFeedKey);
return mLoader;
}
@Override
public void onLoadFinished(Loader<ArrayList<RssFeed.Article>> arg0, ArrayList<RssFeed.Article> result) {
Log.d(LOG_TAG, "onLoadFinished with " + result.size() + " records from " + mRssFeedKey);
//update the listview with the combined results list
if (adapter == null) {
adapter = new ArticleAdapter(this.getActivity(), result,true);
mListView.setAdapter(adapter);
} else {
insertNewArticles(result);
adapter.notifyDataSetChanged();
}
//TODO use these methods to reset the list position ?
//mListView.setSelectionFromTop(currentFirstVisibleItem, 0);
//mListView.getFirstVisiblePosition();
}
@Override
public void onLoaderReset(Loader<ArrayList<RssFeed.Article>> arg0) {
Log.v(LOG_TAG, "onLoaderReset");
// TODO what do we need to do here?
}
public void updateContent(int newRecords , long date) {
if (date == DownloadFeedService.NULL_DATE) {
Log.d(LOG_TAG, "updateContent requesting " + newRecords + " new records.");
//this is when some new recent content has been downloaded
mLoader.setDownloadParameters(newRecords, 0);
getActivity().getSupportLoaderManager().restartLoader(0, null, this);
} else {
//this was probably downloaded cuz we're scrolling near the end
}
}
//both lists should already be sorted in date desc order
private void insertNewArticles(ArrayList<RssFeed.Article> listB) {
//TODO - we need to make sure we only add new entries
int listPosition = 0;
for (Article a : listB ) {
for (int i = listPosition; i < adapter.getCount(); i++) {
Article b = adapter.getItem(i);
//already in the list - skip over it
if (a.getInternalId() == b.getInternalId()) {
listPosition = i+1;
break;
}
//our new item is published after - it shows at the front of the list
if (a.getPublicationDate().before(b.getPublicationDate())) {
adapter.insert(a, i-1);
listPosition = i;
break;
}
}
//when we get to new items that pre-date our current list items, add them at the end
if (listPosition == adapter.getCount()) {
adapter.insert(a, listPosition);
listPosition++;
}
}
}
}
ArticleLoader.java
public class ArticleLoader extends AsyncTaskLoader<ArrayList<RssFeed.Article>> {
private static final String LOG_TAG = "dd-ArticleLoader";
ArrayList<RssFeed.Article> mArticles;
final String mSource;
int mOffset = 0;
int mDownloadCount;
public ArticleLoader(Context context, String source, int max) {
super(context);
mSource = source;
mDownloadCount = max;
}
public void setDownloadParameters(int count, int offset) {
mOffset = offset;
mDownloadCount = count;
}
/**
* This is where the bulk of our work is done. This function is
* called in a background thread and should generate a new set of
* data to be published by the loader.
*/
@Override public ArrayList<RssFeed.Article> loadInBackground() {
Log.d(LOG_TAG, "loadInBackground: find " + mDownloadCount + " articles from " + mSource);
mArticles = ArticleManager.findArticles(getContext().getContentResolver(), mSource, mDownloadCount, mOffset);
return mArticles;
}
@Override
protected void onStartLoading() {
if(mArticles != null) {
deliverResult(mArticles);
} else {
forceLoad();
}
}
}
答案 0 :(得分：4)
此处的问题是，当您在getActivity().getSupportLoaderManager().restartLoader(0, null, this);方法中致电updateContent()时，它会再次调用onCreateLoader(...)。然后，您的onCreateLoader(..)方法将返回与第一次相同的加载程序。这个加载器已经有一个注册的监听器。
要解决此问题，您只需要onCreateLoader(..)每次都返回一个新的加载程序。
更改自：
@Override
public Loader<ArrayList<RssFeed.Article>> onCreateLoader(int arg0, Bundle bundle) {
Log.d(LOG_TAG, "onCreateLoader: find " + mDefaultLoad + " articles from " + mRssFeedKey);
return mLoader;
}
为：
@Override
public Loader<ArrayList<RssFeed.Article>> onCreateLoader(int arg0, Bundle bundle) {
Log.d(LOG_TAG, "onCreateLoader: find " + mDefaultLoad + " articles from " + mRssFeedKey);
return new ArticleLoader(getActivity(), mRssFeedKey,mDefaultLoad);
}