我的问题与此问题基本相同：Sometimes don't get onCreateLoader callback after calling initLoader
我有2 ListFragments个ViewPager。它们首先加载正常，但是当我更改方向时，initLoader方法不会调用onCreateLoader。
但是，如果我恢复到初始方向，一切都很好。
以下是FragmentActivity的代码：
import java.util.Locale;
import com.d.camera.R;
import com.d.camera.R.id;
import com.d.camera.R.layout;
import com.d.camera.R.menu;
import com.d.camera.R.string;
import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.NavUtils;
import android.support.v4.view.ViewPager;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class HistoryFragments extends FragmentActivity implements
ActionBar.TabListener {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {@link android.support.v4.app.FragmentPagerAdapter} derivative, which
* will keep every loaded fragment in memory. If this becomes too memory
* intensive, it may be best to switch to a
* {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history_fragments);
// Set up the action bar.
final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
actionBar.setDisplayShowTitleEnabled(false);
actionBar.setDisplayShowHomeEnabled(false);
// Create the adapter that will return a fragment for each of the three
// primary sections of the app.
mSectionsPagerAdapter = new SectionsPagerAdapter(
getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
// When swiping between different sections, select the corresponding
// tab. We can also use ActionBar.Tab#select() to do this if we have
// a reference to the Tab.
mViewPager
.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
// Create a tab with text corresponding to the page title defined by
// the adapter. Also specify this Activity object, which implements
// the TabListener interface, as the callback (listener) for when
// this tab is selected.
actionBar.addTab(actionBar.newTab()
.setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.history, menu);
return true;
}
@Override
public void onTabSelected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
// When the given tab is selected, switch to the corresponding page in
// the ViewPager.
mViewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}
@Override
public void onTabReselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a DummySectionFragment (defined as a static inner class
// below) with the page number as its lone argument.
Fragment fragment = null;
if (position == 0) {
fragment = new HistoryListFragment();
} else{
fragment = new HistoryElemListFragment();
}
return fragment;
}
@Override
public int getCount() {
// Show 2 total pages.
return 2;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
case 2:
return getString(R.string.title_section3).toUpperCase(l);
}
return null;
}
}
}
以下是其中一个ListFragments：
import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import com.d.camera.HistoryContentProvider;
import com.d.camera.HistoryDatabase;
import com.d.camera.HistoryEntry;
import com.d.camera.R;
import android.app.LoaderManager;
import android.content.Context;
import android.content.CursorLoader;
import android.content.Intent;
import android.content.Loader;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.util.Log;
import android.view.ContextMenu;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.ViewGroup;
import android.widget.FilterQueryProvider;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;
import android.widget.AdapterView.AdapterContextMenuInfo;
import android.widget.SimpleCursorAdapter.ViewBinder;
public class HistoryListFragment extends ListFragment implements LoaderManager.LoaderCallbacks<Cursor>{
private static final int LOADER_ID = 0x01;
private static final int DELETE_ID = Menu.FIRST + 1;
public static final String SECTION_NUMBER = "section_number";
private SimpleCursorAdapter adapter;
private Context context;
public HistoryListFragment() {
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
context = getActivity();
fillData();
registerForContextMenu(getListView());
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.list_fragment, container, false);
return rootView;
}
private void fillData() {
getActivity().getLoaderManager().initLoader(LOADER_ID, null, this);
String[] from = new String[] {
HistoryDatabase.MOBILE_RESULT,
HistoryDatabase.FP_TIMESTAMP,
HistoryDatabase.PRODUCT_IMAGE,};
int[] to = new int[] {
R.id.resultImage,
R.id.time,
R.id.productImage,};
adapter = new SimpleCursorAdapter(context, R.layout.history_element, null, from, to, 0);
// We want monitor the list setup and change the milliseconds time to a readable format.*******
adapter.setViewBinder(new ViewBinder(){
public boolean setViewValue(View v, Cursor c, int columnIndex) {
if(columnIndex == c.getColumnIndex(HistoryDatabase.FP_TIMESTAMP))
{
Long timeInMilli = c.getLong(c.getColumnIndex(HistoryDatabase.FP_TIMESTAMP));
SimpleDateFormat sdf = new SimpleDateFormat("EEE MMM dd HH:mm:ss z yyyy", Locale.ENGLISH);
String formatedTime = sdf.format(new Date(timeInMilli));
TextView tv = (TextView)v;
tv.setText(formatedTime);
return true;
}
return false;
}
});
//*********************************************************************************************
setListAdapter(adapter);
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v,
ContextMenuInfo menuInfo) {
super.onCreateContextMenu(menu, v, menuInfo);
menu.add(0, DELETE_ID, 0, R.string.menu_delete);
}
@Override
public boolean onContextItemSelected(MenuItem item) {
//...
return super.onContextItemSelected(item);
}
// Reaction to the menu selection
@Override
public boolean onOptionsItemSelected(MenuItem item) {
//...
return super.onOptionsItemSelected(item);
}
@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
String[] projection = new String[]{HistoryDatabase.ID, HistoryDatabase.MOBILE_RESULT, HistoryDatabase.MOBILE_SCORE, HistoryDatabase.FP_TIMESTAMP, HistoryDatabase.PRODUCT_IMAGE, HistoryDatabase.QR_MESSAGE};
return new CursorLoader(context, HistoryContentProvider.CONTENT_URI, projection, null, null, HistoryDatabase.ID + " DESC");
}
@Override
public void onLoadFinished(Loader<Cursor> cursorLoader, Cursor cursor) {
adapter.swapCursor(cursor);
}
@Override
public void onLoaderReset(Loader<Cursor> cursorLoader) {
adapter.swapCursor(null);
}
public void onListItemClick(ListView l, View v, int position, long id) {
//do something
}
}
我尝试过这些方法destroyLoader，restartLoader的不同组合，但没有任何成功......有谁知道发生了什么？
修改
使用LoaderManager.enableDebugLogging(true)我得到以下日志：
第一次加载给出了这个
initLoader in LoaderManager{424a7950 in HistoryFragments{42507c68}}: args=null
Starting: LoaderInfo{424a7da0 #1 : CursorLoader{42faae18}}
Created new loader LoaderInfo{424a7da0 #1 : CursorLoader{42faae18}}
initLoader in LoaderManager{424a7950 in HistoryFragments{42507c68}}: args=null
Starting: LoaderInfo{42e5a280 #2 : CursorLoader{42e5a2f8}}
Created new loader LoaderInfo{42e5a280 #2 : CursorLoader{42e5a2f8}}
onLoadComplete: LoaderInfo{424a7da0 #1 : CursorLoader{42faae18}}
onLoadFinished in CursorLoader{42faae18 id=1}: CursorWrapperInner{42506d58}
onLoadComplete: LoaderInfo{42e5a280 #2 : CursorLoader{42e5a2f8}}
onLoadFinished in CursorLoader{42e5a2f8 id=2}: CursorWrapperInner{42fab1f0}
然后当我改变方向时，它会给出这个
Retaining in LoaderManager{424a7950 in HistoryFragments{42507c68}}
Retaining: LoaderInfo{42e5a280 #2 : CursorLoader{42e5a2f8}}
Retaining: LoaderInfo{424a7da0 #1 : CursorLoader{42faae18}}
Destroying Inactive in LoaderManager{424a7950 in HistoryFragments{42507c68}}
initLoader in LoaderManager{424a7950 in HistoryFragments{426d0af0}}: args=null
Re-using existing loader LoaderInfo{424a7da0 #1 : CursorLoader{42faae18}}
initLoader in LoaderManager{424a7950 in HistoryFragments{426d0af0}}: args=null
Re-using existing loader LoaderInfo{42e5a280 #2 : CursorLoader{42e5a2f8}}
Finished Retaining in LoaderManager{424a7950 in HistoryFragments{426d0af0}}
Finished Retaining: LoaderInfo{42e5a280 #2 : CursorLoader{42e5a2f8}}
Stopping: LoaderInfo{42e5a280 #2 : CursorLoader{42e5a2f8}}
Finished Retaining: LoaderInfo{424a7da0 #1 : CursorLoader{42faae18}}
Stopping: LoaderInfo{424a7da0 #1 : CursorLoader{42faae18}}
然后，当我回到初始方向时，我收到错误，但随后一切都被重新加载：
Retaining in LoaderManager{424a7950 in HistoryFragments{426d0af0}}
Called doRetain when not started: LoaderManager{424a7950 in HistoryFragments{426d0af0}}
java.lang.RuntimeException: here
at android.app.LoaderManagerImpl.doRetain(LoaderManager.java:795)
at android.app.Activity.performStop(Activity.java:5497)
at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3591)
at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3654)
at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3854)
at android.app.ActivityThread.access$800(ActivityThread.java:159)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1322)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:176)
at android.app.ActivityThread.main(ActivityThread.java:5419)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862)
at dalvik.system.NativeStart.main(Native Method)
Destroying Active in LoaderManager{424a7950 in HistoryFragments{426d0af0}}
Destroying: LoaderInfo{42e5a280 #2 : CursorLoader{42e5a2f8}}
Reseting: LoaderInfo{42e5a280 #2 : CursorLoader{42e5a2f8}}
Destroying: LoaderInfo{424a7da0 #1 : CursorLoader{42faae18}}
Reseting: LoaderInfo{424a7da0 #1 : CursorLoader{42faae18}}
Destroying Inactive in LoaderManager{424a7950 in HistoryFragments{426d0af0}}
Destroying Active in LoaderManager{424a7950 in HistoryFragments{426d0af0}}
Destroying Inactive in LoaderManager{424a7950 in HistoryFragments{426d0af0}}
initLoader in LoaderManager{4271b070 in HistoryFragments{42702c68}}: args=null
Starting: LoaderInfo{4271b690 #1 : CursorLoader{4271b708}}
Created new loader LoaderInfo{4271b690 #1 : CursorLoader{4271b708}}
initLoader in LoaderManager{4271b070 in HistoryFragments{42702c68}}: args=null
Starting: LoaderInfo{42720ab8 #2 : CursorLoader{42720b30}}
Created new loader LoaderInfo{42720ab8 #2 : CursorLoader{42720b30}}
onLoadComplete: LoaderInfo{4271b690 #1 : CursorLoader{4271b708}}
onLoadFinished in CursorLoader{4271b708 id=1}: CursorWrapperInner{4271f518}
onLoadComplete: LoaderInfo{42720ab8 #2 : CursorLoader{42720b30}}
onLoadFinished in CursorLoader{42720b30 id=2}: CursorWrapperInner{427222c0}
然后日志重复进行以进一步改变方向。为什么CursorLoaders被停止而没有重新启动？我该如何重新启动它们？
编辑2
由于nikis，我解决了我的问题，但他提出了一个有趣的问题：
为什么android.app.LoaderManager无效？
这是使用支持版本后的日志。 第一个加载提供与上面相同的内容，但在方向更改后，重新使用游标不会阻止它们。
Retaining in LoaderManager{43945c70 in HistoryFragments{427cb468}}
Retaining: LoaderInfo{439d8a58 #2 : CursorLoader{439d8ad0}}
Retaining: LoaderInfo{432dea88 #1 : CursorLoader{4393ad48}}
Destroying Inactive in LoaderManager{43945c70 in HistoryFragments{427cb468}}
initLoader in LoaderManager{43945c70 in HistoryFragments{438f0a38}}: args=null
Re-using existing loader LoaderInfo{432dea88 #1 : CursorLoader{4393ad48}}
initLoader in LoaderManager{43945c70 in HistoryFragments{438f0a38}}: args=null
Re-using existing loader LoaderInfo{439d8a58 #2 : CursorLoader{439d8ad0}}
Starting in LoaderManager{43945c70 in HistoryFragments{438f0a38}}
Finished Retaining in LoaderManager{43945c70 in HistoryFragments{438f0a38}}
Finished Retaining: LoaderInfo{439d8a58 #2 : CursorLoader{439d8ad0}}
onLoadFinished in CursorLoader{439d8ad0 id=2}: CursorWrapperInner{43952be0}
Finished Retaining: LoaderInfo{432dea88 #1 : CursorLoader{4393ad48}}
onLoadFinished in CursorLoader{4393ad48 id=1}: CursorWrapperInner{43952fa8}
当我回到初始方向时，结果就是这样：
Retaining in LoaderManager{43945c70 in HistoryFragments{438f0a38}}
Retaining: LoaderInfo{439d8a58 #2 : CursorLoader{439d8ad0}}
Retaining: LoaderInfo{432dea88 #1 : CursorLoader{4393ad48}}
Destroying Inactive in LoaderManager{43945c70 in HistoryFragments{438f0a38}}
initLoader in LoaderManager{43945c70 in HistoryFragments{432cab50}}: args=null
Re-using existing loader LoaderInfo{432dea88 #1 : CursorLoader{4393ad48}}
initLoader in LoaderManager{43945c70 in HistoryFragments{432cab50}}: args=null
Re-using existing loader LoaderInfo{439d8a58 #2 : CursorLoader{439d8ad0}}
Starting in LoaderManager{43945c70 in HistoryFragments{432cab50}}
Finished Retaining in LoaderManager{43945c70 in HistoryFragments{432cab50}}
Finished Retaining: LoaderInfo{439d8a58 #2 : CursorLoader{439d8ad0}}
onLoadFinished in CursorLoader{439d8ad0 id=2}: CursorWrapperInner{43952be0}
Finished Retaining: LoaderInfo{432dea88 #1 : CursorLoader{4393ad48}}
onLoadFinished in CursorLoader{4393ad48 id=1}: CursorWrapperInner{43952fa8}
答案 0 :(得分：13)
您可以使用LoaderManager.enableDebugLogging(true)调试加载程序行为，也可以尝试使用getSupportLoadermanager()代替getLoaderManager()
答案 1 :(得分：4)
当您将支持库中的一些活动与android.app.LoaderManager组合时，似乎会出现此问题。
我与android.support.v7.app.ActionBarActivity和android.app.LoaderManager存在完全相同的问题：
通过使用android.support.v4.app.LoaderManager，一切都开始完美了！
答案 2 :(得分：2)
我遇到与OP相同的问题，因为在配置更改后没有调用class Duration {
public static final Duration ONE_HOUR = new Duration(1, DurationUnit.HOUR );
...
private final int quantity;
private DurationUnit unit;
//constructor and getters
}
。但是，这不是真正的问题（因为使用onCreateLoader表明我的加载器被成功重用，所以不需要重新创建新的加载器。）
所以我查看了我的getSupportLoaderManager().enableDebugLogging(true);方法，发现与onLoadFinished(Loader<Cursor> loader, Cursor cursor)不同，它总是在配置更改后调用。每次都会填充onCreateLoader。 ： - ）
问题是光标的位置在结果集的 end ，所以我尝试迭代它导致没有动作（因此，我的UI没有被填充）。
有效的解决方案是在第一个之前将光标位置移回：
cursor我把它放在// Move cursor before first so we can still iterate after config change
cursor.moveToPosition(-1);
方法的开头。
答案 3 :(得分：1)
有关您引用的问题的文档已记录在案。在onResume中调用restartLoader而不是在别处创建加载器。如有必要，restartLoader将创建。