我正在开发一个使用ActionBarSherlock和ViewPagerIndicator构建的Android应用程序，其minSDK为8（Android 2.2），targetSDK为16（Android 4.1），使用Android兼容性库。我有一个应用程序的消息传递部分，其中消息存储在SQLite数据库中，我使用CommonsWare的cwac-loaderex来使用SQLite数据库的游标加载器。当活动加载时，一切都运行良好并显示消息，但是当我旋转设备时，它只显示带有加载cicle的ListFragment。
启用LoaderManager.enableDebugLogging（true）当我旋转时重用现有的加载器，我也在onDestroy中尝试了getSupportLoaderManager（）。destroyLoader（ID）并且正在创建新的加载器但我仍然有相同的结果，一个ListFragment加载圈。我在打开消息传递活动之前已经在两个方向进行了测试，并且它们都工作正常，当我在消息传递活动可见时轮换时，这只是一个问题。我还尝试以纵向方式进入消息传递活动，单击一条消息，将我带到另一个活动而不破坏消息传递活动，更改为格局，然后按回消息传递活动，一切正常。
我无法弄清楚为什么在旋转后没有显示消息。我会非常感谢任何想法或帮助。我在下面列出了我的消息传递活动。
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.ListFragment;
import android.support.v4.app.LoaderManager;
import android.support.v4.content.Loader;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.SimpleCursorAdapter;
import com.actionbarsherlock.app.SherlockFragmentActivity;
import com.actionbarsherlock.view.Menu;
import com.actionbarsherlock.view.MenuItem;
import com.commonsware.cwac.loaderex.acl.SQLiteCursorLoader;
import com.viewpagerindicator.TitlePageIndicator;
import com.lukekorth.DB.DatabaseHelper;
import com.lukekorth.Helpers.MessageFragment;
public class MyMessagesActivity extends SherlockFragmentActivity implements
LoaderManager.LoaderCallbacks<Cursor> {
private FragmentAdapter mFragmentAdapter;
private ViewPager mPager;
private DatabaseHelper mDB;
private SimpleCursorAdapter mInboxCursorAdapter;
private SimpleCursorAdapter mArchiveCursorAdapter;
private MessageFragment[] content = new MessageFragment[2];
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.messages);
getSupportActionBar().setHomeButtonEnabled(true);
getSherlock().getActionBar().setDisplayHomeAsUpEnabled(true);
mDB = new DatabaseHelper(this);
content[0] = new MessageFragment();
content[1] = new MessageFragment();
/////////--------------------///////
LoaderManager.enableDebugLogging(true);
mInboxCursorAdapter = new SimpleCursorAdapter(this, R.layout.message_item, null, new String[] { DatabaseHelper.senderName,
DatabaseHelper.lastUpdate, DatabaseHelper.subject, DatabaseHelper.lastSnippet }, new int[] { R.id.name, R.id.date,
R.id.subject, R.id.snippet });
mArchiveCursorAdapter = new SimpleCursorAdapter(this, R.layout.message_item, null, new String[] { DatabaseHelper.senderName,
DatabaseHelper.lastUpdate, DatabaseHelper.subject, DatabaseHelper.lastSnippet }, new int[] { R.id.name, R.id.date,
R.id.subject, R.id.snippet });
content[0].setListAdapter(mInboxCursorAdapter);
content[1].setListAdapter(mArchiveCursorAdapter);
getSupportLoaderManager().initLoader(0, null, this);
getSupportLoaderManager().initLoader(1, null, this);
///////////////------------------////////////
mFragmentAdapter = new FragmentAdapter(getSupportFragmentManager());
mFragmentAdapter.updateContent(content);
mPager = (ViewPager) findViewById(R.id.pager);
mPager.setAdapter(mFragmentAdapter);
TitlePageIndicator indicator = (TitlePageIndicator) findViewById(R.id.indicator);
indicator.setViewPager(mPager);
}
@Override
public void onDestroy() {
super.onDestroy();
getSupportLoaderManager().destroyLoader(0);
getSupportLoaderManager().destroyLoader(1);
mDB.close();
}
@Override
public Loader<Cursor> onCreateLoader(int folder, Bundle arg1) {
String query = "select " + DatabaseHelper.threads + "." + DatabaseHelper.threadKey + "," + DatabaseHelper.subject +
"," + DatabaseHelper.archive + "," + DatabaseHelper.otherUser + "," + DatabaseHelper.lastUpdate + "," +
DatabaseHelper.lastSnippet + "," + DatabaseHelper.senderPicture + "," + DatabaseHelper.senderName + " from " +
DatabaseHelper.threads + " left join " + DatabaseHelper.senders + " on " + DatabaseHelper.threads + "." +
DatabaseHelper.otherUser + " = " + DatabaseHelper.senders + "." + DatabaseHelper.senderKey + " where " +
DatabaseHelper.archive;
if(folder == 0)
query += " = 0 order by ";
else
query += " = 1 order by ";
query += DatabaseHelper.lastUpdate + " desc";
return new SQLiteCursorLoader(this, mDB, query, null);
}
@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
if(loader.getId() == 0)
mInboxCursorAdapter.swapCursor(cursor);
else
mArchiveCursorAdapter.swapCursor(cursor);
}
@Override
public void onLoaderReset(Loader<Cursor> loader) {
if(loader.getId() == 0)
mInboxCursorAdapter.swapCursor(null);
else
mArchiveCursorAdapter.swapCursor(null);
}
}
class FragmentAdapter extends FragmentPagerAdapter {
protected static final String[] TITLE = new String[] { "Inbox", "Archive", };
private ListFragment[] mContent;
private int mCount = TITLE.length;
public FragmentAdapter(FragmentManager fm) {
super(fm);
}
public void updateContent(MessageFragment[] content){
mContent = content;
}
@Override
public Fragment getItem(int position) {
return mContent[position % mContent.length];
}
@Override
public int getCount() {
return mCount;
}
@Override
public CharSequence getPageTitle(int position) {
return FragmentAdapter.TITLE[position % TITLE.length];
}
}
答案 0 :(得分：1)
事实证明，ViewPager和片段标签存在一些奇怪之处。我的解决方案是在onSaveInstanceState()中的事务中添加片段，然后在onCreate()（第二段代码）中添加片段，以使用ViewPager中生成的标记通过标记获取片段。我能够找出this question中使用的标签方案。希望这可以节省一些人工作。
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.add(content[0], content[0].getTag());
ft.add(content[1], content[1].getTag());
ft.commit();
}
FragmentManager fm = getSupportFragmentManager();
content[0] = (MessageFragment) fm.findFragmentByTag("android:switcher:"+ R.id.pager + ":0");
content[1] = (MessageFragment) fm.findFragmentByTag("android:switcher:"+ R.id.pager + ":1");
if(content[0] == null || content[1] == null){
content[0] = new MessageFragment();
content[1] = new MessageFragment();
content[0].setListAdapter(mInboxCursorAdapter);
content[1].setListAdapter(mArchiveCursorAdapter);
}