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Android 方向更改时未调用onCreateLoader

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Android 方向更改时未调用onCreateLoader,android,Android,我的问题基本上和这个一样： 我有两个列表片段，它们包含在ViewPager中。它们一开始加载正常，但当我更改方向时，initLoader方法不会调用onCreateLoader。 但是，如果我恢复到初始方向，一切又会好起来 这是我的片段活动的代码： 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.

我的问题基本上和这个一样：

我有两个
列表片段
，它们包含在
ViewPager
中。它们一开始加载正常，但当我更改方向时，
initLoader
方法不会调用
onCreateLoader
。 但是，如果我恢复到初始方向，一切又会好起来

这是我的
片段活动的代码
：

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;
    }
}


}
我尝试了这些方法的不同组合，
destroiloader
，
restartLoader
，但没有成功。。。有人知道发生了什么事吗

编辑 使用
LoaderManager.enableDebugLogging（true）
我可以获得以下日志： 第一个载荷给出了这个结果

 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}

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}}
当我改变方向时，它给出

 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}

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，我得到一个错误，但随后再次加载所有内容：

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，日志会重复它们自己，以进行进一步的方向更改。为什么停止而不重新启动
游标加载程序
？如何重新启动它们

编辑2

多亏了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不工作

以下是使用支持版本后的日志。
第一次加载与上面给出的内容相同，但是在方向更改之后，重新使用游标并不会停止它们


 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，结果是：


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}



您可以使用
LoaderManager.EnableDebuggerLogging（true）
来调试您的加载程序行为，也可以尝试使用
getSupportLoadermanager（）
而不是
getLoaderManager（）
您提到的问题有一个解决方法。在onResume中调用restartLoader，而不是在别处创建加载程序。如果需要，将创建restartLoader。
当您将支持库中的某些活动与android.app.LoaderManager组合时，似乎会出现此问题

我在android.support.v7.app.ActionBarActivity和android.app.LoaderManager上遇到了完全相同的问题：


    

  • 初装工程
    • 

  • 然后，当方向改变时，加载程序将完成
    • 

  • 然后当回到原来的方向时，它又开始工作了



通过使用android.support.v4.app.LoaderManager，一切又开始完美地工作了
 我遇到了与OP相同的问题，即配置更改后没有调用
onCreateLoader
。然而，这并不是真正的问题（因为使用
getSupportLoaderManager（）.enableddebuglogging（true）；
表明我的加载程序被成功重用，因此不需要重新创建新的加载程序）

因此，我查看了我的
onLoadFinished（Loader-Loader，Cursor-Cursor）
方法，发现它与
onCreateLoader
不同，总是在配置更改后调用。每次都会填充
光标
。：-）

问题是光标的位置在resultset的末尾，因此我尝试遍历它时没有导致任何操作（因此，我的UI没有被填充）

有效的解决方案是先将光标位置向后移动，然后再执行以下操作：


// Move cursor before first so we can still iterate after config change
cursor.moveToPosition(-1);



我把它放在我的
onLoadFinished
方法的开头。
移动fillData（）方法不起作用，它在
onCreateLoader
方法中生成了一个
nullPointerException
，感谢
LoaderManager.enableDebugLogging（true）
技巧，我已经使用了它并更新了我的问题。嗯，请尝试android.support.v4.*版本的加载程序API，而不是android.app.LoaderManager。有帮助吗？谢谢nikis，你让我走上了正确的道路！我使用的是
getLoaderManager（）
而不是
getSupportLoaderManager（）
！你让我开心！仅供参考，FragmentActivity的文档说明：“当使用这个类而不是新平台的内置片段和加载程序支持时，必须分别使用getSupportFragmentManager（）和getSupportLoaderManager（）方法来访问这些功能。”我在第一次看这个问题时已经尝试过这个方法。它不起作用问题依然存在，我也有同样的问题。这是否意味着在方向更改后，相同的游标实例会传递给
onLoadFinished
？这是我所能看到的该职位最终落幕的唯一原因。我希望如此。可能值得做一个测试来检查：将原始游标保存到一个静态变量（如果静态变量为null），然后将其与“新”游标进行比较。这对我来说现在更有意义了。我重新阅读了这篇文章，其中解释了LoaderManager在方向更改期间保留状态，因此无需再次查询数据。谢谢，这节省了我的时间，但我使用了cursor.moveToFirst（）；奇怪的是，这也正是我观察到的。我在getLoaderManager中使用了AppCompativeActivity，它在旋转时不断丢失加载程序，一旦我更改为getSupportLoaderManager，它就工作得很好，谢谢！这里的答案解决了我的问题：