android-CursorLoader和CursorTreeAdapter

2024-04-08 20:37:12

我正在尝试将CursorLoader与CursorTreeAdapter一起使用,但是遇到了我无法解决的问题. (如果您有一个可行的示例,请随时跳过其余内容,并附在下面.我将非常感谢)
我第一次打开群组时,一切正常.如果然后关闭并重新打开该组,则会收到溢出错误.这是错误：

V/SpellBook(29520): Activity being created 
D/SpellBook(29520): onCreateLoader for id 123456 
V/SpellBook(29520): Resuming 
V/SpellBook(29520): Processing query for uri content://com.zalzala.spellbook.SpellProvider/levels/bard 
D/SpellBook(29520): onl oadFinished() for id 123456 
D/SpellBook(29520): onCreateLoader for id 3 
V/SpellBook(29520): Processing query for uri content://com.zalzala.spellbook.SpellProvider/class/bard/3 
D/SpellBook(29520): onl oadFinished() for id 3

这里一切都很好.到目前为止,我已经打开了活动并打开了组3.这是如果我关闭组3并再次打开它会发生的情况：

D/SpellBook(29520): onl oadFinished() for id 3 
D/SpellBook(29520): onl oadFinished() for id 3 
D/SpellBook(29520): onl oadFinished() for id 3 
D/SpellBook(29520): onl oadFinished() for id 3 
D/SpellBook(29520): onl oadFinished() for id 3 
(... and a lot more of these) 
    E/AndroidRuntime(29520): FATAL EXCEPTION: main 
E/AndroidRuntime(29520): java.lang.*Error 
E/AndroidRuntime(29520):    at java.util.HashMap.get(HashMap.java:302) 
E/AndroidRuntime(29520):    at android.database.sqlite.SQLiteCursor.getColumnIndex(SQLiteCursor.java:355)
E/AndroidRuntime(29520):    at android.database.CursorWrapper.getColumnIndex(CursorWrapper.java:67) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment$MyExpandableListAdapter.getChildrenCursor(SpellListView.java:216) 
E/AndroidRuntime(29520):    at android.widget.CursorTreeAdapter.getChildrenCursorHelper(CursorTreeAdapter.java:106) 
E/AndroidRuntime(29520):    at android.widget.CursorTreeAdapter.setChildrenCursor(CursorTreeAdapter.java:159) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment.onLoadFinished(SpellListView.java:183) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment.onLoadFinished(SpellListView.java:1) 
E/AndroidRuntime(29520):    at android.support.v4.app.LoaderManagerImpl$LoaderInfo.callOnLoadFinished(LoaderManager.java:413) 
E/AndroidRuntime(29520):    at android.support.v4.app.LoaderManagerImpl.initLoader(LoaderManager.java:547) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment$MyExpandableListAdapter.getChildrenCursor(SpellListView.java:217) 
E/AndroidRuntime(29520):    at android.widget.CursorTreeAdapter.getChildrenCursorHelper(CursorTreeAdapter.java:106) 
E/AndroidRuntime(29520):    at android.widget.CursorTreeAdapter.setChildrenCursor(CursorTreeAdapter.java:159) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment.onLoadFinished(SpellListView.java:183) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment.onLoadFinished(SpellListView.java:1) 
E/AndroidRuntime(29520):    at android.support.v4.app.LoaderManagerImpl$LoaderInfo.callOnLoadFinished(LoaderManager.java:413) 
E/AndroidRuntime(29520):    at android.support.v4.app.LoaderManagerImpl.initLoader(LoaderManager.java:547) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment$MyExpandableListAdapter.getChildrenCursor(SpellListView.java:217) 
E/AndroidRuntime(29520):    at android.widget.CursorTreeAdapter.getChildrenCursorHelper(CursorTreeAdapter.java:106) 
E/AndroidRuntime(29520):    at android.widget.CursorTreeAdapter.setChildrenCursor(CursorTreeAdapter.java:159) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment.onLoadFinished(SpellListView.java:183) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment.onLoadFinished(SpellListView.java:1) 
E/AndroidRuntime(29520):    at android.support.v4.app.LoaderManagerImpl$LoaderInfo.callOnLoadFinished(LoaderManager.java:413) 
E/AndroidRuntime(29520):    at android.support.v4.app.LoaderManagerImpl.initLoader(LoaderManager.java:547) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment$MyExpandableListAdapter.getChildrenCursor(SpellListView.java:217) 
E/AndroidRuntime(29520):    at android.widget.CursorTreeAdapter.getChildrenCursorHelper(CursorTreeAdapter.java:106) 
E/AndroidRuntime(29520):    at android.widget.CursorTreeAdapter.setChildrenCursor(CursorTreeAdapter.java:159) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment.onLoadFinished(SpellListView.java:183) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment.onLoadFinished(SpellListView.java:1) 
E/AndroidRuntime(29520):    at android.support.v4.app.LoaderManagerImpl$LoaderInfo.callOnLoadFinished(LoaderManager.java:413) 
E/AndroidRuntime(29520):    at android.support.v4.app.LoaderManagerImpl.initLoader(LoaderManager.java:547) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment$MyExpandableListAdapter.getChildrenCursor(SpellListView.java:217) 
E/AndroidRuntime(29520):    at android.widget.CursorTreeAdapter.getChildrenCursorHelper(CursorTreeAdapter.java:106) 
E/AndroidRuntime(29520):    at android.widget.CursorTreeAdapter.setChildrenCursor(CursorTreeAdapter.java:159) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment.onLoadFinished(SpellListView.java:183) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment.onLoadFinished(SpellListView.java:1) 
E/AndroidRuntime(29520):    at android.support.v4.app.LoaderManagerImpl$LoaderInfo.callOnLoadFinished(LoaderManager.java:413) 
E/AndroidRuntime(29520):    at android.support.v4.app.LoaderManagerImpl.initLoader(LoaderManager.java:547) 
E/AndroidRuntime(29520):    at com.zalzala.spellbook.SpellListView$ExpandableListCursorLoaderFragment$MyExpandableListAdapter.getChildrenCursor(SpellListView.java:217) 
E/AndroidRuntime(29520):    at android.widget.CursorTreeAdapter.getChildrenCursorHelper(CursorTreeAdapter.ja 
W/ActivityManager( 6887):   Force finishing activity com.zalzala.spellbook/.SpellListView

因此,由于某些原因,在重新打开组时会反复为子游标调用onLoadFinished().

这是我的加载程序实现：

    @Override
    public Loader<Cursor> onCreateLoader(int id, Bundle args) {
        // TODO Auto-generated method stub
        Log.d(Spellbook.TAG,"onCreateLoader for id "+id);
        if (id <123456){
            Uri spellUri = Uri.withAppendedPath(SpellProvider.CONTENT_URI, "class");
            spellUri = Uri.withAppendedPath(spellUri, mCLASS);
            spellUri = ContentUris.withAppendedId(spellUri, id);
            return new CursorLoader(getActivity(), spellUri, null, null, null, null);
        }else {
            //get group cursor
            Uri groupUri = Uri.withAppendedPath(SpellProvider.CONTENT_URI, "levels");
            groupUri = Uri.withAppendedPath(groupUri, mCLASS);
            return new CursorLoader(getActivity(), groupUri, null, null, null, null);
        }
    }

    @Override
    public void onl oadFinished(Loader<Cursor> loader, Cursor data) {
        // TODO Auto-generated method stub
        int id = loader.getId();
        Log.d(Spellbook.TAG,"onLoadFinished() for id "+id);
        if (id < 123456){
            //child cursor
            ((CursorTreeAdapter) mAdapter).setChildrenCursor(id, data);
        } else {
            ((CursorTreeAdapter) mAdapter).setGroupCursor(data);
        }

    }

    @Override
    public void onl oaderReset(Loader<Cursor> loader) {
        // TODO Auto-generated method stub
        int id = loader.getId();
        Log.d(Spellbook.TAG,"onLoaderReset() for id "+id);
        if (id < 123456){
            //child cursor
            ((CursorTreeAdapter) mAdapter).setChildrenCursor(id, null);
        } else {
            ((CursorTreeAdapter) mAdapter).setGroupCursor(null);
        }

    }

我用构造函数调用CursorTreeAdapter,该构造函数将自动重新查询指定为false.

    public class MyExpandableListAdapter extends CursorTreeAdapter {

        public MyExpandableListAdapter(Cursor cursor, Context context) {
            super(cursor, context, false); //do not auto requery. pretty sure CursorLoader needs this.
        }

        @Override
        protected Cursor getChildrenCursor(Cursor groupCursor) {
            // Given the group, we return a cursor for all the children within that group 
            int id = groupCursor.getInt(groupCursor.getColumnIndex(SpellDbAdapter.KEY_LEVEL));
            getLoaderManager().initLoader(id, null, ExpandableListCursorLoaderFragment.this);
            return null;
        }

谢谢你的帮助！

解决方法:

在onGroupCollapsed()上调用destroyLoader().但是它不能完全解决问题.看一下CursorTreeAdapter实现,请确保不要将其与CursorLoader一起使用.

扩展BaseExpandableAdapter确实更好.这种方式可以避免不必要的内容观察者使用(在使用加载程序的情况下).在我的自定义适配器中,我将以稀疏数组形式创建的加载器保留下来,并在组崩溃时销毁它们.效果很好：)

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