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SQLite query is executed in the user interface thread using ExpandableListView / SimpleCursorTreeAdapter

I am developing an Android application for displaying a number of RSS feeds (yes, I know that there are already many such applications). The data that will be displayed is supported by the content provider, and I want to be backward compatible with API level 4.

I use ExpandableListViewto display the contents of three different RSS feeds. The adapter is ExpandableListViewimplemented as a subclass of the class SimpleCursorTreeAdapter:

private class RssFeedLatestListAdapter extends SimpleCursorTreeAdapter {

    public static final String FEED_NAME_COLUMN = "feedName";

    public RssFeedLatestListAdapter(Context ctx, Cursor groupCursor, int groupLayout,
            String[] groupFrom, int[] groupTo, int childLayout, String[] childFrom,
            int[] childTo) {
        super(ctx, groupCursor, groupLayout, groupLayout, groupFrom, groupTo, childLayout, childFrom, childTo);
    }

    @Override
    protected Cursor getChildrenCursor(final Cursor groupCursor) {
        final String feedName = groupCursor.getString(groupCursor.getColumnIndex(FEED_NAME_COLUMN));
        return managedQuery(LATEST_URI, null,
                FeedItemColumns.CATEGORY + " = ? AND " + FeedItemColumns.FEED + " = ?",
                new String[] { mCategory.getId(), feedName }, null);
    }

    @Override
    protected void bindGroupView(View view, Context context, Cursor cursor, boolean isExpanded) {
        super.bindGroupView(view, context, cursor, isExpanded);

        // Bind group view (impl details not important) ...
    }

    @Override
    protected void bindChildView(View view, Context context, Cursor cursor, boolean isLastChild) {
        super.bindChildView(view, context, cursor, isLastChild);

        // Bind child view (impl details not important) ...
    }
}

With this setting, all content loads as expected. However, the user interface freezes / stutters randomly while loading the contents of the list. Usually not enough to get ANR, but still noticeable and very annoying!

, android.os.StrictMode( / btw!) ( Android 2.3). , StrictMode:

D/StrictMode(  395): StrictMode policy violation; ~duration=1522 ms: android.os.StrictMode$StrictModeDiskReadViolation: policy=23 violation=2
D/StrictMode(  395):  at android.os.StrictMode$AndroidBlockGuardPolicy.onReadFromDisk(StrictMode.java:745)
D/StrictMode(  395):  at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1345)
D/StrictMode(  395):  at android.database.sqlite.SQLiteQueryBuilder.query(SQLiteQueryBuilder.java:330)
D/StrictMode(  395):  at com.mycompany.myapp.provider.RSSFeedProvider.query(RSSFeedProvider.java:128)
D/StrictMode(  395):  at android.content.ContentProvider$Transport.query(ContentProvider.java:187)
D/StrictMode(  395):  at android.content.ContentResolver.query(ContentResolver.java:262)
D/StrictMode(  395):  at android.app.Activity.managedQuery(Activity.java:1550)
D/StrictMode(  395):  at com.mycompany.myapp.activity.MultipleFeedsActivity$RssFeedLatestListAdapter.getChildrenCursor(MultipleFeedsActivity.java:388)
D/StrictMode(  395):  at android.widget.CursorTreeAdapter.getChildrenCursorHelper(CursorTreeAdapter.java:106)
D/StrictMode(  395):  at android.widget.CursorTreeAdapter.getChildrenCount(CursorTreeAdapter.java:178)
D/StrictMode(  395):  at android.widget.ExpandableListConnector.refreshExpGroupMetadataList(ExpandableListConnector.java:561)
D/StrictMode(  395):  at android.widget.ExpandableListConnector.expandGroup(ExpandableListConnector.java:682)
D/StrictMode(  395):  at android.widget.ExpandableListConnector.expandGroup(ExpandableListConnector.java:636)
D/StrictMode(  395):  at android.widget.ExpandableListView.expandGroup(ExpandableListView.java:608)
D/StrictMode(  395):  at com.mycompany.myapp.activity.MultipleFeedsActivity.onReceiveResult(MultipleFeedsActivity.java:335)
D/StrictMode(  395):  at com.mycompany.myapp.service.FeedResultReceiver.onReceiveResult(FeedResultReceiver.java:40)
D/StrictMode(  395):  at android.os.ResultReceiver$MyRunnable.run(ResultReceiver.java:43)
D/StrictMode(  395):  at android.os.Handler.handleCallback(Handler.java:587)
D/StrictMode(  395):  at android.os.Handler.dispatchMessage(Handler.java:92)
D/StrictMode(  395):  at android.os.Looper.loop(Looper.java:123)
D/StrictMode(  395):  at android.app.ActivityThread.main(ActivityThread.java:3647)
D/StrictMode(  395):  at java.lang.reflect.Method.invokeNative(Native Method)
D/StrictMode(  395):  at java.lang.reflect.Method.invoke(Method.java:507)
D/StrictMode(  395):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
D/StrictMode(  395):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
D/StrictMode(  395):  at dalvik.system.NativeStart.main(Native Method)

! SimpleCursorTreeAdapter.getChildrenCursor() , , , , !

JavaDoc ( API 4) CursorTreeAdapter ( SimpleCursorTreeAdapter) getChildrenCursor() :

" , null setChildrenCursor (int, Cursor).".

! ! getChildrenCursor(), , , children . null getChildrenCursor():

@Override
protected Cursor getChildrenCursor(final Cursor groupCursor) {
    final String feedName = groupCursor.getString(groupCursor.getColumnIndex(FEED_NAME_COLUMN));
    new RefreshChildrenCursorTask(groupCursor.getPosition()).execute(feedName);
    return null;
}

RefreshChildrenCursorTask :

private class RefreshChildrenCursorTask extends AsyncTask<String, Void, Cursor> {

    private int mGroupPosition;

    public RefreshChildrenCursorTask(int groupPosition) {
        this.mGroupPosition = groupPosition;
    }

    @Override
    protected Cursor doInBackground(String... params) {
        String feedName = params[0];
        return managedQuery(LATEST_URI, null,
                FeedItemColumns.CATEGORY + " = ? AND " + FeedItemColumns.FEED + " = ?",
                new String[] { mCategory.getId(), feedName }, null);
        }

        @Override
        protected void onPostExecute(Cursor childrenCursor) {
            mLatestListAdapter.setChildrenCursor(mGroupPosition, childrenCursor);
        }
    }
}

2.3 . , , ! ... , , - ( Samsung Galaxy S Android 2.2). Exception :

E/AndroidRuntime(23191): FATAL EXCEPTION: main
E/AndroidRuntime(23191): java.lang.NullPointerException
E/AndroidRuntime(23191):  at android.widget.SimpleCursorTreeAdapter.initFromColumns(SimpleCursorTreeAdapter.java:194)
E/AndroidRuntime(23191):  at android.widget.SimpleCursorTreeAdapter.initChildrenFromColumns(SimpleCursorTreeAdapter.java:205)
E/AndroidRuntime(23191):  at android.widget.SimpleCursorTreeAdapter.init(SimpleCursorTreeAdapter.java:186)
E/AndroidRuntime(23191):  at android.widget.SimpleCursorTreeAdapter.(SimpleCursorTreeAdapter.java:136)
E/AndroidRuntime(23191):  at com.mycompany.myapp.activity.MultipleFeedsActivity$RssFeedLatestListAdapter.(MultipleFeedsActivity.java:378)
E/AndroidRuntime(23191):  at com.mycompany.myapp.activity.MultipleFeedsActivity$2.run(MultipleFeedsActivity.java:150)
E/AndroidRuntime(23191):  at android.os.Handler.handleCallback(Handler.java:587)
E/AndroidRuntime(23191):  at android.os.Handler.dispatchMessage(Handler.java:92)
E/AndroidRuntime(23191):  at android.os.Looper.loop(Looper.java:123)
E/AndroidRuntime(23191):  at android.app.ActivityThread.main(ActivityThread.java:4627)
E/AndroidRuntime(23191):  at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(23191):  at java.lang.reflect.Method.invoke(Method.java:521)
E/AndroidRuntime(23191):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:871)
E/AndroidRuntime(23191):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:629)
E/AndroidRuntime(23191):  at dalvik.system.NativeStart.main(Native Method)

SimpleCursorTreeAdapter , getChildrenCursor(). , Android 2.3, Android? CursorTreeAdapter, ?

- , , () ? , - , !? , !

!

, Jacob

+3
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, API API, .

+2

, mp2526! !

! , , ( ) API 8 - ... -, ( , SimpleCursorTreeAdapter)

, API 8 API 9 SimpleCursorTreeAdapter, , Android 2.3, , childFrom groupFrom , .. . bindView(). , . , , API API 4 API 9 ( setViewText()), API 9 ! , !

, mp2526!

+2

Source: https://habr.com/ru/post/1785018/

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