Loader not loading data when source data changes

Android Documentation states that LOADERS - They monitor the source of their data and deliver new results when the content changes. I have changed CursorAdapter to work for a SQLite Database.

import android.content.ContentResolver;
import android.content.Context;
import android.database.ContentObserver;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v4.content.AsyncTaskLoader;
import android.support.v4.content.Loader.ForceLoadContentObserver;
import android.util.Log;


public class SimpleCursorLoader extends AsyncTaskLoader<Cursor> {

final ForceLoadContentObserver mObserver;

String mTable;
String[] mColumns;
String mSelection;
String[] mSelectionArgs;
String mGroupBy;
String mHaving;
String mOrderBy;
String mLimit;

Cursor mCursor;
SQLiteDatabase mDb;
 /**
 * Creates an empty unspecified CursorLoader.  You must follow this with
 * calls to {@link #setUri(Uri)}, {@link #setSelection(String)}, etc
 * to specify the query to perform.
 */
public SimpleCursorLoader(Context context) {
    super(context);
    mObserver = new ForceLoadContentObserver();
}

/**
 * Creates a fully-specified SimpleCursorLoader.  See
 * {@link ContentResolver#query(Uri, String[], String, String[], String)
 * ContentResolver.query()} for documentation on the meaning of the
 * parameters.  These will be passed as-is to that call.
 */
public SimpleCursorLoader(Context context,String table, String[] columns, String      selection, 
        String[] selectionArgs, String groupBy, String having, String orderBy, String limit, SQLiteDatabase db) {

    super(context);
    mObserver = new ForceLoadContentObserver();
    mTable = table;
    mColumns = columns; //copying array
    mSelection = selection;
    mSelectionArgs = selectionArgs;
    mG开发者_如何学JAVAroupBy = groupBy;
    mHaving = having;
    mOrderBy =  orderBy;
    mLimit = limit;
    mDb = db;
}       

    /* Runs on a worker thread */
@Override
public Cursor loadInBackground() {
    Cursor cursor = mDb.query(mTable, mColumns, mSelection, mSelectionArgs, mGroupBy, mHaving, mOrderBy, mLimit);
    if (cursor != null) {
        // Ensure the cursor window is filled
        cursor.getCount();
        Log.d("SimpleCursorLoader","Cursor.getCount()= " + String.valueOf(cursor.getCount()));
        registerContentObserver(cursor, mObserver);
    }
    return cursor;
}

/**
 * Registers an observer to get notifications from the content provider
 * when the cursor needs to be refreshed.
 */
void registerContentObserver(Cursor cursor, ContentObserver observer) {
    cursor.registerContentObserver(mObserver);
}

/* Runs on the UI thread */
@Override
public void deliverResult(Cursor cursor) {
    Log.d("Gaurav","Inside SimpleCursorLoader - deliverResult");
    if (isReset()) {
        // An async query came in while the loader is stopped
        if (cursor != null) {
            cursor.close();
        }
        return;
    }
    Cursor oldCursor = mCursor;
    mCursor = cursor;

    if (isStarted()) {
        super.deliverResult(cursor);
    }

    if (oldCursor != null && oldCursor != cursor && !oldCursor.isClosed()) {
        oldCursor.close();
    }
}


/**
 * Starts an asynchronous load of the contacts list data. When the result is ready the callbacks
 * will be called on the UI thread. If a previous load has been completed and is still valid
 * the result may be passed to the callbacks immediately.
 *
 * Must be called from the UI thread
 */
@Override
protected void onStartLoading() {
    Log.d("Gaurav", "onStartLoading");
    if (mCursor != null) {
        deliverResult(mCursor);
    }
    if (takeContentChanged() || mCursor == null) {
        forceLoad();
    }
}

/**
 * Must be called from the UI thread
 */
@Override
protected void onStopLoading() {
    // Attempt to cancel the current load task if possible.
    cancelLoad();
}

@Override
public void onCanceled(Cursor cursor) {
    if (cursor != null && !cursor.isClosed()) {
        cursor.close();
    }
}

@Override
protected void onReset() {
    super.onReset();

    // Ensure the loader is stopped
    onStopLoading();

    if (mCursor != null && !mCursor.isClosed()) {
        mCursor.close();
    }
    mCursor = null;
}

}

The CursorLoader works in a ListFragment with a custom adapter which extends SimpleCursor Adapter and passes FLAG_REGISTER_CONTENT_OBSERVER in constructor but the cursor does changes when underlying data is changed by used response in the list.

---

I had the same problem albeit I was using a different implementation than you. I was able to correct my problem by explicitly stating notification URI to something less specific. I'm sure there are other problems with my code that caused me to need to do this but it fixed my issue. So, my Cursor query in my content provider went from:

@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,  String sortOrder) {

................
................
................

Cursor cursor = queryBuilder.query(mDB.getReadableDatabase(),
                projection, selection, selectionArgs, null, null, sortOrder);
                cursor.setNotificationUri(getContext().getContentResolver(), uri);
cursor.setNotificationUri(getContext().getContentResolver(), uri;)

to

@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,  String sortOrder) {

................
................
................

Cursor cursor = queryBuilder.query(mDB.getReadableDatabase(),
                projection, selection, selectionArgs, null, null, sortOrder);
                cursor.setNotificationUri(getContext().getContentResolver(), uri);
cursor.setNotificationUri(getContext().getContentResolver(), MYURI;)

where MYURI is variable of the URI type that I know will cover everything I'm watching.

Hope this helps someone out.

---

You need to override the dump method.

@Override
    public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) {
        super.dump(prefix, fd, writer, args);
        writer.print(prefix); writer.print("mTable="); writer.println(mTable);
        writer.print(prefix); writer.print("mDB=");writer.println(mDb);
        writer.print(prefix); writer.print("mProjection=");
                writer.println(Arrays.toString(mProjection));
        writer.print(prefix); writer.print("mSelection="); writer.println(mSelection);
        writer.print(prefix); writer.print("mSelectionArgs=");
                writer.println(Arrays.toString(mSelectionArgs));
        writer.print(prefix); writer.print("mSortOrder="); writer.println(mSortOrder);
        writer.print(prefix); writer.print("mCursor="); writer.println(mCursor);
        writer.print(prefix); writer.print("mContentChanged="); writer.println(mContentChanged);
    }