Return an empty cursor when a content provider app op is disabled

import android.content.res.AssetFileDescriptor;

import android.content.res.Configuration;

import android.database.Cursor;

import android.database.MatrixCursor;

import android.database.SQLException;

import android.net.Uri;

import android.os.AsyncTask;

            validateIncomingUri(uri);

            uri = getUriWithoutUserId(uri);

            if (enforceReadPermission(callingPkg, uri, null) != AppOpsManager.MODE_ALLOWED) {

                return rejectQuery(uri, projection, selection, selectionArgs, sortOrder,

                        CancellationSignal.fromTransport(cancellationSignal));

                // The caller has no access to the data, so return an empty cursor with

                // the columns in the requested order. The caller may ask for an invalid

                // column and we would not catch that but this is not a problem in practice.

                // We do not call ContentProvider#query with a modified where clause since

                // the implementation is not guaranteed to be backed by a SQL database, hence

                // it may not handle properly the tautology where clause we would have created.

                return new MatrixCursor(projection, 0);

            }

            final String original = setCallingPackage(callingPkg);

            try {

    public void onTrimMemory(int level) {

    }

    /**

     * @hide

     * Implementation when a caller has performed a query on the content

     * provider, but that call has been rejected for the operation given

     * to {@link #setAppOps(int, int)}.  The default implementation

     * rewrites the <var>selection</var> argument to include a condition

     * that is never true (so will always result in an empty cursor)

     * and calls through to {@link #query(android.net.Uri, String[], String, String[],

     * String, android.os.CancellationSignal)} with that.

     */

    public Cursor rejectQuery(Uri uri, String[] projection,

            String selection, String[] selectionArgs, String sortOrder,

            CancellationSignal cancellationSignal) {

        // The read is not allowed...  to fake it out, we replace the given

        // selection statement with a dummy one that will always be false.

        // This way we will get a cursor back that has the correct structure

        // but contains no rows.

        if (selection == null || selection.isEmpty()) {

            selection = "'A' = 'B'";

        } else {

            selection = "'A' = 'B' AND (" + selection + ")";

        }

        return query(uri, projection, selection, selectionArgs, sortOrder, cancellationSignal);

    }

    /**

     * Implement this to handle query requests from clients.

     * This method can be called from multiple threads, as described in