email/widget/EmailWidgetLoader.java

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.email.widget;

import com.android.email.R;
import com.android.email.data.ThrottlingCursorLoader;
import com.android.emailcommon.provider.Account;
import com.android.emailcommon.provider.EmailContent;
import com.android.emailcommon.provider.EmailContent.Message;
import com.android.emailcommon.provider.EmailContent.MessageColumns;
import com.android.emailcommon.provider.Mailbox;

import android.content.Context;
import android.content.res.Resources;
import android.database.Cursor;
import android.database.CursorWrapper;

/**
 * Loader for {@link EmailWidget}.
 *
 * This loader not only loads the messages, but also:
 * - The number of accounts.
 * - The message count shown in the widget header.
 *   It's currently just the same as the message count, but this will be updated to the unread
 *   counts for inboxes.
 */
class EmailWidgetLoader extends ThrottlingCursorLoader {
    private static final String SORT_TIMESTAMP_DESCENDING = MessageColumns.TIMESTAMP + " DESC";

    // The projection to be used by the WidgetLoader
    private static final String[] WIDGET_PROJECTION = new String[] {
            EmailContent.RECORD_ID, MessageColumns.DISPLAY_NAME, MessageColumns.TIMESTAMP,
            MessageColumns.SUBJECT, MessageColumns.FLAG_READ, MessageColumns.FLAG_FAVORITE,
            MessageColumns.FLAG_ATTACHMENT, MessageColumns.MAILBOX_KEY, MessageColumns.SNIPPET,
            MessageColumns.ACCOUNT_KEY, MessageColumns.FLAGS
            };
    public static final int WIDGET_COLUMN_ID = 0;
    public static final int WIDGET_COLUMN_DISPLAY_NAME = 1;
    public static final int WIDGET_COLUMN_TIMESTAMP = 2;
    public static final int WIDGET_COLUMN_SUBJECT = 3;
    public static final int WIDGET_COLUMN_FLAG_READ = 4;
    public static final int WIDGET_COLUMN_FLAG_FAVORITE = 5;
    public static final int WIDGET_COLUMN_FLAG_ATTACHMENT = 6;
    public static final int WIDGET_COLUMN_MAILBOX_KEY = 7;
    public static final int WIDGET_COLUMN_SNIPPET = 8;
    public static final int WIDGET_COLUMN_ACCOUNT_KEY = 9;
    public static final int WIDGET_COLUMN_FLAGS = 10;

    private long mAccountId;
    private long mMailboxId;

    /**
     * Cursor data specifically for use by the Email widget. Contains a cursor of messages in
     * addition to a message count and account name. The later elements were opportunistically
     * placed in this cursor. We could have defined multiple loaders for these items.
     */
    static class WidgetCursor extends CursorWrapper {
        private final int mMessageCount;
        private final String mAccountName;
        private final String mMailboxName;

        public WidgetCursor(Cursor cursor, int messageCount, String accountName,
                String mailboxName) {
            super(cursor);
            mMessageCount = messageCount;
            mAccountName = accountName;
            mMailboxName = mailboxName;
        }

        /**
         * Gets the count to be shown on the widget header. If the currently viewed mailbox ID is
         * not {@link Mailbox#QUERY_ALL_FAVORITES}, it is the unread count, which is different from
         * number of records returned by {@link #getCount()}.
         */
        public int getMessageCount() {
            return mMessageCount;
        }
        /** Gets the display name of the account */
        public String getAccountName() {
            return mAccountName;
        }
        /** Gets the display name of the mailbox */
        public String getMailboxName() {
            return mMailboxName;
        }
    }

    private final Context mContext;

    EmailWidgetLoader(Context context) {
        super(context, Message.CONTENT_URI, WIDGET_PROJECTION, null,
                null, SORT_TIMESTAMP_DESCENDING);
        mContext = context;
    }

    @Override
    public Cursor loadInBackground() {
        final Cursor messagesCursor = super.loadInBackground();

        // Reset the notification Uri to our Message table notifier URI
        messagesCursor.setNotificationUri(mContext.getContentResolver(), Message.NOTIFIER_URI);

        final int messageCount;
        if (mMailboxId != Mailbox.QUERY_ALL_FAVORITES) {
            String selection = "(" + getSelection() + " ) AND " + MessageColumns.FLAG_READ + " = 0";
            messageCount = EmailContent.count(mContext, Message.CONTENT_URI, selection,
                    getSelectionArgs());
        } else {
            // Just use the number of all messages shown.
            messageCount = messagesCursor.getCount();
        }
        Account account = Account.restoreAccountWithId(mContext, mAccountId);
        final String accountName;
        if (account != null) {
            accountName = account.mDisplayName;
        } else {
            if (mAccountId == Account.ACCOUNT_ID_COMBINED_VIEW) {
                int accountCount = EmailContent.count(mContext, Account.CONTENT_URI);
                Resources res = mContext.getResources();
                String countString =
                        res.getQuantityString(R.plurals.picker_combined_view_account_count,
                        accountCount, accountCount);
                accountName = res.getString(R.string.picker_combined_view_fmt, countString);
            } else {
                // TODO What to use here? "unknown"? Account is real, but, doesn't exist.
                accountName = null;
            }
        }
        final String mailboxName;
        if (mMailboxId > 0) {
            Mailbox mailbox = Mailbox.restoreMailboxWithId(mContext, mMailboxId);
            if (mailbox != null) {
                mailboxName = mailbox.mDisplayName;    // regular mailbox
            } else {
                // TODO What use here? "unknown"? Mailbox is "real", but, doesn't exist.
                mailboxName = null;
            }
        } else {
            if (mMailboxId == Mailbox.QUERY_ALL_INBOXES) {
                mailboxName = mContext.getString(R.string.picker_mailbox_name_all_inbox);
            } else { // default to all unread for the account's inbox
                mailboxName = mContext.getString(R.string.picker_mailbox_name_all_unread);
            }
        }

        return new WidgetCursor(messagesCursor, messageCount, accountName, mailboxName);
    }

    /**
     * Stop any pending load, reset selection parameters, and start loading.
     *
     * Must be called from the UI thread
     *
     * @param accountId The ID of the account. May be {@link Account#ACCOUNT_ID_COMBINED_VIEW}.
     * @param mailboxId The mailbox to load; may either be a real mailbox or the pseudo mailbox
     *          {@link Mailbox#QUERY_ALL_INBOXES} or {@link Mailbox#QUERY_ALL_UNREAD}. If it's
     *          neither of these pseudo mailboxes, {@link Mailbox#QUERY_ALL_UNREAD} will be used.
     */
    void load(long accountId, long mailboxId) {
        reset();
        mAccountId = accountId;
        mMailboxId = mailboxId;
        setSelectionAndArgs();
        startLoading();
    }

    /** Sets the loader's selection and arguments depending upon the account and mailbox */
    private void setSelectionAndArgs() {
        if (mAccountId == Account.ACCOUNT_ID_COMBINED_VIEW) {
            if (mMailboxId == Mailbox.QUERY_ALL_INBOXES) {
                setSelection(Message.ALL_INBOX_SELECTION);
            } else { // default to all unread
                setSelection(Message.ALL_UNREAD_SELECTION);
            }
            setSelectionArgs(null);
        } else {
            if (mMailboxId > 0L) {
                // Simple mailbox selection
                setSelection(
                    MessageColumns.ACCOUNT_KEY + "=? AND " +
                    MessageColumns.MAILBOX_KEY + "=?");
                setSelectionArgs(
                        new String[] { Long.toString(mAccountId), Long.toString(mMailboxId) });
            } else {
                if (mMailboxId == Mailbox.QUERY_ALL_INBOXES) {
                    setSelection(Message.PER_ACCOUNT_INBOX_SELECTION);
                } else { // default to all unread for the account's inbox
                    setSelection(Message.PER_ACCOUNT_UNREAD_SELECTION);
                }
                setSelectionArgs(new String[] { Long.toString(mAccountId) });
            }
        }
    }
}