MatrixCursor和MergeCursor

1、MatrixCursor创建记录

ContentProvider对外共享数据的时候的query()方法是需要一个cursor的，

但是如果没有数据库，而项目又需要从ContentProvider读取数据的时候怎么办？

更糟糕的是其他方法操作也都是需要cursor的。

此时就需要MatrixCursor了。相当有趣，它相当于为你模拟了一个表。

 

?

@Override

 

public Cursor query(Uri uri, String[] projection, String selection,

   String[] selectionArgs, String sortOrder) {

  String[] tableCursor = new String[] { "name","job","salary" };

  MatrixCursor cursor = new MatrixCursor(tableCursor);

  cursor.addRow(new Object[] { "1111","1111","1111" });

  return cursor;

}

2、MergeCursor 记录的合并

Cursor c0 = MailboxList.this.managedQuery(
                    EmailContent.Mailbox.CONTENT_URI,
                    MailboxList.this.mListAdapter.PROJECTION,
                    MAILBOX_SELECTION0,
                    new String[] { String.valueOf(mAccountKey) },
                    MailboxColumns.TYPE);
            Cursor c1 = MailboxList.this.managedQuery(
                        EmailContent.Mailbox.CONTENT_URI,
                        MailboxList.this.mListAdapter.PROJECTION,
                        MAILBOX_SELECTION,
                        new String[] { String.valueOf(mAccountKey) },
                        MailboxColumns.TYPE/* + "," + MailboxColumns.DISPLAY_NAME*/);
            Cursor c2 = MailboxList.this.managedQuery(
                    EmailContent.Mailbox.CONTENT_URI,
                    MailboxList.this.mListAdapter.PROJECTION,
                    MAILBOX_SELECTION1,
                    new String[] { String.valueOf(mAccountKey) },
                    MailboxColumns.TYPE/* + "," + MailboxColumns.DISPLAY_NAME*/);

            Cursor[] cursors = new Cursor[] { c0, c1, c2 };
            Cursor c = new MergeCursor(cursors);

Cursor c0 = MailboxList.this.managedQuery(
                    EmailContent.Mailbox.CONTENT_URI,
                    MailboxList.this.mListAdapter.PROJECTION,
                    MAILBOX_SELECTION0,
                    new String[] { String.valueOf(mAccountKey) },
                    MailboxColumns.TYPE);
        	Cursor c1 = MailboxList.this.managedQuery(
                        EmailContent.Mailbox.CONTENT_URI,
                        MailboxList.this.mListAdapter.PROJECTION,
                        MAILBOX_SELECTION,
                        new String[] { String.valueOf(mAccountKey) },
                        MailboxColumns.TYPE/* + "," + MailboxColumns.DISPLAY_NAME*/);
        	Cursor c2 = MailboxList.this.managedQuery(
                    EmailContent.Mailbox.CONTENT_URI,
                    MailboxList.this.mListAdapter.PROJECTION,
                    MAILBOX_SELECTION1,
                    new String[] { String.valueOf(mAccountKey) },
                    MailboxColumns.TYPE/* + "," + MailboxColumns.DISPLAY_NAME*/);
               
            Cursor[] cursors = new Cursor[] { c0, c1, c2 };
            Cursor c = new MergeCursor(cursors);