我需要绘制2个折线图（在单个图表中），但其中一个图表的值（点数）多于另一个图表。在两种情况下，我的x轴标签都是字符串（表示从MySQL数据库中提取的日期）。
例如，这里有两个我需要绘制的标签值对：
{"time":"2015-09-08 14:22:27.0","value":"313"},{"time":"2015-09-08 14:22:32.0","value":"294"},{"time":"2015-09-08 14:22:37.0","value":"303"},{"time":"2015-09-08 14:22:41.0","value":"313"},{"time":"2015-09-08 14:22:46.0","value":"365"}
{"time":"2015-09-08 13:00:07.0","value":"245"},{"time":"2015-09-08 13:00:17.0","value":"245"},{"time":"2015-09-08 13:00:27.0","value":"245"},{"time":"2015-09-08 13:00:37.0","value":"245"},{"time":"2015-09-08 13:00:47.0","value":"245"},{"time":"2015-09-08 13:00:57.0","value":"245"},{"time":"2015-09-08 13:01:07.0","value":"245"},{"time":"2015-09-08 14:19:51.0","value":"248"},{"time":"2015-09-08 14:20:01.0","value":"248"},{"time":"2015-09-08 14:20:11.0","value":"248"},{"time":"2015-09-08 14:20:21.0","value":"248"},{"time":"2015-09-08 14:20:31.0","value":"248"},{"time":"2015-09-08 14:20:41.0","value":"248"},{"time":"2015-09-08 14:20:51.0","value":"248"},{"time":"2015-09-08 14:21:00.0","value":"248"},{"time":"2015-09-08 14:21:10.0","value":"248"},{"time":"2015-09-08 14:21:20.0","value":"248"}
现在，我有两个包含上述“时间”值的字符串ArrayList（每个图表一个），在绘制图表时我需要将它们用作我的x轴标签。我怎么能用MPAndroidChart做到这一点？