【背景】
此处Android中显示出来的TextView中的内容，水平中间不对其。
想要实现水平居中对齐。
【折腾过程】
1.搜：
android RelativeLayout horizontal center
参考：
试过了：
android:layout_centerHorizontal="true"
但没用。
2.后来看到：
去试了试：
android:layout_centerVertical="true"
才明白：
我上面是错误的搜了horizontal ，实际上该去搜Vertical才对。
现在效果是所需要的了：
【总结】
想要水平居中对齐，则只需要去设置：
android:layout_centerVertical="true"
即可。
【引申】
更多的其他参数，可以去官网：
中找到：
| Attribute Name | Related Method | Description |
| Positions the bottom edge of this view above the given anchor view ID. | ||
| Positions the baseline of this view on the baseline of the given anchor view ID. | ||
| Makes the bottom edge of this view match the bottom edge of the given anchor view ID. | ||
| Makes the end edge of this view match the end edge of the given anchor view ID. | ||
| Makes the left edge of this view match the left edge of the given anchor view ID. | ||
| If true, makes the bottom edge of this view match the bottom edge of the parent. | ||
| If true, makes the end edge of this view match the end edge of the parent. | ||
| If true, makes the left edge of this view match the left edge of the parent. | ||
| If true, makes the right edge of this view match the right edge of the parent. | ||
| If true, makes the start edge of this view match the start edge of the parent. | ||
| If true, makes the top edge of this view match the top edge of the parent. | ||
| Makes the right edge of this view match the right edge of the given anchor view ID. | ||
| Makes the start edge of this view match the start edge of the given anchor view ID. | ||
| Makes the top edge of this view match the top edge of the given anchor view ID. | ||
| If set to true, the parent will be used as the anchor when the anchor cannot be be found for layout_toLeftOf, layout_toRightOf, etc. | ||
| Positions the top edge of this view below the given anchor view ID. | ||
| If true, centers this child horizontally within its parent. | ||
| If true, centers this child horizontally and vertically within its parent. | ||
| If true, centers this child vertically within its parent. | ||
| Positions the start edge of this view to the end of the given anchor view ID. | ||
| Positions the right edge of this view to the left of the given anchor view ID. | ||
| Positions the left edge of this view to the right of the given anchor view ID. | ||
| Positions the end edge of this view to the start of the given anchor view ID. |
至于每个都是什么效果，就可以自己去多试试就知道了。