问题描述
我需要在RelativeLayout中的Button上方放置一个TextView.但它不起作用:TextView 总是在按钮下,即使我将它移动到按钮之前.我还尝试了 bringChildToFront()
函数将 textview 移动到前面,但没有运气.
I need to place a TextView above the Button in RelativeLayout. But it is not working: TextView is always under the Button, even if I move it before the button.I also tried bringChildToFront()
function to move textview on front, but no luck.
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/rlBottom"
android:layout_width="fill_parent"
android:layout_height="match_parent">
<Button
android:id="@+id/bVio"
android:layout_width="wrap_content"
android:layout_height="50dip"
android:layout_alignParentLeft="true"
android:text="VIO"></Button>
<TextView
android:id="@+id/bVio_count"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="@+id/bVio"
android:layout_marginTop="6dip"
android:layout_marginRight="6dip"
android:text="00"
android:textSize="15dip"
android:textColor="#FF0000"/>
</RelativeLayout>
推荐答案
在 API 级别为 21 (Lollipop/Android 5.0) 及更高级别的 Android 上,当您处理具有高度的项目(例如 Button)时,会出现此问题.
The problem occurs on Android with an API level 21 (Lollipop/Android 5.0) and above when you work with items which have an elevation, such as the Button.
在 Lollipop 之前的设备上订购布局时,Android 将查看 XML 中项目的顺序.项目在 XML 中越靠下,它在 Z-index 中的位置就越高.所以如果你先把 Button 放在它下面,然后把 TextField 放在它下面,它就会起作用.
When ordering the layout on pre Lollipop devices Android will look to the order of the items in the XML. The further down an item is in the XML the higher up it is in Z-index. So if you place the Button first and the TextField below it, it will work.
但是,在 Android 高于 API 21 的设备上决定 z-index 的顺序时,系统还会查看项目的高度并将具有较高高度值的项目呈现在具有较低高度值的项目之上.因此,为了让您的设计工作,您必须确保您的 TextField 具有比您的 Button 更高的高度,您可以通过在您的项目上定义 android:elevation
来实现这一点.下面的模拟 XML 适用于 API 级别 21 之前和之后的设备:
However, when deciding the order of the z-index on devices with Android above API 21 the system will also look at the items elevation and render items with a higher elevation value above items with a lower elevation value. So to get your design to work you must make sure that your TextField has a higher elevation than your Button which you can achieve by defining android:elevation
on your items. The mock XML below works on devices pre and post API level 21:
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/rlBottom"
android:layout_width="fill_parent"
android:layout_height="match_parent">
<Button
android:id="@+id/bVio"
android:layout_width="wrap_content"
android:layout_height="50dip"
android:layout_alignParentLeft="true"
android:text="VIO"
android:elevation="0dp"
/>
<TextView
android:id="@+id/bVio_count"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="@+id/bVio"
android:layout_marginTop="6dip"
android:layout_marginRight="6dip"
android:text="00"
android:textSize="15dip"
android:textColor="#FF0000"
android:elevation="10dp"
/>
</RelativeLayout>
这篇关于相对布局中的 z-index的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!