在相对布局中将视图的顶部与另一个视图的底部对齐

Question

How can I align a View 's top to another View 's bottom? I need two views one on top of another. I achieved the right vertical position with a simple android:layout_below="id_of_the_top_view" , but I can't manage to align the View s horizontally. I would something like android:layout_alignTopToBottomOf="id_of_the_top_view" , or in general something that lets me align a View center (horizontal or vertical) to another View center.

<RelativeLayout
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

<!-- center picker @ minutes -->
<NumberPicker
    android:id="@+id/npicker_minutes"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerInParent="true"
    android:layout_marginLeft="20dp"
    android:layout_marginRight="20dp" />

<!-- left picker @ hours -->
<NumberPicker
    android:id="@+id/npicker_hours"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerVertical="true"
    android:layout_toLeftOf="@id/npicker_minutes" />

<!-- right picker @ seconds -->
<NumberPicker
    android:id="@+id/npicker_seconds"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerVertical="true"
    android:layout_toRightOf="@id/npicker_minutes" />

<TextView
    android:id="@+id/tv_minutes"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_below="@id/npicker_minutes"
    android:layout_marginTop="20dp"
    android:paddingBottom="15dp"
    android:text="@string/minutes_short" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/npicker_hours"
    android:layout_toLeftOf="@id/tv_minutes"
    android:layout_marginTop="20dp"
    android:paddingBottom="15dp"
    android:text="@string/hours_short" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/npicker_seconds"
    android:layout_toRightOf="@id/tv_minutes"
    android:layout_marginTop="20dp"
    android:paddingBottom="15dp"
    android:text="@string/seconds_short" />

</RelativeLayout>

What I've got is this:

And what I need to achieve is that the three TextView s ("hh", "mm" and "ss"), are placed each one below one of the number pickers, with the horizontal center of the TextView aligned to the horizontal center of the NumberPicker .

Answer 1

You need to add this lines to your TextViews:

android:layout_alignLeft="@id/npicker_minutes"
android:layout_alignRight="@id/npicker_minutes"
android:gravity="center_horizontal"

Complete sample of your code:

<!-- center picker @ minutes -->

<NumberPicker
    android:id="@+id/npicker_minutes"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerInParent="true"
    android:layout_marginLeft="20dp"
    android:layout_marginRight="20dp" />

<!-- left picker @ hours -->

<NumberPicker
    android:id="@+id/npicker_hours"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerVertical="true"
    android:layout_toLeftOf="@id/npicker_minutes" />

<!-- right picker @ seconds -->

<NumberPicker
    android:id="@+id/npicker_seconds"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerVertical="true"
    android:layout_toRightOf="@id/npicker_minutes" />

<TextView
    android:id="@+id/tv_minutes"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@id/npicker_minutes"
    android:layout_alignRight="@id/npicker_minutes"
    android:gravity="center_horizontal"
    android:layout_below="@id/npicker_minutes"
    android:layout_marginTop="20dp"
    android:paddingBottom="15dp"
    android:text="@string/minutes_short" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/npicker_hours"
    android:layout_alignRight="@+id/npicker_hours"
    android:gravity="center_horizontal"
    android:layout_below="@id/npicker_hours"
    android:layout_marginTop="20dp"
    android:paddingBottom="15dp"
    android:text="@string/hours_short" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@id/npicker_seconds"
    android:layout_alignRight="@id/npicker_seconds"
    android:gravity="center_horizontal"
    android:layout_below="@id/npicker_seconds"
    android:layout_marginTop="20dp"
    android:paddingBottom="15dp"
    android:text="@string/seconds_short" />

The alternative way is to use tree LinearLayouts, every with one NumberPicker and one TextView inside.

Answer 2

You can use the following properties to align the first and the third text view:

      android:layout_alignLeft="@+id/your_first_number_picker" //your first text view

 android:layout_alignRight="@+id/your_third_number_picker" //your third text view

Answer 3

in my case i use android:layout_above

 <androidx.core.widget.NestedScrollView
        android:id="@+id/nestedScrollView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_above="@+id/layout_bottom"
        >