Android，CustomView布局未显示

Question

I've done this before with no issue so i know my mistake is subtle.

<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="left|center_horizontal"
        android:id="@+id/pickerDialog_title"
        android:text="HELLO WORLD!!"/>
    <NumberPicker
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignTop="@+id/pickerDialog_title"
        android:id="@+id/pickerDialog_selector"/>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignTop="@+id/pickerDialog_selector"
        android:orientation="horizontal">
        <Button
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="5"
            android:id="@+id/pickerDialog_cancel"
            android:gravity="center"
            android:text="Cancel"/>
        <Button
            android:layout_height="match_parent"
            android:layout_width="0dp"
            android:layout_weight="5"
            android:id="@+id/pickerDialog_set"
            android:gravity="center"
            android:text="Set"/>
    </LinearLayout>
</merge>

During the Custom Class constructor, PickerDialog(Context context, AttributeSet attrs, int defStyle) i call:

LayoutInflater.from(context).inflate(R.layout.picker_dialog_layout, this);

And in the parent XML:

<com.company.simonaddicott.controlpanel_1.PickerDialog
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/pickerDialog" />

The view itself does show, and from using layout bound tools in developer tools i can identify that the ui elements are present, or at least the boundaries are present (see below)

Answer 1

My mistake was that I extended the custom view by LinearLayout , but was using RelativeLayout positioning on the picker_dialog_layout.xml .

The elements inside the layout were not showing as they had no relative parent element to be positioned against