Toggle visibility of custom view in XML via Databinding

Question

I have a fragment layout fragment_config.xml, which cointains the following:

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:bind="http://schemas.android.com/tools">
    <data>
        <import type="android.view.View"/>
        <variable name="viewModel" type ="...GlobalConfigViewModel"/>
    </data>
        ...
            <ToggleButton
                android:id="@+id/btnShowAdvanced"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:textOff="Show Advanced"
                android:textOn="Hide Advanced"
                android:checked="@={viewModel.advancedShown}"/>


            <com.minh.minh.pumpnotifier.global.configuration.AdvancedBox
                android:id="@+id/advancedBox"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:visibility="@{viewModel.advancedShown ? View.VISIBLE : View.GONE}"
                app:viewModel = "@{viewModel}"/>

    ...
</layout>

What is supposed to happen is that the visibility of Advanced Box toggles with the "checked"-state of the toggle button. I already confirmed that the two-way-databinding in the toggle-button sets the boolean "advancedShown" in the viewModel correctly. The "setVisibility"-method however is never called in the AdvancedBox-class (which extends LinearLayout).

Something else I tried is to set the visibility binding in the root element of the advanced_box.xml, since it also has a reference to the viewModel:

<?xml version="1.0" encoding="utf-8"?>
<layout>
    <data>
        <import type="android.view.View"/>
        <variable
            name="viewModel"
            type="...GlobalConfigViewModel" />
    </data>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:id="@+id/advancedSettings"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:visibility="@{viewModel.advancedShown ? View.VISIBLE : View.GONE}"
        android:orientation="vertical">

Both methods do not work out though. My question is why it does not work and what would be the correct way to use databinding in this case?

Answer 1

Your viewModel.advancedShown should be ObservableField or marked with @Bindable annotation (in the second variant you need manually invoke notifyPropertyChanged(BR.advancedShown) on your GlobalConfigViewModel to trigger changes). You can find more information in official docs