Android, create rounded custom view with checked and unchecked cases

Question

I need to create a custom image view for choosing color by design. When user click the circle, inner white circle with a tick should appear, like in example below:

Otherwise, it should be just a circle shape with some color (unchecked state), like below:

The main problem, that I do not know how to create a selector with the inner circle inside and with keeping the ability to setup color programmatically.

Simple rounded shape I can setup, for example, like this:

<de.hdodenhof.circleimageview.CircleImageView
    android:id="@+id/circle_crop"
    android:layout_width="32dp"
    android:layout_height="32dp"
    android:layout_gravity="center"
    android:src="@android:color/holo_red_dark" />

How to modify it to setup white circle with tick inside on a checked state (when user click on it)?

Answer 1

So easy.

1. Create layer-list Drawable Called "icon_check"

<layer-list 
    xmlns:android="http://schemas.android.com/apk/res/android">

    <item                                           //for the round white background
        android:bottom="10dp"                       //margin, "<size>" tag doesn't work
        android:end="10dp"
        android:start="10dp"
        android:top="10dp">

        <shape 
            android:shape="oval">

            <solid 
                android:color="@color/white" />

        </shape>

    </item>

    <item
        android:drawable="@drawable/check"          //check mark from built-in asset
        android:bottom="14dp"                       //margin, extra 4dp is prefered
        android:end="14dp"
        android:start="14dp"
        android:top="14dp" />

</layer-list>

2. Create selector Drawable Called "foreground_check"

<selector
    xmlns:android="http://schemas.android.com/apk/res/android">

    <item
        android:drawable="@drawable/icon_check"             //layer-list created above
        android:state_selected="true" />

    <item
        android:drawable="@android:color/transparent"       //key point, 【"@null" doesn't work!!】
        android:state_selected="false" />

</selector>

3. Setup CardView

<androidx.cardview.widget.CardView                  //【MaterialCardView doesn't work!!】
    android:id="@+id/cardView"
    android:layout_width="40dp"
    android:layout_height="40dp"
    android:foreground="@drawable/foreground_check" //apply layer-list drawable
    app:cardBackgroundColor="@color/black"
    app:cardCornerRadius="20dp" />                  //half of side length

4. Setup Ui Controller

cardView.setOnClickListener {
    it.isSelected = !it.isSelected
}

Result: