How to put a triangle gray corner on a ImageButton?

Question

I have a square ImageButton defined in the xml whose source image may change programmatically. Regardless of what's the image inside I want to display a little gray triangle in the bottom right corner (the goal is to suggest the user to click on the image and to pick another icon from a list). Here's an example I found on Marshmallow:

How to do it?

Answer 1

You can do something like this

           <RelativeLayout
                    android:id="@+id/image_holder"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:layout_gravity="center"
                    android:gravity="center"
                    android:visibility="visible">

                    <ImageView
                        android:id="@+id/chosenThing"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_centerInParent="true"
                        android:layout_gravity="center"
                        android:adjustViewBounds="true"
                        android:contentDescription="@string/chosen_image"
                        android:scaleType="centerInside"/>


                    <ImageView
                        android:id="@+id/corner"
                        style="@style/Base.Widget.AppCompat.Button.Borderless"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:layout_alignBottom="@id/chosenThing"
                        android:layout_alignLeft="@id/chosenThing"
                        android:layout_alignRight="@id/chosenThing"
                        android:layout_centerHorizontal="true"
                        android:clickable="true"
                        android:padding="8dp"
                        android:src="@drawable/ic_corner"
                        android:tint="@color/white"
                        android:gravity="bottom|right" />
                </RelativeLayout>