Why background color are included in png image of ImageView?

Question

I am an absolute beginner to Android. I am learning how to design a layout. But I am having problem with ImageView:

When I set the src of ImageView with a PNG file, the dark color background is automatically added to all the images like in screenshot:

The real image of is like this: (There's no background)

This is the xml layout for my toolbar and I did not set any background for the ImageView:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/toolbar"
    android:fitsSystemWindows="true"
    android:minHeight="?attr/actionBarSize"
    app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
    android:background="?attr/colorPrimaryDark">
        <ImageButton
            android:id="@+id/btn_open_sidebar"
            android:src="@drawable/open_icon"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />

        <ImageButton
            android:layout_alignParentRight="true"
            android:id="@+id/btn_calendar"
            android:src="@drawable/calendar"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
</RelativeLayout>

So how can I make that PNG image transparent or with the same background as the toolbar? I mean, how to remove that default dark background color?

Answer 1

I think because you are using ImageButton android adds a default background to it. you can add android:backgroud="@android:color/transparent" to your ImageButtons and force android to use transparent background.