Digging StackOverflow for answers on the similar issue I found people usually suggesting 2 approaches:
- Load a drawable into memory and compare ConstantState or bitmap itself to other one.
- Set a tag with drawable id into a view and compare tags when you need
that.
Personally, I like the second approach for performance reason but tagging bunch of views with appropriate tags is painful and time consuming. This could be very frustrating in a big project. In my case I need to write a lot of Espresso tests which require comparing TextView
drawables, ImageView
resources, View
background and foreground. A lot of work.
So I eventually came up with a solution to delegate a 'dirty' work to the custom inflater. In every inflated view I search for a specific attributes and and set a tag to the view with a resource id if any is found. This approach is pretty much the same guys from Calligraphy used. I wrote a simple library for that: TagView
If you use it, you can retrieve any of predefined tags, containing drawable resource id that was set in xml layout file:
TagViewUtils.getTag(view, ViewTag.IMAGEVIEW_SRC.id)
TagViewUtils.getTag(view, ViewTag.TEXTVIEW_DRAWABLE_LEFT.id)
TagViewUtils.getTag(view, ViewTag.TEXTVIEW_DRAWABLE_TOP.id)
TagViewUtils.getTag(view, ViewTag.TEXTVIEW_DRAWABLE_RIGHT.id)
TagViewUtils.getTag(view, ViewTag.TEXTVIEW_DRAWABLE_BOTTOM.id)
TagViewUtils.getTag(view, ViewTag.VIEW_BACKGROUND.id)
TagViewUtils.getTag(view, ViewTag.VIEW_FOREGROUND.id)
The library supports any attribute, actually. You can add them manually, just look into the Custom attributes section on Github.
If you set a drawable in runtime you can use convenient library methods:
setImageViewResource(ImageView view, int id)
In this case tagging is done for you internally. If you use Kotlin you can write a handy extensions to call view itself. Something like this:
fun ImageView.setImageResourceWithTag(@DrawableRes int id) {
TagViewUtils.setImageViewResource(this, id)
}
You can find additional info in Tagging in runtime