How to create an ImageView that fills the parent height and displays an Image as big as possible?
If I'm understanding you correctly, what you need to use is the centerCrop scaleType. fitStart scales the image proportionally, but neither the width nor height will exceed the size of the view, and the image will, as you said, have a top|left gravity.
Using centerCrop scales the image proportionally, but causes the shortest edge of the image to match the size of the view, and if there is additional data on the long side that does not fit, it is simply cropped off. The gravity is, of course, center. The below worked for me:
<ImageView android:src="@drawable/image_placeholder" android:id="@+id/cover_view" android:layout_width="fill_parent" android:layout_height="fill_parent" android:scaleType="centerCrop"/>