Q:

How do I get my ImageButton to resize correctly for an asset image?

My app has an Activity that displays a vertically scrolling list of ImageButtons. I want each buttons image to (A) come from the assets folder and (B) retain it's aspect ratio as it scales. Unfortunately, my ImageButton doesn't size correctly when it's image comes from the assets folder.
ImageButton src set from drawable
The first screenshot is my test app where the images all come from my apps drawables. That's the "correct" aspect ratio for that image, which is what I want to keep (all of the image buttons have been given scaleType "fitXY" "centerCrop").

ImageButton src set from assets
The second screenshot is my test app where the images all come from my apps "assets" folder — as you can see, the images are stretched out to the full width of the screen as desired, but the original aspect ratio has been lost:

Activity code (MainActivity.java)
LinearLayout buttons = (LinearLayout) findViewById(R.id.buttons);
View button = layoutInflater.inflate(R.layout.snippet_imagebutton, null);
ImageButton imageButton = (ImageButton) button.findViewById(R.id.imageButton);
if (GET_IMAGE_FROM_ASSETS) {
    InputStream s = assetManager.open("image.png");
    Bitmap bmp = BitmapFactory.decodeStream(s);
    imageButton.setImageBitmap(bmp);
} else {
    imageButton.setImageResource(R.drawable.image);
}
TextView buttonText = (TextView) button.findViewById(R.id.textView);
buttonText.setText("Button text!");
buttons.addView(button,
    new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));

Button layout (snippet_imagebutton.xml)
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="8dp">
    <ImageButton
        android:id="@+id/imageButton"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:scaleType="centerCrop"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true" />
    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:gravity="center"
        android:textColor="#FFF"
        android:background="#88000000"
        android:textAppearance="?android:attr/textAppearanceMedium" />
</RelativeLayout>

Dodgy hack
I've found a dodgy hack which achieves what I want and illustrates the problem — the ImageButton will size correctly to match a scaled up image from the resources, but it won't size correctly to match a scaled up image from the assets. I'd prefer a "real" solution over the dodgy hack if there is one. :)
// to start with, scale the ImageButton based on an image in our
// resources that has the same dimensions as the image in our assets
imageButton.setImageResource(R.drawable.image);
// when we eventually render (we don't have width / height yet)...
imageButton.post(new Runnable() {
    public void run() {
        int height = imageButton.getHeight();
        int width = imageButton.getWidth();
        // replace our "resource" image with our "asset" image
        imageButton.setImageBitmap(bmp);
        // and force the ImageButton to keep the same scale as previously
        imageButton.setLayoutParams(
            new RelativeLayout.LayoutParams(width, height));
    }
});

Summary
I want to get the images for these buttons from my apps "assets" folder. How do I fix my app so that the button images are all scaled properly (i.e. retain their original aspect ratio)?
I'm assuming this has something to do with the framework not actually knowing the width / height of the image before it renders the ImageButton to screen — so how do I fix that? I tried setting adjustViewBounds to "true" on both the RelativeLayout and the ImageButton itself, but that didn't seem to have any effect.

A:

From what I gather, AdjustViewBounds is actually the method that provides the exact functionality you need. However, as Roman Nurik explains here, AdjustViewBounds does NOT increase the ViewBounds beyond the natural dimensions of the drawable.
Without seeing how you allocated resources/assets, my suspicion would be that this is why you see a difference when loading from Resources and when loading from Assets. Your resource file is - presumably - being scaled up when you load it (since that is the default behavior for resources), so that the actual size of the drawable returned from /res is significantly larger than the bitmap you decode from /assets.
Overriding ImageButton (as Nurik suggests), is of course one option, but probably overkill.
Assuming I am correct about the problem, you should be able to fix it simply by setting your BitmapFactory.options correctly when you load the Assets file. You need to set inDensity and inTargetDensity correctly according to your device (get DisplayMetrics), and set inScaled to true.
Alternatively, you can always rescale the bitmap manually before loading it on the ImageButton. Just grab the screen width to determine how large you need to make it.
P.S.
Auto-scaling is obviously the elegant solution, but it does have a weakness (which applies equally to both resources and assets) - if the width of your display > bitmap witdh when scaled up, you'll likely still have the aspect ratio messed up. You can check this pretty easily by going to landscape mode and seeing whether the resource file still result in the right aspect ratio. If you have a large enough base image (or use different layouts according to the screen size/orientation), then this should not be a problem though. Just something to keep in mind.

