android - Stretch Image to Fit

Question

The src should stretch its width to match_parent, while keeping aspect ratio. When the image is larger than the parent, it scales down correctly. But when the image is smaller, it does not scale up. (illustration shows desired behavior).

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <ImageView
        android:id="@+id/banner"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:scaleType="fitCenter"
        android:adjustViewBounds="true"
        android:src="@drawable/foo"
        />

</RelativeLayout>

Using ScaleType.fitXY stretches the width only

Answer 1

I believe that is not possible, at least not with the options provided by scaleType attribute.
Your best option in this case is to use centerCrop, but only the center of the picture will be visible.

However, if you are not ok with this option, then you could scale the image programatically without loosing aspect ratio. In order to achieve this you'll need to calculate a scale factor based on the screen width, and then use this scale factor to know the new height of the image.

Like this:

ImageView imageView = (ImageView)findViewById(R.id.imageView);
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.foo);

int imageWidth = bitmap.getWidth();
int imageHeight = bitmap.getHeight();

int newWidth = getScreenWidth(); //this method should return the width of device screen.
float scaleFactor = (float)newWidth/(float)imageWidth;
int newHeight = (int)(imageHeight * scaleFactor);

bitmap = Bitmap.createScaledBitmap(bitmap, newWidth, newHeight, true);
imageView.setImageBitmap(bitmap);

Also, you'll need to adjust the declaration of ImageView in layout file:

<ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />