/**
* Updates the given measure spec with respect to the aspect ratio.
*
* <p>Note: Measure spec is not changed if the aspect ratio is not greater than zero or if
* layoutParams is null.
*
* <p>Measure spec of the layout dimension (width or height) specified as "0dp" is updated to
* match the measure spec of the other dimension adjusted by the aspect ratio. Exactly one layout
* dimension should be specified as "0dp".
*
* <p>Padding is taken into account so that the aspect ratio refers to the content without
* padding: {@code aspectRatio == (viewWidth - widthPadding) / (viewHeight - heightPadding)}
*
* <p>Updated measure spec respects the parent's constraints. I.e. measure spec is not changed if
* the parent has specified mode {@code EXACTLY}, and it doesn't exceed measure size if parent has
* specified mode {@code AT_MOST}.
*
* @param spec in/out measure spec to be updated
* @param aspectRatio desired aspect ratio
* @param layoutParams view's layout params
* @param widthPadding view's left + right padding
* @param heightPadding view's top + bottom padding
*/
public static void updateMeasureSpec(
Spec spec,
float aspectRatio,
@Nullable ViewGroup.LayoutParams layoutParams,
int widthPadding,
int heightPadding) {
if (aspectRatio <= 0 || layoutParams == null) {
return;
}
if (shouldAdjust(layoutParams.height)) {
int widthSpecSize = View.MeasureSpec.getSize(spec.width);
int desiredHeight = (int) ((widthSpecSize - widthPadding) / aspectRatio + heightPadding);
int resolvedHeight = View.resolveSize(desiredHeight, spec.height);
spec.height = View.MeasureSpec.makeMeasureSpec(resolvedHeight, View.MeasureSpec.EXACTLY);
} else if (shouldAdjust(layoutParams.width)) {
int heightSpecSize = View.MeasureSpec.getSize(spec.height);
int desiredWidth = (int) ((heightSpecSize - heightPadding) * aspectRatio + widthPadding);
int resolvedWidth = View.resolveSize(desiredWidth, spec.width);
spec.width = View.MeasureSpec.makeMeasureSpec(resolvedWidth, View.MeasureSpec.EXACTLY);
}
}
