Implementation of onMeasure to ensure a square aspect ratio.

gistfile1.java

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    int heightMode = MeasureSpec.getMode(heightMeasureSpec);

    int widthSize = MeasureSpec.getSize(widthMeasureSpec);
    int heightSize = MeasureSpec.getSize(heightMeasureSpec);
    
    int width, height;

    // If one of the measures is match_parent, use that one to determine the size.
    // If not, use the default implementation of onMeasure
    if(widthMode == MeasureSpec.EXACTLY && heightMode != MeasureSpec.EXACTLY) {
        width = height = widthSize;
        if(heightMode == MeasureSpec.AT_MOST)
            height = Math.min(height, heightSize);
    } else if(heightMode == MeasureSpec.EXACTLY && widthMode != MeasureSpec.EXACTLY) {
        width = height = heightSize;
        if(widthMode == MeasureSpec.AT_MOST)
            width = Math.min(width, widthSize);
    } else {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        return;
    }
    
    setMeasuredDimension(width, height);
}