Enlargable ImageView implementation

/*
 * $URL: $
 * $Revision: $
 * $Date: $
 * $Author: tprochazka $
 *
 * Author:  Tomáš Procházka <tomas.prochazka@atomsoft.cz>
 * Licence: Commercial
 */

package cz.atomsoft.android.test;

import android.content.Context;
import android.util.AttributeSet;

/**
 * Special version of ImageView which allow enlarge width of image if android:adjustViewBounds is true.
 *
 * <p>This simulate HTML behaviour &lt;img src="" widh="100" /&gt;</p>
 * <p><a href="http://stackoverflow.com/questions/6202000/imageview-one-dimension-to-fit-free-space-and-second-evaluate-to-keep-aspect-rati">Stackoverflow question link</p>
 *
 * @author Tomáš Procházka &lt;<a href="mailto:tomas.prochazka@atomsoft.cz">tomas.prochazka@atomsoft.cz</a>&gt;
 * @version $Revision: 0$ ($Date: 6.6.2011 18:16:52$)
 */
public class ImageView extends android.widget.ImageView {

    private int mDrawableWidth;
    private int mDrawableHeight;
    private boolean mAdjustViewBounds;
    private int mMaxWidth;
    private int mMaxHeight;

    public ImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    public ImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public ImageView(Context context) {
        super(context);
    }

    public void setAdjustViewBounds(boolean adjustViewBounds) {
        super.setAdjustViewBounds(adjustViewBounds);
        mAdjustViewBounds = adjustViewBounds;
    }

    public void setMaxWidth(int maxWidth) {
        super.setMaxWidth(maxWidth);
        mMaxWidth = maxWidth;
    }

    public void setMaxHeight(int maxHeight) {
        super.setMaxHeight(maxHeight);
        mMaxHeight = maxHeight;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        mDrawableWidth = getDrawable().getIntrinsicWidth();
        mDrawableHeight = getDrawable().getIntrinsicHeight();

        int w = 0;
        int h = 0;

        // Desired aspect ratio of the view's contents (not including padding)
        float desiredAspect = 0.0f;

        // We are allowed to change the view's width
        boolean resizeWidth = false;

        // We are allowed to change the view's height
        boolean resizeHeight = false;

        if (mDrawableWidth > 0) {
            w = mDrawableWidth;
            h = mDrawableHeight;
            if (w <= 0) w = 1;
            if (h <= 0) h = 1;

            // We are supposed to adjust view bounds to match the aspect
            // ratio of our drawable. See if that is possible.
            if (mAdjustViewBounds) {

                int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);
                int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);

                resizeWidth = widthSpecMode != MeasureSpec.EXACTLY;
                resizeHeight = heightSpecMode != MeasureSpec.EXACTLY;

                desiredAspect = (float) w / (float) h;
            }
        }

        int pleft = getPaddingLeft();
        int pright = getPaddingRight();
        int ptop = getPaddingTop();
        int pbottom = getPaddingBottom();

        int widthSize;
        int heightSize;

        if (resizeWidth || resizeHeight) {
            /* If we get here, it means we want to resize to match the
                drawables aspect ratio, and we have the freedom to change at
                least one dimension.
            */

            // Get the max possible width given our constraints
            widthSize = resolveAdjustedSize(w + pleft + pright,
                                                                                                mMaxWidth, widthMeasureSpec);

            // Get the max possible height given our constraints
            heightSize = resolveAdjustedSize(h + ptop + pbottom,
                                                                                            mMaxHeight, heightMeasureSpec);

            if (desiredAspect != 0.0f) {
                // See what our actual aspect ratio is
                float actualAspect = (float) (widthSize - pleft - pright) /
                                                                            (heightSize - ptop - pbottom);

                if (Math.abs(actualAspect - desiredAspect) > 0.0000001) {

                    boolean done = false;

                    // Try adjusting width to be proportional to height
                    if (resizeWidth) {
                        int newWidth = (int) (desiredAspect *
                                                                                    (heightSize - ptop - pbottom))
                                                                                    + pleft + pright;
                        if (newWidth <= widthSize) {
                            widthSize = newWidth;
                            done = true;
                        }
                    }

                    // Try adjusting height to be proportional to width
                    if (!done && resizeHeight) {
                        int newHeight = (int) ((widthSize - pleft - pright)
                                                                                    / desiredAspect) + ptop + pbottom;
                        //if (newHeight <= heightSize) {
                        heightSize = newHeight;
                        //}
                    }
                }
            }
        } else {
            /* We are either don't want to preserve the drawables aspect ratio,
               or we are not allowed to change view dimensions. Just measure in
               the normal way.
            */
            w += pleft + pright;
            h += ptop + pbottom;

            w = Math.max(w, getSuggestedMinimumWidth());
            h = Math.max(h, getSuggestedMinimumHeight());

            widthSize = resolveSize(w, widthMeasureSpec);
            heightSize = resolveSize(h, heightMeasureSpec);
        }

        setMeasuredDimension(widthSize, heightSize);
    }

    private int resolveAdjustedSize(int desiredSize, int maxSize,   int measureSpec) {
        int result = desiredSize;
        int specMode = MeasureSpec.getMode(measureSpec);
        int specSize = MeasureSpec.getSize(measureSpec);
        switch (specMode) {
        case MeasureSpec.UNSPECIFIED:
            /* Parent says we can be as big as we want. Just don't be larger
            than max size imposed on ourselves.
            */
            result = Math.min(desiredSize, maxSize);
            break;
        case MeasureSpec.AT_MOST:
            // Parent says we can be as big as we want, up to specSize.
            // Don't be larger than specSize, and don't be larger than
            // the max size imposed on ourselves.
            result = Math.min(Math.min(desiredSize, specSize), maxSize);
            break;
        case MeasureSpec.EXACTLY:
            // No choice. Do what we are told.
            result = specSize;
            break;
        }
        return result;
    }
}