ImageView.java

/*
 * Copyright (C) 2013 Tomáš Procházka
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package eu.inmite.android.fw.view;

import java.lang.reflect.Field;

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

import eu.inmite.android.fw.DebugLog;

/**
 * Special version of ImageView which allow enlarge width of image if android:adjustViewBounds is true.
 *
 * <p>It 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</a></p>
 *
 * <p>It also allow set related view which will be used as reference for size measure.</p>
 *
 * @author Tomáš Procházka &lt;<a href="mailto:tomas.prochazka@inmite.eu">tomas.prochazka@gmail.com</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 mAdjustViewBoundsL;
	private int mMaxWidthL = Integer.MAX_VALUE;
	private int mMaxHeightL = Integer.MAX_VALUE;
	private View relatedView;

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

		// hack for acces some private field of parent :-(
		Field f;
		try {
			f = android.widget.ImageView.class.getDeclaredField("mAdjustViewBounds");
			f.setAccessible(true);
			setAdjustViewBounds((Boolean) f.get(this));

			f = android.widget.ImageView.class.getDeclaredField("mMaxWidth");
			f.setAccessible(true);
			setMaxWidth((Integer) f.get(this));

			f = android.widget.ImageView.class.getDeclaredField("mMaxHeight");
			f.setAccessible(true);
			setMaxHeight((Integer) f.get(this));
		} catch (Exception e) {
			DebugLog.e("Access to parent private field failed", e);
		}
	}

	public ImageView(Context context, AttributeSet attrs) {
		this(context, attrs, 0);
	}

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

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

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

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

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

		if (getDrawable() == null) {
			setMeasuredDimension(0, 0);
			return;
		}

		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 (mAdjustViewBoundsL) {

				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,
				mMaxWidthL, widthMeasureSpec);

			// Get the max possible height given our constraints
			heightSize = resolveAdjustedSize(h + ptop + pbottom,
				mMaxHeightL, 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) {

					// Try adjusting width to be proportional to height
					if (resizeWidth) {
						int newWidth = (int) (desiredAspect * (heightSize - ptop - pbottom)) + pleft + pright;
						if (/*newWidth <= widthSize &&*/newWidth > 0) {
							widthSize = Math.min(newWidth, mMaxWidthL);
							heightSize = (int) ((widthSize - pleft - pright) / desiredAspect) + ptop + pbottom;
						}
					}

					// Try adjusting height to be proportional to width
					if (resizeHeight) {
						int newHeight = (int) ((widthSize - pleft - pright) / desiredAspect) + ptop + pbottom;
						if (/*newHeight <= heightSize && */newHeight > 0) {
							heightSize = Math.min(newHeight, mMaxHeightL);
							widthSize = (int) (desiredAspect * (heightSize - ptop - pbottom)) + pleft + pright;
						}
					}
				}
			}
		} 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);
		}

		//Log.d(Constants.LOGTAG, mDrawableWidth + ":" +  mDrawableHeight + " to " + widthSize + ":" + heightSize);

		setMeasuredDimension(widthSize, heightSize);

		if (relatedView != null) {
			//Log.i(Constants.LOGTAG, getTag() +  " onMeasure:" +  widthSize + ", " + heightSize + " update size of related view!");
			relatedView.getLayoutParams().width = widthSize;
			relatedView.getLayoutParams().height = heightSize;
		}

	}

	@Override
	protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
		super.onLayout(changed, left, top, right, bottom);
		//Log.d(Constants.LOGTAG, getTag() +  " onLayout:" +  left + ", " + top + ", " + right + ", " + bottom);
	}

	/**
	 * Experimental. This view will be set to the same size as this image.
	 */
	public void setRelatedView(View view) {
		relatedView = view;
	}

	@Override
	protected void onSizeChanged(int w, int h, int oldw, int oldh) {
		super.onSizeChanged(w, h, oldw, oldh);
		//Log.d(Constants.LOGTAG, getTag() + " onSizeChanged:" +  w + ", " + h + ", " + oldw + ", " + oldh);
	}

	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;
	}
}

While your code works great for the case where you need to expand a smaller image to a bigger size, it doesn't work for the opposite case which ImageView supports of shrinking and maintaining aspect ratio. I was able to hack it to work for me using:

                    if (/*newWidth <= widthSize &&*/newWidth > 0) {
                        widthSize = Math.min(Math.min(newWidth, mMaxWidthL), widthSize);
                        heightSize = (int) ((widthSize - pleft - pright) / desiredAspect) + ptop + pbottom;
                    }

Which only works for me because my limiting factor is always width and not height.