androidx/transition/ChangeImageTransform.java

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * 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 androidx.transition;

import android.animation.Animator;
import android.animation.ObjectAnimator;
import android.animation.TypeEvaluator;
import android.content.Context;
import android.graphics.Matrix;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Property;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import androidx.annotation.NonNull;

import java.util.Map;

/**
 * This Transition captures an ImageView's matrix before and after the
 * scene change and animates it during the transition.
 *
 * <p>In combination with ChangeBounds, ChangeImageTransform allows ImageViews
 * that change size, shape, or {@link android.widget.ImageView.ScaleType} to animate contents
 * smoothly.</p>
 */
public class ChangeImageTransform extends Transition {

    private static final String PROPNAME_MATRIX = "android:changeImageTransform:matrix";
    private static final String PROPNAME_BOUNDS = "android:changeImageTransform:bounds";

    private static final String[] sTransitionProperties = {
            PROPNAME_MATRIX,
            PROPNAME_BOUNDS,
    };

    private static final TypeEvaluator<Matrix> NULL_MATRIX_EVALUATOR = new TypeEvaluator<Matrix>() {
        @Override
        public Matrix evaluate(float fraction, Matrix startValue, Matrix endValue) {
            return null;
        }
    };

    private static final Property<ImageView, Matrix> ANIMATED_TRANSFORM_PROPERTY =
            new Property<ImageView, Matrix>(Matrix.class, "animatedTransform") {
                @Override
                public void set(ImageView view, Matrix matrix) {
                    ImageViewUtils.animateTransform(view, matrix);
                }

                @Override
                public Matrix get(ImageView object) {
                    return null;
                }
            };

    public ChangeImageTransform() {
    }

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

    private void captureValues(TransitionValues transitionValues) {
        View view = transitionValues.view;
        if (!(view instanceof ImageView) || view.getVisibility() != View.VISIBLE) {
            return;
        }
        ImageView imageView = (ImageView) view;
        Drawable drawable = imageView.getDrawable();
        if (drawable == null) {
            return;
        }
        Map<String, Object> values = transitionValues.values;

        int left = view.getLeft();
        int top = view.getTop();
        int right = view.getRight();
        int bottom = view.getBottom();

        Rect bounds = new Rect(left, top, right, bottom);
        values.put(PROPNAME_BOUNDS, bounds);
        values.put(PROPNAME_MATRIX, copyImageMatrix(imageView));
    }

    @Override
    public void captureStartValues(@NonNull TransitionValues transitionValues) {
        captureValues(transitionValues);
    }

    @Override
    public void captureEndValues(@NonNull TransitionValues transitionValues) {
        captureValues(transitionValues);
    }

    @Override
    public String[] getTransitionProperties() {
        return sTransitionProperties;
    }

    /**
     * Creates an Animator for ImageViews moving, changing dimensions, and/or changing
     * {@link android.widget.ImageView.ScaleType}.
     *
     * @param sceneRoot   The root of the transition hierarchy.
     * @param startValues The values for a specific target in the start scene.
     * @param endValues   The values for the target in the end scene.
     * @return An Animator to move an ImageView or null if the View is not an ImageView,
     * the Drawable changed, the View is not VISIBLE, or there was no change.
     */
    @Override
    public Animator createAnimator(@NonNull ViewGroup sceneRoot, TransitionValues startValues,
            final TransitionValues endValues) {
        if (startValues == null || endValues == null) {
            return null;
        }
        Rect startBounds = (Rect) startValues.values.get(PROPNAME_BOUNDS);
        Rect endBounds = (Rect) endValues.values.get(PROPNAME_BOUNDS);
        if (startBounds == null || endBounds == null) {
            return null;
        }

        Matrix startMatrix = (Matrix) startValues.values.get(PROPNAME_MATRIX);
        Matrix endMatrix = (Matrix) endValues.values.get(PROPNAME_MATRIX);

        boolean matricesEqual = (startMatrix == null && endMatrix == null)
                || (startMatrix != null && startMatrix.equals(endMatrix));

        if (startBounds.equals(endBounds) && matricesEqual) {
            return null;
        }

        final ImageView imageView = (ImageView) endValues.view;
        Drawable drawable = imageView.getDrawable();
        int drawableWidth = drawable.getIntrinsicWidth();
        int drawableHeight = drawable.getIntrinsicHeight();

        ImageViewUtils.startAnimateTransform(imageView);

        ObjectAnimator animator;
        if (drawableWidth == 0 || drawableHeight == 0) {
            animator = createNullAnimator(imageView);
        } else {
            if (startMatrix == null) {
                startMatrix = MatrixUtils.IDENTITY_MATRIX;
            }
            if (endMatrix == null) {
                endMatrix = MatrixUtils.IDENTITY_MATRIX;
            }
            ANIMATED_TRANSFORM_PROPERTY.set(imageView, startMatrix);
            animator = createMatrixAnimator(imageView, startMatrix, endMatrix);
        }

        ImageViewUtils.reserveEndAnimateTransform(imageView, animator);

        return animator;
    }

    private ObjectAnimator createNullAnimator(ImageView imageView) {
        return ObjectAnimator.ofObject(imageView, ANIMATED_TRANSFORM_PROPERTY,
                NULL_MATRIX_EVALUATOR, null, null);
    }

    private ObjectAnimator createMatrixAnimator(final ImageView imageView, Matrix startMatrix,
            final Matrix endMatrix) {
        return ObjectAnimator.ofObject(imageView, ANIMATED_TRANSFORM_PROPERTY,
                new TransitionUtils.MatrixEvaluator(), startMatrix, endMatrix);
    }

    private static Matrix copyImageMatrix(ImageView view) {
        switch (view.getScaleType()) {
            case FIT_XY:
                return fitXYMatrix(view);
            case CENTER_CROP:
                return centerCropMatrix(view);
            default:
                return new Matrix(view.getImageMatrix());
        }
    }

    /**
     * Calculates the image transformation matrix for an ImageView with ScaleType FIT_XY. This
     * needs to be manually calculated as the platform does not give us the value for this case.
     */
    private static Matrix fitXYMatrix(ImageView view) {
        final Drawable image = view.getDrawable();
        final Matrix matrix = new Matrix();
        matrix.postScale(
                ((float) view.getWidth()) / image.getIntrinsicWidth(),
                ((float) view.getHeight()) / image.getIntrinsicHeight());
        return matrix;
    }

    /**
     * Calculates the image transformation matrix for an ImageView with ScaleType CENTER_CROP. This
     * needs to be manually calculated for consistent behavior across all the API levels.
     */
    private static Matrix centerCropMatrix(ImageView view) {
        final Drawable image = view.getDrawable();
        final int imageWidth = image.getIntrinsicWidth();
        final int imageViewWidth = view.getWidth();
        final float scaleX = ((float) imageViewWidth) / imageWidth;

        final int imageHeight = image.getIntrinsicHeight();
        final int imageViewHeight = view.getHeight();
        final float scaleY = ((float) imageViewHeight) / imageHeight;

        final float maxScale = Math.max(scaleX, scaleY);

        final float width = imageWidth * maxScale;
        final float height = imageHeight * maxScale;
        final int tx = Math.round((imageViewWidth - width) / 2f);
        final int ty = Math.round((imageViewHeight - height) / 2f);

        final Matrix matrix = new Matrix();
        matrix.postScale(maxScale, maxScale);
        matrix.postTranslate(tx, ty);
        return matrix;
    }

}